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Everything posted by tupp

  1. What makes a format necessary are what someone considers to be desirable qualities. We are discussing the desirable qualites of larger formats vs. smaller formats -- which involves FF.
  2. No. You are mistaken. You need to more carefully read what I have said. I usually attribute differences in equivalency comparisons to failures of the testers. It might be helpful for you to actually read what I wrote. How is this relevant? By the way, if you use mirrorless cameras with shallow mounts, a tilt/shift adapter works with many lenses. So, are you saying that larger formats have qualities that are lacking in smaller formats? 600mm 8"x10" lens is more like an 80mm FF lens (or like a 40mm M4/3 lens). There are a few 80mm FF lenses. There would likely be a difference between the look of two formats with such a narrow focal length and with the apertures set for a shallow DOF. Well, that would actually qualify as a look inherent in a larger format that is impossible in a smaller format, wouldn't it? You really need to read what I wrote in regards to optics and sensor size. The failure to get a match is usually due to tester mistakes. In addition, all of the testers so far were not actually testing DOF. Incidentally, in regards to your earlier claim about it being impossible to get an exact match with two lenses that have the same focal length and that are designed for the same format, here is that very comparison by Shane Hurlbut. It looks like an exact DOF/focus match to me, but the exposure is slightly different (likely due to a difference in lens transmission). So, exact focus matches are possible.
  3. Well, not exactly. If you use a S16 lens on a 4"x5" sensor, you will likely see substantial vignetting that won't appear with the same lens on a S16 sensor. The image inside the vignette probably will appear softer, as the pixels on the 4"x5" sensor are likely coarser. Likewise, if one applies a S16 crop inside the image circle of a lens made for 4"x5", most of the lines of resolution will be thrown away, and the image will appear much softer (which can affect the appearance of the DOF) than using that same lens on a 4"x5" sensor. That's not too difficult. Earlier in this thread, I picked the S16, M4/3 and 8"x10" formats, and I found several manufactured lenses for those formats that gave around a 98% match on the equivalence calculator that was linked earlier in this thread. That's a good start, and most of the other variables can be adjusted slightly without suffering invalid results. In regards to knowing the exact focal length when it changes after focusing on the subject, as long as the focal lengths remain in a nominal range there really is no problem, as one can make adjust the aperture so that the results match more closely (as I have already explained in this thread). This is where you (along with the legions of equivalency testers that precede you) and I depart. There is absolutely no need to stand on the formality of getting the numbers to exactly match the figures dictated by the DOF/equivalency formula, and trying to do so will only lead to difficulty and mismatched, invalid results. The aperture markings on lenses are not accurate enough (and T-stops are useless for such a test). Also, aperture markings don't account for the change in focal length when the lens is adjusted to put the subject in critical focus. If you wanted to get a precise number match to the DOF formula, you would have to measure the exact focal length when focused and the exact aperture diameter, which is somewhat challenging considering there is no tangible focal point marking on lenses and considering that the aperture is usually inside the lens. Trying to get the numbers to precisely match the DOF/equivalency formula is a fools errand. On the other hand, there is nothing wrong with setting up the test with two camera/lens combinations that match as closely as possible, and then merely adjusting the aperture ring on one of the cameras until the two DOF ranges match by eye. If the adjusted aperture reads a little off from where the DOF/equivalency formula says it should be, simply make a note of that adjustment and include that note in the test report. That's unnecessary, and you would only need to crop one of the images if you want to exactly match the frames. No. If you use T-stops markings, you are making an even bigger error than if you just rely on the accuracy of F-stop markings. The aperture markings on the lens are inaccurate and mostly irrelevant. Well, if you like to do things the hard way as prescribed in your method, you will have a tough time and will unlikely get valid results. I agree that your method might not work in a lifetime. I would think that this point of this exercise was obvilus by now -- to demonstrate similarities and/or differences between optics made for different formats. Good for you! There are tests that got a close enough match with the equipment. However, they suffered the maladies that afflict most other tests: they didn't show the delineation of the DOF limits; they used wide angle lenses and/or deep DOF; they used a zoom lens; they had camera sharpening enabled; and, of course, they didn't adjust the aperture by eye to match the DOF.
