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11-29-2008, 07:31 PM   #1
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Manual lens with built-in flash issue

Hi there, I got some old M42 and k mount manual lenses, they all work great without using the built in flash, but when i use those lens with my K10D built in flash, they always over exposure, the only way i do it is to reduce the aperture to F11 or up and set exposure to 1/150, still take a few try to get a ok Pic. Any advice for this issue? thanx all.

11-29-2008, 07:48 PM   #2
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You have to do it the old-fashioned way. The Guide Number of the built-in flash is 13m @ ISO 100. Divide the distance into 13 to get the shooting aperture at ISO100. You can make adjustments to ISO, with appropriate adjustments to aperture as well.

For example:

Subject 3 meters away......13 divided by 3 = f4 (roughly) at ISO 100. For ISO 200 use f5.6, for ISO 400 use f8, etc etc.
11-29-2008, 08:47 PM   #3
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QuoteOriginally posted by winglik Quote
Hi there, I got some old M42 and k mount manual lenses, they all work great without using the built in flash, but when i use those lens with my K10D built in flash, they always over exposure
Right - with manual lenses, the built-in flash always fires at full power, o you have to use the guide number formula to set an appropriate aperture for the subject distance & ISO, as described above. Note shutter speed doesn't really matter unless it is so slow that ambient light starts to dominate - otherwise, the flash duration is far too short for shutter speed to make any difference.
11-29-2008, 11:38 PM   #4
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Great, thank you all for the advice, i'll put it in practice.

11-30-2008, 01:19 PM   #5
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Love that sig Mr. Cash !
12-01-2008, 02:44 AM   #6
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QuoteOriginally posted by TourDeForce Quote
Love that sig Mr. Cash !
Thanks, but I'm afraid it may be a bit irresponsible. For all we know, Jesus has a Spotmatic, after all. The Bible is silent on the matter.
12-01-2008, 03:48 AM   #7
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Well, you can also trick the k10 into thinking an A lens is used, by grounding both the A and Data electrical pins of the mount.
While doing so with the Data pin is quite easy, the A pin is recessed, and thus is a little harder to short.

Anyway, once done, the flash will work properly in P-TTL mode with your manual lenses...
Maybe it will lead to some inconsistent exposure, due to the lack of some information being transmitted to the body (focal length, aperture, and so on...), but I still has to witness this!

Only setback is that you have to manually select the widest aperture available on the k10 (as it now thinks it has an A lens attached), otherwise you'll end-up with overexposed pictures...
12-01-2008, 05:15 AM   #8
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QuoteOriginally posted by dlacouture Quote
Well, you can also trick the k10 into thinking an A lens is used, by grounding both the A and Data electrical pins of the mount.
While doing so with the Data pin is quite easy, the A pin is recessed, and thus is a little harder to short.

Anyway, once done, the flash will work properly in P-TTL mode with your manual lenses...
Maybe it will lead to some inconsistent exposure, due to the lack of some information being transmitted to the body (focal length, aperture, and so on...), but I still has to witness this!

Only setback is that you have to manually select the widest aperture available on the k10 (as it now thinks it has an A lens attached), otherwise you'll end-up with overexposed pictures...
this is still not perfect as there is a metering issue with the K10D and manual apature lenses, and this may (I have not personally tested) also cause over and under exposure with the flash.

If you are interested in doing a lot with manual lenses, and want the fullest performance from them, (whether it is flash, accurate metering etc) get an *istD

12-01-2008, 07:28 AM   #9
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Of course...
In my mind, that was once you had a LL-60 screen installed...
Otherwise, this is the same old story...
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