Re: First non DSLR digicam with 10MP APS sensor- contradiction
keith_w wrote: John Francis wrote: On Mon, Sep 12, 2005 at 09:16:42AM -0700, keith_w wrote: [...] No-one on earth can measure the difference in angles involved . . Oh yes they can. In fact it's quite easy to do, even with the naked eye (as long as you use a piece of smoked glass or some other sun filter). There's around half a degree of difference in the angle of light from one side of the sun to the other - that's why the sun appears as a disc instead of a point light source. I don't know where this is going, but...your 1/2 degree equates to 0.00873 inches of horizontal displacement, per inch of distance from the emitter, which I am assuming is the rear face of the rear element. Ain't much... keith But it's a gargantuan amount when you are talking about lens construction. See my previous post on this matter. m
Re: First non DSLR digicam with 10MP APS sensor- contradiction
keith_w wrote: Godfrey DiGiorgi wrote: On Sep 12, 2005, at 1:42 AM, mike wilson wrote: A "large parallel cylinder of light" is the same thing as light coming from an infinitely distant point source. Consider light from the sun: all rays are parallel at 92 million miles distance, unless scattered by atmosphere. In the vacuum of space, they are absolutely parallel. So even though the sun is several hundred times the diameter of the Earth and is a light source, it is a point light source. Point of information: 8-) The sun's light rays are not parallel. If they were, then it would appear the same size at whatever distance you saw it. Think of a laser spot from a pointer. Apart from atmospheric diffusion and the flaws of production, the spot should be the same at one foot, one hundred yards or one mile. _Because the sun is so far away_, the light rays are very close to parallel. But they are not. True, point taken. But they are very close to parallel, the deviation being extremely small across so short a distance as the diameter of the earth. I should have written "... all rays are 'effectively' parallel at 92 Milliion miles distance ... ". Godfrey He may indeed have scored a point, but the net result is, it doesn't really matter one tiny bit. It's calculable, but not observable... No point scoring involved; just making a small clearup of detail. SMC coatings are about 1/4 of a wavelength of light in thickness - you can't see the difference _they_ make? No-one on earth can measure the difference in angles involved, and for certain, no-one would actually SEE any difference in his photography, so...it's argument for the sake of argument ~ period. I would have to disagree with you there... keith whaley ;-) Indeed.
Re: First non DSLR digicam with 10MP APS sensor- contradiction
John Francis wrote: On Mon, Sep 12, 2005 at 09:16:42AM -0700, keith_w wrote: [...] No-one on earth can measure the difference in angles involved . . Oh yes they can. In fact it's quite easy to do, even with the naked eye (as long as you use a piece of smoked glass or some other sun filter). There's around half a degree of difference in the angle of light from one side of the sun to the other - that's why the sun appears as a disc instead of a point light source. I don't know where this is going, but...your 1/2 degree equates to 0.00873 inches of horizontal displacement, per inch of distance from the emitter, which I am assuming is the rear face of the rear element. Ain't much... keith
Re: First non DSLR digicam with 10MP APS sensor- contradiction
On Mon, Sep 12, 2005 at 09:16:42AM -0700, keith_w wrote: > Godfrey DiGiorgi wrote: > > >On Sep 12, 2005, at 1:42 AM, mike wilson wrote: > > > >>>A "large parallel cylinder of light" is the same thing as light > >>>coming from an infinitely distant point source. Consider light from > >>>the sun: all rays are parallel at 92 million miles distance, unless > >>>scattered by atmosphere. In the vacuum of space, they are absolutely > >>>parallel. So even though the sun is several hundred times the > >>>diameter of the Earth and is a light source, it is a point light > >>>source. > >> > >> > >>Point of information: 8-) > >> > >>The sun's light rays are not parallel. If they were, then it would > >>appear the same size at whatever distance you saw it. Think of a > >>laser spot from a pointer. Apart from atmospheric diffusion and the > >>flaws of production, the spot should be the same at one foot, one > >>hundred yards or one mile. _Because the sun is so far away_, the > >>light rays are very close to parallel. But they are not. > > > > > >True, point taken. But they are very close to parallel, the deviation > >being extremely small across so short a distance as the diameter of the > >earth. I should have written "... all rays are 'effectively' parallel > >at 92 Milliion miles distance ... ". > > > >Godfrey > > He may indeed have scored a point, but the net result is, it doesn't > really matter one tiny bit. It's calculable, but not observable... > > No-one on earth can measure the difference in angles involved . . Oh yes they can. In fact it's quite easy to do, even with the naked eye (as long as you use a piece of smoked glass or some other sun filter). There's around half a degree of difference in the angle of light from one side of the sun to the other - that's why the sun appears as a disc instead of a point light source.
