Re: Silly HDR Question
Thanks Rob. I find that if I think of the data captured by the sensor as a piece of film it makes sense. The lightest areas, total white, can be made darker, but they contain no detail. The darkest areas, total black, can be made lighter, but they contain no detail. The only way those areas of the frame could contain meaningful information is to adjust exposure up or down at the time of capture, moving, as Godfrey terms it, the window. Well, I think I understand it now (whethr it sounds like it or not). :-) Tom C. >From: "Digital Image Studio" <[EMAIL PROTECTED]> >Reply-To: Pentax-Discuss Mail List >To: "Pentax-Discuss Mail List" >Subject: Re: Silly HDR Question >Date: Sun, 5 Nov 2006 08:43:18 +1100 > >On 05/11/06, Tom C <[EMAIL PROTECTED]> wrote: > > If I take a RAW .PEF file and adjust exposure -1 and +1 stop, saving >each as > > another .PEF in Adobe Camera Raw, would that not for all intents and > > purposes, be the same as having taken three separate exposures at >-1/0/+1 ? > > > > Could I conceivably then process the three as an HDR and get the same > > results and have the same flexibility in post-processing as if I took >three > > exposures in-camera? > >Not even close Tom, if you have more than one frame at different >exposures you have an absolute differential of the difference between >the exposures beyond the absolute range of the RAW file. By carefully >controlling the adjustments during RAW conversion the entire latitude >of any exposure can be realised in a single conversion. If your RAW >converter doesn't have a curves tool then of course there is limited >scope to control the gamma via contrast if you need to push the >brightness to extremes. However if you generate a 16 bit output files >then fine gamma adjustments can be effected without loss in any >decent image editor using a curves tool. > >Of course the validity of even applying HDR techniques depends upon >the subject matter and lighting. IOW if the subject brightness range >lies within the latitude of a single exposure then the technique may >yield very marginal advantage. > >-- >Rob Studdert >HURSTVILLE AUSTRALIA >Tel +61-2-9554-4110 >UTC(GMT) +10 Hours >[EMAIL PROTECTED] >http://home.swiftdsl.com.au/~distudio//publications/ >Pentax user since 1986, PDMLer since 1998 > >-- >PDML Pentax-Discuss Mail List >PDML@pdml.net >http://pdml.net/mailman/listinfo/pdml_pdml.net -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net
Re: Silly HDR Question
Got it. Thanks. Tom C. >From: Godfrey DiGiorgi <[EMAIL PROTECTED]> >Reply-To: Pentax-Discuss Mail List >To: Pentax-Discuss Mail List >Subject: Re: Silly HDR Question >Date: Sat, 4 Nov 2006 14:38:53 -0800 > >No, that's not the right way to think about it. Read what I wrote >below carefully. > >The sensor has an absolute dynamic range. Exposure settings establish >the environment in which that dynamic range operates electically, >essentially setting the gain "window" over which the sensor can >capture intensity values. You can adjust what HAS been captured >within certain boundaries mathematically after the fact, which is >what you're doing when you modify the gamma correction curve in a RAW >converter, but you cannot change what has been captured. That can >only be adjusted by exposure at the time of capture. > >An HDR technique of taking multiple exposures at different settings >than merging them together allows the sensor's absolute dynamic range >to be extended, synthesizing a larger dynamic range through repeated >and different 'windows' on the subject intensities. > >Godfrey > >On Nov 4, 2006, at 1:56 PM, Tom C wrote: > > > What you say makes sense excpet when I think of it like this: > > > > I was thinking of the data captured by the sensor as basically a > > bitmap. If > > all adjusting gain (up/down) on the sensor effectively does, is to > > make an > > individual pixel, lighter or darker than it would have been > > otherwise, then > > it *seems* that the same thing could be done post-capture, sans- > > sensor. > > > > So is my thinking basically correct in principle, but not > > necessarially so > > in practice? > > > >> In simple terms: > >> > >> - Making one exposure and than adjusting it once out of the camera > >> always locks you into whatever happens to be the maximum analog > >> dynamic range of the sensor. If elements of a scene fall outside that > >> dynamic range, you get black/noise or total saturation, no matter how > >> much adjustability a RAW converter might have or how much data > >> recovery it can do. > >> > >> - Making a set of exposures at different exposure settings and then > >> integrating them together allows you to window the scene with a > >> dynamic range wider than what the sensor can acquire in one exposure. > > >-- >PDML Pentax-Discuss Mail List >PDML@pdml.net >http://pdml.net/mailman/listinfo/pdml_pdml.net -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net
