Originally Posted by atyab
I bought the SMC Pentax M 50mm F1.7 yesterday. Haven't yet fully experimented with it.
Now for using it I set the aperture ring setting to "Permitted". Now when ever the M 50mm is on the body and I turn the camera on, it asks me the focal length of the lens.
Why does it need the focal length?
I know the k200D has a smaller sensor so 50mm of the lens is not a 50mm for the sensor. So, what is the crop factor for the K200D?
Like the previous member said it is asking this to set the SR. Older lenses lack the ability to communicate this information to the camera. Newer lenses have this ability, that's why it never asks the question when using a DA lens.
Crop factor is still 1.5X, but when it asks that question you should input the length of the lens; i.e. 50mm.
Simple answer - a 50 mm lens is
always a 50mm lens; regardless of crop factor.