Re: First non DSLR digicam with 10MP APS sensor- contradiction
Godfrey DiGiorgi wrote: On Sep 12, 2005, at 1:42 AM, mike wilson wrote: A "large parallel cylinder of light" is the same thing as light coming from an infinitely distant point source. Consider light from the sun: all rays are parallel at 92 million miles distance, unless scattered by atmosphere. In the vacuum of space, they are absolutely parallel. So even though the sun is several hundred times the diameter of the Earth and is a light source, it is a point light source. Point of information: 8-) The sun's light rays are not parallel. If they were, then it would appear the same size at whatever distance you saw it. Think of a laser spot from a pointer. Apart from atmospheric diffusion and the flaws of production, the spot should be the same at one foot, one hundred yards or one mile. _Because the sun is so far away_, the light rays are very close to parallel. But they are not. True, point taken. But they are very close to parallel, the deviation being extremely small across so short a distance as the diameter of the earth. I should have written "... all rays are 'effectively' parallel at 92 Milliion miles distance ... ". Godfrey He may indeed have scored a point, but the net result is, it doesn't really matter one tiny bit. It's calculable, but not observable... No-one on earth can measure the difference in angles involved, and for certain, no-one would actually SEE any difference in his photography, so...it's argument for the sake of argument ~ period. keith whaley ;-)
Re: First non DSLR digicam with 10MP APS sensor- contradiction
On Sep 12, 2005, at 1:42 AM, mike wilson wrote: A "large parallel cylinder of light" is the same thing as light coming from an infinitely distant point source. Consider light from the sun: all rays are parallel at 92 million miles distance, unless scattered by atmosphere. In the vacuum of space, they are absolutely parallel. So even though the sun is several hundred times the diameter of the Earth and is a light source, it is a point light source. Point of information: 8-) The sun's light rays are not parallel. If they were, then it would appear the same size at whatever distance you saw it. Think of a laser spot from a pointer. Apart from atmospheric diffusion and the flaws of production, the spot should be the same at one foot, one hundred yards or one mile. _Because the sun is so far away_, the light rays are very close to parallel. But they are not. True, point taken. But they are very close to parallel, the deviation being extremely small across so short a distance as the diameter of the earth. I should have written "... all rays are 'effectively' parallel at 92 Milliion miles distance ... ". Godfrey
Re: Re: First non DSLR digicam with 10MP APS sensor- contradiction
> > From: Godfrey DiGiorgi <[EMAIL PROTECTED]> > A "large parallel cylinder of light" is the same thing as light > coming from an infinitely distant point source. Consider light from > the sun: all rays are parallel at 92 million miles distance, unless > scattered by atmosphere. In the vacuum of space, they are absolutely > parallel. So even though the sun is several hundred times the > diameter of the Earth and is a light source, it is a point light source. Point of information: 8-) The sun's light rays are not parallel. If they were, then it would appear the same size at whatever distance you saw it. Think of a laser spot from a pointer. Apart from atmospheric diffusion and the flaws of production, the spot should be the same at one foot, one hundred yards or one mile. _Because the sun is so far away_, the light rays are very close to parallel. But they are not. Interesting discussion. Carry on. m - Email sent from www.ntlworld.com Virus-checked using McAfee(R) Software Visit www.ntlworld.com/security for more information
Re: First non DSLR digicam with 10MP APS sensor- contradiction
On Sep 11, 2005, at 8:23 PM, J. C. O'Connell wrote: If I am getting what you are saying, you are talking about a special optical device BETWEEN the image forming lens and the sensor. If that's what your talking about then yes that would always be "active" but we havent been discussing something like that, we have been discussing an image forming camera "lens" and they do NOT do that. What your talking about is more like a secondary otical system in addition to the "lens" Yes, that's what a dedicated digital sensor lens design is, in conceptual terms. It's what the Sony R1 lens is almost certainly like if you look at the ray trace. Secondly in the case of a camera "lens" the size of the rear element has little to do with "active area" or percentage of its area in the optical path. You're the one who was talking of "active area" vis a vis the rear elements. I'm just trying to use your terminology. well this makes no sense to me. enlarger lamp houses convert the bulb (point) source to a large parallel cylinder of light to illuminate the negative evenly. A "large parallel cylinder of light" is the same thing as light coming from an infinitely distant point source. Consider light from the sun: all rays are parallel at 92 million miles distance, unless scattered by atmosphere. In the vacuum of space, they are absolutely parallel. So even though the sun is several hundred times the diameter of the Earth and is a light source, it is a point light source. a camera lens forms an IMAGE, the raya coming out of a camera lens towards the film/sensor is diverging to form an image. If you had a camera lens in an enlarger lamp house your would get an IMAGE of a light bulb illuminating the negative which would of course be terrible. It's an analogy, JCO. The nodal point of a lens is that dimensionless point through which all the light paths intersect. It is, from the point of view of the focal plane, the same as a point light source. The fact that the light rays which intersect there are coming from spatially different places and are of different intensities is inconsequential to their trace path. Fagehddaboudit. yes but its WORSE because with 35mm FF or film cameras All normals and even slight wide angles can be done without the need for retrofocus. With APS sensor in camera with same 45.5 mm registration, even normal lenses (~30-35mm on APS ) have to be retrofocus as well as all wide angles its worse not better to have the flange so far away on such a small sensor. The closer the better on ALL cameras all else being equal because it give the optical designers more options- like this new non SLR 10MP camera we are talking about. Since most of the best short lenses now in existence are now inverted telephoto designs (even for rangefinder cameras with a 29mm register like the Leica M), return both resolution and contrast comparable to or surpassing the best non-inverted-telephoto, and better evenness of illumination, I would consider the distinction to be moot. The price for this is more complexity in lens formulae and more complexity in construction, but we seem to have overcome the technical challenges required. Godfrey
RE: First non DSLR digicam with 10MP APS sensor- contradiction
