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tupp

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Posts posted by tupp

  1. 7 hours ago, seanzzxx said:

    PLEASE point me to that test then,

    Most of the test parameters are given in the second half of this post from earlier in this thread.

     

     

    7 hours ago, seanzzxx said:

    because I feel like whatever magic properties that should be inherent to sensor size should manifest in sóme way under a controlled test.

    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.

     

     

    7 hours ago, seanzzxx said:

    So far you are just shooting down any test provided as not being rigorous enough

    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.

     

     

    7 hours ago, seanzzxx said:

    (why on Earth would foreground unsharpness matter in any way when according to your last example provided the special properties of large format are abundantly clear in a shot that has just as much elements in front of the focus point, that is a nose, as in the examples provided by Yedlin)

    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.

     

     

    7 hours ago, seanzzxx said:

    but if the differences were significant so as to be meaningful there should be a way to test for this relatively easily right?

    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.
  2. 8 hours ago, hyalinejim said:

    Well, I think that DOF as defined by circle of confusion etc can be matched because equivalence theory states that you can, if the lens for the smaller format is bright enough. However, I would expect to see a considerably softer image with lots of vignetting as you'd need a very fast lens to replicate the narrow DOF of this shot, and that's how lenses behave wide open. So although the DOF might be technically the same, the images will look different.

    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.

     

     

    8 hours ago, hyalinejim said:

    But this is caused by the glass, not sensor size.

    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.

     

     

    8 hours ago, hyalinejim said:

    So your choice of format will have an impact on the look of the image. But I think a lot of people are making the point that those differences are derived from the glass and are not inherent to the sensor size.

    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.

     

     

    8 hours ago, hyalinejim said:

    So theoretically, sensor size makes no difference to DOF.

    Yes, unless one crops too severely into the image circle of a lens.

     

     

    8 hours ago, hyalinejim said:

    But in practice DOF is rendered qualitatively differently because the lenses are different / behave differently / must be set differently for different formats.

    Agreed.

     

     

    8 hours ago, hyalinejim said:

    But it does suggest that any equivalence test is really just a comparison of two different lenses. In the same way that one of my 50mm lenses looks different from the other 50mm lenses I have for the same format.  So would you agree that once you match focal length and aperture for the same shot on different formats, you're comparing lenses?

    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).

  3. 12 hours ago, hyalinejim said:

    It still sounds intriguing though 🙂 You misunderstood my proposed comparison though. The simulated crop on the 50 would simulate a notional sensor 1/4 the size of full frame. But I suspect that any differences observed would have more to do with the glass involved (and the necessary apertures) than the sensor size. Perhaps this is what accounts for your observation that the differences in rendering of DOF are greater when the disparity of sensor size is increased: to maintain equivalence, one lens is quite wide open and/or the other is quite stopped down.

    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:

    DSC08356-800x800.jpg

    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?

  4. 12 hours ago, noone said:

    The numbers to get an exact match between an 8,8mm lens on the RX100 and the 24mm on FF I use are aprox and the crop factors used are aprox.     This is why it would be almost impossible to get an exact match and I doubt even Lens Rentals and their optical bench could get one.

    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.

     

      

    12 hours ago, noone said:

    Read the other thread linked to earlier and what Dr Caldwell said (he designed the Metabones SpeedBooster as well as one of the highest performance lenses ever).

    Caldwell mentioned some of the differences in  optical qualities inherent in different sized formats:   

    On 6/20/2016 at 12:46 PM, Brian Caldwell said:

    One advantage that larger formats have is that you can use a smaller relative aperture to achieve a given DOF.  Since aberration correction tends to be very non-linear with respect to f/# you often wind up with better correction on a larger format.  For instance, I used to shoot 11x14" film a fair amount, and aside from an advantage in film grain it allowed me to shoot at f/16 instead of the ~f/1.4 I would have had to use on 24x36 format to achieve an equivalent picture.  Focal lengths scaled accordingly, naturally.  At f/16 the ultra large format lens was nearly diffraction-limited, whereas a small format lens at f/1.4 is nowhere near that limit.

