Compatible “K” Lenses?

As noted in an earlier post one of the main reasons I decided on Pentax “K’ mount bodies and lenses when I went shopping for a new 35mm SLR was availability and the apparent interchangeability between the SLR lenses and the AF lenses used on the new Pentax DSLRs. Olympus and Pentax are the only camera manufacturers that consistently maintained lens compatibility and interchangeability over the years and Olympus gave it up when they switched from film to digital. Everyone else seemed to change lens mounts whenever the urge hit them.

Well, I finally got a chance to experiment a bit and determine whether or not the old “K” lenses I bought for my 35mm SLR will actually fit and work on the Pentax DSLR’s. Good news - they do!

There are some restrictions, of course; and you have to dig through the menus to “Settings” or “Custom Settings” (depending on which Pentax DSLR you happen to have) and set the “Using Aperture Ring” to “Permitted.” Once that is done and you set the camera on the “M” manual mode, you are fully operational. You still must focus manually of course, and you must set the aperture and shutter manually. You can get a meter reading only when using the depth of field preview (Optical Preview) function.

What I did was set the aperture I wanted, focus, take my best guess at shutter speed and then check it using the “Optical Preview” function. Depending on which Pentax DSLR I was using I either got a scale with a “+” pr “–“ reading or I got a numeric over/under indication with a “+” or “-“. Either way I just adjusted the shutter speed (using the wheel) until I got desired EV setting and then took the shot.

Yeah, it’s a little tedious so I wouldn’t want to have to do it all the time but it works and allows me to use my much faster “K” mount lenses on the Pentax DSLRs when I want or need to. It should be noted that the reverse is not true. I do not believe there is any way to use the AF lenses bought for the DSLR’s on the SLR because there is no easy way to manually adjust the aperture or focus.