-Original Message- From: Godfrey DiGiorgi [mailto:[EMAIL PROTECTED] Sent: Sunday, September 11, 2005 7:39 PM To: pentax-discuss@pdml.net Subject: Re: First non DSLR digicam with 10MP APS sensor- contradiction On Sep 11, 2005, at 3:51 PM, J. C. O'Connell wrote: > My sketch was a simple sketch ( that obviously not > a real lens design with two convex lenses) and I > explaied I was showing the ACTIVE area of the rear > element so it does not matter where the nodal point > because if the entire active area gets closer to the > sensor then the angles to the corners of the sensors > get further away from perpendicular/ideal. This makes no sense. In a lens with a set of rear elements designed to correct light path to orthogonal, a large percentage of the rear element of the lens is *always* active. That is the point of the design: direct the light to be orthogonal to the sensor. If the rear elements are close to the imaging plane, and far from the nodal point, the correction is small and most of the rear element is being used. If the rear elements are far from the imaging plane and close to the nodal point, a smaller percentage of the rear elements are being used and the correction possible is reduced. == === REPLY REPLY REPLY If I am getting what you are saying, you are talking about a special optical device BETWEEN the image forming lens and the sensor. If that's what your talking about then yes that would always be "active" but we havent been discussing something like that, we have been discussing an image forming camera "lens" and they do NOT do that. What your talking about is more like a secondary otical system in addition to the "lens" Secondly in the case of a camera "lens" the size of the rear element has little to do with "active area" or percentage of its area in the optical path. some lenses have very oversized rear elements and the optical path even wide open is not using all the glass, and the matter I brought up before, when you stop down the lens the percentage of the rear element glass area in the optical path goes down even more. = >> ... a condenser enlarger head does: it >> positions a collimating lens group very close to the film plane in >> order to make the light pass evenly through all points of the >> negative, right to the corners, and oriented orthogonally through the >> film so that a flat field imaging objective (the enlarging lens) will >> exhibit very little light falloff at corners and edges. > > I totally disagree with the englarger light house > because the output of an enlarger condensor assembly > is PARALLEL light rays going to the film form a point > light source. A camera, digital or otherwise has a > POINT SOURCE image formed at the film/sensor from a point source REAL > OBJECT, in other words the output of a camera lens is an image of the > real object formed on the film/sensor while the output of an enlager > condensor lamphouse is completely different, its NOT forming an image > of the enlarger lamp, its forming a cylinder of parallel light rays > instead of an image at the film. The use of a condenser enlarger as example is illustrate simulating a point light source at infinity such that the ray trace over the area of the film would be parallel. This is indeed the way light coming from a point source at infinity would be oriented. In the camera lens/ sensor system, the point source can be seen as the lens' nodal point. == === REPLY REPLY REPLY well this makes no sense to me. enlarger lamp houses convert the bulb (point) source to a large parallel cylinder of light to illuminate the negative evenly. a camera lens forms an IMAGE, the raya coming out of a camera lens towards the film/sensor is diverging to form an image. If you had a camera lens in an enlarger lamp house your would get an IMAGE of a light bulb illuminating the negative which would of course be terrible. >> A large diameter element at the rear of a lens designed for the >> digital sensor helps in promoting this even illumination of the >> entire sensor area. Placing this rear lens group close to the sensor, >> relatively distant from the nodal point, allows the strength of the >> elements to be lower and thus promotes less distortion from the >> correction. > > You are overlooking that the "diameter" of the rear element is not > "fixed" and it gets s
RE: First non DSLR digicam with 10MP APS sensor- contradiction
-Original Message- From: Godfrey DiGiorgi [mailto:[EMAIL PROTECTED] Sent: Sunday, September 11, 2005 7:39 PM To: pentax-discuss@pdml.net Subject: Re: First non DSLR digicam with 10MP APS sensor- contradiction On Sep 11, 2005, at 3:51 PM, J. C. O'Connell wrote: > My sketch was a simple sketch ( that obviously not > a real lens design with two convex lenses) and I > explaied I was showing the ACTIVE area of the rear > element so it does not matter where the nodal point > because if the entire active area gets closer to the > sensor then the angles to the corners of the sensors > get further away from perpendicular/ideal. This makes no sense. In a lens with a set of rear elements designed to correct light path to orthogonal, a large percentage of the rear element of the lens is *always* active. That is the point of the design: direct the light to be orthogonal to the sensor. If the rear elements are close to the imaging plane, and far from the nodal point, the correction is small and most of the rear element is being used. If the rear elements are far from the imaging plane and close to the nodal point, a smaller percentage of the rear elements are being used and the correction possible is reduced. >> ... a condenser enlarger head does: it >> positions a collimating lens group very close to the film plane in >> order to make the light pass evenly through all points of the >> negative, right to the corners, and oriented orthogonally through the >> film so that a flat field imaging objective (the enlarging lens) will >> exhibit very little light falloff at corners and edges. > > I totally disagree with the englarger light house > because the output of an enlarger condensor assembly > is PARALLEL light rays going to the film form a point > light source. A camera, digital or otherwise has a > POINT SOURCE image formed at the film/sensor from a point source REAL > OBJECT, in other words the output of a camera lens is an image of the > real object formed on the film/sensor while the output of an enlager > condensor lamphouse is completely different, its NOT forming an image > of the enlarger lamp, its forming a cylinder of parallel light rays > instead of an image at the film. The use of a condenser enlarger as example is illustrate simulating a point light source at infinity such that the ray trace over the area of the film would be parallel. This is indeed the way light coming from a point source at infinity would be oriented. In the camera lens/ sensor system, the point source can be seen as the lens' nodal point. >> A large diameter element at the rear of a lens designed for the >> digital sensor helps in promoting this even illumination of