Using a K10D, I want to use AUTO ISO with a manual Tamron SP500 Mirror lens.
The shutter speed has to be set high to stop camera shake.
TAv mode would be ideal, but choosing it sets Av mode instead.
I can get Av mode to use AUTO ISO (after pressing the green button), but the ISO changes only kick in when the shutter speed drops to 1/100th or 1/90th sec (seems to vary for no reason I can think of). That speed is too low for a 500mm lens. The camera knows the focal length of the lens because it is set at startup in the shake reduction option and it correctly sets it in the EXIF data.
So how can I set my shutter speed at say 1/500th sec and get the camera to adjust the ISO according to light conditions. The camera can set the shutter speed OK when I fix the ISO, so it should be able to let me set the shutter speed and change the ISO. Isn't that what AUTO ISO is for?
Would a different lens mount help? Is one available? I think the camera is holding back on the TAv option because it doesnt know the aperture setting on the lens. Although when you press the green button that should tell the camera all it needs to know.
The best compromise I have found is to manually change the ISO settings for each shot using the front E-Dial to keep the shutter speed close to what I want - a sort of manual TAv mode. This is frustrating when AUTO ISO promises just what I want and yet doesn't deliver.
Any suggestions??
Last edited by kevbirder; 11-11-2008 at 04:54 PM.
Reason: clarification