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 <[email protected]> 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 <[email protected]> >> 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 <[email protected]> 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 >>> [email protected] >>> 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 > [email protected] > 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 [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
