Help judging performance of my FE55z, FE35f2.8z horizon/infinity

Started Jul 5, 2016 | Questions
JimKasson
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Re: Full sized images

l_d_allan wrote:

JimKasson wrote:

These are full frame. Sorry for the earlier error. Comments?

Non-IQ comments (as I have negligible experience with using "tilted near-infinity horizons" (TNIH) for "good copy vs bad copy testing" (GCVBCT):

Lotsa questions. I'll just deal with one for now, and circle back in the morning.

  • .
  • How far away would you estimate the tree line is at the horizon? Half mile? Full mile? Less? More? Ever actually stepped it off, if that would be feasible?

I estimate the tree line at between 500 and 800 meters. Using the formula in this post:

http://www.dpreview.com/forums/post/58031944

(I can't believe there have been no comments on that), (35/55)^2 = 0.4, so I should be OK with anything beyond about 200m, even with a much sharper lens that's just as sharp at the edges as at the center.

The hillside you're looking at is very steep, and thickly wooded. I couldn't possible climb it. The vertical rise to the ridge is about 700 feet from my yard at the low point.

Jim

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OP slstr Senior Member • Posts: 1,029
Re: Full sized images

JimKasson wrote:

l_d_allan wrote:

JimKasson wrote:

These are full frame. Sorry for the earlier error. Comments?

Non-IQ comments (as I have negligible experience with using "tilted near-infinity horizons" (TNIH) for "good copy vs bad copy testing" (GCVBCT):

Lotsa questions. I'll just deal with one for now, and circle back in the morning.

  • .
  • How far away would you estimate the tree line is at the horizon? Half mile? Full mile? Less? More? Ever actually stepped it off, if that would be feasible?

I estimate the tree line at between 500 and 800 meters. Using the formula in this post:

http://www.dpreview.com/forums/post/58031944

(I can't believe there have been no comments on that), (35/55)^2 = 0.4, so I should be OK with anything beyond about 200m, even with a much sharper lens that's just as sharp at the edges as at the center.

Haven't checked this chart in full resolution yet but thanks for explaining how to use it, was wondering about that when you posted it on your blog.

The hillside you're looking at is very steep, and thickly wooded. I couldn't possible climb it. The vertical rise to the ridge is about 700 feet from my yard at the low point.

Jim

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JimKasson
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Re: Full sized images
1

l_d_allan wrote:

JimKasson wrote:

These are full frame. Sorry for the earlier error. Comments?

Non-IQ comments (as I have negligible experience with using "tilted near-infinity horizons" (TNIH) for "good copy vs bad copy testing" (GCVBCT):

  • Odd that when you click on the image itself, you get use of the Loupe, and can view much closer than when you click on "Original Size". Has DPR always been that way? "Original Size" is not nearly 1:1 pixel peeking, and neither does the Loupe. Any idea what the viewing ratio is with the Loupe with a7Rii captures of 7952 horizontal pixels?

I have no idea on any of that.

  • Since you don't care whether the sky blows out or not, seems like you could use a longer exposure ... the EXIF shows EC of -1.3 EV. Do recall if you used "A" mode with EC, or "M" exposure with EC ignored?

A mode with EC set to -1.3. Noise is not a problem in this scene, and I didn't want to blow the highlights on the leaves, which don't show up in blinkies or the histogram.

  • However, "Sunny 16" with ISO 100 would be 1/3200s at f/2.8, so you clearly didn't use "Sunny 16" (if I did the reciprocity correctly). 1/2000s is actually about +0.7 EV, so perhaps the EXIF value of -1.3 EV reflects where the EC dial was?

That's what goes in the EXIF. The EXIF has no idea what the "correct" exposure is.

  • Do you recall if you used UniWB with Zebras to decide on exposure? If so, what Zebra setting ... I use 100+? Was the sky blinking or not? Or did you back off a click or so from the tree leaves blinking?

No blinking, even at EC = 0.

  • ...
  • I don' t have that lens, so have no basis of comparison on what the center, near edges at the APS-C off-axis, and extreme corners should look like.
  • I also don't enough experience with TNIH to comment on perceived IQ.
  • We apparently differ on whether validly done TNIH captures tends to be better, worse, or about the same as a validly done brick wall IQ test for GCVBCT.

Ideally, we could test with a very large brick wall 500m away.:-)

  • How far away would you estimate the tree line is at the horizon? Half mile? Full mile? Less? More? Ever actually stepped it off, if that would be feasible?

Answered earlier.

