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11-18-2007, 05:11 AM   #1
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M 50mm f/1.4 on K10D... Super dark exposures with high f stops

Hey folks, I recently acquired a M 50mm f1.4 lens that ive been using on my k10d. With it being the M series i have to use it in Manual mode and use the green button to light meter... I was playing around with it inside one night with dim lighting. I had my white balance set for indoor light bulb light... When taking pictures with small apertures on the tripod, i noticed that my images were very VERY dark... almost black in some instances other than a few highlights.... is this just something more than the camera's metering system can do when using a manual lens and metering with the green button, or should i be worried about something?

11-18-2007, 05:36 AM   #2
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My experience with the older lenses and a K10D are that the meter gives you a rough estimate of the correct meter setting. It may be because the K100D and K10D use a 'crippled KAF2 mount' which although compatible is not really designed for full functionality of the older lenses. So I just learned with each lens what the exposure compensation needed is for a given scene.

In my case I use a K mount 300mm F4 lens quite a bit and find it needs 2 stops of under exposure from the camera's meter reading, to get the correct exposure. It may be that with your lens, it needs 2 stops of over exposure in dark scenes to get the correct exposure. I would set the camera up on a tripod and meter a scene. Then take a green button metered shot as a reference. Then decrease the shutter speed by one stop per shot and see what setting gets you the correct exposure. You may also have to increase the ISO to get a hand holdable shutter speed to work with.

It's basically a process of getting used to your lens. Once you do, you'll know how to use it in almost any situation and get great images.

Do you have a newer A, F, FA or DA lens close to the same focal length? Try that against the older M series lens in the same scene. This is again another tripod test. See what it will do and what settings it needs for a correctly exposed shot. Then set the 50mm up for the exact same settings and see if you get about the same exposure levels and image quality.
11-18-2007, 10:24 AM   #3
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there has been a lot of talk about the manual exposure on the K10D.

I went through and mapped out all my lenses and found that you can go from -1 stop wide open on the 50mm f1.4 wide open to about +1.5 stops in middle range of apatures to about+.75 stops fully stopped down.

I have sent the data to pentax, and one thing (although not advertized in the upgrade to V1.3) that they seem to have done is to increase the time the lens is stopped down. I noticed this doubled between V1.2 and V1.3. Some pentax people also recommend using the DOF to set the metering.

Note that the *ixtD is very accurate with manual lenses

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