Re: [Leica] Leica: MTF question.

[Duncan Young <dunk@mincom.com>]

On Fri, 24 Apr 1998, Dan Post wrote:

> I hope this doesn't start a flame war, but the recent discussion of
> Modulation Transfer Function, aside from the concommitant copyright
> discussion has me a bit confused.
> In Neblette's book on photography, he holds that the MTF is a 'system'
> measurement and includes not just the camera and lens, but the film, and
> processing, at the very least. This would mean that for each film/developer
> combination, there would be a different MTF chart, even with the same lens
> and camera combination. I got the impression that the MTF was of limited use
> for judging a camera/lens. It rather gave a generalized idea of the
> performance, that taken with other data, the MTF is merely a component of a
> method for evaluating optical systems.

One can create a MTF chart for just a lens ( use an arial image ) and one
can create an MTF chart for film ( use contact printing ).

> I could see that if the tester standardized his film and development, say
> with Hurter and Driffield's formulas for sensitometric evaluation, and
> tested many camera and lens combinations, that you could make judgements for
> that 'population' of cameras, at that particular time, and for under that
> particular film andeveloper combination.
> If one goes on to make prints, then MTF data should include testing the
> camera/lens combinations with the particular enlarger lens/paper/development
> data... I can understand the concept of multivariant analysis, but it seems
> that pretty soon, you end up picking the fly spots out of the pepper, and
> really not getting anywhere.
> I can tell you that when I started to use a Leica, I had to hustle to get a
> lens on my enlarger that could do justice to the negatives. I use Vivitar
> VHE lenses- they were the best I could get, and I am sure that if I got a
> Leitz lens, I could even see more improvement!
> Do they now use lasers for MTF? What is the process today? Is it able to be
> standardized so that a lab on one continent can reproduce the results of a
> lab elsewhere?

Duncan