     

     

    By the way, Caldwell also admitted that refractive optics can affect DOF:

    On 2/27/2017 at 2:29 PM, Brian Caldwell said:

    techically, aberrations can and do influence DOF.

     

  5. 12 hours ago, seanzzxx said:

    I feel like you are kind of moving the goalposts. This guy has a use case where he has shot hundreds of shots on cameras with all kinds of film backs (for camera comparisons), and somehow this does not count because his lenses are too wide?

    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:

    23 hours ago, tupp said:

    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.

    13 hours ago, seanzzxx said:

    There is an interesting post from cinematographer Steve Yedlin talking about this exact issue.

     

    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.

     

     

    12 hours ago, seanzzxx said:

    This is based on real-world experience with everything from an IMAX down to a super 35 camera.

    So what?  I have real-world experience shooting most formats from 8"x10" reversal film down to 8mm reversal film.

     

     

    12 hours ago, seanzzxx said:

    He even admits in the article that his matching is not perfect due to practical limitations (t-stops and f-stops not aligning, lenses not matching exactly to their equivalent counterparts, etc.),

    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.

     

     

    12 hours ago, seanzzxx said:

    but his argument is that the likeness between shots is so convincing and consistent that the sensor size obviously does not play a role in the actual image,

    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.

     

     

    12 hours ago, seanzzxx said:

    and that any perceived difference is due to bias or particular (non image circle-related) lens characteristics, not due to the size of the film back.

    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.

     

     

    12 hours ago, seanzzxx said:

    In fact, where you have been previously arguing about recognizing a larger format due to increased lens blur (in your examples where you are circling a number of shots),

    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.

     

     

    13 hours ago, seanzzxx said:

    the Alexa 65 actually seems to have slightly LESS lens blur in the examples provided by Steve Yedlin, likely due to my aforementioned reasons.

    Agreed.  Yedlin's comparison has problems, so his test isn't conclusive

     

     

    13 hours ago, seanzzxx said:

    This, again, seems to provide an argument that any perceived differences are more likely to be due to individual lens characteristiscs or other uncontrolled variables which are not related to the film back size.

    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.

     

     

    13 hours ago, seanzzxx said:

    EDIT: I hope this does not come off as argumentative, as I do appreciate -and enjoy- the discussion!

    This is an Internet forum.  No worries.

  6. 14 minutes ago, seanzzxx said:

    There is an interesting post from cinematographer Steve Yedlin talking about this exact issue.

    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.

     

     

    13 minutes ago, seanzzxx said:

    He has some pretty rigorous testing to go with it.

    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.

  7. 30 minutes ago, hyalinejim said:

    How about a test where you simulate a small sensor by using a center crop from a full frame stills camera? Like this:

    Full frame
    200mm, f7.1

    Simulated 4x crop sensor
    50mm, f1.8

    These would be different lenses. I could do this (when I have time) with a Canon 50 1.8 and Sigma 70-200 f2.8 and use ACR to correct for lens aberrations. Or instead with an OM Zuiko 50 1.8 and OM Zuiko 200mm f4 (possibly similar primes? But can't correct for aberrations)

    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.

  8. 6 hours ago, tupp said:

    However, there is more involved in "format specific looks"

    5 hours ago, hyalinejim said:

    This implies that you maintain that there is a look inherent to a format, independent of variations between lenses.

     

    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.

     

     

    6 hours ago, hyalinejim said:

    If so, it should be consistent as format size changes and it should be describable.  How does the look of small format compare to the look of a larger format, at equivalent focal lengths and apertures?

    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.

     

     

    6 hours ago, hyalinejim said:

    I'm just interested here, as I use DOF calculators to help my understanding when moving between FF, micro 4/3 and speedboosted micro 4/3.

    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.

     

     

    6 hours ago, hyalinejim said:

    But I also see a huge difference in the images posted, which I would not have expected.

    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.

  9. 2 hours ago, hyalinejim said:

    So is it fair to say that your position is something like this:  "Even though DOF calculators show that the theoretical DOF of equivalent shots is the same, in practice there is an observable difference in how DOF is rendered between equivalent shots"?

