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11-20-2010, 06:14 AM   #121
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QuoteOriginally posted by alohadave Quote
What you really need to do is hack the firmware to allow the camera to change the aperture lever movement based on what lens is detected on the mount.
This is just a start of the way to do it.
I posted it probably several years ago on another forum, but the only safe and foolproof way to convert M/K lenses to A functionality requires help from Pentax.
The lensmount of the K mount lens must be 'upgraded'.
The bayonet part of most M/K mount lenses is the same, and should get the contacts for the A functionality, and additional the extra contact the autofocus lenses have, and a sensor for the aperture ring position.
This extra contact should inform the camera what lens/aperture is present, and what the relation is between aperture lever movement and aperture.
Then the camera can actuate the aperture like the A series lenses, but not without a firmware change, and there we need Pentax.

11-20-2010, 09:00 AM   #122
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QuoteOriginally posted by newarts Quote
As I recall, this modification to my K100D helped me get more consistent exposures with my m42 and other pre-set lenses in both flash & non-flash modes (Av mode worked IIRC.)
so when you use the m42 lens with the foil trick the camera told you the apture setting then you just set it on the lens and then shoot away right?
11-20-2010, 10:15 AM   #123
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The K100D has a known exposure bug when the contacts aren't shorted. I don't think other bodies have this issue.

I first noticed it because someone I knew used a K100D and M42 lenses without issues and I was underexposing by 1-2 stops. He was using a flanged adapter which shorted the contacts; I was using the genuine adapter which doesn't.
11-20-2010, 10:59 AM   #124
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QuoteOriginally posted by jslifoaw Quote
The K100D has a known exposure bug when the contacts aren't shorted. I don't think other bodies have this issue.

I first noticed it because someone I knew used a K100D and M42 lenses without issues and I was underexposing by 1-2 stops. He was using a flanged adapter which shorted the contacts; I was using the genuine adapter which doesn't.
This may be true but it is easy to compensate for with a single test shot

11-20-2010, 01:12 PM   #125
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QuoteOriginally posted by lguckert79 Quote
so when you use the m42 lens with the foil trick the camera told you the apture setting then you just set it on the lens and then shoot away right?
No.

I only reported my experience using the foil trick with K-x in M mode with m42 or other lenses without an aperture lever in this thread.

Basically, with K-x in M mode with non-A lens:
Turn the e-wheel to a particular aperture number for your particular lens (like f2.8)
Turn the lens' aperture ring to the setting you want
Press the green button to set the shutter speed.
(the e-wheel aperture can now be changed to record the actual f-stop in EXIF)

As I recall (but do not guarantee) with the K100D in Av mode with non-A lens:
Set the e-wheel to the minimum f-stop (like f1.2).
Set the lens aperture to what you want.
The camera adjusts the shutter speed for the correct exposure.

I have not attempted to do what you suggest with a K100D.

I just tried a K-x in Tv mode with a m42 Macro-Tak 50:4 with the foil trick:
Open the lens to f:4 to focus
Use the e-wheel to select the shutter speed.
The camera indicates what f-stop to set on the aperture ring.
The exposures were good from lens aperture settings f4 to f16.

I have no idea if this will work ok with other lenses.

I'm afraid you are expecting miracles which are physically not possible with no aperture lever or the wrong aperture lever.

Dave
11-21-2010, 08:17 AM   #126
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well i tried it last night and it worked just fine so i thank you all very much for all the help talk to you later larry G.
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