Cross platform equivalency

Started Apr 25, 2014 | Discussions thread
Rick Knepper
OP Rick Knepper Forum Pro • Posts: 16,348
Re: Cross platform equivalency

meland wrote:

Rick Knepper wrote:

PhotoKhan wrote:

Rick Knepper wrote:

The cons: 3 fps.

Another drawback: It seems there are no faster lens than f/2.8 on the DFA/FA and Pentax 67 lineups.

Not a drawback for many types of landscape (and for most of my style). Maybe for some types of landscape and some types studio work - for isolation purposes.

The equivalent would be f2.2 on FF. I have three Zeiss f2 lenses and I rarely use them wide open in most of my landscape endeavors (infinity distances) because, frankly, they aren't sharp enough (Otus style ) in the corners wide open. If any of the f2.8 645Z lenses are sharp into the corners wide open or a stop down, that'll be good enough for me.

That may be the stumbling block Rick. Historically very few MF lenses have been as high resolution, or as even in resolution across the frame as those for 35mm. It's not that they couldn't be but the minute volumes produced (in comparison with 35mm / FF lenses) means that to build the things to provide the same IQ as the best 35mm lenses would make them incredibly expensive. Throw AF into the mix which requires internal focussing and things get hard.

However the additional area of coverage required for the 645Z lenses is not actually that much greater than 35mm so by keeping the max aperture to a reasonable limit one hopes that Pentax manage to design (and actually realise in production) lenses that won't disappoint.

As someone else suggested, there may not be a linear equivalency in sharpness.

I am looking for a source of MTF charts for the Pentax 645 lenses but so far, no luck.

-Rick Knepper, photographer, shooting for pleasure. It is better to have It and not need It than need It and not have It. Various RAW comparisons at Link below. Includes 5D3 vs D800E (new uploads), 5D3 vs. 6D, Zeiss lenses etc.

 Rick Knepper's gear list:Rick Knepper's gear list
Pentax 645Z Canon EOS 5DS R Fujifilm GFX 50S Pentax smc D FA 645 55mm F2.8 AL (IF) SDM AW Pentax DA645 28-45mm F4.5 +8 more
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