RogerCicala said:3kramd5 said:RogerCicala said:3kramd5 said:ahsanford said:3kramd5 said:Much like nobody outside a semiconductor OEM is likely to have good reason to test a sensor without a lens, nobody is going to use a camera lens without a camera (unlike say a microscope or binoculars).
Obi Rog Kenobi at LR pets his beloved OLAF... and feels a powerful disturbance in the force.
- A
Right. There he is testing it, but not using it. I betcha when Roger uses his camera lenses, they’re mounted to cameras
Granted you have to have to use it to test it, but the distinction is clear enough.
Science, as I was trained to do it, is about eliminating as many variables as possible to test one variable in a reasonably large sample size. Hence, we test just the lenses and a reasonably large sample size of the lenses.
Carefully measuring one third grader and then stating that all third graders are 67.325 secret measurements tall is bad science.
Agreed, however
1) some of those variables are pertinent and may be unwise to eliminate (for example if an 85mm lens from brand A has fewer losses than an 85mm lens from brand B, it matters little to someone who can not use brand B lenses. Similarly, if you want an 85mm lens, focal length is a variable which should not be eliminated, whereas if you’re after the most perfect optics and will work around focal length, it can be), and
2) not all scientific data is readily usable. Your work is great and very interesting; I read your blogs including bench level lens testing. However I’ve yet to come up with a way to use an MTF chart.
In this particular instance, the variable I question eliminating is the camera sensor's optical stack.
I think we can agree that
A) the MTF of an optical system is a function of the MTF of the constituent members. That is true even when the optical system is a camera lens: each element has a transfer function, which contribute to the lens transfer function as a whole. Some elements are included to correct the affects of others.
B) since the advent of digital ILCs, lenses have been designed for the cameras to which they'll be mounted, ergo the sensor and its optical stack (as opposed to lenses designed for film cameras).
Some third party lenses may be sensor agnostic, but they probably should not be. Interviews with both Sigma and Laowa/Venus refer to the importance of designing for the optical stack. It's part of the path, indeed it's the final element before the sensor. Putting a lens on an optical bench without that stack to eliminate the variable eliminates the proper environment for the lens, similar to (though less impactful than) pulling the rear element off a camera lens.
Occam's razor and all, maybe I'm just dense. However, it seems to me that by isolating the variables to [camera lens], one introduces the risk that the remaining variable is being used inappropriately.
You do realize ... that we place the appropriate sensor stack in the optical path for each lens tested?
Clearly I did not. I did read in a blog (I believe) about optical glass being added for a given test but did not know it is done as a matter of course.
Kudos. My above post is redundant.
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