ampguy Posted June 23, 2010 Share #1 Posted June 23, 2010 Advertisement (gone after registration) I've put together a spreadsheet that explains why the M8 still has the same DOF behavior as the M9 and FF 35mm cameras, when using Leica lenses. I hope you find it interesting, it is located here, the file is dof.xls May also justify why you might want to spend a couple extra $$ or Euro for a Leica lens... Index of /photography Thanks! Link to post Share on other sites More sharing options...
Advertisement Posted June 23, 2010 Posted June 23, 2010 Hi ampguy, Take a look here spreadsheet showing why M8 and FF have same DOF. I'm sure you'll find what you were looking for!
01af Posted June 23, 2010 Share #2 Posted June 23, 2010 Your spreadsheet is nonsense. Link to post Share on other sites More sharing options...
bawang Posted June 23, 2010 Share #3 Posted June 23, 2010 Your spreadsheet is nonsense. Would you mind explaining what makes you say that? Link to post Share on other sites More sharing options...
mjh Posted June 23, 2010 Share #4 Posted June 23, 2010 Calculations based on mistaken assumptions are bound to lead to misleading results. May also justify why you might want to spend a couple extra $$ or Euro for a Leica lens... While there are lots of excellent reasons for getting a Leica lens, depth of field is not among those. DOF doesn’t depend on the lens; any other lens with the same focal length would behave the same. Link to post Share on other sites More sharing options...
lct Posted June 23, 2010 Share #5 Posted June 23, 2010 We should do a FAQ about those DoF questions. Whatever value one chooses for FF CoC, the M8 CoC will always be 1.33x smaller for the simple reason that the diagonal of its sensor (32.5mm) is 1.33x smaller than that of FF cams like the M9 (43.2mm). Then at the same aperture, the same lens will always have 1.33x more DoF. Link to post Share on other sites More sharing options...
jaapv Posted June 23, 2010 Share #6 Posted June 23, 2010 Your spreadsheet is nonsense. A bit harshly said, but yes, it is indeed nonsense. Link to post Share on other sites More sharing options...
viramati Posted June 23, 2010 Share #7 Posted June 23, 2010 Advertisement (gone after registration) if you have an iphone get this app myPhotoDOF for iPhone - Free iPhone software downloads and software reviews - CNET Download.com Link to post Share on other sites More sharing options...
wstotler Posted June 24, 2010 Share #8 Posted June 24, 2010 He obviously thought he was onto something and was enthusiastic about it--wouldn't "enthusiatic but misguided" be better than "nonsense"? I'm hoping that "mis-worded" is the accurate description. So. . . . Bad science, but would a different hypothesis/conclusion get something constructive/meaningful out of this data? For example, does this demonstrate an outcome comparison of the DOF *scales* for Leica lenses on M8 vs. FF--not DOF itself? Cheers! Will Link to post Share on other sites More sharing options...
luigi bertolotti Posted June 24, 2010 Share #9 Posted June 24, 2010 There have been, in this forum, some very deep (and heated) discussions on the DOF topic... I do not pretend to give a "final word" on, but seems to me that the conclusion is that a SCIENTIFICALLY RIGOROUS computation of DOF simply does not exist, for both the starting assumption (CoC dimension) and the final practical effect (DOF perceived looking at a print) have a degree of undetermination. The rest is rather simple math, that can be indeed plainly carried on : not so well in the attached spreadsheet, indeed. Link to post Share on other sites More sharing options...
!Nomad64 Posted June 24, 2010 Share #10 Posted June 24, 2010 There's an article about CoC on wikipedia: Circle of confusion - Wikipedia, the free encyclopedia Check for the paragraph captioned "Adjusting the circle of confusion diameter for a lens’s DoF scale". Seems yr spreadsheet was a nice effort made on wrong assumptions. Regards, Bruno Link to post Share on other sites More sharing options...
Rick Posted June 24, 2010 Share #11 Posted June 24, 2010 Time and time again it has been proven on this forum that this concept has been aptly named. Link to post Share on other sites More sharing options...
Guest mc_k Posted June 24, 2010 Share #12 Posted June 24, 2010 ...I hope you find it interesting, it is located here, the file is dof.xls ... no Excel to read this ... Link to post Share on other sites More sharing options...
cocker Posted June 24, 2010 Share #13 Posted June 24, 2010 no Excel to read this ... Is that his fault! Link to post Share on other sites More sharing options...
