MF lenses on 35mm bodies???

[stradibarrius]

If I use a Mamiya M645 lens on my Nikon 35mm body with and adapter, how do I figure to focal length?

A 150mm M645 lens is what when placed on the 35mm body? The focal length is longer than my 35mm, 150mm lens.

[BetterSense]

Why would the focal length of the lens change when you put it on a different camera? If it's a 150mm lens, it's a 150mm lens.

[keithwms]

Yep, the field of view changes, not the focal length.

[stradibarrius]

Well a 645 lens is times .6 is approximately the 35mm equiv. When I put the 645 format 150mm lens on the 35mm nikon body it is longer than the 35mm, 150mm lense.

[keithwms]

No, a small format 150 and an MF 150 are equally "long" on the 35mm body. When you put the MF 150 on there, you simply throw away all the image circle outside the 35mm frame. Nothing magical happens to the focal length.

[MattKing]

As others have posted, the focal length doesn't change, but the field of view does.

I expect though that what you are asking is different from what you want to find out. I expect that you are really trying to determine something about equivalencies. Guess what - you will find that a 150mm lens for 6x4.5 is equivalent to ... a 150mm lens for 35mm.

You can work it out as follows (this is a very rough calculation).

It may be easiest to look at angles of view. The 150mm lens has a 26 degree angle of view on 6x4.5 film. The diagonal of 6x4.5 is about 75mm.

The 35mm frame has a diagonal of about 43mm.

So of those 26 degrees covered by the 150mm lens, about 43/75 x 26 = 15 degrees are captured by the 35mm frame.

What lens for 35mm format covers about 15 degrees? A 180mm lens covers 14 degrees, so that is close. A 150mm lens would be even closer .

[Curt]

I have have had that adapter for my m645 to Nikon for years but never used it very much. I forget even how the exposure works with it. If the center of the field is used would the image be a bit sharper? IDK.

[kauffman v36]

Curt, theoretically yes. Since the 35mm image uses only the center of the 645 lens its taking the sharpest part of the lens. BUT....many will argue that MF lenses (most) are not built to be as sharp as some 35mm lenses because they dont need to be enlarged so much....so it kinda cancels itself out. NOW, if you find a way to mount a mamiya 7 65 or 80mm lens on a 35mm body you will have one hell of a sharp image. but the counter argument is just get a zeiss or leica 35mm lens and itll be just as sharp.

[stradibarrius]

Matt, I think you have answered my question. The angle of the view is what I guess is different.

[2F/2F]

If I use a Mamiya M645 lens on my Nikon 35mm body with and adapter, how do I figure to focal length?

A 150mm M645 lens is what when placed on the 35mm body? The focal length is longer than my 35mm, 150mm lens.

If you read the lens focal length that is on the front of the lens (near the glass, written in a semicircular pattern) when it is on the Nikon, you will have your answer.