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8 hours ago, hyalinejim said:

 

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

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

 

When I use my two different FF 24mm lenses both made by Canon but one EF and the other FD (both quite old though), I can often  see almost as big a difference as between my FD 24 1.4 L and my RX100 iv at 24mm equivalent (actually the EF 20-35 2.8 lens is a closer match usually maybe because it fully passes exif to the camera while the FD adapter is dumb).     As with all of these, the small difference are down to many reasons mostly including the lens design but also the settings are usually not exact (IE one 24mm lens might be 24.5 while another might be 23.8mm).     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.    Since I very much doubt you will EVER see an exact match, some people will never accept the theory matches the practice and hence discussion like this are pointless (the why /why not use FF or any other format can be a very valid discussion but not the equivalence is real ones).

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).    

Back to (trying to) be a spectator.

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Sad day .  To find out I’ve only been using parts of my images for years?  Bummer. 

You must have a very large penis. 

can i get you boys dueling pistols for xmas ? then we can settle it once and for all 🙄

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2 hours ago, seanzzxx said:

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.

I would say that this is very likely.

2 hours ago, tupp said:

He does not show how the limits of DOF are delineated. 

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.

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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.

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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.

 

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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?

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

And yes, the selection of lenses available for different formats is different. 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.

So theoretically, sensor size makes no difference to DOF. But in practice DOF is rendered qualitatively differently because the lenses are different / behave differently / must be set differently for different formats.

If true, it's an interesting dichotomy. 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?

 

 

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On 9/10/2020 at 9:20 AM, kye said:

Yes, there are small pockets of uniqueness right at the edges of what is possible that maybe can only be achieved with one camera system or other.  I experience that when I am shooting 120p on my GH5 and I enable ETC mode on the 70-210mm + 2x TC to get a FF equivalent focal length of 2100mm, which isn't something many camera systems can do.

Having shot some Olympic snowboarding from the stands with a GH5+PL100-400 and some sailing from shore with the same camera and also the Olympus E-m5iii + 12-100 the results are actually quite good hand-held with their dual IS systems.  It's just a shame they never got together to have dual IS compatible across systems.  The Panasonic digital teleconverter (true crop) seems better than the Olympus implementation which seems like some resampling.  On the other hand, the Olympus PDAF autofocus makes stable shooting and focusing at 800mm+ FF equivalent much easier.

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4 hours ago, tupp said:

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.

PLEASE point me to that test then, because I feel like whatever magic properties that should be inherent to sensor size should manifest in sóme way under a controlled test. So far you are just shooting down any test provided as not being rigorous enough (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), but if the differences were significant so as to be meaningful there should be a way to test for this relatively easily right? I

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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).

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Actually, that's not quite the point I was making. I don't know much about large format lenses.

My point was that any observed differences might be due to the difference in aperture required to maintain equivalence between formats. But I'm certainly open to the idea that there are other factors that also contribute. 

Are there any conclusions you would draw on the pros and cons  of large formats versus small in terms of the qualities of images afforded by the glass associated with each? For example, are large format lenses well suited to narrow DOF pics that maintain sharpness and small format lenses well suited to deep DOF without suffering as much from diffraction?

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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.
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11 hours ago, tupp said:

 

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

 

Of course he did.    But if you use the same optics in different formats you get the same result...it is not the format that makes the difference it is the lenses.

To get an exact match to satisfy everyone, 

You would need to firstly pick your cameras of different formats and get the EXACT crop factor.

Next you need a lens for one format.
You would need to know the actual focal length (not just the marked focal length),
You would need the  diameter and could then work out the exact f stop.

Using the crop factor to get an exact match, you would then need to do the same for the second format.

You will also probably need to have the exact same lens formula though to get the same T stop (and take away any possibility of being a difference for other reasons).

Yeah, it probably IS possible (maybe even easy for some).

I could not do it in a lifetime though and again, beyond being a academic exercise, what is the point?

It would HAVE to be done this way because otherwise some will point out (often tiny) differences but those differences .

So, unless you (or someone else) does THAT, I will always accept that the theory matches the practice and to date, all tests have satisfied me they do.    

Are there ANY tests that have been done matching equipment EXACTLY? 

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1 hour ago, hyalinejim said:

Are there any conclusions you would draw on the pros and cons  of large formats versus small in terms of the qualities of images afforded by the glass associated with each? For example, are large format lenses well suited to narrow DOF pics that maintain sharpness and small format lenses well suited to deep DOF without suffering as much from diffraction?