  4. I'll just repeat what has been mentioned in this thread. The lenses for the smaller formats have to use larger apertures to match the DOF of larger format lenses. So, if one is shooting large format with shallow DOF (as in the above photo), matching that DOF with a with a smaller format lens will require its aperture to be wide open, which not only affects the overall sharpness (As you surmised), but it can also produce a difference in the relative sharpness between center and edges of the frame. This characteristic with the smaller format lessens as the aperture is reduced. The above 8"x10" photo was shot with a roughly 600mm lens (not sure on the aperture), and the closet lens match that I could find in a smaller format is the Nokton 42.5mm f0.95 for M4/3. Here is a test of that lens set at f.0.95 that not quite as close/tight as the above photo, but it gives a rough idea of how it might behave close and wide open. It doesn't seem as sharp wide open as it does at smaller apertures, and, unfortunately, the DOF isn't quite shallow enough to match that of the above 8"x10" lens. In addition, at wider apertures, there generally seems to be a faster transition from sharp to soft at the rear DOF limit on lenses made for larger formats. This quality might relate to why the plane of focus seems more solid, more well-defined and flatter on larger formats. Also, the softness/bokeh outside of the DOF seems cleaner and less mushy. Here is a photo shot with an 8x10 camera that shows that shows a solid, flat focus plane (although the lens appears to be swung slightly to the right), with the subject nicely separating from the clean and not too mushy background.
  5. I don't have any conclusions in regards to larger formats vs. smaller formats other than the ones I have mentioned in this thread and in other threads. Larger formats don't usually suffer from diffraction with deep DOF, hence the f/64 club.
  6. Most of the test parameters are given in the second half of this post from earlier in this thread. The format related properties are inherent in their optics, but the format and its optics are married to each other in regards to the look/sharpness. I agree that a controlled test should reveal general differences in optics for made for different formats. No. The problem with the tests are not their degree of rigor -- the problem is that every DOF test presented so far completely misses the point of what it is that is being tested. If one is testing DOF, it is sort of necessary to show the actual DOF. Instead, almost all such tests so far have merely shown the subject and an arbitrarily soft background at some arbitrary distance. Here is the typical set-up that we see in these comparisons; camera >> AIR >> sharp subject >> AIR >> soft background The limits of the DOF invariably are located in the "AIR" where there is no object nor surface visible to show the location nor the transitional character of those important limits. So, instead of testing the DOF, these comparisons actually just show how closely the tester can match the soft background using math along with the aperture markings on the lens. Usually, these tests also suffer other significant mistakes, such as in-camera sharpening, using zoom lenses, using wide lenses with deep DOF, etc. Additionally, the "soft background" in most of these tests is usually a wall or some other obstruction, beyond which no detail nor focus falloff is visible. Obviously, the foreground limit of DOF is important in DOF tests, because that limit is a major element that determines the DOF. In addition, the transitional characteristic of the foreground limit and the character of the softness beyond that frontA limit are both crucial to a lot of cinematography. For instance, consider any focus rack from far to near (or vice versa). When the camera is focused on the distant subject, the look of the soft near subject is determined by the DOF. In regards to Yedlin's test images showing the same elements characteristics as those in the 8"x10" photo that I linked above, there is one important and conspicuous difference -- the 8"x10" image shows the rear DOF limit and its distinctive transitional character quite clearly, while the rear DOF limit in Yedlin's shots are lost in the air. And, again, Yedlin used wider lenses with a deeper DOF. Not so with my linked image. Yes. The parameters are: Use dramatically different sized formats (with their corresponding optics); Use a continuously visible surface (preferably ruled) or a row of uniform objects that starts far in front of the subject and that recedes far behind the subject; Use narrow lenses; Use a shallow DOF; First set the DOF of the smaller format, then match by eye the DOF of the larger format.
