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02-01-2007, 09:09 AM   #16
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I have some lenses from an old Mamiya 645 and an adapter (Zork) to use them on a K mount body. Have tried one lens, an 80mm f1.8, on my DS.
Have only done some quick test shots and assumed that the effective focal length was +/- 120mm. I thought that I might use it as a fast, short telephoto in low light situations (fully manual).
If I've read these posts right, it really is effectively around 200mm. Might be more useful than I thought.

02-01-2007, 01:23 PM   #17
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boy the crop factor thing is still confusing people.

80mm lens is 80 mm no matter what camera you attach it to. The camera cannot physically change the lens.

The amount of magnification is related to the sensor size, the pixel size the print size etc... effectively, the crop factor of 1.5 for Pentax DSLR's is to translate what you were used to with your old 35m camera.

the sensor on the DSLR is smaller than the 35mm film, so that the image resulting from using your 80mm lens is only coming from the center of the image circle. An 80mm lens on the 645 system is a normal lens right? seems like a 50mm on 35mm systems, or a 35mm on your DSLR?

but an 80 mm lens on the DSLR is not a normal lens, it is a short telephoto ... similar field of view as a (80*1.5=120) 120mm gives on a 35mm camera.

I hope I am helping not hurting...
02-01-2007, 03:04 PM   #18
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CORRECT!! a 300mm lens is still a 300mm lens no matter how much of the image circle you are using. it'll be the same size no matter what format the lens is made to. that's why the DA50-200 with the crop factor is equivalent to a 75-300 (35mm) even tho it's a digital only lens.

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