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06-02-2007, 01:05 PM   #1
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what a GREAT day at the flea market!! Need help! (thanks!)

Having just bought my Pentax K100D, I decided I should hit up the local outdoor flea market today and see what I could pick up in terms of lenses, bag, etc etc..

I was handsomely rewarded :beer:

I picked up a 28mm and 135mm lens, but now I need to know if they will work with my camera! They each had a rear cap bearing the "PK" text, which I had assumed to be Pentax, K-mount. The lenses each bore 52, the diameter of my lens, and the words "AUTO", as seen in the pictures below. The mount appears to be the K-bayonette style.

They fit my camera perfectly, but the "AV" symbol flashes blank on the upper LCD when I turn it on with these lenses in place, and it won't let me actuate the shutter.

Any advice on making these lenses work? Even without the auto focus feature, it would be great to have these lenses to use. I wonder if maybe they aren't the right lenses for my camera, or they just won't work? The kit lens only reaches 55mm, and the 135mm would be much better for the airshow I'm attending tomorrow.

Oh, and I picked up a great tripod for $5 and a bag for $15, overall a great day!

Thanks as always for your help, and now on to the pictures!

06-02-2007, 10:36 PM   #2
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You can use the lenses. You first need to change the default setting.

Go to Menu > Custom setting and change use aperture ring to enable (pg 107 of the K100D manual). Refer to pg 188 (Notes on using aperture ring) as well. Focusing switch on front of camera to set to MF.
06-03-2007, 03:17 AM   #3
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You're my hero! Worked like a charm! Thanks! I'm going to assume I can't use these lenses with AF, but I'll need to check the manual again thanks again!
06-03-2007, 05:06 AM   #4
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Save yourself a trip to the manual. Your assumption that these lenses aren't AF-capable is a safe one.

06-03-2007, 09:06 AM   #5
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just be sure you use these in M mode and that once you set the aperture you press the AE-L or green button so the cam can take a reading.
06-03-2007, 03:05 PM   #6
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You already have been told the, "big secret", the default is the shutter is blocked unless you change option in the setup. It took me awhile to find that for my wife's istD with K1000 lenses.

Most manual "K" lenses can be used in Auto Aperture if you can set the Aperture ring to "A". You then control the exposure and the camera will control the aperture. I have some fairly old K1000 lenses that have "A" for Auto Aperture printed next to the hightest f-stop. Warning: I don't have personal experiance doing this, I prefer to turn the ring manually.

The diameter of the lens you mention is seldom indicated (for telescopes it is always indicated). It can be approximated by dividing the focal length by the focal ratio.

The "theta" number of 52 is the size of the filter threads if you decide to attach a filter.

I'll stand back and await someone to correct me since I'm a novice at this....
06-03-2007, 08:36 PM   #7
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From your pictures, it looks like these are either K or M mount lenses - no "A" setting on the aperture ring. You can use them in one of two ways - either using the "M" (manual) mode like Roy mentioned, setting the aperture on the ring, then pushing the AE-L button to let the camera meter. If you have the mode dial set to anything else (i.e., Av, Tv, P etc.), the camera will not stop down the lens. It will still meter automatically (no need to push the AE-L button) but you will be shooting wide open. I find that convenient when I'm using manual lenses in low light and would be using them wide open anyway.

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