Re: ye olde film v D debate, a bit long

[graywolf]

Come on now, Bill. He just did it for 36 lpm. 40 lpm is an overall system 
figure. The arial resolution of the lens is much higher, as is the film 
resolution. Folks have explained all this on the list over and over. Still we 
keep getting these outbursts of mumble-jumble. Tom gave the formula for any 
number of items in the system.

Overall-res = 1/((1/lens-res) + (1/film-res) + (1/enlarger-lens-res) + 
(1/elargeing-paper-res) + (1/viewing-loupe-res))

you can add any thing else you can think of to the equation, the answer will 
always be lower than the lowest figure in the equation. A diffraction limited 
large aperture lens can have arial resolutions around 600 lpm. The finest grain 
B&W film around 200 lpm. 1/(1/600) + (1/200) = 150 lpm. Which is about the 
maximum resolution for a film based system. We are talking Tech Pan here, and 
maybe a $5000 50mm lens.  With a good 50/1.4 Pentax lens we are talking maybe 
100 lpm. The same Pentax lens with color negative film you are talking that 40 
lpm you mention (on film, a print would be far lower).

--

William Robb wrote:
----- Original Message ----- 
From: "Tom Addison"
Subject: Re: ye olde film v D debate, a bit long




Time for maths!


Figure out what it needs to be for 40 lpmm, which more closely
resembles what the finest lenses really churn out.
William Robb



--
graywolf
http://graywolfphoto.com
"You might as well accept people as they are,
you are not going to be able to change them anyway."