Re: Silly HDR Question
No, that's not the right way to think about it. Read what I wrote below carefully. The sensor has an absolute dynamic range. Exposure settings establish the environment in which that dynamic range operates electically, essentially setting the gain "window" over which the sensor can capture intensity values. You can adjust what HAS been captured within certain boundaries mathematically after the fact, which is what you're doing when you modify the gamma correction curve in a RAW converter, but you cannot change what has been captured. That can only be adjusted by exposure at the time of capture. An HDR technique of taking multiple exposures at different settings than merging them together allows the sensor's absolute dynamic range to be extended, synthesizing a larger dynamic range through repeated and different 'windows' on the subject intensities. Godfrey On Nov 4, 2006, at 1:56 PM, Tom C wrote: > What you say makes sense excpet when I think of it like this: > > I was thinking of the data captured by the sensor as basically a > bitmap. If > all adjusting gain (up/down) on the sensor effectively does, is to > make an > individual pixel, lighter or darker than it would have been > otherwise, then > it *seems* that the same thing could be done post-capture, sans- > sensor. > > So is my thinking basically correct in principle, but not > necessarially so > in practice? > >> In simple terms: >> >> - Making one exposure and than adjusting it once out of the camera >> always locks you into whatever happens to be the maximum analog >> dynamic range of the sensor. If elements of a scene fall outside that >> dynamic range, you get black/noise or total saturation, no matter how >> much adjustability a RAW converter might have or how much data >> recovery it can do. >> >> - Making a set of exposures at different exposure settings and then >> integrating them together allows you to window the scene with a >> dynamic range wider than what the sensor can acquire in one exposure. -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net
Re: Silly HDR Question
On 05/11/06, Tom C <[EMAIL PROTECTED]> wrote: > What you say makes sense excpet when I think of it like this: > > I was thinking of the data captured by the sensor as basically a bitmap. If > all adjusting gain (up/down) on the sensor effectively does, is to make an > individual pixel, lighter or darker than it would have been otherwise, then > it *seems* that the same thing could be done post-capture, sans-sensor. The is no variation of the sensor capture range unless the physical exposure is altered (either shutter period or lens aperture). -- Rob Studdert HURSTVILLE AUSTRALIA Tel +61-2-9554-4110 UTC(GMT) +10 Hours [EMAIL PROTECTED] http://home.swiftdsl.com.au/~distudio//publications/ Pentax user since 1986, PDMLer since 1998 -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net
Re: Silly HDR Question
What you say makes sense excpet when I think of it like this: I was thinking of the data captured by the sensor as basically a bitmap. If all adjusting gain (up/down) on the sensor effectively does, is to make an individual pixel, lighter or darker than it would have been otherwise, then it *seems* that the same thing could be done post-capture, sans-sensor. So is my thinking basically correct in principle, but not necessarially so in practice? Tom C. >From: Godfrey DiGiorgi <[EMAIL PROTECTED]> >Reply-To: Pentax-Discuss Mail List >To: Pentax-Discuss Mail List >Subject: Re: Silly HDR Question >Date: Sat, 4 Nov 2006 13:29:05 -0800 > >In simple terms: > >- Making one exposure and than adjusting it once out of the camera >always locks you into whatever happens to be the maximum analog >dynamic range of the sensor. If elements of a scene fall outside that >dynamic range, you get black/noise or total saturation, no matter how >much adjustability a RAW converter might have or how much data >recovery it can do. > >- Making a set of exposures at different exposure settings and then >integrating them together allows you to window the scene with a >dynamic range wider than what the sensor can acquire in one exposure. > >Godfrey > >On Nov 4, 2006, at 11:56 AM, Tom C wrote: > > > OK. That being the case, how is adjusting the exposure of a .PEF > > file after > > the fact different than doing it in camera? I realize there *is a* > > difference because a .PEF file is not really raw, and obviously the > > sensor > > gain is out of the picture. What *is* the difference? > > > > Maybe I don't really care about the technical details as long as > > the results > > are what I want > > >-- >PDML Pentax-Discuss Mail List >PDML@pdml.net >http://pdml.net/mailman/listinfo/pdml_pdml.net -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net
