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01-14-2007, 03:30 PM   #1
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K/M Lenses and the Green Button

Today, I finally got around to tryng my K28/2 on the K10D that Amazon delivered at the end of November. After "permitting" the camera to recognize lens openings from an aperature ring, I mounted the lens, set the camera to M and MF and, aimed, pressed the green button and . . . . . . got a wildly overexposed shot. I've seen this issue mentioned, but I don't recall if the consensus is that the problem is a firmware related or something requiring adjustment. Has anybody followed this subject closer than I have?

I have a bag full of legacy lenses dating back to the late '70's, including the 28, an FA 50/1.4, an A* 85/1.4 and a K300/4. Since I bought a DS2 a little over a year ago, I've updated my collection with a number of DA lenses and an FA 32/2, and I use the K lenses far too infrequently (read: virtually not at all) to send the camera back for repair simply for this problem alone. Even so, it would be nice if this defect could be corrected by a future firmware update.

I'd appreciate any info. Maybe I ought to email Pentax tech service, as well; I've never tried that and it would be an interesting experiment.

Thanks,

Jerry

01-14-2007, 04:17 PM   #2
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I have 135 and 200 M lenses that I use once in a while with the DL and the K10 with good results. Not sure what the problem could be, especially with a 28mm fl. Have you tried actuating the stop down lever around the shutter button to get a meter reading instead of the green button. They are both supposed to work equally well, ie, the same.

Walt
01-14-2007, 04:29 PM   #3
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QuoteOriginally posted by newtmaker Quote
I have 135 and 200 M lenses that I use once in a while with the DL and the K10 with good results. Not sure what the problem could be, especially with a 28mm fl. Have you tried actuating the stop down lever around the shutter button to get a meter reading instead of the green button. They are both supposed to work equally well, ie, the same.

Walt
Yeah, Walt, I have. Same results.

Jer
01-14-2007, 04:32 PM   #4
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Jerry,

Funny you mention the green button and M lenses... Just last night I finally decided to experiment with Sears MC 50mm f/1.4 for the first time (got it while back) . I had to set the Green Button to "Tv shift" in the "C Custom Setting" menu, and it works like a charm. Indoors, almost no light - I would say 9 out of 10 shots pretty accurate at various aperture settings (via the lens ring). Once the green button is pressed, camera stops down automatically and locks the "proposed" shutter speed.

And to be honest with you (just a personal preference), I find that using the green button instead of the "stopdown" ring easier on the fingers.

The only thing is a no-go is any shots with the in-camera flash, all overexposed... Anyone knows any work around it - please, chime in!

Regards,
D

01-14-2007, 04:43 PM   #5
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QuoteOriginally posted by Sailor Quote
Today, I finally got around to tryng my K28/2 on the K10D that Amazon delivered at the end of November. After "permitting" the camera to recognize lens openings from an aperature ring, I mounted the lens, set the camera to M and MF and, aimed, pressed the green button and . . . . . . got a wildly overexposed shot. I've seen this issue mentioned, but I don't recall if the consensus is that the problem is a firmware related or something requiring adjustment. Has anybody followed this subject closer than I have?

I have a bag full of legacy lenses dating back to the late '70's, including the 28, an FA 50/1.4, an A* 85/1.4 and a K300/4. Since I bought a DS2 a little over a year ago, I've updated my collection with a number of DA lenses and an FA 32/2, and I use the K lenses far too infrequently (read: virtually not at all) to send the camera back for repair simply for this problem alone. Even so, it would be nice if this defect could be corrected by a future firmware update.

I'd appreciate any info. Maybe I ought to email Pentax tech service, as well; I've never tried that and it would be an interesting experiment.

Thanks,

Jerry
Hi Jerry,

I wrote a post explaining M/K metering here: https://www.pentaxforums.com/forums/pentax-dslr-discussion/1313-metering-smc-m-lens.html

Hope it helps!

Adam
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01-14-2007, 05:36 PM   #6
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QuoteOriginally posted by Mo Quote
Hi Jerry,

I wrote a post explaining M/K metering here: https://www.pentaxforums.com/forums/pentax-dslr-discussion/1313-metering-smc-m-lens.html

Hope it helps!
Thanks, Adam. However, I tried what (I think) you're suggesting; using either the green button or the stop down lever gives the same - over exposed results. However, see my next reply . . .
01-14-2007, 05:52 PM   #7
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New Data - Problem Solved (?)