the >> entire sensor area. Placing this rear lens group close to the sensor, >> relatively distant from the nodal point, allows the strength of the >> elements to be lower and thus promotes less distortion from the >> correction. > > You are overlooking that the "diameter" of the rear element is not > "fixed" and it gets smaller in its active area ( optical path), quite > small in fact at small fstops like f11/16 so that is changing with > lens settings and cannot be maintained constant...So if the advantage > of the large rear element is there its not constant and the angle at > which the light rays hit the sensor corners is worse when the lens is > stopped down. See above. Perhaps I'll draw a diagram or two for you. > Secondly, I totally agree that increasing > the nodal point away from the sensor while > maintaining the same focal length will help > the digital sensor / lens interface with respect > to keep the lens rays more parallel incidence > at sensor plane but there is a heavy price > for that , the retrofocus lenses that do that > are far larger, heaver, worse optically, and > more expensive than if you don't need to do that. > That's why the Pentax and other cameras that > use APS sensors in old FF 35mm body designed > lenses are at a disadvantage, the 45.5mm sensor > plane to lens flange distance is way too large > relative to the small format (APS), I'm not exactly sure what you're trying to say here. Yes, inverted telephoto designs are typically more complex, heavier and more expensive than non-inverted-telephoto designs. They are a result of the need for more clearance with SLR bodies as focal length is reduced. On the other hand, evenness of illumination is typically better with inverse telephoto designs. As far as I'm aware, nearly all modern 35mm and shorter focal length lenses designed for 35mm and digital SLRs are inverse telephoto designs. Most of the better, modern wide angles used for rangefinder cameras are as well, be
Re: First non DSLR digicam with 10MP APS sensor- contradiction
On Sep 11, 2005, at 3:51 PM, J. C. O'Connell wrote: My sketch was a simple sketch ( that obviously not a real lens design with two convex lenses) and I explaied I was showing the ACTIVE area of the rear element so it does not matter where the nodal point because if the entire active area gets closer to the sensor then the angles to the corners of the sensors get further away from perpendicular/ideal. This makes no sense. In a lens with a set of rear elements designed to correct light path to orthogonal, a large percentage of the rear element of the lens is *always* active. That is the point of the design: direct the light to be orthogonal to the sensor. If the rear elements are close to the imaging plane, and far from the nodal point, the correction is small and most of the rear element is being used. If the rear elements are far from the imaging plane and close to the nodal point, a smaller percentage of the rear elements are being used and the correction possible is reduced. ... a condenser enlarger head does: it positions a collimating lens group very close to the film plane in order to make the light pass evenly through all points of the negative, right to the corners, and oriented orthogonally through the film so that a flat field imaging objective (the enlarging lens) will exhibit very little light falloff at corners and edges. I totally disagree with the englarger light house because the output of an enlarger condensor assembly is PARALLEL light rays going to the film form a point light source. A camera, digital or otherwise has a POINT SOURCE image formed at the film/sensor from a point source REAL OBJECT, in other words the output of a camera lens is an image of the real object formed on the film/sensor while the output of an enlager condensor lamphouse is completely different, its NOT forming an image of the enlarger lamp, its forming a cylinder of parallel light rays instead of an image at the film. The use of a condenser enlarger as example is illustrate simulating a point light source at infinity such that the ray trace over the area of the film would be parallel. This is indeed the way light coming from a point source at infinity would be oriented. In the camera lens/ sensor system, the point source can be seen as the lens' nodal point. A large diameter element at the rear of a lens designed for the digital sensor helps in promoting this even illumination of the entire sensor area. Placing this rear lens group close to the sensor, relatively distant from the nodal point, allows the strength of the elements to be lower and thus promotes less distortion from the correction. You are overlooking that the "diameter" of the rear element is not "fixed" and it gets smaller in its active area ( optical path), quite small in fact at small fstops like f11/16 so that is changing with lens settings and cannot be maintained constant...So if the advantage of the large rear element is there its not constant and the angle at which the light rays hit the sensor corners is worse when the lens is stopped down. See above. Perhaps I'll draw a diagram or two for you. Secondly, I totally agree that increasing the nodal point away from the sensor while maintaining the same focal length will help the digital sensor / lens interface with respect to keep the lens rays more parallel incidence at sensor plane but there is a heavy price for that , the retrofocus lenses that do that are far larger, heaver, worse optically, and more expensive than if you don't need to do that. That's why the Pentax and other cameras that use APS sensors in old FF 35mm body designed lenses are at a disadvantage, the 45.5mm sensor plane to lens flange distance is way too large relative to the small format (APS), I'm not exactly sure what you're trying to say here. Yes, inverted telephoto designs are typically more complex, heavier and more expensive than non-inverted-telephoto designs. They are a result of the need for more clearance with SLR bodies as focal length is reduced. On the other hand, evenness of illumination is typically better with inverse telephoto designs. As far as I'm aware, nearly all modern 35mm and shorter focal length lenses designed for 35mm and digital SLRs are inverse telephoto designs. Most of the better, modern wide angles used for rangefinder cameras are as well, because the even illumination is useful. Only a few are not, and those generally demonstrate corner/edge falloff to a greater degree. The register distance could be shorter in dedicated lenses for a DSLR due to the shorter mirror required, but the whole point of using the current register distance is to enable use of existing lens and mount designs. IF, however, you're designing a mount and lens from scratch for a digital sensor, you'd use a wider diameter mount with a shorter register. This lets you place large diameter, corrective rear elements closer to the sensor without ha
RE: First non DSLR digicam with 10MP APS sensor- contradiction
