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

Started Jul 5, 2016 | Questions thread
JimKasson
JimKasson Forum Pro • Posts: 26,539
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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