Pentax FF lens linup based on Canon L

npc · 05-21-2015, 10:16 PM

If you mount a FF lens on ASPC .. say 43 ltd. The only thing that changes is the field of view simply because the rest of the image projected gets cropped.
F-stop is the same, DoF is the same, amount of light hitting a square mm is the same, diffraction is the same and so on. On ASPC diffraction will be visible earlier compared to FF if pixel count is same. Actually even DoF will be theoretically thinner on ASPC since circle of confusion will get bigger than the pixel size sooner (same for diffraction). If pixel size is constant say 36Mpix FF vs 16Mpix ASPC really only FoV changes if you switch from FF to crop mode.

aleonx3 · 05-21-2015, 11:18 PM

Originally posted by npc

If you mount a FF lens on ASPC .. say 43 ltd. The only thing that changes is the field of view simply because the rest of the image projected gets cropped.
F-stop is the same, DoF is the same, amount of light hitting a square mm is the same, diffraction is the same and so on. On ASPC diffraction will be visible earlier compared to FF if pixel count is same. Actually even DoF will be theoretically thinner on ASPC since circle of confusion will get bigger than the pixel size sooner (same for diffraction). If pixel size is constant say 36Mpix FF vs 16Mpix ASPC really only FoV changes if you switch from FF to crop mode.

That's the advantage of using FF lens on an APS-C camera only you said it better than me. I think probably more people will be going after good/fast k-mount and m42 manual lenses once the Pentax FF camera is released later this year.

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05-21-2015, 10:16 PM	#31
npc Veteran Member Join Date: Apr 2013 Posts: 313	If you mount a FF lens on ASPC .. say 43 ltd. The only thing that changes is the field of view simply because the rest of the image projected gets cropped. F-stop is the same, DoF is the same, amount of light hitting a square mm is the same, diffraction is the same and so on. On ASPC diffraction will be visible earlier compared to FF if pixel count is same. Actually even DoF will be theoretically thinner on ASPC since circle of confusion will get bigger than the pixel size sooner (same for diffraction). If pixel size is constant say 36Mpix FF vs 16Mpix ASPC really only FoV changes if you switch from FF to crop mode.

05-21-2015, 11:18 PM	#32
aleonx3 Veteran Member Join Date: Jul 2007 Location: Brampton, Ontario Photos: Gallery \| Albums Posts: 3,996	Originally posted by npc If you mount a FF lens on ASPC .. say 43 ltd. The only thing that changes is the field of view simply because the rest of the image projected gets cropped. F-stop is the same, DoF is the same, amount of light hitting a square mm is the same, diffraction is the same and so on. On ASPC diffraction will be visible earlier compared to FF if pixel count is same. Actually even DoF will be theoretically thinner on ASPC since circle of confusion will get bigger than the pixel size sooner (same for diffraction). If pixel size is constant say 36Mpix FF vs 16Mpix ASPC really only FoV changes if you switch from FF to crop mode. That's the advantage of using FF lens on an APS-C camera only you said it better than me. I think probably more people will be going after good/fast k-mount and m42 manual lenses once the Pentax FF camera is released later this year.