Secondly, I totally agree that increasing the nodal point away from the sensor while maintaining the same focal length will help the digital sensor / lens interface with respect to keep the lens rays more parallel incidence at sensor plane but there is a heavy price for that , the retrofocus lenses that do that are far larger, heaver, worse optically, and more expensive than if you don't need to do that. That's why the Pentax and other cameras that use APS sensors in old FF 35mm body designed lenses are at a disadvantage, the 45.5mm sensor plane to lens flange distance is way too large relative to the small format (APS), jco -Original Message- From: Godfrey DiGiorgi [mailto:[EMAIL PROTECTED] Sent: Sunday, September 11, 2005 6:05 PM To: pentax-discuss@pdml.net Subject: Re: First non DSLR digicam with 10MP APS sensor- contradiction On Sep 9, 2005, at 2:27 PM, J. C. O'Connell wrote: > I did a quick sketch to clarify what I said: > http://www.jcoconnell.com/temp/rearanglediagram.jpg Your sketch is misleading: it exaggerates the relative sizing of the sensor target compared to the lens and also does not indicate where the nodal point is. In a typical Cooke triplet, it's the distance from the nodal point to the imaging plane that determines the deviation from the orthogonal as you approach the edge of the film/ sensor format, not the distance between the rear element and the film/ sensor. The point of having a lens designed for a digital sensor that has its rearmost element very close to the sensor plane is that the rearmost elements of the lens performs correction designed to orient the light path from the nodal point (placed sufficiently far forward in the lens) such that the ray trace to the photosite plane is orthogonal, not that you'd place the nodal point further rearwards in the lens. This is quite similar to what a condenser enlarger head does: it positions a collimating lens group very close to the film plane in order to make the light pass evenly through all points of the negative, right to the corners, and oriented orthogonally through the film so that a flat field imaging objective (the enlarging lens) will exhibit very little light falloff at corners and edges. A large diameter element at the rear of a lens designed for the digital sensor helps in promoting this even illumination of the entire sensor area. Placing this rear lens group close to the sensor, relatively distant from the nodal point, allows the strength of the elements to be lower and thus promotes less distortion from the correction. Godfrey
RE: First non DSLR digicam with 10MP APS sensor- contradiction
-Original Message- From: Godfrey DiGiorgi [mailto:[EMAIL PROTECTED] Sent: Sunday, September 11, 2005 6:05 PM To: pentax-discuss@pdml.net Subject: Re: First non DSLR digicam with 10MP APS sensor- contradiction On Sep 9, 2005, at 2:27 PM, J. C. O'Connell wrote: > I did a quick sketch to clarify what I said: > http://www.jcoconnell.com/temp/rearanglediagram.jpg Your sketch is misleading: it exaggerates the relative sizing of the sensor target compared to the lens and also does not indicate where the nodal point is. In a typical Cooke triplet, it's the distance from the nodal point to the imaging plane that determines the deviation from the orthogonal as you approach the edge of the film/ sensor format, not the distance between the rear element and the film/ sensor. ===== My sketch was a simple sketch ( that obviously not a real lens design with two convex lenses) and I explaied I was showing the ACTIVE area of the rear element so it does not matter where the nodal point because if the entire active area gets closer to the sensor then the angles to the corners of the sensors get further away from perpendicular/ideal. = The point of having a lens designed for a digital sensor that has its rearmost element very close to the sensor plane is that the rearmost elements of the lens performs correction designed to orient the light path from the nodal point (placed sufficiently far forward in the lens) such that the ray trace to the photosite plane is orthogonal, not that you'd place the nodal point further rearwards in the lens. This is quite similar to what a condenser enlarger head does: it positions a collimating lens group very close to the film plane in order to make the light pass evenly through all points of the negative, right to the corners, and oriented orthogonally through the film so that a flat field imaging objective (the enlarging lens) will exhibit very little light falloff at corners and edges. === I totally disagree with the englarger light house because the output of an enlarger condensor assembly is PARALLEL light rays going to the film form a point light source. A camera, digital or otherwise has a POINT SOURCE image formed at the film/sensor from a point source REAL OBJECT, in other words the output of a camera lens is an image of the real object formed on the film/sensor while the output of an enlager condensor lamphouse is completely different, its NOT forming an image of the enlarger lamp, its forming a cylinder of parallel light rays instead of an image at the film. == A large diameter element at the rear of a lens designed for the digital sensor helps in promoting this even illumination of the entire sensor area. Placing this rear lens group close to the sensor, relatively distant from the nodal point, allows the strength of the elements to be lower and thus promotes less distortion from the correction. == You are overlooking that the "diameter" of the rear element is not "fixed" and it gets smaller in its active area ( optical path), quite small in fact at small fstops like f11/16 so that is changing with lens settings and cannot be maintained constant...So if the advantage of the large rear element is there its not constant and the angle at which the light rays hit the sensor corners is worse when the lens is stopped down. JCO ==
Re: First non DSLR digicam with 10MP APS sensor- contradiction
On Sep 9, 2005, at 2:27 PM, J. C. O'Connell wrote: I did a quick sketch to clarify what I said: http://www.jcoconnell.com/temp/rearanglediagram.jpg Your sketch is misleading: it exaggerates the relative sizing of the sensor target compared to the lens and also does not indicate where the nodal point is. In a typical Cooke triplet, it's the distance from the nodal point to the imaging plane that determines the deviation from the orthogonal as you approach the edge of the film/ sensor format, not the distance between the rear element and the film/ sensor. The point of having a lens designed for a digital sensor that has its rearmost element very close to the sensor plane is that the rearmost elements of the lens performs correction designed to orient the light path from the nodal point (placed sufficiently far forward in the lens) such that the ray trace to the photosite plane is orthogonal, not that you'd place the nodal point further rearwards in the lens. This is quite similar to what a condenser enlarger head does: it positions a collimating lens group very close to the film plane in order to make the light pass evenly through all points of the negative, right to the corners, and oriented orthogonally through the film so that a flat field imaging objective (the enlarging lens) will exhibit very little light falloff at corners and edges. A large diameter element at the rear of a lens designed for the digital sensor helps in promoting this even illumination of the entire sensor area. Placing this rear lens group close to the sensor, relatively distant from the nodal point, allows the strength of the elements to be lower and thus promotes less distortion from the correction. Godfrey