  • What magnification of focal length would your estimate work out to be? 1000X or greater? Much greater?

I don't understand the question. Are you talking about the object field to image plane ratio?

  • It wouldn't surprise me if you have a laser range estimator with at least a high degree of accuracy.

I don't. If I worked often with technical cameras, I would, but I don't, unless you count a Linhof Technika as a technical camera.

  • If so, have you checked out how far trees at the "left horizon" are vs the "middle horizon" vs "right horizon"? My experience is there is a definite "learning curve" to estimating distances, but with practice you can get pretty good at it ... such as golfers and hunters.

Everything is well over the critical 200m.

  • Are those distances within +/- [fill-in-the-blank]?

Everything is well over the critical 200m.

  • ....
  • OT?
    I've been pondering how much "field curvature" and "focus shift when stopping down" (which this example doesn't do) really matter with the relatively large DOF of a f/2.8 lens and relatively wide 35mm FL. Even with a very small CoC, I doubt even a large print or the DPR Loupe would have these issues be noticeable ... if you print full frame.

Hard to measure. I could try focusing on the corners and see if that makes a difference, but this test is unrelentingly qualitative, and there's no way to measure focus shift with it. How about a huge ISO 12233 chart 500m away?

  • However, those issues seems maybe relevant for non-IQ test images if you need to crop the image for a print or upload ... then the effective CoC can be truly minuscule.

Jim

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OP slstr Senior Member • Posts: 1,029
Re: Full sized images
1

You crack me up Jim, yes we need that large brick wall to hold up the iso chart, it will become a place of pilgrimage.

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JimKasson
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Bench testing

slstr wrote:

You crack me up Jim, yes we need that large brick wall to hold up the iso chart, it will become a place of pilgrimage.

Seriously, this is the kind of thing you want to do on a optical bench with a collimator.

There are only four things keeping me from doing that kind of testing:

  • A spare $199-250K
  • A place to put the bench
  • The skill necessary to operate it properly.
  • It seems like shooting fish in a barrel; it's lots of fun to invent "kitchen optics" test methods.

Jim

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osv Veteran Member • Posts: 9,970
Re: Full sized images

JimKasson wrote:

These are full frame. Sorry for the earlier error. Comments?

landscapes shot wide open are problematic, but if that's all we could judge by, i'd have returned that lens for a refund, not an exchange.

the lack of vignetting indicates that it's been massaged(in camera?), so if that's the criteria, here is my fdn 35/2.8 wide open, with some vignetting correction and a bit of sharpening... i sold the lens because one side didn't clean up when stopped down, but now i'm wondering if that was a mistake.

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dan

OP slstr Senior Member • Posts: 1,029
Re: Bench testing

Out of curiosity, just how tall and wide would said wall and iso chart have to be at 500 meter distance to fill the frame with a 35mm lens on full frame ? Something like the Hoover dam?

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JimKasson
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Re: Bench testing
1

slstr wrote:

Out of curiosity, just how tall and wide would said wall and iso chart have to be at 500 meter distance to fill the frame with a 35mm lens on full frame ? Something like the Hoover dam?

Lemme think.

A 35mm lens on a FF camera has a FOV of 37 degrees horizontally. Half that is 18.5 degrees. Tangent of 18.5 degrees is 0.33. So the half-width is 500*0.33 = 167 meters. And the full width is 333 meters. I didn't make a diagram, just set it up in my head. Did I do it right?

Jim

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l_d_allan
l_d_allan Veteran Member • Posts: 5,087
Re: Full sized images

JimKasson wrote:

l_d_allan wrote:
Since you don't care whether the sky blows out or not, seems like you could use a longer exposure ... the EXIF shows EC of -1.3 EV. Do recall if you used "A" mode with EC, or "M" exposure with EC ignored?

A mode with EC set to -1.3. Noise is not a problem in this scene, and I didn't want to blow the highlights on the leaves, which don't show up in blinkies or the histogram.

Good point.

  • I don' t have that lens, so have no basis of comparison on what the center, near edges at the APS-C off-axis, and extreme corners should look like.
  • I also don't enough experience with TNIH to comment on perceived IQ.
  • We apparently differ on whether validly done TNIH captures tends to be better, worse, or about the same as a validly done brick wall IQ test for GCVBCT.

Ideally, we could test with a very large brick wall 500m away.:-)

Roger C at LR has wistfully written about renting a billboard in order to get far enough away ... and not just for super-telephotos as I recall.