    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.

     

     

    2 hours ago, hyalinejim said:

    If so, and if I understand you correctly, that would mean that a DOF calculator is showing us 2 points on the DOF continuum, the point of near focus and the point of far focus, and these are the same for both formats if the focal length and aperture is equivalent. But it's not telling us anything about the DOF characteristics elsewhere on the continuum, which is noticeably different.

    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.

     

     

    2 hours ago, hyalinejim said:

    But others may notice and be very interested in differences in DOF behaviour that's not described by equivalence theory...if what you say is true!

    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."

     

     

    2 hours ago, hyalinejim said:

    So we would be talking about a kind of DOF rolloff, which is shorter on larger formats and longer on small formats, according to equivalence sceptics.

    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.

     

  10. 20 hours ago, SteveV4D said:

    Thats odd as S35 cinema cameras cost a lot more than many fullframe hybrids..   and I'd rather have the money to buy a C300, a Red Komodo or an URSA 12k over a fullframe A7C,  or any other fullframe hybrids for that matter...

    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.

  11. On 9/15/2020 at 11:13 AM, noone said:

    The differences are quite minor to the point of it proves theory and practice match to me

    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.

     

     

    On 9/15/2020 at 11:48 AM, Jay60p said:

    To test this you could use:

    standard 16mm, Bolex (Kern Paillard 10mm at f/1.8

    4/3rds, 17mm at f/3.2

    APS-C (Nikon DX), 22mm at f/4

    Full Frame, 34mm at f/6.3

    8x10, 256mm at f/45

    The 16mm would have to be wide open and the 8x10 would have to be completely stopped down (my 8x10 270mm is f/4.4 - 45)

    This is according to this calculator:

    https://www.pointsinfocus.com/tools/depth-of-field-and-equivalent-lens-calculator/#{"c":[{"f":13,"av":"8","fl":50,"d":3048,"cm":"0"}],"m":0}

    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!

  12. 29 minutes ago, noone said:

    make sure you have multiple lenses and cameras for each format otherwise I will just point out the differences why the equipment is not going to be an exact match and say it is invalid.

    Uhm... okay.

     

     

    29 minutes ago, noone said:

    ALL the photos I have seen about this prove to my satisfaction the theory matches reality and even my crappy photos are close enough to prove that.

    Right.  So, let's just dismiss outright the discrepancies shown within the colored outlines, without any consideration nor response.

     

     

    29 minutes ago, noone said:

    Beyond that I disagree.

    Well, denial is not a river in Egypt...

  13. 14 hours ago, noone said:

    if someone really went to the trouble of trying for an EXACT match they would need to take into account everything including each individual lenses characteristics, and that would be almost as difficult to do with two M43 lenses of the same focal length as it would with a Pentax Q and a Mamiya 7 with a digital back (assuming you can find lenses to match).

    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.

     

     

    14 hours ago, noone said:

    I am satisfied the photos I posted show enough similarity to prove my point and just to satisfy myself I DID test with my Sony Zeiss 55 1.8 VS the RX100 iv Sony Zeiss lens  and it is as i suspected a closer match still.....now since it is not an EXACT match and was also just a quick and dirty comparison, there is zero point posting because you would just say it is different.

    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:

    dof_comparison2.gif.005abd986051526fff7b95e3417e89ae.gif

    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.

     

     

    14 hours ago, noone said:

    Feel free to set things up to match theoretically lenses of two (or more) different formats but include a couple of lenses for each format used....If you do that, I am sure the photos would be the same, if you are not, then maybe you should disprove it...

    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.

     

     

    14 hours ago, noone said:

    Lastly regards Dr Caldwell,

    "Do the experiment properly and you'll find that the perspective is the same.  Surely you must have heard countless times before that perspective depends only on the subject distance.  This is a truth that you shouldn't ignore.  More precisely, perspective depends on the distance from the subject to the entrance pupil of the lens.  For this reason, the entrance pupil is sometimes called the center of perspective. "

    I disagreed with you in that thread and I disagree with you in this one hence why this is pointless now.

