Using The Pentax *ist DS With A Manual Lens

Submitted by Mile23 on Sun, 07/10/2005 - 16:07

Note: I wrote this a while back, when the *ist DS wasn't three product cycles ago... However, the advice should still apply, even to the K100D, the K110D, the K10D, and the Samsung GX-10. In the case of the K10D and the GX-10, stop-down metering is accomplished with the green button, rather than AE-lock.

The *ist DS is a nifty neeto digital SLR camera made by Pentax.

One of its many useful features is the fact that any K-mount lens (with a few caveats) can be used on it. This includes lenses going back to the 1970s.

However, the manual included with the camera is a little vague on how this is accomplished, and what limitations there will be on the process of taking a picture.

So, with that in mind, here's a little bit of a crib sheet.

How to use a manual lens on your Pentax *ist digital camera:

  • You have to change the custom setting for 'Using aperture ring' to permitted, which is a silly setting, but you have to set it. Then you're full manual.
  • If you have focus set to AF, the camera won't fire until it believes the image is in focus, so set it to MF.
  • Using any mode setting other than M will yield a wide-open aperture regardless of aperture ring setting.
  • You can meter by pressing the AE-LOCK button (this is on the *ist DS... Dunno about the D). You're limited to spot or center-weighted metering; if you have the camera set to multi-meter, it will switch to center-weight.

Get a lens with an A setting on the aperture and all these limitations go away, with the possible exception of not being able to use multi-metering.

Here's a typical process for using a lens without an A setting on the aperture ring... Let's say it's an SMC-M 50mm/2 lens, of which I happen to have two. :-)

Assuming the camera's on and all that, you have to do the following.

  • Set camera to M mode for manual. You can use other modes, but they'll all shoot with the aperture wide open.
  • Select an aperture. This usually comes before most photography (since it's unlikely to change per situation), and is first in line because you have to look at the outside of the lens to see where the ring is set. There's an 'F--' display in the finder, to let you know the camera has no idea what the aperture setting is. (But what is it really trying to say? :-)
  • Point and frame. Optionally zoom, if you have a zoom lens.
  • Focus, unless it's autofocus, a highly unlikely scenario.
  • Meter. I use a sort of abbreviated zone system where I find a mid-tone. Grass works, or dark pavement, or dark-ish flesh tones... Read up on the zone system if you want to find out the best way to do spot-metered exposure.
  • Meter off the mid-tone by pressing the AE-Lock button. If the lens' aperture is set to A, pressing AE-Lock will cause the camera to guess both a shutter speed and an aperture, so be careful. (Note: This behavior has changed with the 2.0 firmware update. With this new update, you have a custom setting for an aperture-priority or shutter-speed-priority meter when you press AE-L. The firmware upgrade is very much worth the effort.)
  • Now you're ready to shoot. So shoot.

It's much more intuitive and easy than it sounds. Once you get the aperture it's just focus, meter, shoot. Once you've got a useable shutter speed for a situation, you probably won't even need to meter.

See also this discussion.