Old Lenses on Pentax dSLRs

March 30th, 2009  |  Published in pictures and photography

One of the big lures of the Pentax K-series dSLRs is their backward compatibility with a huge range of lenses made for Pentax film cameras. With a few caveats, you can take a lens that worked great with your workhorse K1000 and use it on a K10/20/100/110/200. Because the camera’s shake reduction is built into the body instead of the lenses, a 20-year-old lens gets the benefits of newer tech, and the user gets to enjoy lenses with decent optical properties for a lot less than a new digital lens.

I’ve been on the lookout for a decent wide angle prime for a little while now, and noticed an SMC Pentax-M 2.8/28mm come through Citizens Photo last week. It was still there on Saturday, so I picked it up. It’s faster than the kit 18-55mm zoom that came with the camera and provides a nice general purpose focal length for carrying around.

There are some tradeoffs involved with this and other older lenses. It’s a manual focus lens, and it doesn’t support automatic aperture settings, so you have to take a few steps to get it to work. This is what it took for my K100D:

  1. Under the “C(ustom)” section of the menu, scroll down to “Using aperture ring” and set it to “2.” That allows the camera to recognize that the aperture ring is in use. Otherwise, it will ignore that setting.

  2. If you use the camera’s built-in shake reduction, the next time you power it up you’ll get a screen that asks for the lens focal length. Use the left/right buttons on the d-pad to scroll through your choices and use the “OK” button to finalize your selection.

  3. Set the camera to manual focus. (On the K100D, that’s on a switch to the left of the lens.)


Shooting with manual focus is not as bad as I thought it might be. You just tap the shutter button and use the focus ring. If you’ve got the camera set to beep when it gets focus, you’ll hear that. If you don’t, you can always keep an eye out for the focus hex next to the shutter speed in the viewfinder. When it goes solid, you’ve got focus.

The focus ring on the lens is a lot nicer than it is on any of the made-for-digital-autofocus lenses I’ve got. There’s just enough resistance that I don’t worry about overshooting or accidentally jostling it out of focus, and it’s very smooth. It’s a little odd to shoot manual focus without the traditional split-prism focusing screen, so I think some of the proceeds from the sale of my Canon PowerShot G9 might go toward a Katz Eye focusing screen, which provides a split prism and removes the need to either keep the focus beep turned on or consult the focus hex when composing. Considering the way some of my other lenses take forever to find focus, I think it’ll be a relief to get back in the habit of focusing manually.

One other drawback of shooting with an older manual lens is the lack of feedback on the aperture. You have to set it by looking at the actual ring because there’s no viewfinder or LCD indicator for it.

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