  • If so, have you checked out how far trees at the "left horizon" are vs the "middle horizon" vs "right horizon"? My experience is there is a definite "learning curve" to estimating distances, but with practice you can get pretty good at it ... such as golfers and hunters.

Everything is well over the critical 200m.

Is that from your "Object DOF" studies? With the earlier link regarding the Otus 55mm at various apertures focused at 10,000 meters (10 km).
http://www.dpreview.com/forums/post/58031944

If so, the "200" seems associated with the MTF-50 label with units of cy/ph. Does that indicate relatively poor (if not grossly unacceptable) 200 cy/ph IQ? Wrong link? Low or no comprehension on my part?

My experiences seem different, but the FL and aperture are very different:
With a fast zoom at 4x longer 200mm but two stops slower f/2.8, focus still mattered more than I expected. My rusty math is that for DOF purposes,  I can't use the the chart for the Otus 55mm f/1.4 and the 200mm f/2.8.

Even ignoring that the Otus is sharper by at least 100 cy/ph at f/2.8 that the zoom, aperture is non-linear square, but FL may be linear? Or is it more complicated than that, and I need to carefully read 100's of pages of TLW blog articles ... after retaking some math classes and taking one or several courses in Optics?

Back to my fast zoom at 200mm f/2.8:
There were neighborhoods perhaps several miles away. Focus was still critical. With magnified LiveView, focus on the roof tiles of the Red house was obviously invalid for the Blue house just to the front of it or rear of it.

Focus at near infinity to Cheyenne Mountain signal towers at perhaps 20 miles away was obviously unacceptable for the Red house maybe 2 miles away. Also unacceptable for signal towers maybe 5 miles away?

I've never tried it, but my speculation is that at dusk and if I focused on a partial moon, that might not to appropriate for the Cheyenne Mountain towers.

Going back to the 200m issue with your Otus 55mm ... I will reluctantly concede that if I made a large'ish print with the focus distance recommended by the Object DOF approach, that DOF / CoC might be adequate ... if I used the full frame.

To me, that ignores the factor of cropping, which I don't think can and should be ignored. If the lens + sensor is critically focused and is capable of A3+ 13x19" prints from 25% of the full frame, that's how I want to focus. And that includes for GCVBCT.

I think the argument that "as long as you can make large prints at 300 dpi, it doesn't matter" is maybe obsolete with Super-Exmor's with 42 mpx that encourage and allow significant cropping. I'll admit I need to think that through more carefully.

I'll look for the .DNG's. If necessary, I'll add to my "to do list" to re-take those images on another super clear day, and be that much more careful.

Is that consistent to the "extinction graphs" for a 200mm lens at f/2.8? It might be just an average 'L' prime, but it's a zoom with a reputation for stellar IQ, world class build quality / control.

I will attempt to read and comprehend what I think of as your Object DOF related extinction graphs. Maybe a light will go on?

Is there a graph on your web-site that would have 'extinction lines" that reflect a high quality 200mm lens?

Would I be better off testing my admittedly less capable FE55, and attempting to extrapolate to your Otus 55? If I went back thru the previously ignored 20+ articles of the Object Mode + Protocol, would I find a "extinction graph" for the FE55?

I realize those graphs aren't answering the questions I'm asking. I'm being slow how they relate to GCVBCT, other than maybe how critical alignment is or isn't.

BTW, my impression is that you ended up your Object Model DOF in general or specific agreement with the paper that had the concluding summary  like, "focus at infinity with the aperture being FL / 5". Or did you closely study  that, more or less reject it, and came up with a different, but perhaps equally unconventional approach?

I'll address my confusion on the issue of just how accurately it seems you'd have to have the horizon trees at the center, APS-C rule-of-thirds, and extreme corners in terms of distance in a separate post later.

And really, I want to be once again in error ... that TNIHT (tilted near-infinity horizon testing) is a relative "piece of cake" compared to brick-wall testing and still provides valid captures for whether to return a lens.

I learn less on the rare occasions when I'm correct than on the more typical posts when you point out my ignorance / misconceptions / carelessness.

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JimKasson
JimKasson Forum Pro • Posts: 26,866
Re: Full sized images
1

l_d_allan wrote:

JimKasson wrote:

l_d_allan wrote:
Since you don't care whether the sky blows out or not, seems like you could use a longer exposure ... the EXIF shows EC of -1.3 EV. Do recall if you used "A" mode with EC, or "M" exposure with EC ignored?

A mode with EC set to -1.3. Noise is not a problem in this scene, and I didn't want to blow the highlights on the leaves, which don't show up in blinkies or the histogram.

