Pentax ist DS aperture setting problems

That means your camera is in aperture priority mode. Try setting it to something else like the "green"mode or "P" mode.

Although your lens is an older manually operated K mount and will physically fit onto your camera, there are incompatibilities which limit the level to which it is compatible with your *ist DS.

Ignoring the really obvious difference that your lens is totally incapable of autofocus, the first real incompatibility is that your camera body has one of the "crippled" versions of the KAF (autofocus) mount. This means that it lacks the mechanical stop-down coupler/indicator used on the original K mount. The result is that your camera body does not sense which aperture the lens is set to and will not stop the lens down to the selected aperture when you press the shutter release. The full specification KAF mount maintains these old mechanical legacy couplings, but as most owners don't use older lenses any more the crippled KAF isn't an issue to most users and significantly reduces manufacturing costs. Crippled KAF lenses can still use some manual K lenses, but only the ones which have the A setting on the aperture ring and your lens pre-dates this development.

Your only realistic fixes for this are to either replace the camera body with a model supporting the full KAF mount (expensive) or to use later K lenses with the description SMC Pentax A instead of earlier SMC Pentax M. You'll still lack autofocus but as long as the lens aperture ring is set to the A position then it will work when the body is set to shutter priority and Automatic modes. There are far more Pentax A lenses remaining in good condition than Pentax M so you should have no trouble finding them, but because of their compatibility with later mounts you'll find that prices are somewhat higher.

Note that there is no adaptor which will allow you to improve compatibility between your present camera and the lens you have asked about.

I hope that I've answered your question, if so please take a moment to rate my reply. If not, perhaps you should add a comment to further explain in which way your camera doesn't work with your lens and I'll then try to assist you further.

Use "exposure compensation" (the button with a plus/minus symbol). It allows you to lighten (toward the + side) or darken (toward the - side).

Try using another lens, if this solves the problem you have a lens problem. If not the camera is the problem.

Custom white balance can only be set in P, Tv, Av, or M modes. The auto modes are, well, automatic. They are all preconfigured and intended for ease of use not configurability.

I have old Lenses that I use; you must set your lens to manual, Switch left hand front of body. That should resolve the problem.

i found this which seems similar

http://www.pentaxuser.co.uk/forum/topic/ist-D--HELP-444/p-0#comm_2164

"I know this is late, but the issue sounds to me like the aperture ring is not on A. and if this is a manual lens then you have to set the mode to hyper-program mode and set it to work with "other than A" on aperture."

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this was my issue, i never knew that has i bought the camera 2nd hand without a manual - your issue might be something else but it's worth posting just incase

First make sure the camera is not set to No Flash on the shooting mode dial.Also, in P, Tv, Av or M modes the flash reverts to manual and must be raised manually by pressing the button next to the viewfinder.

They will - fully open in Av mode, and with any aperture in manual mode - after you allow the Ds through the custom settings menu to use aperture settings different then "A". To choose correct exposure with such a lens in manual mode you can use the AE-button - it stops down the aperture, reads the EV and sets the shutter speed according to the chosen aperture.

Auto Picture-selects on of the picture mode such as landscape(mountain), macro(flower), sport/action(running man) mode, etc. P-sets shutter and aperture. You set everything else. happy face- sets shutter, aperture and everything else.