Older Pentax lenses do not have the electronics to support autofocus or auto aperture.
These are referred to as manual lenses.
Some are auto aperture only, these are A lenses.
Any of the K-mount lenses will fit Pentax digital cameras.
Any of the M42 screw mount lenses will fit with an adaptor ring.
But you will need to permit the digital camera to use these manual lenses by making a settings adjustment.
The settings required to use manual focus and aperture K or M42 mount lenses are as follows.
K-5/K-7/K20D/K10D/K-r:
1) Custom function "Using aperture ring" must be set to "2 Permitted".
2) In manual exposure mode "M": Set the lens to the desired aperture, compose the shot, press the green button (this will set the correct exposure), shoot.
*ist DS, DL, K100D (super), K110D, K200D, K-m:
1) Custom function "Using aperture ring" must be set to "2 Permitted".
2) In manual exposure mode "M": Set the lens to the desired aperture, compose the shot, press the "AE-L" button (this will set the correct exposure), shoot.
*ist D:
1) The firmware must be 1.10 or higher.
2) Custom function "F stop other than A" must be set to "on".
3) In manual exposure mode "M": Set the lens to the desired aperture, compose the shot, press the green button (this will set the correct exposure), shoot.
Another method is to engage the optical preview (stop down) button in manual exposure mode. This turns on the lightmeter and the exposure bar. While keeping the optical preview engaged, adjust aperture or shutter speed until the exposure bar shows the correct exposure or shows over/under exposure to you liking. Also when using this method the "Using aperture ring" custom function must be set as described above.
It is mandatory to set the body in MF (manual focus) mode otherwise the shutter will not trigger unless the target is in focus (as detected by the AF). Note: AF still detects in MF mode so you become the lens servo.
With most models you can also switch the preview between:
1. Live View – sensor output in real time.
2. Digital Preview – result of a temporary shot shown for up to 30s – can be zoomed in on and saved, if required.
3. Optical Preview – aperture stopped down to see the actual DOF (requires a Pentax-A lens or later because it uses the "A" aperture setting) or shows exposure meter and allows shutter speed adjustment (M42, K, M).
Further general information:
http://anusf.anu.edu.au/~aab900/phot...s/adapters.htm
http://en.wikipedia.org/wiki/K_mount
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To set up your PENTAX K-x to use older PENTAX lenses:
Press the Menu button
Press the left button on the four-way controller to get to page 4 of the Rec. Mode menu
Press the down button on the four-way controller, select Green Button and press the right button on the four-way controller.
Press the down button on the four-way controller, select Action in M Mode
then press the right button on the four-way controller and select Tv SHIFT.
Press the OK button then the Menu button twice.
(This setting allows easy and accurate exposure metering using older lenses without an "A" setting on the aperture ring.
When the Green button is pressed in Manual exposure mode, the lens "stops down", the camera's meter measures the light passing through the lens, and an appropriate shutter speed is automatically set based on that measurement).
Press the Menu button
Press the left button on the four-way controller to get to the Custom Settings menu
Press the down button on the four-way controller and select
Using Aperture Ring
Press the down button on the four-way controller, select
Permitted and press the OK button.
Press the Menu button to exit the Custom Settings menu
Note: when using lenses without an "A" setting on the aperture ring, Manual exposure mode must be used. Exposure can be set by adjusting the lens aperture ring and/or adjusting the shutter speed on the camera.
Note: pressing the Exposure Compensation button (the +/- button) on the K-x will automatically set an appropriate shutter speed in Manual exposure mode when using non-"A" series lenses.
If Shake Reduction is enabled when using an older lens, you will need to manually select the closest matching focal length from the Input Focal Length menu.
To do this:
Turn the camera off. Mount the non-"A" series lens. Turn the camera on.The Input Focal Length screen will appear. Use the rear e-dial to select a focal length which is closest to the focal length of the lens you are using.
If you are using a zoom lens, choose a focal length close to the midpoint of the zoom range of the camera.
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