Good point.

  • I don' t have that lens, so have no basis of comparison on what the center, near edges at the APS-C off-axis, and extreme corners should look like.
  • I also don't enough experience with TNIH to comment on perceived IQ.
  • We apparently differ on whether validly done TNIH captures tends to be better, worse, or about the same as a validly done brick wall IQ test for GCVBCT.

Ideally, we could test with a very large brick wall 500m away.:-)

Roger C at LR has wistfully written about renting a billboard in order to get far enough away ... and not just for super-telephotos as I recall.

  • If so, have you checked out how far trees at the "left horizon" are vs the "middle horizon" vs "right horizon"? My experience is there is a definite "learning curve" to estimating distances, but with practice you can get pretty good at it ... such as golfers and hunters.

Everything is well over the critical 200m.

Is that from your "Object DOF" studies? With the earlier link regarding the Otus 55mm at various apertures focused at 10,000 meters (10 km).
http://www.dpreview.com/forums/post/58031944

Yes.

If so, the "200" seems associated with the MTF-50 label with units of cy/ph.

You're thinking about the chart wrong. To get to 200, take the f.2,8 (yellow( curve, and track it back to where it starts bending down at 500m. Then convert 500m for a 55mm lens to 200m for a 35mm lens by multiplying by the square of the focal length ratio.

That puts the relevant MTF50 over 1600 cy/pn.

Does that indicate relatively poor (if not grossly unacceptable) 200 cy/ph IQ? Wrong link? Low or no comprehension on my part?

See above.

My experiences seem different, but the FL and aperture are very different:
With a fast zoom at 4x longer 200mm but two stops slower f/2.8, focus still mattered more than I expected. My rusty math is that for DOF purposes, I can't use the the chart for the Otus 55mm f/1.4 and the 200mm f/2.8.

with a 200mm lens, you'd multiply the 500m by (200/55)^2 = 3.6 and get almost 2 km. That would be incredibly conservative for a zoom, but maybe not for the Nikon or Canon 200/2 lenses.

Even ignoring that the Otus is sharper by at least 100 cy/ph at f/2.8 that the zoom, aperture is non-linear square, but FL may be linear?

As you have seen, hyperfocal distance varies as the square of the focal length.

Or is it more complicated than that, and I need to carefully read 100's of pages of TLW blog articles ... after retaking some math classes and taking one or several courses in Optics?

Sounds fun to me...

Back to my fast zoom at 200mm f/2.8:
There were neighborhoods perhaps several miles away. Focus was still critical. With magnified LiveView, focus on the roof tiles of the Red house was obviously invalid for the Blue house just to the front of it or rear of it.

I've notices with my Nikon 500/4 that I can focus on something half a mile away and have hills 5 miles away be obviously OOF.

Focus at near infinity to Cheyenne Mountain signal towers at perhaps 20 miles away was obviously unacceptable for the Red house maybe 2 miles away. Also unacceptable for signal towers maybe 5 miles away?

I've never tried it, but my speculation is that at dusk and if I focused on a partial moon, that might not to appropriate for the Cheyenne Mountain towers.

A doubt that; see the above 200mm lens calculation.

Going back to the 200m issue with your Otus 55mm ... I will reluctantly concede that if I made a large'ish print with the focus distance recommended by the Object DOF approach, that DOF / CoC might be adequate ... if I used the full frame.

To me, that ignores the factor of cropping, which I don't think can and should be ignored.

Cropping linearly affects cy/ph.

If the lens + sensor is critically focused and is capable of A3+ 13x19" prints from 25% of the full frame, that's how I want to focus. And that includes for GCVBCT.

I think the argument that "as long as you can make large prints at 300 dpi, it doesn't matter" is maybe obsolete with Super-Exmor's with 42 mpx that encourage and allow significant cropping. I'll admit I need to think that through more carefully.

I'll look for the .DNG's. If necessary, I'll add to my "to do list" to re-take those images on another super clear day, and be that much more careful.

Is that consistent to the "extinction graphs" for a 200mm lens at f/2.8? It might be just an average 'L' prime, but it's a zoom with a reputation for stellar IQ, world class build quality / control.

I will attempt to read and comprehend what I think of as your Object DOF related extinction graphs. Maybe a light will go on?

Is there a graph on your web-site that would have 'extinction lines" that reflect a high quality 200mm lens?

Take the 55mm graphs and multiply the distances by 3.6.

