06-28-2016, 10:27 PM
The 70D should behave like any (older or newer) Canon DSLR, even with manual focus lenses. And like the 6D. Only with live view metering with "unknown" lenses (without aperture value), some cameras mess up where others get "correct" exposures (in manual exposure mode). My EOS M messes things up, my 6D gets exposure and exposure simulation right.
But with cameras that mess that up, set the camera in Av mode and things work like they should.
I use old manual focus lenses and because of the big apertures I like, I put a Canon Eg-S Super Precision focus screen in my 6D. It helps with judging if the image is in focus. With small aperture lenses, however, the image gets much more darkened than with the standard focus screen (like when I use my Tamron SP 500mm f8).
If you shoot at 160mm f4 on FF, and at 100mm f4 on APS-C, the FF shot will be shot with a larger aperture size. So, you get less DOF and more blur. Because you are not using equivalent f-stops. If you however shoot the FF image with f4 x 1.6 = 6.4 (so f6.3), you will get very similar images.
But with cameras that mess that up, set the camera in Av mode and things work like they should.
I use old manual focus lenses and because of the big apertures I like, I put a Canon Eg-S Super Precision focus screen in my 6D. It helps with judging if the image is in focus. With small aperture lenses, however, the image gets much more darkened than with the standard focus screen (like when I use my Tamron SP 500mm f8).
If you shoot at 160mm f4 on FF, and at 100mm f4 on APS-C, the FF shot will be shot with a larger aperture size. So, you get less DOF and more blur. Because you are not using equivalent f-stops. If you however shoot the FF image with f4 x 1.6 = 6.4 (so f6.3), you will get very similar images.