  7. Agreed (except for the smaller format having more vignetting), and I think that you have hit upon a prominent general difference between larger and smaller formats. However, I think that there are other general differences between different sized formats. Of course, but, again, cropping into the image circle of a lens reduces the visible lines of resolution (which are related to focus/DOF). So, a lens and it's format are integrated in that sense. Regarding points in this thread about lenses having their own particular look, many of those arguments are attempts to dismiss the idea that lenses made for larger formats generally share characteristics that are lacking in lenses made for smaller formats (and vice versa). Again, it is obvious that optical characteristics are inherent to the lens, but the camera lens and its format cannot be divorced without affecting the look/sharpness. Yes, unless one crops too severely into the image circle of a lens. Agreed. Not exactly. Of course, different lenses of the same focal length made for the same format can have differing looks/sharpness. However, as you have noted, there are general characteristics inherent in lenses made for larger formats that are lacking in lenses designed for smaller formats (and vice versa).
  8. I'm not sure that I understand what you are doing with your proposed comparison, but in any DOF equivalence test it is imperative to use the actual lenses designed for the formats that are being compared. It is also required that one uses the actual sensor/film format appropriate for each lens -- one can't crop in very much without ruining the results. Look at this image taken with an 8"x10" camera: This is a very common look with large format photography. Note the abrupt transition out of the DOF. Look at the quality of the soft edge on the subject's collar and shoulders. Note the character of the softness of the subject's out of focus hair on his shadow side. Even if one could get that shallow DOF, do you honestly think that this look can be duplicated on a S16 or M4/3 camera?
  9. The trick is to first set the smaller format lens to yield the desired DOF and shoot an image/footage. Then, match by eye the larger format lens to the DOF in the first image/footage. It probably also helps if the entrance pupil of the two lenses are positioned at the same location. The thing is, with your test set-up (and with almost every previous equivalency test set-up), you would merely be matching the focus/softness of the foreground and background, but you wouldn't be matching the DOF. To match the DOF, the front and back limits of the DOF need to be visible on objects/surfaces in the frame. Caldwell mentioned some of the differences in optical qualities inherent in different sized formats: By the way, Caldwell also admitted that refractive optics can affect DOF:
  10. Ten hours before you first posted about your guy's format test, I stated that equivalency comparisons need to be done in focal lengths narrower than a wide angle lens: I welcome your explanation as to how I am moving the goal posts. Furthermore, if you reread my post, you will see that the second and most important objection that I made to his test was that he shows no delineation of the front and rear DOF limits. With those details missing, the test is not useful. So what? I have real-world experience shooting most formats from 8"x10" reversal film down to 8mm reversal film. His admission of the inherent problem in his methods does not make the test valid. Going by the f-stop/t-stop markings is a universal mistake that seems to afflict the every single one of the mathematical equivalency testers. Of course, t-stops are different from f-stops, and the markings aren't accurate. So, the DOF has to be matched by eye. By the way, the two lenses that I chose earlier in this thread (a 16mm Zeiss Superspeed for S16 and a standard 360mm for 8"x10") should be about a 98% match. It's convincing if you want to see a match, but his comparison lacks crucial information and there are devastating, uncontrolled variables. So, his test is not really valid. In regards to the notion that sensor size does not play a role in the image, I strongly disagree. Lenses made for particular formats give a certain number of lines of resolution within that format. If one crops into that format, one throws away lines of resolution and the overall image is softer/mushier. In addition, cropping into a format can destroy the particular image character inherent with a lens. The thing is, optics made for larger formats posses characteristics that are lacking in lenses made for smaller formats (and vice versa). I have mentioned some of those characteristics in this thread and elsewhere in this forum. You are mistaken. I was not arguing that I recognized the larger format due to increased lens blur. I was merely pointing out the dramatic differences in the two images, which the conductor of the comparison evidently still can't discern. Agreed. Yedlin's comparison has problems, so his test isn't conclusive Or, it provides the argument that such comparisons should be conducted by someone who understands the fundamentals of what is necessary for such a test to be valid. This is an Internet forum. No worries.