Would I be better off testing my admittedly less capable FE55, and attempting to extrapolate to your Otus 55?

Those lenses aren't very far apart at all  in the middle of the frame, at f/4 and narrower.

If I went back thru the previously ignored 20+ articles of the Object Mode + Protocol, would I find a "extinction graph" for the FE55?

No. I never modeled it. I haven't collected sufficient data.

I realize those graphs aren't answering the questions I'm asking. I'm being slow how they relate to GCVBCT, other than maybe how critical alignment is or isn't.

BTW, my impression is that you ended up your Object Model DOF in general or specific agreement with the paper that had the concluding summary like, "focus at infinity with the aperture being FL / 5". Or did you closely study that, more or less reject it,

Yes.

and came up with a different, but perhaps equally unconventional approach?

No.

I'll address my confusion on the issue of just how accurately it seems you'd have to have the horizon trees at the center, APS-C rule-of-thirds, and extreme corners in terms of distance in a separate post later.

And really, I want to be once again in error ... that TNIHT (tilted near-infinity horizon testing) is a relative "piece of cake" compared to brick-wall testing and still provides valid captures for whether to return a lens.

I learn less on the rare occasions when I'm correct than on the more typical posts when you point out my ignorance / misconceptions / carelessness.

I hope the above helps.

Jim

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JimKasson
JimKasson Forum Pro • Posts: 26,866
Re: Full sized images

osv wrote:

JimKasson wrote:

These are full frame. Sorry for the earlier error. Comments?

landscapes shot wide open are problematic, but if that's all we could judge by, i'd have returned that lens for a refund, not an exchange.

the lack of vignetting indicates that it's been massaged(in camera?),

Shading Comp was set to "Auto". It would be hard to judge sharpness with no corner boost at all, but I probably should have done the boos in post.

so if that's the criteria, here is my fdn 35/2.8 wide open, with some vignetting correction and a bit of sharpening... i sold the lens because one side didn't clean up when stopped down, but now i'm wondering if that was a mistake.

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dan

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l_d_allan
l_d_allan Veteran Member • Posts: 5,087
Bottom line: Are we in 'heated agreement' that Advanced DOF calculators With.Flexible.CoC's are OK?

JimKasson wrote:

Skipping to the "bottom line" of this post with

  • "Yes .. we both reject the pdf paper from the 1990's for view cameras (I don't recall the professors name ... started with "M"? ... advocated by Jerry F.)(?
    and
  • "No ... not a different approach" ...

Does that mean that we have been in "heated agreement" all along that advanced DOF calculators with flexible CoC's are fine?

Hmmmm ... I suspect I could do a Google search for "site:dpreview.com l_d_allan advanced DOF calculator", and probably find at least 5 times over the past 3 years where I'm suggested more or less that. (checked ... 56 hits, with Google removing some but nearly all duplicates, from less than a year ago)

However, I suspect that it might be a worthwhile exercise to understand DOF to "switch gears" from my standard, conventional DOF understanding to what you are advocating.

I recall when I was writing compilers and then assemblers, I could get them to work with an iterative approach, but "recursive descent" was much preferred once my brain adjusted.

If we have been in "heated/violent agreement", please ignore the remainder of this post.

If not ...

l_d_allan wrote:

If so, the "200" seems associated with the MTF-50 label with units of cy/ph.

You're thinking about the chart wrong. To get to 200, take the f.2,8 (yellow( curve, and track it back to where it starts bending down at 500m. Then convert 500m for a 55mm lens to 200m for a 35mm lens by multiplying by the square of the focal length ratio.

That puts the relevant MTF50 over 1600 cy/pn.

OK (and again thanks for your patience). It is added motivation to tackle the related TLW blog articles.

Does that indicate relatively poor (if not grossly unacceptable) 200 cy/ph IQ? Wrong link? Low or no comprehension on my part?

See above.

My experiences seem different, but the FL and aperture are very different:
With a fast zoom at 4x longer 200mm but two stops slower f/2.8, focus still mattered more than I expected. My rusty math is that for DOF purposes, I can't use the the chart for the Otus 55mm f/1.4 and the 200mm f/2.8.

with a 200mm lens, you'd multiply the 500m by (200/55)^2 = 3.6 and get almost 2 km. That would be incredibly conservative for a zoom, but maybe not for the Nikon or Canon 200/2 lenses.

At least by reputation, it's a darn good zoom. However, DxoMark res numbers do indicate the Canon 200mm f/2L is significantly sharper at f/2.8.

