Shake reduction/focal length

[ATD]

I just got a Pentax 100K and an adapter for medium format lens (6x7). The camera has a Shake Reduction feature that works great for the digital lens. When I put on one of the 6x7 lens, the camera asks me for the focal length of the lens I'm putting on. It would be easy enough but medium format lens are a different scale than 35mm lens. Should I use the 6x7 scale or the conversion to 35mm scale? Does anyone know that conversion?

 

[balofagus]

Well, from what I've been reading, just plug in the focal length labelled on the lens. You could try that, then try using a conversion scale and then plug in a different number and see which gives better results. The people over HERE or HERE might be able to help you out a little better.

 

[ChrisA]

I just got a Pentax 100K and an adapter for medium format lens (6x7). The camera has a Shake Reduction feature that works great for the digital lens. When I put on one of the 6x7 lens, the camera asks me for the focal length of the lens I'm putting on. It would be easy enough but medium format lens are a different scale than 35mm lens. Should I use the 6x7 scale or the conversion to 35mm scale? Does anyone know that conversion?

It is asking for the focal lenght enter the lenght printed on the lens.

Here is an eay way to understand it. Pretend the lens is just a pin hole one focal lenght away from the sensor or film plane. On a paper make a diagram. Draw a line as wide as the frame. That would be 7cm (for the MF camera) or about 2cm (for the DSRL) next make a dot 100mm (for a 100mm focal lenght lens) centers over and above the line that represents the frame width. Connect the edgas of the frame to the dot. You will now have a triagle.

Measure the angle at the apex of the triangle. This is the field of view. Or better use a calultor with trig functions and compute the angle. Notice how a 100mm lens is a telephoto on the DSRL and a wide angle lens on the 6x7

Could you post some pictures of the DSLR with a 6x7 lens mounted. Those lenses are huge and cost more than the DSLR when they were new.

 

[ATD]

Could you post some pictures of the DSLR with a 6x7 lens mounted. Those lenses are huge and cost more than the DSLR when they were new.

This is with a 67 Macro 135mm, it's the only one I have on me. I have a 67 300mm that would swallow that camera body whole, it's huge. I have close to 10K invested in 67 lens/body, I'm so glad to be able to use them on a digital body now.

BTW, thanks guys.