Re: First non DSLR digicam with 10MP APS sensor- contradiction
In a message dated 9/9/2005 11:59:48 AM Pacific Standard Time, [EMAIL PROTECTED] writes: What you're saying is, the rear element really doesn't collimate the light bundle, that about right? Are you also saying it can't happen, according to the laws of optics as you understand them? I thought that was the reason for the odd shapes some lenses are ground to, to set up the refraction so it DID control where the light went and how it looked after it exited the last surface... I'm not dissing you here. I am not capable of anything but the most rudimentary ray tracing and today, so many years after I learned how, not even that! keith whaley == I think I am getting a headache. Marnie aka Doe :-)
RE: First non DSLR digicam with 10MP APS sensor- contradiction
OK, I did a quick sketch to clarify what I said: http://www.jcoconnell.com/temp/rearanglediagram.jpg Later, jco -Original Message- From: Derek [mailto:[EMAIL PROTECTED] Sent: Friday, September 09, 2005 4:36 PM To: pentax-discuss@pdml.net Subject: RE: First non DSLR digicam with 10MP APS sensor- contradiction Can I please get a diagram of this? Derek > Its very simple. If the working diameter of the rear element and the > diagonal size (format) of the sensor remain constant, then the further > the rear element is from the sensor the NARROWER the corner to corner > angle cone angle becomes eminating from the rear element and the > deviation from pendicular in the corner of the sensor becomes > smaller (better) as the lens is moved away. Do not confuse > this angle with the angle of view, they don't have to match > and will vary depending on optical design... > JCO > > -Original Message- > From: keith_w [mailto:[EMAIL PROTECTED] > Sent: Friday, September 09, 2005 2:18 PM > To: pentax-discuss@pdml.net > Subject: Re: First non DSLR digicam with 10MP APS sensor- contradiction > > > J. C. O'Connell wrote: > > > Isnt is a contradiction that the lens is CLOSER > > to the sensor and its an improvement because that > > means the light it hitting the corners of the sensor > > at a GREATER angle away from perpendicular which > > is BAD (perpendicular being ideal)? > > I don't understand. > The light cone exiting a lens assembly will have a certain value, in > degrees, total or half-angle, as you say, from the perpendicular. > > Move the lens along it's axis toward or further away from the sensor, > to > exactly cover the corners, it always has the same angle. The only thing > that changes is area of coverage. Not the angle of the exiting light bundle. > If you insist what you say is true, I have misunderstood you. Please > elaborate. > > keith whaley > > > > -- > -- > >J.C. O'Connell mailto:[EMAIL PROTECTED] http://jcoconnell.com > > > > -- > > -- > >
RE: First non DSLR digicam with 10MP APS sensor- contradiction
Can I please get a diagram of this? Derek > Its very simple. If the working diameter of the rear element > and the diagonal size (format) of the sensor remain constant, then > the further the rear element is from the sensor the > NARROWER the corner to corner angle cone angle becomes eminating > from the rear element and the deviation > from pendicular in the corner of the sensor becomes > smaller (better) as the lens is moved away. Do not confuse > this angle with the angle of view, they don't have to match > and will vary depending on optical design... > JCO > > -Original Message- > From: keith_w [mailto:[EMAIL PROTECTED] > Sent: Friday, September 09, 2005 2:18 PM > To: pentax-discuss@pdml.net > Subject: Re: First non DSLR digicam with 10MP APS sensor- contradiction > > > J. C. O'Connell wrote: > > > Isnt is a contradiction that the lens is CLOSER > > to the sensor and its an improvement because that > > means the light it hitting the corners of the sensor > > at a GREATER angle away from perpendicular which > > is BAD (perpendicular being ideal)? > > I don't understand. > The light cone exiting a lens assembly will have a certain value, in > degrees, total or half-angle, as you say, from the perpendicular. > > Move the lens along it's axis toward or further away from the sensor, to > exactly cover the corners, it always has the same angle. The only thing > that changes is area of coverage. Not the angle of the exiting light bundle. > If you insist what you say is true, I have misunderstood you. Please > elaborate. > > keith whaley > > > > > >J.C. O'Connell mailto:[EMAIL PROTECTED] http://jcoconnell.com > > -- > > -- > >
RE: First non DSLR digicam with 10MP APS sensor- contradiction
Its very simple. If the working diameter of the rear element and the diagonal size (format) of the sensor remain constant, then the further the rear element is from the sensor the NARROWER the corner to corner angle cone angle becomes eminating from the rear element and the deviation from pendicular in the corner of the sensor becomes smaller (better) as the lens is moved away. Do not confuse this angle with the angle of view, they don't have to match and will vary depending on optical design... JCO -Original Message- From: keith_w [mailto:[EMAIL PROTECTED] Sent: Friday, September 09, 2005 2:18 PM To: pentax-discuss@pdml.net Subject: Re: First non DSLR digicam with 10MP APS sensor- contradiction J. C. O'Connell wrote: > Isnt is a contradiction that the lens is CLOSER > to the sensor and its an improvement because that > means the light it hitting the corners of the sensor > at a GREATER angle away from perpendicular which > is BAD (perpendicular being ideal)? I don't understand. The light cone exiting a lens assembly will have a certain value, in degrees, total or half-angle, as you say, from the perpendicular. Move the lens along it's axis toward or further away from the sensor, to exactly cover the corners, it always has the same angle. The only thing that changes is area of coverage. Not the angle of the exiting light bundle. If you insist what you say is true, I have misunderstood you. Please elaborate. keith whaley > >J.C. O'Connell mailto:[EMAIL PROTECTED] http://jcoconnell.com > -- > --
Re: First non DSLR digicam with 10MP APS sensor- contradiction