And ... even though I'm aware than non-linear relationships increase quickly, I probably don't fully appreciated how much.

Even ignoring that the Otus is sharper by at least 100 cy/ph at f/2.8 that the zoom, aperture is non-linear square, but FL may be linear?

As you have seen, hyperfocal distance varies as the square of the focal length.

No yet seen, but maybe after a careful reading (and a good night's sleep)

Or is it more complicated than that, and I need to carefully read 100's of pages of TLW blog articles ... after retaking some math classes and taking one or several courses in Optics?

Sounds fun to me...

I don't disagree, but I'll be missing some deadlines shortly.

** EDIT ** I'll hold off on continuing and assume we have been in "heated agreement".

Back to my fast zoom at 200mm f/2.8:
There were neighborhoods perhaps several miles away. Focus was still critical. With magnified LiveView, focus on the roof tiles of the Red house was obviously invalid for the Blue house just to the front of it or rear of it.

I've notices with my Nikon 500/4 that I can focus on something half a mile away and have hills 5 miles away be obviously OOF.

Focus at near infinity to Cheyenne Mountain signal towers at perhaps 20 miles away was obviously unacceptable for the Red house maybe 2 miles away. Also unacceptable for signal towers maybe 5 miles away?

I've never tried it, but my speculation is that at dusk and if I focused on a partial moon, that might not to appropriate for the Cheyenne Mountain towers.

A doubt that; see the above 200mm lens calculation.

Going back to the 200m issue with your Otus 55mm ... I will reluctantly concede that if I made a large'ish print with the focus distance recommended by the Object DOF approach, that DOF / CoC might be adequate ... if I used the full frame.

To me, that ignores the factor of cropping, which I don't think can and should be ignored.

Cropping linearly affects cy/ph.

If the lens + sensor is critically focused and is capable of A3+ 13x19" prints from 25% of the full frame, that's how I want to focus. And that includes for GCVBCT.

I think the argument that "as long as you can make large prints at 300 dpi, it doesn't matter" is maybe obsolete with Super-Exmor's with 42 mpx that encourage and allow significant cropping. I'll admit I need to think that through more carefully.

I'll look for the .DNG's. If necessary, I'll add to my "to do list" to re-take those images on another super clear day, and be that much more careful.

Is that consistent to the "extinction graphs" for a 200mm lens at f/2.8? It might be just an average 'L' prime, but it's a zoom with a reputation for stellar IQ, world class build quality / control.

I will attempt to read and comprehend what I think of as your Object DOF related extinction graphs. Maybe a light will go on?

Is there a graph on your web-site that would have 'extinction lines" that reflect a high quality 200mm lens?

Take the 55mm graphs and multiply the distances by 3.6.

Would I be better off testing my admittedly less capable FE55, and attempting to extrapolate to your Otus 55?

Those lenses aren't very far apart at all in the middle of the frame, at f/4 and narrower.

If I went back thru the previously ignored 20+ articles of the Object Mode + Protocol, would I find a "extinction graph" for the FE55?

No. I never modeled it. I haven't collected sufficient data.

I realize those graphs aren't answering the questions I'm asking. I'm being slow how they relate to GCVBCT, other than maybe how critical alignment is or isn't.

BTW, my impression is that you ended up your Object Model DOF in general or specific agreement with the paper that had the concluding summary like, "focus at infinity with the aperture being FL / 5". Or did you closely study that, more or less reject it,

Yes.

and came up with a different, but perhaps equally unconventional approach?

No.

I'll address my confusion on the issue of just how accurately it seems you'd have to have the horizon trees at the center, APS-C rule-of-thirds, and extreme corners in terms of distance in a separate post later.

And really, I want to be once again in error ... that TNIHT (tilted near-infinity horizon testing) is a relative "piece of cake" compared to brick-wall testing and still provides valid captures for whether to return a lens.

I learn less on the rare occasions when I'm correct than on the more typical posts when you point out my ignorance / misconceptions / carelessness.

I hope the above helps.

Jim

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JimKasson
JimKasson Forum Pro • Posts: 26,866
Heated agreement?

l_d_allan wrote:

JimKasson wrote:

Skipping to the "bottom line" of this post with

  • "Yes .. we both reject the pdf paper from the 1990's for view cameras (I don't recall the professors name ... started with "M"? ... advocated by Jerry F.)(?
    and
  • "No ... not a different approach" ...

Does that mean that we have been in "heated agreement" all along that advanced DOF calculators with flexible CoC's are fine?

