LF resolution compared to smaller formats?

[Bill Glickman]

Danny, you sure did start a popular thread! The only other item I think was missed, and it seems we nailed them all, great contributions... the part of the image circle you are capturing in your film is very important also. If you are at the edge of the image circle, you can find very significant sharpness fall off. In the tests done by C. Perez, many of the edges fall offs can be 50%! And his test was only testing the edge of the film, not the edge of the image circle! It gets worse! This is very significant if the best part of the lens is only delivering 50 lpmm. The other related issue I would mention is this... for some reason, some lenses have f stop "sweet spots" that resolve excellent in comparison to the other f stops. My Fuji 600C shoots very poor at f11... If you look at the tests by C. Perez linked to this home page, you will see exactly what I am talking about. We are all interested to hear what Ron Wisner says also, he sure is a good resorice for this information. Since you already bought a camera from him, you can be assured his response will be non biased. Thank you for sharing on this thread...

[Ron Shaw]

Check out this site for a lot of useful info on large format lenses: http://www.hevanet.com/cperez/index.html Check out the lens tests, and especially the heading 'How to determine usable/meaningful resolution limits'.

[Patrick Chase]

Hi All;

Great thread!

One apology/clarification: Glenn Kroeger rightly points out that I got my estimates of diffraction-limited resolution wrong. Specifically, I used a relation (the Rayleigh criterion) which is specific to resolvability of adjacent point sources, and the way I used it to estimate the continuous (i.e. non-point sorce) case of an MTF target was very pessimistic. All that I'm really sure of now is that the real diffraction-limited resolution numbers are somewhere between what I posted and double what I posted.

Sorry about the confusion!

-- Patrick

[heidis]

Hello again! I'm back with interesting news to report. Today I picked up my test shot of trees/twigs shot with the Schneider 150mm Super Symmar XL. And...it's *very* sharp. Detail of tree bark and individual twigs can easily be seen with the 8x loupe. I didn't do any simultaneous shots with the Mamiya 7, so it's difficult to make a precise comparison based on non-identical subjects...but I'd have to say that it is only a *slight* amount less sharp than my Mamiya 6x7 chromes.

So...right now it looks like the Fuji 300mm lens is the likely culprit. I'm sending it to Ron Wisner for testing per his offer, and will await the results. Has anyone here gotten a brand-new major- brand lens that proved to have poor focus or other technical problems? Just bad beginner's luck, maybe?

I'll post additional info when I know more about the lens. Thanks again and happy shooting!

[Wayne_6692]

Don't rule out instability as a possible culprit. The 300mm requires 2x more bellows than the 150mm, wind or balance may have been a factor. I would have tested the lens with flash before sending it back.