Using M Series Lenses on a K10D

PENTAX:  "Pentax K-mount, M-series and S (screw) mount lenses without auto-aperture control (an “A” setting on the aperture ring) can be used in Manual exposure mode using stop-down metering and manual focus. This is the exposure mode which will give accurate exposures when using these older lenses on our digital SLRs. If older lenses without an "A" setting on the aperture ring are used in Av (Aperture Priority) Mode, an exposure error may occur. "


Up until today I had a hard time believing the above statement.  Whenever I use manual mode I have to do some compensation.  If I use the reading the "green button" comes up with, my images will come out overexposed.  I have to adjust my exposures using a histogram to guide me.  I have read posts on several sites from people having similar results.  If I shoot in Av mode the exposures are right on (contrary to the above statement).  The problem is that when shooting in Av mode, you are shooting wide open no matter which F-stop you select.  


I thought it odd that the exposures can be so far off in manual mode.  A little research shows that the problem is easily resolved by changing a custom setting:


Go to Custom Settings


 Step down to Green button in Manual
Press the right arrow and select Tv Shift
Press OK
(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).

By default this setting is on "Program Line."  Change it to "Tv Shift" and the problem is resolved.  For those of you new to this, here are all the settings you need to change:

Press the Menu button

Go to Custom Settings
Step down to Green button in TAv & M (K10D/K20D).
Step down to Green button in Manual (K200D)
Press the right arrow and select Tv Shift
Press OK
(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).

Step down to Preview Method
Press the right arrow and select Optical Preview
Press OK
(This setting enables the camera to "stop down" the lens to a selected aperture when the On/Off button is rotated clocwise).

Step down to Using aperture ring
Press the right arrow and select Permitted
Press OK.
(This setting allows the camera to operate with older K-mount or S-mount lenses that do not have an “A” setting on the aperture ring).

If Shake Reduction is enabled when using an older lens, you will need to manually select the closest matching focal length from the Shake Reduction (K10D) or Input Focal Length (K20D/K200D) menu. Press the Menu button, step down to Shake Reduction (K10D) or Input Focal Length (K20D/K200D) then press the right arrow. Scroll left and right to select the closest match for the focal length lens you are using. Press OK, then Menu.