On 22 Jul 2002 01:56:37 GMT, artkramr@aol.com (ArtKramr) wrote:

>>Subject: Re: How To Test My Lenses
>>From: "Alan Chan" wlachan@telus.net
>>Date: 7/21/02 6:28 PM Pacific Daylight Time
>>Message-id: <3dJ_8.18090$8D4.548263@news2.telusplanet.net>
>>
>>I have not followed this closely so I might miss something. What I have
>>noticed is that most people who so concerned about sharpness or resolution
>>of their lenses, often missed other characteristics of their lenses which
>>might affect the final output in practice. A sharper lens is not necessarily
>>a better lens imo.

>>> Yes - that is why I test. The results tell me if the lens
>>> is substandard or not (a simple comparison of the two short
>>> edges of subsequent frames, shot at the same wide stop and
>>> focus, of the same distant detailed subject, tells me if
>>> the lens is optically well-aligned, and if so, it is likely
>>> also to be about as sharp as another good sample of the
>>> same lens), and how it compares with other similar-FL
>>> lenses... In the process of simple alignment, wide vs.
>>> middle aperture sharpness, and corner vs. center sharpness
>>> testing on film, you can also get info on distortion, flare,
>>> etc. by using simple VF tests.
>>> (See: www.David-Ruether-Photography.com/slemn.html.)
>>> DR

>Your post brings to mind a series of landmark optical tests that Kodak ran some
>years back. They were known as the JND tests. JND stands for "Just Noticeable
>Difference". Kodak was out to determine how small a difference in results the
>human eye could detect. They made hundreds of prints and showed them to a wide
>variety of viewers from professional photographers to amateurs to casual
>snapshooters. The got the information they wanted, but something else emerged
>that was even more important than the original test goals. They found out that
>prints that were of higher contrast were perceived as being sharper even though
>they were actually less sharp. Of course, in lens design we balance contrast
>and resolution. If the greatest sharpness [resolution] is wanted, it is at the price of
>contrast and conversely. As a result Kodak designed the Commercial Ektars which
>optimized contrast. Nobody noticed that they weren't all that sharp.
>Arthur Kramer
>Visit my WW II B-26 website at:
>http://www.coastcomp.com/artkramer

I suspect that commonly, "sharpness" is taken as the
subjective combination of resolution and contrast...
In video this is a common problem - people have
trouble seeing that certain camcorders have (rather
obviously) lower resolution capability than some others
that have lower (and more suitable for general use)
image contrast. With lenses for stills, though, it is
preferable to maximize both contrast and resolution
(through good design), though ultimately there is a
need to trade off one for the other, and arrive at the
most ideal balance.
One example supporting what you report: I bought a
Rollei 35 with a 4-element Tessar-type lens that tests
not very high in resolution toward the image corners.
I sold it in favor of the model with a 5-element lens
that had obviously higher resolution in the corners.
My slides never had the "snap" of those shot with the
earlier camera, *even in the corners*. I sold the
"better" version and returned to using the "worse"...;-)