BrianO

Check with Pentax to see if your lens is compatible. They claim their DSLRs work with older Pentax lenses, but they don't say "all". I believe their DSLRs use the Pentax K-mount, but I could be wrong on that score. But if your lens has the old Pentax screw-mount, it is definitely incompatible.

What Loves2Watch says is true for most DSLRs. For example, The Sony Alpha line can use any lens ever made for the Minolta Maxxum but cannot use the older MC and MD series Rokkor-X and Minolta lenses because Minolta changed the lens mount when they introduced the Maxxum in the fall of 1984.

However, Let's assume that your lens is compatible. Then there is something that you need to be aware of. It's known as the 35mm equivalence factor. For the Pentax DSLRs it is 1.5. That means that if your zoom lens has a focal length range of say 80mm to 200 mm then your lens, when attached to the DSLR, will act like a 120 mm to 300 mm lens would on a 35mm SLR. A 50mm "normal" lens would act like a 75 mm lens (short telephoto) would on a 35mm SLR. So, if you are into wide-angle lens photography, you might need to buy a new wide angle lens or wide andle zoom.

The reason for this is that a standard 35mm SLR capatures an image that is 36 mm wide and 24 mm high (to nearest mm) in landscape mode. Most DSLR models use a sensor which is 24mm wide and 16mm high (to nearest mm) so they capture a smaller portion of the image that the lens captures than a 35mm camera would. It's as if the lens has zoomed in by a factor of 1.5 from its actual setting. This smaller size is known as the APS-C size.

While most camera manufacturers use the true APS-C sensor size in their DSLRs, there are exceptions. The equivalence factors used by the major players in their various models are:

Nikon: 1.5 and 1.0
Canon: 1.6, 1.3 and 1.0
Sony: 1.5 and 1.0
Pentax: 1.5
Olympus: 2.0
Minolta: No longer in the camera business*

The cameras with a factor of 1.0 are high-end professional cameras with high-end prices to match: about $3,000 for the camera body alone.


* Konica-Minolta sold their camera/lens division to Sony in early 2006, so the Sony Alpha line is actually a continuation of the now-discontinued Minolta Maxxum line.