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.

 

[2F/2F]

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 .

I'd think the closest common focal length would be a 135mm, not a 180mm. 135mm is 10 percent shorter than 150mm, and 180mm is 20 percent longer than 150mm.

 

[BrianL]

To see what happens and the effects of puting a mf lens on a 35mm camera find soeone with a Bronica ETRS series camera who has a 35mm back. You will see there is neither magnification or reduction in image size and the image size stays the same but the area covered is reduced. When you read that a 75mm mf lens is an equiv to about a 50mm 35mm lens, it refers to the area of coverage and not the magnification. If your friend has both the 50mm and 75mm lens switching to the 35m back and from the 75mm lens to the 50mm lens and you will see the area of coverage with the 35mm back and 50mm lens is very close to the 120 back with the 75mm lens.

This seems to be very confusing to the average person on the street now because of the digital advertising of focal lens lengths being published and then noting their equiv 35mm lengths.

 

[Q.G.]

I'd think the closest common focal length would be a 135mm, not a 180mm. 135mm is 10 percent shorter than 150mm, and 180mm is 20 percent longer than 150mm.

If 15 degrees over the diagonal is needed, the calculator says about 163 mm.

A 150 mm lens on 35 mm format has a diagonal angle of view of 16.4 degrees.

 

[Loris Medici]

- Lens focal length doesn't change between formats. Focal length is the property of the lens, NOT the format!
OTOH, as a side note, image circle / coverage requirements change between formats and this fact has to be taken into account when using lenses at different film formats, specifically in the case you plan to use a lens on a larger format. (Since you're currently reducing the format, image circle won't be a problem in your case; because the lens covers / was designed for a larger area than what is needed for the 35mm format...)

- A 150mm MF lens mounted on a 6x4.5 camera will give the equivalent (diagonal) field of view of a 92mm lens mounted on a 35mm camera. (I think this is where people got confused; what changes between formats is the field of view, again, not the focal length!)

- A 150mm MF lens will give the equivalent field of view of a ...SURPRISE!!!... 150mm lens when mounted on a 35mm camera!

Hope this helps & thanks for the funny thread!