Within their limitations. They don't take into account diffraction or lens aberrations, or the blurring effect of modern camera's nearly 100% fill factor.

Hmmmm ... I suspect I could do a Google search for "site:dpreview.com l_d_allan advanced DOF calculator", and probably find at least 5 times over the past 3 years where I'm suggested more or less that. (checked ... 56 hits, with Google removing some but nearly all duplicates, from less than a year ago)

However, I suspect that it might be a worthwhile exercise to understand DOF to "switch gears" from my standard, conventional DOF understanding to what you are advocating.

I recall when I was writing compilers and then assemblers, I could get them to work with an iterative approach, but "recursive descent" was much preferred once my brain adjusted.

If we have been in "heated/violent agreement", please ignore the remainder of this post.

If not ...

Not(ish)

l_d_allan wrote:

If so, the "200" seems associated with the MTF-50 label with units of cy/ph.

You're thinking about the chart wrong. To get to 200, take the f.2,8 (yellow( curve, and track it back to where it starts bending down at 500m. Then convert 500m for a 55mm lens to 200m for a 35mm lens by multiplying by the square of the focal length ratio.

That puts the relevant MTF50 over 1600 cy/pn.

OK (and again thanks for your patience). It is added motivation to tackle the related TLW blog articles.

Does that indicate relatively poor (if not grossly unacceptable) 200 cy/ph IQ? Wrong link? Low or no comprehension on my part?

See above.

My experiences seem different, but the FL and aperture are very different:
With a fast zoom at 4x longer 200mm but two stops slower f/2.8, focus still mattered more than I expected. My rusty math is that for DOF purposes, I can't use the the chart for the Otus 55mm f/1.4 and the 200mm f/2.8.

with a 200mm lens, you'd multiply the 500m by (200/55)^2 = 3.6 and get almost 2 km. That would be incredibly conservative for a zoom, but maybe not for the Nikon or Canon 200/2 lenses.

At least by reputation, it's a darn good zoom.

It can be a darn good zoom and still not be as sharp as a darn good prime.

However, DxoMark res numbers do indicate the Canon 200mm f/2L is significantly sharper at f/2.8.

And ... even though I'm aware than non-linear relationships increase quickly, I probably don't fully appreciated how much.

Even ignoring that the Otus is sharper by at least 100 cy/ph at f/2.8 that the zoom, aperture is non-linear square, but FL may be linear?

As you have seen, hyperfocal distance varies as the square of the focal length.

No yet seen, but maybe after a careful reading (and a good night's sleep)

Or is it more complicated than that, and I need to carefully read 100's of pages of TLW blog articles ... after retaking some math classes and taking one or several courses in Optics?

Sounds fun to me...

I don't disagree, but I'll be missing some deadlines shortly.

** EDIT ** I'll hold off on continuing and assume we have been in "heated agreement".

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l_d_allan
l_d_allan Veteran Member • Posts: 5,087
Re: Heated agreement?

JimKasson wrote:

l_d_allan wrote:

JimKasson wrote:

Skipping to the "bottom line" of this post with

  • "Yes .. we both reject the pdf paper from the 1990's for view cameras (I don't recall the professors name ... started with "M"? ... advocated by Jerry F.)(?
    and
  • "No ... not a different approach" ...

Does that mean that we have been in "heated agreement" all along that advanced DOF calculators with flexible CoC's are fine?

Within their limitations. They don't take into account diffraction or lens aberrations,

I infer that the DOF calculators would assume a "Perfect Lens". Thus, the usable DOF would invariably be less than the distance value from a DOF calculator, for a specific cy/ph value?

I guess the way of thinking you are advocating might be:

  • If you are expecting or need at least 1000 cy/ph with a real world lens
  • Then don't depend on DOF calculators
  • Which ignore lens imperfections.
  • The near and far objects will be softer than you expect.
  • (and I realize that no DOF calculator I've seen works in terms of numerical resolution values like cy/ph )

OK ... that's worth knowing. Thanks!

or the blurring effect of modern camera's nearly 100% fill factor.

Due to "blooming"? From non-perfect electronics? Cross-talk (or rough equivalent)?

If we have been in "heated/violent agreement", please ignore the remainder of this post.

If not ...

Not(ish)

Thanks for your thoroughness (and patience).

My experiences seem different, but the FL and aperture are very different:
With a fast zoom at 4x longer 200mm but two stops slower f/2.8, focus still mattered more than I expected. My rusty math is that for DOF purposes, I can't use the the chart for the Otus 55mm f/1.4 and the 200mm f/2.8.

with a 200mm lens, you'd multiply the 500m by (200/55)^2 = 3.6 and get almost 2 km. That would be incredibly conservative for a zoom, but maybe not for the Nikon or Canon 200/2 lenses.