01af Posted June 24, 2010 Share #14 Posted June 24, 2010 Time and time again it has been proven on this forum that this concept has been aptly named. circle of confusion (abbr. COC) n. group of photographers desperately trying to understand —> DOF Link to post Share on other sites More sharing options...
roguewave Posted June 25, 2010 Share #15 Posted June 25, 2010 I will state up front that I'm not a lens designer, engineer or math wiz. Here's a real world scenario I have wrestled with. I often shoot with my R8/DMR with the same crop as the M8 (maybe not exactly, but close enough) & also with my other R8 with film (FF). Depending on the lens I'm using one can get some very conflicting results. Psychologically, I have noticed that people have quite a difference of opinion when I lay out various prints or have them view images on the screen. I often limit myself to 3 lenses, the R19, R24 & R80. I have been surprised many times, as other photographers try to make sense of the "feeling" about the DOF in the image difference of FF & the crop with wide lenses. What I find most interesting is the effect that the "lost" portion of the "ideal" FF frame with the DMR/19 & DMR/24 renders. Most often, people think that the DOF is shallower at the same aperture, with the crop. I am not sure I can be objective as I have come to see the POV from the 19 & 24 as "normal". However, my guess is that as the outer fringes of the frame appear more "peripheral" in both emotional content & "distant through distortion", that the images I make with the DMR are actually stronger & fudge or play with the sense of DOF. There's less of a reference for the mind, so we adjust. I'm also seeing this same effect with Zeiss 21 & my M8. I'm all in for a FF sensor & the M9. but somehow it would be cool to have a lens that renders the images I'm getting with the crop in the full frame. I know this isn't making sense, but it's how I experience it. Link to post Share on other sites More sharing options...
01af Posted June 25, 2010 Share #16 Posted June 25, 2010 Most often, people think that the DOF is shallower at the same aperture, with the crop. Well ... that's because DOF actually is shallower on the smaller-format camera—using the same lens, that is (as opposed to using a shorter lens that has the same angle of view). Link to post Share on other sites More sharing options...
01af Posted June 25, 2010 Share #17 Posted June 25, 2010 Providing the following are true: [...] 2. You move nearer the subject so that you have an identical field of view. Umm ... with the same lens on the smaller-format camera you'll have a narrower field of view to start with; when moving closer then it will become even narrower. If you stay in the same place and enlarge your crop-sensor and full-frame photos by the same amount*, the DOF will be identical. [...] [* The M8 has a ×1.3 crop, i. e its sensor is 1/1.3 = 0.77× smaller than that of the M9. Therefore, "same amount" means that M8 photos must be printed/viewed at about three-quarters the size of M9 photos for them to be directly comparable.] That's trivially true ... but you can't call photographs with different content and different sizes "comparable." You're going to print M8 and M9 photos at the same size, of course—meaning that M8 photos will be enlarged by ×1.3. This magnifies the out-of-focus areas, so the area that the eye would accept as in focus in a smaller print is thus reduced. In other words, the DOF is reduced when we enlarge an M8 photo to match the size of an M9 full-frame print. Exactly. I really fail to understand why a lot of people are unable to grasp the concept of DOF ... Same here. Link to post Share on other sites More sharing options...
roguewave Posted June 25, 2010 Share #18 Posted June 25, 2010 Although the 2 above comments are very cogent, they are only rationalities for a point of view & indeed are not scientific at all. Indeed, one's perception of "what's in focus" is the real determinate. As a psychologist, I firmly hue to this. In matter of practical fact, it is often the close focusing distance that gives one the best account of this phenomenon. In the R system, the close focus range of the 19 & 24 is far greater than in the M system. I can get with an inch or 2 with my 19 & often do. The M 18 & 21 are more like 6-7 inches. They have a completely different overall perspective, as much more of the "closest" content appears in focus, but it's further away. What's really important is how the images are experience by individuals & not the math. I still hold that there is not a single, definitive answer to this question, only a subjective account of one's perception. Link to post Share on other sites More sharing options...
wparsonsgisnet Posted June 25, 2010 Share #19 Posted June 25, 2010 ... [*The M8 has a x1.3 crop, i.e it's sensor is 1/1.3 = 0.77 smaller than that of the M9. .... I believe the M9 sensor is 1 1/3 times larger than that of the M8, and that the M8 is 3/4, or.75, times that of the M9. Once in a while fractions makes life easier for calculations. Link to post Share on other sites More sharing options...
luigi bertolotti Posted June 25, 2010 Share #20 Posted June 25, 2010 I believe the M9 sensor is 1 1/3 times larger than that of the M8, and that the M8 is 3/4, or.75, times that of the M9. Once in a while fractions makes life easier for calculations. Yep... ... RichC forgot that his "1/1.3" must be read "1/1.333333...." = 0,75 Link to post Share on other sites More sharing options...
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