PS: *ist-d is 3008x2008 pixels...so 2:2.996. You really noticed a difference of .03?
On Sun, Sep 8, 2013 at 8:31 PM, Zos Xavius <zosxav...@gmail.com> 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. -- 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.