At least by reputation, it's a darn good zoom.

It can be a darn good zoom and still not be as sharp as a darn good prime.

However, DxoMark res numbers do indicate the Canon 200mm f/2L is significantly sharper at f/2.8 [than the fast zoom]

Good catch ... thx. I carelessly left off the essential clause to convey "prime at f/2.8 significantly better than zoom at wide open f/2.8".

And mea culpa I was even more careless. There actually aren't DxO numbers for the very pricey Canon 200mm f/2L. I think I may have been referring to the fast zoom compared to the also pricey, but tested Canon EF 400mm f/2.8L IS ii ?

http://www.dxomark.com/Lenses/Compare/Side-by-side/Canon-EF70-200mm-f28L-IS-II-USM-on-Canon-EOS-5DS-R-versus-Canon-EF-400mm-F28L-IS-II-USM-on-Canon-EOS-5DS-R__408_1009_401_1009

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JimKasson
JimKasson Forum Pro • Posts: 26,866
Re: Heated agreement?

l_d_allan wrote:

JimKasson wrote:

l_d_allan wrote:

JimKasson wrote:

Skipping to the "bottom line" of this post with

  • "Yes .. we both reject the pdf paper from the 1990's for view cameras (I don't recall the professors name ... started with "M"? ... advocated by Jerry F.)(?
    and
  • "No ... not a different approach" ...

Does that mean that we have been in "heated agreement" all along that advanced DOF calculators with flexible CoC's are fine?

Within their limitations. They don't take into account diffraction or lens aberrations,

I infer that the DOF calculators would assume a "Perfect Lens". Thus, the usable DOF would invariably be less than the distance value from a DOF calculator, for a specific cy/ph value?

I guess the way of thinking you are advocating might be:

  • If you are expecting or need at least 1000 cy/ph with a real world lens
  • Then don't depend on DOF calculators
  • Which ignore lens imperfections.
  • The near and far objects will be softer than you expect.
  • (and I realize that no DOF calculator I've seen works in terms of numerical resolution values like cy/ph )

OK ... that's worth knowing. Thanks!

It can be looked at the other way, too. Lens aberrations, etc, make defocusing relatively less important near the in-focus point.

or the blurring effect of modern camera's nearly 100% fill factor.

Due to "blooming"? From non-perfect electronics? Cross-talk (or rough equivalent)?

Nope. Because the camera isn't a bunch of point samplers in an array. It gathers light from nearly the whole pixel area, thanks to things like BSI and micro lenses. That makes it more blurry than a perfect point sampler, but also more resistant to aliasing.

If we have been in "heated/violent agreement", please ignore the remainder of this post.

If not ...

Not(ish)

Thanks for your thoroughness (and patience).

My experiences seem different, but the FL and aperture are very different:
With a fast zoom at 4x longer 200mm but two stops slower f/2.8, focus still mattered more than I expected. My rusty math is that for DOF purposes, I can't use the the chart for the Otus 55mm f/1.4 and the 200mm f/2.8.

with a 200mm lens, you'd multiply the 500m by (200/55)^2 = 3.6 and get almost 2 km. That would be incredibly conservative for a zoom, but maybe not for the Nikon or Canon 200/2 lenses.

At least by reputation, it's a darn good zoom.

It can be a darn good zoom and still not be as sharp as a darn good prime.

However, DxoMark res numbers do indicate the Canon 200mm f/2L is significantly sharper at f/2.8 [than the fast zoom]

Good catch ... thx. I carelessly left off the essential clause to convey "prime at f/2.8 significantly better than zoom at wide open f/2.8".

And mea culpa I was even more careless. There actually aren't DxO numbers for the very pricey Canon 200mm f/2L. I think I may have been referring to the fast zoom compared to the also pricey, but tested Canon EF 400mm f/2.8L IS ii ?

http://www.dxomark.com/Lenses/Compare/Side-by-side/Canon-EF70-200mm-f28L-IS-II-USM-on-Canon-EOS-5DS-R-versus-Canon-EF-400mm-F28L-IS-II-USM-on-Canon-EOS-5DS-R__408_1009_401_1009

The Canon has a great rep. I have the Nikon 200/2 VRI, and I can assure you that it is one sharp lens. I'll bet the Canon is as well.

Jim

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