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

Started Jul 5, 2016 | Questions thread
JimKasson Forum Pro • Posts: 26,554
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.)(?
  • "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 " 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.

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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