Doesn't look like a mystery to me. Forgetting all the MTF stuff and
just using the old system resolution formula 1/R_system = 1/R_film +
1/R_lens it would appear to me that your lenses are resolving near 150
lines or better. Remember that you're not measuring the lens but rather
the combination of lens and film.
The resolution of Velvia 100F is stated by Fuji to be 80 lines/mm at
contrast 1.6:1. Substitute that in the formula above and you'll find
you need a lens with 150 lines/mm to get a system resolution of 52
lines/mm. Even if your lenses could resolve 1000 lines/mm you still
only get a system resolution of 74 lines/mm using Velvia 100F.
Chuck Norcutt
james king wrote:
> I decided that it was time to try to have a go at measuring the
> performance of the lenses I have (both olympus and bronica partly to
> compare lenses across the two systems and partly because I was
> interested in the results.
> I use the norman koren MTF chart a large 1m square peice of board and
> assembled a test target. I bought a x20, x50 and x100 microscope used
> fuji velvia 100F with an om4ti using mirror and app prefire and a cable
> release on the bronica. I have a beattie grid screen with 45 degree
> split in the om4ti and used the olympus varimagnifier to check focusing
> and a maxwell grid screen with horizontal split in the bronica and used
> its pop up magnifier.
>
> I did the bronie first and was a little disconcerted by the results. As
> far as I could see at F8 and F11 I was not getting much output past 50
> or 60 line pairs per milimeter on any of the 7 lenses tested.
>
> Yesterday I got the olympus tests back
> olympus 24mm,28mm,35mm f2
> 35-70 f3.6
> 21 f3.5
>
> tamron 90mm f2.5
> tamron 80-200 f2.8 ed
> tamron 60-300
>
> the best of the results where no beter than the bronica in terms of line
> pairs per milimeter. I was careful to make sure that the mtf graphs are
> the same size on the film for both systems. Therefore the bronica shoots
> coverred more wall area than the olympus. What I did consistently
> observe was that wide open none of the 35mm film lenses could complete
> with the bronica lenses wide open but the performance of the tamron and
> olympus lenses did not degrade that much from f11 onwards. Whereas the
> bronica lenses do and at f32 the bronica lenses are nowhere near as
> sharp as the tamron 90mm at f32 for example.
> So drawing a graph of performance vs appature the bronic starts fairly
> good open drops a little at the next stop and then is best f5.6-11 and
> then tails fairly rapidly. The 35mm film lenses are poor wide open
> improve and tail off in many cases very slowly.
>
> Looking on the web good lenses are considered to be in the 80 line pairs
> per mm range and ziess claim 100 pairs plus for some of their lenses. I
> can see no way I can get anywhere near that with my setup...
> It is possible that I am asking too much of the lenses and that easily
> visible line pairs at 50 or 60 pairs per mm on the film is all the
> camera system/experimental setup can do?
>
> Regards
> James
>
>
>
>
>
>
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