Yuh. k-7 and k20D have the same sensor. A samsung sensor. Its true there is no standard for aps-c. Generally canon is a 1.6x crop and nikon/sony/everyone else is a 1.5x crop. I don't know about you, but I'm rather glad I'm not a canon crop-sensor user and not just because of the reduced FoV.....
On Sun, Sep 8, 2013 at 10:10 PM, P.J. Alling <webstertwenty...@gmail.com> wrote: > DPReview seems to think that the K-5 and K-7 have exactly the same size > sensor. I don't remember where I got those numbers from but IIRC they came > from the Pentax web site when I first bought my K20D. When the K-7 was > released the sensor was reported to be the same as the K-20D. I could be > wrong in the particular. However there is no generally accepted standard > specification for the dimensions of APS-C sensors. > > > On 9/8/2013 8:31 PM, Zos Xavius wrote: >> >> Hmmm....according to dxomark: >> >> >> K-7 - 23.4x15.6mm >> K-5 - 23.7x15.7mm >> >> If those numbers are right, the k-7 is exactly 3:2 while the k-5 is >> slightly wider. >> >> Comparing pixel dimensions I get the following aspect ratios: >> >> K-5 - 2:3.02 >> K-7 - 2:3.01 >> >> Fairly negligible if you ask me. >> >> On Sun, Sep 8, 2013 at 8:11 PM, P.J. Alling <webstertwenty...@gmail.com> >> wrote: >>> >>> The Samsung sensor family used in the K20D and K-7 has a slightly smaller >>> footprint on the order of 10ths of a mm than the Sony sensors used before >>> in >>> the *ist-D and all the other Pentax DSLRs. It seems like a small enough >>> difference. but that can mean a huge difference in AOV when dealing with >>> wide angle lenses. >>> >>> The K-20D and K-7 use a 16x23mm sensor with a ~28.02mm diagonal. >>> >>> The other Pentax DSLRS, (and Nikon DX DSLRs) use a 15.7x23.7mm sensor >>> with a >>> ~28.4mm diagonal. >>> >>> Besides being slightly smaller the Samsung sensor isn't exactly the 2:3 >>> aspect ratio ratio either. When switching between my *ist-Ds and my K20D >>> I >>> actually notice the difference in aspect ratio quite noticeable >>> especially >>> when printing. >>> >>> Canon uses a 14.9 x 22.3mm sensor for it's APS-C sensor cameras with a >>> diagonal of ~26.8mm >>> >>> So there is a much larger difference between Canon and any of the Samsung >>> or >>> Sony sensor cameras, but if you buy a say a 10mm fisheye lens from a >>> third >>> party manufacture that comes in multiple mounts, it may be actually be >>> 180° >>> over the diagonal of one of those sensors or none of them. >>> >>> >>> >>> On 9/8/2013 7:11 PM, Zos Xavius wrote: >>>> >>>> Correct me if I am totally wrong, but isn't the k-7 sensor size the >>>> same as sony sensors with a 1.5x crop? Canon is the only oddball I >>>> know of with their slightly smaller 1.6x crop sensor. Ok....I just >>>> googled it. The difference is .1mm horizontally between the k-7 and >>>> k-5. Not enough to even noticable. >>>> >>>> On Sun, Sep 8, 2013 at 1:54 PM, P.J. Alling <webstertwenty...@gmail.com> >>>> wrote: >>>>> >>>>> That's true, it's "around" 7.5mm. However almost all of this is pretty >>>>> fuzzy. A full frame fisheye is supposed to cover 180° across the >>>>> diagonal >>>>> of the format. >>>>> >>>>> Depending on the curvature that the lens imparts that can be done with >>>>> a >>>>> number of different focal lengths in the same ball park can be designed >>>>> to >>>>> do that. >>>>> >>>>> Then when you get to APS-C, well, there's Canon's standard sensor size, >>>>> the >>>>> Sony sensors which are slightly larger, the K20D/K-7 with a sensor >>>>> that's >>>>> intermediate between them, and whatever Samsung is using these days. >>>>> >>>>> Hell, even "full frame" digital sensors aren't exactly the same size as >>>>> the >>>>> standard film gate for 35mm film cameras. >>>>> >>>>> So it's unlikely that a full frame fisheye will actually fit the >>>>> classical >>>>> definition on any format. Though it would be easiest to do for m4/3 >>>>> and >>>>> 4/3 >>>>> system cameras since the sensor dimensions are fully specified. >>>>> >>>>> >>>>> On 9/8/2013 1:31 PM, Dario Bonazza wrote: >>>>>> >>>>>> Fisheye for m4/3 is around 7.5mm. This is what I have: >>>>>> >>>>>> >>>>>> >>>>>> http://www.ephotozine.com/article/samyang-7-5mm-f-3-5-umc-fisheye-lens-review-19847 >>>>>> Dario >>>>>> >>>>>> >>>>>> -----Messaggio originale----- From: P.J. Alling >>>>>> Sent: Sunday, September 08, 2013 7:12 PM >>>>>> To: Pentax-Discuss Mail List >>>>>> Subject: Re: Which second party camera system do you like? Mini-survey >>>>>> >>>>>> With rectilinear lenses doing format translations is easy. AOV is >>>>>> AOV, >>>>>> but Fisheye lenses make hash those kinds of comparisons. I have a >>>>>> Pentax >>>>>> 17mm fisheye, and an old 12mm semi circular, (on film), fisheye made >>>>>> by >>>>>> Sigma in the early 60's. I don't have any examples currently, (and >>>>>> don't even have my film scanner attached to my current machine), but >>>>>> the >>>>>> 12mm on APS-C digital actually seemed to cover more than the 17mm did >>>>>> on >>>>>> film even though the 12mm was 18mm/e. I'm pretty sure that comparing >>>>>> fisheye lenses, AOV, by focal length is a fools errand. >>>>>> >>>>>> On 9/8/2013 12:53 PM, Aahz Maruch wrote: >>>>>>> >>>>>>> On Sun, Sep 08, 2013, Godfrey DiGiorgi wrote: >>>>>>>> >>>>>>>> On Sep 7, 2013, at 9:43 PM, Aahz Maruch <a...@pobox.com> wrote: >>>>>>>>> >>>>>>>>> Sure, but there's nothing like the 8mm fisheye you can get for >>>>>>>>> APS-C >>>>>>>>> for >>>>>>>>> 12mm/e. For most purposes, you're correct that's sufficient, but >>>>>>>>> people >>>>>>>>> who really care about extreme wide-angle are likely to be less >>>>>>>>> satisfied >>>>>>>>> with m4/3. >>>>>>>> >>>>>>>> "For most purposes ..." Don't be ridiculous. >>>>>>>> >>>>>>>> A fish-eye lens is a specialty lens, and the ONLY wide-angle lens >>>>>>>> focal length not listed in native Micro-FourThirds mount. Perhaps >>>>>>>> that's because there's a superb fish-eye lens in FourThirds SLR >>>>>>>> mount, >>>>>>>> which work on mFT bodies with any of the four available, dedicated >>>>>>>> Panasonic and Olympus FourThirds to Micro-FourThirds mount adapters >>>>>>>> for 100% full function operation. >>>>>>> >>>>>>> The point is that m4/3 8mm is 16mm/e. >>>>>>> >>>>>>>> Your comment sounds like it fits one of the categories in Ctein's >>>>>>>> most >>>>>>>> recent column on "The Online Photographer": >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> http://theonlinephotographer.typepad.com/the_online_photographer/2013/09/bad-science-vs-good-science-a-guide-for-the-layperson-part-1.html >>>>>>>> >>>>>>>> Check out the "God of the Gaps" category. ;-) >>>>>>> >>>>>>> <shrug> Some people regularly claim that they want FF over APS-C due >>>>>>> to >>>>>>> wide-angle versus crop-factor -- given that Marnie didn't even know >>>>>>> that >>>>>>> m4/3 has 2x crop factor compared with APS-C's 1.5x, I think it was >>>>>>> entirely reasonable to mention the wide-angle issue. I certainly >>>>>>> don't >>>>>>> think it'll play a significant role in her decision given her >>>>>>> telephoto >>>>>>> preference (or if it does, it'll have a reverse significance). >>>>>>> >>>>>>> Side note: most of my shooting is also telephoto (except for macro), >>>>>>> so >>>>>>> I'm definitely not grinding any axe favoring wide-angle and I >>>>>>> consider >>>>>>> the m4/3 crop factor a plus myself because it makes for lighter and >>>>>>> smaller telephoto lenses. >>>>>> >>>>>> >>>>>> >>>>> -- >>>>> A newspaper is a device for making the ignorant more ignorant, and the >>>>> crazy, crazier. >>>>> >>>>> - H.L.Mencken >>>>> >>>>> >>>>> -- >>>>> PDML Pentax-Discuss Mail List >>>>> PDML@pdml.net >>>>> http://pdml.net/mailman/listinfo/pdml_pdml.net >>>>> to UNSUBSCRIBE from the PDML, please visit the link directly above and >>>>> follow the directions. >>> >>> >>> >>> -- >>> A newspaper is a device for making the ignorant more ignorant, and the >>> crazy, crazier. >>> >>> - H.L.Mencken >>> >>> >>> -- >>> PDML Pentax-Discuss Mail List >>> PDML@pdml.net >>> http://pdml.net/mailman/listinfo/pdml_pdml.net >>> to UNSUBSCRIBE from the PDML, please visit the link directly above and >>> follow the directions. > > > > -- > A newspaper is a device for making the ignorant more ignorant, and the > crazy, crazier. > > - H.L.Mencken > > > -- > PDML Pentax-Discuss Mail List > PDML@pdml.net > http://pdml.net/mailman/listinfo/pdml_pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above and > follow the directions. -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
