Re: Kodachrome inventors

[P3D John Ohrt <johrt@xxxxxxx>]

P3D John Fairstein wrote:

> See http://www.kodak.com/ppiHome/technicalPubs/ePubs/e55/f002_0489ac.gif
> for an interesting graph of modulation transfer for Kodachrome 64. Does
> the Realist 3.5 lens rated at 80 lines/mm exceed the resolving power of
> the film?

Modulation transfer function is a measure of "accuatance" (sp?) which is
subtlely different than resolution.

However, (and lacking my notes) Kodachrome 64 likely has a resolution
greater than 100 lpm.

The reason modulation transfer is quoted is that in the old days before
ISO, MTF is a better characteristic to know as it considers the MT at each
point of resolution.  The resolution measurement of the applicable ISO
standard for film only measures the resolution at which lines can be
resolved.

Furthermore MTF uses sinusoidally modulated lines whereas resolution uses
square wave modulation.

Optical engineers still use MTF and optical manufacturers will use it as a
baseline specification.

If all this means nothing, ignore it.  There are few films not having a
resolution meeting or exceeding 80 lpm at high contrast, which are the
conditions you are implicitly quoting.  At low contrast, you will get both
different numbers for the lens and the film.

Regards,

--

John Ohrt * Toronto * ON * Canada






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