Re: LPM on Negative (TECH-3D digest 219)

[T3D John Ohrt <johrt@xxxxxxx>]

T3D Bob Howard wrote:

> RE: John Ohrt asks how one can discuss lpm on negative without
> considering degree of enlargement???
> I think this is implicit in 35mm and some large format photography as
> assuming a final print needing only 7 lpm for eye to look at.
> Eg. Weston's 8 x 10 contact prints didn't care if diffraction at f/64
> limited resolving power to 11 lpm or less as only 7 needed from
> viewing contact print.
> In 35mm work the original Holy Grail was to make a 5x7 print that
> would resemble a large format contact print! This perhaps today is
> now 8 x 10 or larger. So 80 lpm in neg at 10X enlargement would give
> 8 lpm in print (assuming no loss in enlarging lens!) BobH
> (I can't imagine a "portrait photographer" wanting 1600 lpm optical
> resolution to get something very high on film? :-)   )

Sounds good to me.

Thanks for the lesson.

However, for a 20x24 inch enlargement, a 20x enlargement would require
160 lpm registered on the negative.  Kodak ektar 25, royal gold 25,
Agfapan APX 25, Kodak techPan 2415, TMAX 100, can all deliver this with
a reasonable allowance for lens contributions.  I'm not aware of any
other films offering 200 lpm plus resolution.

Of course there are relatively few 20x24 anaglyphs floating around
<grin>.

Regards,


--

John Ohrt * Toronto * ON * Canada





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End of TECH-3D Digest 220
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