RE: 35,MF,LF was RE: [Leica] FIGLIO4CAP@aol.com wrote:

["Jonathan Borden" <jborden@mediaone.net>]

InfinityDT@aol.com wrote:

>
> It seems like the math doesn't agree here.  Taking a 35mm neg and
> enlarging
> it to 6x7 cm (roughly 5x),  would it not produce an image
> equivalent to that
> of an original 6x7cm neg shot with a MF lens with 1/5 the
> resolving power?
> Checking the MTF results of various MF lenses on Photodo one
> finds nowhere
> near that kind of discrepancy.  Glad to hear from any experts in
> the field of
> optics who can authoritatively correct my thinking if it's incorrect.
>
> DT
The issue is the ability to resolve the finest test pattern. Compare the LF
neg using Tri-X with the 35mm neg using TMAX-100 ... there is absolutely NO
argument from me that the 35mm neg using Tri-X is way inferior to the LF neg
using Tri-X, but using TMAX-100 there isn't such a descrepancy.

Remember that the number of resolvable lines per millimeter (or line pairs
per millimeter), has to do with the *subject* not the negative itself.

A couple of edge cases may help to clarify your understanding.

1) Assume a 'perfect' film with no grain and infinite resolving power.
Regardless of the degree of enlargement of such a negative, the number of
LPM will depend on the lens *only*.

2) Assume a 'terrible' film with 1 mm grain. The resolving power of the
subject is *highly* dependent on the amount of film used to record the
subject and hardly on the lens (assuming the lens can resolve at least 1
lpm).

So you see that as the film becomes more fine grained, the quality of the
lens becomes more important and the size of the negative becomes less
important. Of course if an LF lens is produced which has equal resolution to
a 35mm lens in lpm across its field, *and* the film is able to record this
resolution, LF wins.

Jonathan Borden