  11. Thanks for the link! I doubt that he is talking about this exact issue. Like most other folks who do equivalency tests, he likely limits his attention to mathematical DOF, and his tests use wider angle lenses and there is no delineation of the front and rear DOF limits with a lot of other detail thrown away or ignored. I don't have time right now to read the linked page, but if the images shown are the extent of his comparison, his tests are invalid. He does not show how the limits of DOF are delineated. He seems to be using wide angles focal lengths, and I can see a difference in one of the images with just a glance.
  12. Keep in mind that, to do a proper comparison, one must use the optics made for the formats being tested. In addition, testing wide angle focal lengths is going to make it more difficult to discern any differences, so stick to lenses that are a normal focal length or tighter. 200mm is in the normal focal length range for the 4"x5" format. So you need to use a 150mm-210mm lens made for 4"x5" and it has to be focused to a 4"x5" sensor/film sheet/DOF adapter. 50mm is the normal focal length for FF, so you need to use a 50mm FF lens on a FF camera. By the way, here's another yet another overlooked variable -- view camera lenses for large format (2'x3", 4"x5", 8"X10", 11"X14", etc.) are designed produce image circles that are much larger than their format, because they have to allow for tilts, swings and shifts.
  13. The quotation marks that I employed imply something else. I'm saying that refractive optical elements can affect focus and the focus range, and, additionally, that there are general tendencies, advantages and problems inherent in refractive optics designed for larger formats and likewise with refractive optics designed for smaller formats. Of course, there are exceptions and some lenses for smaller formats possess some of the qualities generally found in larger format lenses, and vice versa. There is consistency, but there is also seems to be more than one variable at play, so there is some complexity. I would describe the look of larger formats as generally having a flatter and more "solid" focus plane with a faster "rolloff" at the DOF limits, but with a smoother and better resolved "macro-contrast" outside of the DOF limits. There is not a huge difference between FF and M4/3. Using a speedbooster or focal reducer can allow the qualities of the larger format optics to be captured on a smaller format. The dramatic discrepancies between the two images shown above are not due to any tendencies inherent in different sized formats. My guess is that the DOF was not equivalently matched, plus the 1-inch camera likely had a built-in zoom lens (which can look/behave different than a prime) and excessive in-camera sharpening could have been enabled. There are a lot of variables that need to be controlled in such comparisons, otherwise the tests are invalid.
  14. The A7s with the 8"x10" rig is not really intended for stills.
  15. Yes, but the differences are not contained only within the front and back DOF limits. Additionally, the character of the focus transitions at the DOF limits can differ between optics designed for different sized formats. Likewise, how the focus behaves outside of the DOF limits can generally differ between formats. Yes. However, the differences are very slight (and sometimes non-existent) between optics designed for formats of similar size, for instance, M4/3 and APS-C, or APS-C and FF. The basic idea is that what's in focus is not limited the factors addressed in the DOF calculations (aperture, focal length, subject distance) -- the refractive optical elements have a huge influence over what is in focus, and how things resolve in a camera image. An obvious example of how refractive optics can affect the range of focus is a split diopter. A split diopter can near objects and distant objects into critical focus, regardless of whether the aperture is wide open or closed to its smallest setting. By the same token, a split diopter can be used in "reverse" to make close objects sharp while making distant objects blurry, even if the aperture is stopped down considerably. There are other examples of refractive optics affecting the focus range. However, there is more involved in "format specific looks" than DOF and range of focus. Optics for larger formats are generally less prone to aberrations and can usually resolve more lines per format frame. Optics for smaller formats can require more aberration correction (more glass) and, although they necessarily resolve more lines per mm, optics for smaller formats have a harder time squeezing the same number of lines of resolution into the smaller format frame that is possible with lager formats. These properties and limitations can affect focus, the flatness/shape of the focal plane, resolving and, hence, the "look." DOF "rolloff" is the street name for it. Brian Caldwell expressed it in more technical terms. I wouldn't say that the rolloff is "shorter" or more rapid on larger formats nor "longer" nor slower on smaller formats. Nor would I say that the rate of the falloff is smooth/constant in larger or smaller formats.