Re: Silly HDR Question
On 05/11/06, Tom C <[EMAIL PROTECTED]> wrote: > If I take a RAW .PEF file and adjust exposure -1 and +1 stop, saving each as > another .PEF in Adobe Camera Raw, would that not for all intents and > purposes, be the same as having taken three separate exposures at -1/0/+1 ? > > Could I conceivably then process the three as an HDR and get the same > results and have the same flexibility in post-processing as if I took three > exposures in-camera? Not even close Tom, if you have more than one frame at different exposures you have an absolute differential of the difference between the exposures beyond the absolute range of the RAW file. By carefully controlling the adjustments during RAW conversion the entire latitude of any exposure can be realised in a single conversion. If your RAW converter doesn't have a curves tool then of course there is limited scope to control the gamma via contrast if you need to push the brightness to extremes. However if you generate a 16 bit output files then fine gamma adjustments can be effected without loss in any decent image editor using a curves tool. Of course the validity of even applying HDR techniques depends upon the subject matter and lighting. IOW if the subject brightness range lies within the latitude of a single exposure then the technique may yield very marginal advantage. -- Rob Studdert HURSTVILLE AUSTRALIA Tel +61-2-9554-4110 UTC(GMT) +10 Hours [EMAIL PROTECTED] http://home.swiftdsl.com.au/~distudio//publications/ Pentax user since 1986, PDMLer since 1998 -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net
Re: Silly HDR Question
In simple terms: - Making one exposure and than adjusting it once out of the camera always locks you into whatever happens to be the maximum analog dynamic range of the sensor. If elements of a scene fall outside that dynamic range, you get black/noise or total saturation, no matter how much adjustability a RAW converter might have or how much data recovery it can do. - Making a set of exposures at different exposure settings and then integrating them together allows you to window the scene with a dynamic range wider than what the sensor can acquire in one exposure. Godfrey On Nov 4, 2006, at 11:56 AM, Tom C wrote: > OK. That being the case, how is adjusting the exposure of a .PEF > file after > the fact different than doing it in camera? I realize there *is a* > difference because a .PEF file is not really raw, and obviously the > sensor > gain is out of the picture. What *is* the difference? > > Maybe I don't really care about the technical details as long as > the results > are what I want -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net
Re: Silly HDR Question
OK. That being the case, how is adjusting the exposure of a .PEF file after the fact different than doing it in camera? I realize there *is a* difference because a .PEF file is not really raw, and obviously the sensor gain is out of the picture. What *is* the difference? Maybe I don't really care about the technical details as long as the results are what I want Tom C. >From: Lawrence Kwan <[EMAIL PROTECTED]> >Reply-To: Pentax-Discuss Mail List >To: Pentax-Discuss Mail List >Subject: Re: Silly HDR Question >Date: Sat, 4 Nov 2006 14:36:57 -0500 (EST) > >On Sat, 4 Nov 2006, Tom C wrote: > > If I take a RAW .PEF file and adjust exposure -1 and +1 stop, saving >each as > > another .PEF in Adobe Camera Raw, would that not for all intents and > > purposes, be the same as having taken three separate exposures at >-1/0/+1 ? > >It is different. Adjusting the exposure in camera is similar to changing >the ISO. Changing the ISO in camera is done at the A/D conversion stage. > >Some high ISO settings such as ISO 3200 for the D80 are exceptions. In >this case, it was pure digital post-processing (and not done at A/D >stage). That's why in D80, they called it Hi 1.0 setting instead of >calling it ISO 3200, and not available in Auto ISO range. And you can >achieve the same "ISO 3200" by taking the photos at ISO1600 with EV -1, >and then adjusting the exposure +1 in the RAW files. > >So if you reach the limit of the ISO range, e.g. ISO 1600 in K10D, then >the +1 in camera would be no different than the +1 in PEF file. > > > >-- >--Lawrence [EMAIL PROTECTED] http://www.vex.net/~lawrence -- >--Tungsten T3 Enhanced DIA KeyboardNokia Ringtone Convertor-- > >-- >PDML Pentax-Discuss Mail List >PDML@pdml.net >http://pdml.net/mailman/listinfo/pdml_pdml.net -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net