John Francis wrote: On Fri, Sep 09, 2005 at 06:07:37PM +0200, Dario Bonazza wrote: Isn'it it possible that a large rear element force rays perpendicular to the sensor? This will allow a better image on the sensor and if such an element is part of the lens design, it won't affect lens performance. No. To a first approximation light rays from every part of the rear element contribute to every point of the image. The larger the rear element, the wider this cone of rays is, and so the more deviation there is from the perpendicular (and the wider the range of angles, which makes it hard to compensate by angling the sensor pits). What you're saying is, the rear element really doesn't collimate the light bundle, that about right? Are you also saying it can't happen, according to the laws of optics as you understand them? I thought that was the reason for the odd shapes some lenses are ground to, to set up the refraction so it DID control where the light went and how it looked after it exited the last surface... I'm not dissing you here. I am not capable of anything but the most rudimentary ray tracing and today, so many years after I learned how, not even that! keith whaley
Re: First non DSLR digicam with 10MP APS sensor- contradiction
Dario Bonazza wrote: Isn'it it possible that a large rear element force rays perpendicular to the sensor? This will allow a better image on the sensor and if such an element is part of the lens design, it won't affect lens performance. BTW, Sylwek, I cannot access fotopolis.pl. I tried several times every time you post such links, with no success. Am I the only one? Works for me. Dario - Original Message - From: "J. C. O'Connell" <[EMAIL PROTECTED]> To: Sent: Friday, September 09, 2005 5:42 PM Subject: RE: First non DSLR digicam with 10MP APS sensor- contradiction I didn't say it didn't work, I don't understand WHY closer is better because that increases the incidence angle deviation from perpendicular, which is bad, severely on the edges/corners of the sensor. I can understand why the lens itself is better, it just seems that the lens/sensor interface is much worse when the rear element is so severely close to the sensor. Maybe this sensor is specially designed for this lens and isnt "flat"? jco -Original Message- From: Sylwester Pietrzyk [mailto:[EMAIL PROTECTED] Sent: Friday, September 09, 2005 11:31 AM To: pentax-discuss@pdml.net Subject: Re: First non DSLR digicam with 10MP APS sensor- contradiction J. C. O'Connell wrote on 09.09.05 17:06: Isnt is a contradiction that the lens is CLOSER to the sensor and its an improvement because that means the light it hitting the corners of the sensor at a GREATER angle away from perpendicular which is BAD (perpendicular being ideal)? Actually samples on www.fotopolis.pl has shown, that R1 performs much better than "digital optimised" E-300 ;-) -- Balance is the ultimate good... Best Regards Sylwek
Re: First non DSLR digicam with 10MP APS sensor- contradiction
John, Usually, lenses optimized for digital claim to have a large rear element. Olympus explains this way the reason for their large bayonet and many think that Canon has an edge over Nikon for the wider EF mount over the narrower F. In this case of 2mm between the rear element and the sensor, I'd suggest you think of the rear element (or group) of the R-1 as a meniscus with a curved surface toward the other elements, acting as a focus plane for the rest of the lens + a flat surface toward the sensor, for conveying the image perpendicular on the sensor. Just an idea. Dario - Original Message - From: "John Francis" <[EMAIL PROTECTED]> To: Sent: Friday, September 09, 2005 7:10 PM Subject: Re: First non DSLR digicam with 10MP APS sensor- contradiction On Fri, Sep 09, 2005 at 06:07:37PM +0200, Dario Bonazza wrote: Isn'it it possible that a large rear element force rays perpendicular to the sensor? This will allow a better image on the sensor and if such an element is part of the lens design, it won't affect lens performance. No. To a first approximation light rays from every part of the rear element contribute to every point of the image. The larger the rear element, the wider this cone of rays is, and so the more deviation there is from the perpendicular (and the wider the range of angles, which makes it hard to compensate by angling the sensor pits).
Re: First non DSLR digicam with 10MP APS sensor- contradiction
JCO, In this case of 2mm between the rear element and the sensor, I'd suggest you think of the rear element (or group) of the R-1 as a meniscus with a curved surface toward the other elements, acting as a focus plane for the rest of the lens + a flat surface toward the sensor, for conveying the image perpendicular on the sensor. Just my idea. Dario - Original Message - From: "J. C. O'Connell" <[EMAIL PROTECTED]> To: Sent: Friday, September 09, 2005 7:35 PM Subject: RE: First non DSLR digicam with 10MP APS sensor- contradiction wrong, the closer the rear element. the more that forces greater NON perpendicular incidence angles to the corners of the sensor. It order to approximate true perpendicular incidence, the rear element has to move away infinitly from the sensor. Total opposite of what you just posted. jco -Original Message- From: Adam Maas [mailto:[EMAIL PROTECTED] Sent: Friday, September 09, 2005 1:13 PM To: pentax-discuss@pdml.net Subject: Re: First non DSLR digicam with 10MP APS sensor- contradiction Putting the rear element closer to the sensor allows you to have a perpendicular light path to the sensor without going to an extreme retrofocus design for wide angles. This allows a simplified lens design for equivalent length and zoom range. The Light path only needs to be perpendicular from the last element to the sensor, which is understandably difficult with an SLR and it's relatively long register necessitated by the mirror box. That is one reason that C*n*n developed their EF-S mount, which allows the lens to protrude further into the mirror box, making the 10-22 easier to design. -Adam J. C. O'Connell wrote: Isnt is a contradiction that the lens is CLOSER to the sensor and its an improvement because that means the light it hitting the corners of the sensor at a GREATER angle away from perpendicular which is BAD (perpendicular being ideal)? J.C. O'Connell mailto:[EMAIL PROTECTED] http://jcoconnell.com -- --
Re: First non DSLR digicam with 10MP APS sensor- contradiction
J. C. O'Connell wrote: Isnt is a contradiction that the lens is CLOSER to the sensor and its an improvement because that means the light it hitting the corners of the sensor at a GREATER angle away from perpendicular which is BAD (perpendicular being ideal)? I don't understand. The light cone exiting a lens assembly will have a certain value, in degrees, total or half-angle, as you say, from the perpendicular. Move the lens along it's axis toward or further away from the sensor, to exactly cover the corners, it always has the same angle. The only thing that changes is area of coverage. Not the angle of the exiting light bundle. If you insist what you say is true, I have misunderstood you. Please elaborate. keith whaley J.C. O'Connell mailto:[EMAIL PROTECTED] http://jcoconnell.com
RE: First non DSLR digicam with 10MP APS sensor- contradiction