  16. Have you priced an Alexa 65 lately? If I had the money to buy an C300/Komodo/Ursa-12K, I'd buy an A7s II with an Irix 15mm lens and a shift adapter and build a copy of Zev Hoover's 8"x10" rig. I'd deposit rest of the money.
  17. If you think that an image with a building exhibiting sharp edges matches an image of the same building showing soft edges, so be it. Everyone has a right to an opinion. To me the differences between the images are so blatant that those discrepancies must be due to some uncontrolled variable(s) -- not to the difference in formats. The differing looks/DOF between formats is usually more subtle than what we see in your comparison. My guess is that the apertures were not at their equivalent settings. Plus, the 1-inch camera used a zoom lens, and it might have had sharpening enabled. Thank you for posting this! The comparison would need to employ a narrower focal length -- normal or tighter -- to show a more perceptible delineation of the limits of the DOF range. Also, the DOF should be shallower to possibly show a more dramatic difference between formats. A Zeiss Superspeed 16mm set to f2 would work as the normal lens for the Super 16 format. A standard, normal 360mm lens for 8"x10" is a close equivalent to that 16mm Ziess Superspeed, and the equivalent aperture on the 360mm lens would be somewhere in the range of f40-f51 (this aperture would need to be dialed-in for a visual match). Maybe somebody with the resources and with the gumption will eventually make such a comparison. If so, hopefully they will conduct their test in a setting conducive to revealing DOF/focus limits, perhaps with a receding fence as shown in the photo above. Thank you for the informative and helpful post!
  18. Uhm... okay. Right. So, let's just dismiss outright the discrepancies shown within the colored outlines, without any consideration nor response. Well, denial is not a river in Egypt...
  19. So, if there is no way to get a close enough match in focal length for an equivalency test, how can any of the equivalency tests made so far be accepted as valid? Actually, there are a lot of 16 and Super 16 prime lenses. Start with that format as the smaller camera. There are also plenty of 8"x10" lenses. It shouldn't be too difficult to use the formula behind the equivalency principle to calculate a close enough match with lenses for those two formats. A little cropping of one of the images is okay, but a zoom lens is not okay. Well, everyone has a right to their view. You evidently don't see the stark differences that I can see with just a glance at the full frame and 1-inch images. Perhaps another comparison method of the two images would make the differences more apparent. Here is a gif of the two equivalent images alternately flashed at one-second intervals: Do you not see in the area outlined in red how the distant white building exhibits sharp edges in the 1-inch image, while it is much softer in the full frame image? Likewise, inside the green outline, do you not see how the distant trees are significantly blurry in the FF image, yet we can see their individual branches in the 1-inch image? Closer to the camera, within the blue outline do you not notice how the vertical supports on the fence are softer in the FF image and sharper in the 1-inch image? From your description, I wasn't completely sure which image came from which camera, so please correct me if I got the format labels wrong. Regardless, there is a substantial difference in the look and DOF of the two images. I actually offered to collaborate on an equivalency comparison with an EOSHD poster who is a staunch proponent of the equivalency principle and who happens to reside in my town. The equivalency poster refused my offer. I would not do such a test without an equivalency supporter present to oversee and certify the matching of the DOF. If I did the test alone, without such certification and if the results showed a dramatic difference in look/DOF, folks would just claim that I did something wrong or that I intentionally manipulated the images. Several times in this forum I have pointed out prominent discrepancies in DOF/equivalency tests and those differences were dismissed as unimportant or ignored as unavoidable testing "inaccuracies." I am not going to go through all the effort to do a proper comparison just to have the findings rejected outright. I never disagreed with Caldwell regarding perspective. Certainly, perspective is determined by the distance of the camera/observer from the subject, but there are exceptions to that rule, depending on how one defines "perspective." However, perspective has little to do with the question of whether different sized formats give contrasting looks or exhibit differing DOF. By the way, Caldwell agreed that there is more to DOF than the the factors/variables found in the DOF formula (which is the basis for the equivalency principle).