Re: Silly HDR Question
On Sat, 4 Nov 2006, Tom C wrote: > If I take a RAW .PEF file and adjust exposure -1 and +1 stop, saving each as > another .PEF in Adobe Camera Raw, would that not for all intents and > purposes, be the same as having taken three separate exposures at -1/0/+1 ? It is different. Adjusting the exposure in camera is similar to changing the ISO. Changing the ISO in camera is done at the A/D conversion stage. Some high ISO settings such as ISO 3200 for the D80 are exceptions. In this case, it was pure digital post-processing (and not done at A/D stage). That's why in D80, they called it Hi 1.0 setting instead of calling it ISO 3200, and not available in Auto ISO range. And you can achieve the same "ISO 3200" by taking the photos at ISO1600 with EV -1, and then adjusting the exposure +1 in the RAW files. So if you reach the limit of the ISO range, e.g. ISO 1600 in K10D, then the +1 in camera would be no different than the +1 in PEF file. -- --Lawrence [EMAIL PROTECTED] http://www.vex.net/~lawrence -- --Tungsten T3 Enhanced DIA KeyboardNokia Ringtone Convertor-- -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net
Re: Silly HDR Question
Yes you can. PhotoMatix creates a HDR directly from a PEF file. Toine On 11/4/06, Tom C <[EMAIL PROTECTED]> wrote: > If I take a RAW .PEF file and adjust exposure -1 and +1 stop, saving each as > another .PEF in Adobe Camera Raw, would that not for all intents and > purposes, be the same as having taken three separate exposures at -1/0/+1 ? > > Could I conceivably then process the three as an HDR and get the same > results and have the same flexibility in post-processing as if I took three > exposures in-camera? > > Tom C. > > > > -- > PDML Pentax-Discuss Mail List > PDML@pdml.net > http://pdml.net/mailman/listinfo/pdml_pdml.net > -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net
Re: Silly HDR Question
On 11/4/06, Tom C <[EMAIL PROTECTED]> wrote: > If I take a RAW .PEF file and adjust exposure -1 and +1 stop, saving each as > another .PEF in Adobe Camera Raw, would that not for all intents and > purposes, be the same as having taken three separate exposures at -1/0/+1 ? Somewhat yes, somewhat no. Depends on what the highlights and shadow areas in the picture look like. To further explain: 1. Camera raw has some ability to "fudge" blown-out highlights. When you go beyond the range of the digital sensor, you're always going to lose some information. Camera raw attempts to put some of that back at least. It's not perfect, but it can be enough to salvage a blown-out shot. 2. On the shadow end of things, if the shadows are completely blocked up (black), nothing is going to get you any more information out of them. By "developing" in camera raw for the shadows, you may get yourself image data that is easier to work with WRT shadow details that are there. The technique you are talking about is usable to a certain extent though. If you have a high-contrast scene, it can be useful to save time in post-processing, or to simply make things easier in the realm of dodging and burning. Remember though, if the information isn't there in the original exposure, nothing is going to bring it back. A VERY good primer on the subject is located here: http://www.adobe.com/digitalimag/pdfs/highlight_recovery.pdf -Mat -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net
Silly HDR Question
If I take a RAW .PEF file and adjust exposure -1 and +1 stop, saving each as another .PEF in Adobe Camera Raw, would that not for all intents and purposes, be the same as having taken three separate exposures at -1/0/+1 ? Could I conceivably then process the three as an HDR and get the same results and have the same flexibility in post-processing as if I took three exposures in-camera? Tom C. -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net
