akpo.ca wrote:
Of course MTF charts are theoretical. That's why I mentioned decentering affecting performance and iq varies across different samples of the same lens. My $400 135/2 is pin sharp on a GFX, my 120/4 FAs are not. If you want to compare lenses please compare similar focal lengths and apertures. This is a thread about adapting lenses to the GFX, no?
Wrong again. Not all MTF charts are theoretical. The one's produced by Zeiss are for sure made from real tests with production copies of their lenses. More recently the Lens Rentals blog does tests of many lens on the same sort of equipment that Zeiss uses. The old photodo site also had tests with that same sort of equipment. It isn't clear whether Leica MTFs are from actual lens or not, but their MTF charts match the Photodo site quite closely, so if they aren't actual tests they seem to mirror them well. The Canon MTF are theoretical and do not account for at least one huge factor in real testing--diffraction--so they are not informative of real world performance.
As far as what lenses to compare, I think a lot of different tests are relevant when considering adapting lenses to the GFX. It certainly is relevant to a lot of folks how adapted lenses on the GFX compare to the know performance of excellent lenses on the FF 35mm. I started this thread and when I did I had such comparison in mind, so I think they certainly fall within the scope of this thread. Of course comparing different lenses on the GFX also makes a lot of sense for this thread as well. Both types of comparison, in my view, should be welcome and I don't need you to tell me what types of comparisons can and cannot be made here. Let's welcome all such comparisons.
Aug 20, 2017 at 09:55 AM
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