Originally posted by bull drinkwater it's the same principle as full frame vs a crop sensor. a smaller sensor captures a smaller portion of the image. the 645d has the smallest sensor ,the 645 lens was made for a bigger sensor, so you get a crop factor. if the 645d camera could switch back and forth between 645 and 645d, you'd see it in a hot second.
not meaning to give you a hard time, but I do this all the time. I shoot a sony a-850 a lot. it shifts between ff and asp with Minolta maxxum lenses you can see the diffefence , why wouldn't it be the same btween the 645d-645-and 6x7????
I'm fully aware of the crop factor of the 645D and how it affects the FOV. But if I read your earlier post correctly you said that the 6x7 35mm lens and the 645 35mm lens would give different results on the 645D. And that is the mistake I was trying to point out and correct. A 35mm lens is always a 35mm lens. The only difference between the 6x7 35mm lens and the 645 35mm lens is that the former has a larger image circle and that the former is a fisheye. Of course, depending on what camera the 35mm lens gets attached to and what frame size that camera captures the resulting FOV will be different. So the 645D with it's 44mm x 33mm sensor will crop out a larger percentage of the 6x7 35mm lens than it will when using the 645 35mm lens, but what remains in the captured image will be identical in terms of FOV.
If you want to think about in terms of full frame vs. aps-c, if I attach a Minolta 50/1.4 lens to my A77 camera and take a picture, and then with the help of a mount adapter, attach a medium format 50mm lens such as the Zenza Bronica Zenzanon-S 50/3.5 to the aps-c camera and take a picture, the two pictures will be identical, because a 50mm lens on an aps-c body always yields the same FOV.
Take a look at
this table for the actual FOV numbers in degrees. The far left column is the focal length in mm. The subsequent columns show the FOV in degrees for each frame size. According to this chart a 35mm lens on the 645D will yield a FOV of 64.3 degrees. And that is all I am saying. Regardless of whether the lens was originally designed for the 6x7 frame or the 645 frame, or for large format for that matter, it makes absolutely no difference. On a 645D they will all yield 64.3 degrees. I hope this helps.