    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).

  14. 21 hours ago, BTM_Pix said:

    Having to have the FF at f4 because the APS-C had to be at f2.8 and the MFT with the SB could be f2  is not doing the FF any favours.

    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:

    b7b0e286345bf8d7538f6a068e031d7e.jpg

    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.

     

     

    22 hours ago, BTM_Pix said:

    Matching the focal lengths also make it a challenge without using a zoom as well of course as at least they maintain the same contrast and colour for each camera.

    A small bit of cropping on one of the images probably wouldn't ruin such a test, but using a zoom would.

     

     

    22 hours ago, BTM_Pix said:

    I'm trying to think about which set of cameras and primes that could be used for be a totally accurate test if someone wanted to do it properly and its a tricky ask to get exact matches.

    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.

  15. On 9/12/2020 at 11:03 AM, BTM_Pix said:

    FWIW, I did a very quick basic comparison between MFT, APS-C and FF at a couple of focal lengths a few years ago on here...

    Thank you for doing that comparison!

     

     

    On 9/12/2020 at 11:03 AM, BTM_Pix said:

    ... and the differences in those specific limited instances with zoom lenses to create the correct equivalent focal lengths were marginal.

    ... 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.

     

     

    On 9/12/2020 at 11:08 AM, noone said:

    IF I spent ages and ages, setting it up and trying for an exact match, the photos WOULD look extremely close (24 at f4.8 vs 8.8 at 1.8) even with this apples to fish comparison.

    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".

     

     

    On 9/12/2020 at 11:08 AM, noone said:

    Again though why on Earth would I want to?

    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.

     

     

    On 9/12/2020 at 11:08 AM, noone said:

    Given I used a more than thirty year old prime against  a much more modern fixed lens zoom on a tiny 1 inch sensor camera and to me, the photos are pretty similar (with errors down to me), I think I proved my point.

    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.

     

    On 9/12/2020 at 11:08 AM, noone said:

    Lastly, if you compared different M43 lenses against each other at the same focal length and/or different M43 cameras the look would not be the EXACT same as no two of ANYTHING will be exactly the same.

    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.

     

     

    On 9/12/2020 at 3:30 PM, noone said:

    since people would argue with the bloke who designed the Metabones speedbooster as well as one of the best lenses ever (Coastal Optics 60mm f4),there is zero point in a non entity like me trying any further.

    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!

  16. 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.

  17. 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.

  18. 13 hours ago, noone said:

    A 50mm lens is a 50mm lens no matter the format

    Not really.  A 50mm lens for Super 16mm usually has to pack more lines of resolution into a smaller area than, say, a 50mm lens made for medium format.  That difference in lines-per-mm makes a difference in look and in sharpness (which is involved in DOF).

  19. 1 hour ago, noone said:

    If you took three photos..  50mm f2 on M43, 100mm f2 on FF and 100mm f4 on FF (all things being equal) first and third will look the same second will not.

    Strongly disagree here.  Even if #1 and #3 match according to the "equivalence principle," they won't look the same.

     

    The DOF on a Super 16mm camera can be made to "mathematically" match the DOF on an 8"x10" camera, but they will not look the same.  Furthermore, in the same scenario, the rate and manner in which the DOF "rolls off" will differ between those two different formats.

  20. 4 hours ago, Amazeballs said:

    I think I foind extremly cheap and efficient solution. This device called - a paper bag 😆

    Someone suggest white plastic bags early in the thread.

     

     

    3 hours ago, BenEricson said:

    I think you'll likely kill nearly all of the output with the diffusers people have been suggesting... 

     

    Early in the thread, someone suggested regular diffusion gels, which come in a variety of grades and light transmission rates.

     

     

    3 hours ago, Amazeballs said:

    Sadly those 3x3 inches shower cap diffusors will be too small for my light which is about 3x5 in size, otherwise a nice solution. 

    If you are trying to make the light softer, a 3x5 diffuser on a 3x5 fixture won't help.

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