  20. It's probably best to first set the desired DOF on the smaller format, then match that DOF range on the larger format by eye with a large monitor and/or digital zoom. In addition, it is important to start out with a set-up that gives all of the information on what is happening with the DOF/focus, visible continually from front to back, both inside and outside of the DOF range. An ideal arrangement might be next to a receding fence, like this: Note how the vertical rungs in the fence give a good idea of how/where the rear limit of the DOF range is delineated. It probably would show a more precise DOF limit delineation if the horizontal rung behind the subject's head was visible. Also, this set-up could be improved by panning the camera right and/or pulling the camera back to reveal how the front limit of the DOF is delineated on the fence. Additionally, if there were closer trees or other landscaping visible through the fence, that could add extra information on how background objects are rendered/resolved. A small bit of cropping on one of the images probably wouldn't ruin such a test, but using a zoom would. Using two cameras of dramatically differing formats might exhibit a more conspicuous difference in look/DOF that might help overcome some of the minor inaccuracies afflicting tests with camera formats that are close in size.
  21. Thank you for doing that comparison! ... but, as you state, there were differences, nonetheless, even though zoom lenses were utilized for the test. The differences that I see are significant. In addition, the comparison suffers the same maladies that afflict all equivalency tests so far. The front and and rear limits to the DOF are not clearly shown. Also, not visible is the focus fall-off outside of the DOF range. Furthermore, the DOF is rather deep. The visual benefits of larger formats are more readily revealed by a shallower DOF. I don't think that they would match too much more closely than what is shown -- not with two primes and not with a shallower DOF and not with clearly showing the foreground and background limits of the DOF. Also, there seem to be some problems with the test that make it inconclusive. The images certainly wouldn't match if two dramatically different sized formats were compared, such as Super 16 and 8"x10". Perhaps one would do so to prove one's point. So, far I haven't seen a single equivalency test that actually demonstrates that two prime lenses made for different formats can match. Again, thank you for doing the test, but, unfortunately, the differences between the images are prominent, and the test suffers from many the same problems inherent in every DOF/equivalency comparison so far. The images from two different M4/3 primes of the same focal length would probably not look as different as the images shown in the test. To do a proper test, a lot more of the variables have to be controlled, and crucial data cannot be obscured (as seems to be the case in most such DOF tests). It's not easy to wrangle all of those elements, but nothing will be conclusive until somebody does it correctly. In the meantime, here is footage shot on Zev Hoover's 8"x10", reflective DOF adaper, and here's a video by our own @Gonzalo Ezcurra testing the focus and DOF on his 14"x14" MiniCyclops DOF adapter. Neither clips are making a DOF comparison with another format, but note how some of Gonzalo's shots intentionally show the foreground that is outside of the DOF range. I would like to see someone use M4/3 to match the looks in the above videos. Not sure how someone arguing with Brian Caldwell is relevant to the points made in this thread, but us "non-entities" should hold our ground!
  22. By the way, It's good that you did not use two formats that "contiguous" in size -- most tests are APS-C vs. FF, or M4/3 vs. APS-C. The differences between such similarly sized formats is slight. However, if you do the same test between Super 16 and 8"x10", the differences in DOF roll-off and the in general look of different sized formats is readily apparent.
  23. Thank you for making this comparison. All three of the images differ from each other perceptibly, despite detail missing in the black background areas and despite the fact that the "given" DOF is way too deep for valid test. It's best to start out with a longer focal length and show detail that continually runs from in front of the subject to a far distance in the background. Also, I have never seen a equivalency test that shows how the foreground limit of the DOF -- that's very important in an equivalency test. I think that I have only once seen an equivalency test that actually showed the location of the background limit of the DOF. In addition, is there a zoom lens on the 1 inch camera? Zoom lenses handle focal length differently from primes.
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