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.

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30 minutes ago, tupp said:

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.

Can you link to those posts?

I'm still no clearer on what the differences in DOF rendering due to large/small format lenses actually looks like in an image.

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4 hours ago, hyalinejim said:

Can you link to those posts?  I'm still no clearer on what the differences in DOF rendering due to large/small format lenses actually looks like in an image.

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.

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9 hours ago, noone said:

But if you use the same optics in different formats you get the same result...it is not the format that makes the difference it is the lenses.

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.

 

 

9 hours ago, noone said:

To get an exact match to satisfy everyone,  You would need to firstly pick your cameras of different formats and get the EXACT crop factor.  Next you need a lens for one format. You would need to know the actual focal length (not just the marked focal length),

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).

 

 

9 hours ago, noone said:

You would need the  diameter and could then work out the exact f stop.

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.

 

 

10 hours ago, noone said:

Using the crop factor to get an exact match, you would then need to do the same for the second format.

That's unnecessary, and you would only need to crop one of the images if you want to exactly match the frames.

 

 

10 hours ago, noone said:

You will also probably need to have the exact same lens formula though to get the same T stop (and take away any possibility of being a difference for other reasons).

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.

 

 

10 hours ago, noone said:

Yeah, it probably IS possible (maybe even easy for some).

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.

 

 

10 hours ago, noone said:

I could not do it in a lifetime though and again, beyond being a academic exercise, what is the point?

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.

 

 

10 hours ago, noone said:

So, unless you (or someone else) does THAT, I will always accept that the theory matches the practice and to date, all tests have satisfied me they do

Good for you!

 

 

10 hours ago, noone said:

Are there ANY tests that have been done matching equipment EXACTLY?

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.
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37 minutes ago, tupp said:

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.

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.

There are tests that got a close enough match with the equipment.  However, they suffered the maladies that afflict most other tests:

If you do NOT get things to match exactly there will ALWAYS be a small difference that will just leave SOME to say that because there is a difference the theory does not match the practice and THAT is what makes even trying a "fools errand"

All the tests to date look close enough for me, if they do not for you, that is your problem and you should be doing the tests to match YOUR theory.

You think the tests get close enough but then when you see a(often very small) difference you attribute that to a difference between formats instead of between the optics.

There is no reason you would get a difference in vignetting if you used identical formula lenses to match the crop (IE scaled).

 

As to your 600mm 8x10 above, 

That is a very different argument and actually plays into the original question and is again the reason WHY FF is necessary to ME.

I simply can NOT match my ancient 300 2.8 with M43 (other than the $35000 plus Arri 150 1.3) or my ancient 24 1.4 (because there are no 12mm m43 f0.7 lenses) or my ancient 85 1.2 (again, no 42.5mm f0.65 lenses which is approaching the limit in air).   No high quality tilt shift lenses either like my favourite 17 f4.

If I could do what i can with m43 (or Pentax Q) what i can with FF, I would only be using that.

A 8x10 camera with a 600mm lens will probably be something like a 600 f9 Nikon. 

A 600mm 8x10 f9 lens would be equivalent to about a 90mm 1.4 FF (so about a 45mm f0.7 M43).   If you COULD get a lens to match it  (it IS possible even if there are none) it would yield a very similar photo even without being the exact same lens design.

If the lens was 600mm f8, then that would be almost impossible to match with m43 as that would be about a 90mm f 1.2 FF so you would need an aprox 45 f0.65 to even give a similar if not exact photo.

You have yet to show that there is ANY difference BECAUSE of the differences in sensor size and so far all difference have been because of the optics and not getting an exact match.

After all if the Moon astronauts had been just 2% off course, where would they be now?

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5 minutes ago, noone said:

 

my ancient 85 1.2 (again, no 42.5mm f0.65 lenses which is approaching the limit in air). 

 

A 8x10 camera with a 600mm lens will probably be something like a 600 f9 Nikon. 

A 600mm 8x10 f9 lens would be equivalent to about a 90mm 1.4 FF (so about a 45mm f0.7 M43).   If you COULD get a lens to match it  (it IS possible even if there are none) it would yield a very similar photo even without being the exact same lens design.If the lens was 600mm f8, then that would be almost impossible to match with m43 as that would be about a 90mm f 1.2 FF so you would need an aprox 45 f0.65 

 

Too late to edit 1.2 FF is more like f0.60 M43.

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