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02-11-2009, 02:48 PM   #1
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Use of M lens

I have a number of Pentax M manual lenses. I really enjoy using them, particularly the M135 3.5 lens.
Question is, I like to use them on my K10d with setting on manual focus, of course and manual settings.
However, after I set the F stop and speed, take the photo, I find that the setting for F stop stays (naturally) as it is set on the lens ring, but after every click the speed on the camera changes to any random speed (it appears to be random anyway)

Would be much more convenient if the speed was retained as set.

Am I doing something wrong, or perhaps missing something?
Any help appreciated.

02-11-2009, 04:02 PM   #2
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Sure it's in Manual? Anything else defaults to Av.
02-11-2009, 04:29 PM   #3
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Hello,

I think you are just noticing the fact that, after taking a picture, the camera continues to measure the exposure, thus changing the shutter speed ... I don't know if this is nominal, but my K10D behaves the same ...

What i do with my manual lenses, is to set the f/stop value i want to use, and then, with the camera in M mode, hit the green button before shooting (this will enable the camera exposure measurement, and the shutter speed will be set and remain constant even if the lightning changes) ...
I suppose this is the behaviour you are looking for ...

Hope this helps

Best regards
02-11-2009, 04:49 PM   #4
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I prefer the alternate metering in M for manual mode. I pull over the Depth of Field preview and use the scale in the viewfinder to set the exposure. Just another way of doing the same thing.

02-11-2009, 04:52 PM   #5
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Thanks a lot guys, given me something to work on there.
Perhaps it is just me not grasping whats going on (whats new??) and need to do a bit of trial and error.
Thanks again.
02-11-2009, 07:26 PM   #6
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If you have it in M mode and the switch is not on AF, the camera will continue to meter but you will be able to force the aperture + shutter speed with the dials.

I always use the green button method to meter with my M's, works great, but I
often tweak it to bracket.
02-11-2009, 09:36 PM   #7
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When you use Manual Lens on AV mode, only works on biggest aperture for your lens, even you set it to smaller aperture. Also the exposure will keep changing. On M mode, you can use any aperture. and give you better control on the exposure, and you can use Flash too.
02-11-2009, 09:51 PM   #8
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erratic exposure in M mode

I used my M 50mm F1.7 lens and took a series of shots where I would increment the aperture one click for each shot. I used a tripod.

Focus was set to Manual. Mode switch was on M. Shake reduction off. I used the green button (K10D) to set the exposure for each new f stop.

Most of the shots resulted in very close exposures; a few were very noticeably underexposed. Have any of you had a similar experience?

02-11-2009, 10:16 PM   #9
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QuoteOriginally posted by wiseman Quote
I used my M 50mm F1.7 lens and took a series of shots where I would increment the aperture one click for each shot. I used a tripod.

Focus was set to Manual. Mode switch was on M. Shake reduction off. I used the green button (K10D) to set the exposure for each new f stop.

Most of the shots resulted in very close exposures; a few were very noticeably underexposed. Have any of you had a similar experience?
This is a well known phenomenon. Both my M's meter properly at f/8, so I do that and then interpolate from there. The problem is the metering, not the mechanicals that actually stop down and expose the frame. Often I won't even bother with the meter and just use good old Sunny 16 and its variations.
02-12-2009, 12:05 PM   #10
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QuoteOriginally posted by Bramela Quote
However, after I set the F stop and speed, take the photo, I find that the setting for F stop stays (naturally) as it is set on the lens ring, but after every click the speed on the camera changes to any random speed (it appears to be random anyway)

Would be much more convenient if the speed was retained as set.
If you are using M mod, it should be set, just as it is with any other lens. Perhaps you are accidentally hitting the Green button, which sets the shutter speed for you?

If you are using Av mode (or any other mode), then yes, the shutter speed varies, just as it does with any other lens. But the aperture ring is completely ignored with "M" lenses - the shutter displayed, and used, is the one that makes sense for the lens wide open. And when you take the picture, it will be taken wide open. So if you don't want to shoot wide open, you have to use M mode.
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