wrong, the closer the rear element. the more that forces greater NON perpendicular incidence angles to the corners of the sensor. It order to approximate true perpendicular incidence, the rear element has to move away infinitly from the sensor. Total opposite of what you just posted. jco -Original Message- From: Adam Maas [mailto:[EMAIL PROTECTED] Sent: Friday, September 09, 2005 1:13 PM To: pentax-discuss@pdml.net Subject: Re: First non DSLR digicam with 10MP APS sensor- contradiction Putting the rear element closer to the sensor allows you to have a perpendicular light path to the sensor without going to an extreme retrofocus design for wide angles. This allows a simplified lens design for equivalent length and zoom range. The Light path only needs to be perpendicular from the last element to the sensor, which is understandably difficult with an SLR and it's relatively long register necessitated by the mirror box. That is one reason that C*n*n developed their EF-S mount, which allows the lens to protrude further into the mirror box, making the 10-22 easier to design. -Adam J. C. O'Connell wrote: > Isnt is a contradiction that the lens is CLOSER > to the sensor and its an improvement because that > means the light it hitting the corners of the sensor > at a GREATER angle away from perpendicular which > is BAD (perpendicular being ideal)? > > >J.C. O'Connell mailto:[EMAIL PROTECTED] http://jcoconnell.com > -- > -- >
Re: First non DSLR digicam with 10MP APS sensor- contradiction
Putting the rear element closer to the sensor allows you to have a perpendicular light path to the sensor without going to an extreme retrofocus design for wide angles. This allows a simplified lens design for equivalent length and zoom range. The Light path only needs to be perpendicular from the last element to the sensor, which is understandably difficult with an SLR and it's relatively long register necessitated by the mirror box. That is one reason that C*n*n developed their EF-S mount, which allows the lens to protrude further into the mirror box, making the 10-22 easier to design. -Adam J. C. O'Connell wrote: Isnt is a contradiction that the lens is CLOSER to the sensor and its an improvement because that means the light it hitting the corners of the sensor at a GREATER angle away from perpendicular which is BAD (perpendicular being ideal)? J.C. O'Connell mailto:[EMAIL PROTECTED] http://jcoconnell.com
Re: First non DSLR digicam with 10MP APS sensor- contradiction
On Fri, Sep 09, 2005 at 06:07:37PM +0200, Dario Bonazza wrote: > Isn'it it possible that a large rear element force rays perpendicular to > the sensor? This will allow a better image on the sensor and if such an > element is part of the lens design, it won't affect lens performance. No. To a first approximation light rays from every part of the rear element contribute to every point of the image. The larger the rear element, the wider this cone of rays is, and so the more deviation there is from the perpendicular (and the wider the range of angles, which makes it hard to compensate by angling the sensor pits).
Re: First non DSLR digicam with 10MP APS sensor- contradiction
J. C. O'Connell wrote: I can understand why the lens itself is better, it just seems that the lens/sensor interface is much worse when the rear element is so severely close to the sensor. Maybe this sensor is specially designed for this lens and isnt "flat"? A silicon eye-ball! Now THAT would be interesting. Would solve all sorts of optical problems. It would be a difficult engineering problem however, how do you cut the silicon precisely in a spherical fashion? jco
Re: First non DSLR digicam with 10MP APS sensor- contradiction
Isn'it it possible that a large rear element force rays perpendicular to the sensor? This will allow a better image on the sensor and if such an element is part of the lens design, it won't affect lens performance. BTW, Sylwek, I cannot access fotopolis.pl. I tried several times every time you post such links, with no success. Am I the only one? Dario - Original Message - From: "J. C. O'Connell" <[EMAIL PROTECTED]> To: Sent: Friday, September 09, 2005 5:42 PM Subject: RE: First non DSLR digicam with 10MP APS sensor- contradiction I didn't say it didn't work, I don't understand WHY closer is better because that increases the incidence angle deviation from perpendicular, which is bad, severely on the edges/corners of the sensor. I can understand why the lens itself is better, it just seems that the lens/sensor interface is much worse when the rear element is so severely close to the sensor. Maybe this sensor is specially designed for this lens and isnt "flat"? jco -Original Message- From: Sylwester Pietrzyk [mailto:[EMAIL PROTECTED] Sent: Friday, September 09, 2005 11:31 AM To: pentax-discuss@pdml.net Subject: Re: First non DSLR digicam with 10MP APS sensor- contradiction J. C. O'Connell wrote on 09.09.05 17:06: Isnt is a contradiction that the lens is CLOSER to the sensor and its an improvement because that means the light it hitting the corners of the sensor at a GREATER angle away from perpendicular which is BAD (perpendicular being ideal)? Actually samples on www.fotopolis.pl has shown, that R1 performs much better than "digital optimised" E-300 ;-) -- Balance is the ultimate good... Best Regards Sylwek
RE: First non DSLR digicam with 10MP APS sensor- contradiction
I didn't say it didn't work, I don't understand WHY closer is better because that increases the incidence angle deviation from perpendicular, which is bad, severely on the edges/corners of the sensor. I can understand why the lens itself is better, it just seems that the lens/sensor interface is much worse when the rear element is so severely close to the sensor. Maybe this sensor is specially designed for this lens and isnt "flat"? jco -Original Message- From: Sylwester Pietrzyk [mailto:[EMAIL PROTECTED] Sent: Friday, September 09, 2005 11:31 AM To: pentax-discuss@pdml.net Subject: Re: First non DSLR digicam with 10MP APS sensor- contradiction J. C. O'Connell wrote on 09.09.05 17:06: > Isnt is a contradiction that the lens is CLOSER > to the sensor and its an improvement because that > means the light it hitting the corners of the sensor > at a GREATER angle away from perpendicular which > is BAD (perpendicular being ideal)? Actually samples on www.fotopolis.pl has shown, that R1 performs much better than "digital optimised" E-300 ;-) -- Balance is the ultimate good... Best Regards Sylwek
Re: First non DSLR digicam with 10MP APS sensor- contradiction
J. C. O'Connell wrote on 09.09.05 17:06: > Isnt is a contradiction that the lens is CLOSER > to the sensor and its an improvement because that > means the light it hitting the corners of the sensor > at a GREATER angle away from perpendicular which > is BAD (perpendicular being ideal)? Actually samples on www.fotopolis.pl has shown, that R1 performs much better than "digital optimised" E-300 ;-) -- Balance is the ultimate good... Best Regards Sylwek
First non DSLR digicam with 10MP APS sensor- contradiction
Isnt is a contradiction that the lens is CLOSER to the sensor and its an improvement because that means the light it hitting the corners of the sensor at a GREATER angle away from perpendicular which is BAD (perpendicular being ideal)? J.C. O'Connell mailto:[EMAIL PROTECTED] http://jcoconnell.com