When I saw the radically overexposed shots from my K28/2 in M mode, I tried my A*85/1.4 using the aperature ring (instead of what one normally would do: set the lens to A, and use the e-dials on the camera). I saw the same extreme overexposure.

A few hours later, I was playing with my FA35/2 and decided to try it in M with the aperature ring. Every exposure was spot on, and I wondered why the aperature ring on an FA would behave differently than that of a K or A lens. Then it hit my aging brain; right after I "tested" M mode with the K28 and A* 85, I noticed the battery was low and put in a freshly recharged one. So with the reinvigorated battery, I tried the 28 and the A* with aperature ring and both lenses (with green button or stop down lever) yielded spot on exposures in M mode.

So, was the battery low and causing erratic behavior or did removing the depleted battery (and installing the new one) reboot the system so that it could - as my Dad would have said - straighten up and fly right?

Jerry
01-14-2007, 05:52 PM   #8
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Jerry,
Did you go to custom mode and program the green button for setting "2", tv mode?

Ken

01-14-2007, 06:21 PM   #9
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QuoteOriginally posted by regken Quote
Jerry,
Did you go to custom mode and program the green button for setting "2", tv mode?

Ken
Ken, I tried program, tv and av when I originally "tested" the K and A lenses - all produced the same overexposed result. When I tried again this evening (with the fully charged battery) with the K28, FA35 and A*85, the mode was where I had left it earlier today - Av shift mode (setting 3).

Jerry
01-14-2007, 06:29 PM   #10
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QuoteOriginally posted by Sailor Quote
Ken, I tried program, tv and av when I originally "tested" the K and A lenses - all produced the same overexposed result. When I tried again this evening (with the fully charged battery) with the K28, FA35 and A*85, the mode was where I had left it earlier today - Av shift mode (setting 3).

Jerry
I mean here, of course, Program, Tv and Av settings (1,2, and 3) in the Custom menu for "Green Button in Manual".

Jer
01-15-2007, 09:08 PM   #11
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Are you aware that K and M lenses in Manual can only be used with Center-Weighted metering?

It's a more specific technique than the "matrix" metering nonsense in all the new cameras. You have to actually make sure you're giving the metering area a medium tone to set the exposure.

I've not had any difficulty with K or M lenses on the K10D, but I grew up with center-weighted metering so it's second nature to me.
01-16-2007, 05:38 PM   #12
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QuoteOriginally posted by Dana G Quote
Are you aware that K and M lenses in Manual can only be used with Center-Weighted metering?

It's a more specific technique than the "matrix" metering nonsense in all the new cameras. You have to actually make sure you're giving the metering area a medium tone to set the exposure.

I've not had any difficulty with K or M lenses on the K10D, but I grew up with center-weighted metering so it's second nature to me.
As I understand it, going to manual with a K/M lens automatically sets the camera to center weighting - so I don't think this is the issue.

Jerry
01-16-2007, 05:51 PM   #13
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I Spoke too Soon!!

QuoteOriginally posted by Sailor Quote
When I saw the radically overexposed shots from my K28/2 in M mode, I tried my A*85/1.4 using the aperature ring (instead of what one normally would do: set the lens to A, and use the e-dials on the camera). I saw the same extreme overexposure.

A few hours later, I was playing with my FA35/2 and decided to try it in M with the aperature ring. Every exposure was spot on, and I wondered why the aperature ring on an FA would behave differently than that of a K or A lens. Then it hit my aging brain; right after I "tested" M mode with the K28 and A* 85, I noticed the battery was low and put in a freshly recharged one. So with the reinvigorated battery, I tried the 28 and the A* with aperature ring and both lenses (with green button or stop down lever) yielded spot on exposures in M mode.

So, was the battery low and causing erratic behavior or did removing the depleted battery (and installing the new one) reboot the system so that it could - as my Dad would have said - straighten up and fly right?

Jerry
Pass my a serving of crow.

I got home early enough this evening to retry my K10D and the K28/2 I mentioned in the OP outside in natural light. Sorry to say that it overexposes at lens openings of less than f/4 - as others are reporting. Experiments with my FA35/2 using the A setting and the aperature ring indicate that the overexposure is about 1EV. Guess I was fooled last night by the low light conditions (also I was "testing" durng the cocktail hour).

Anyway, sorry for the misleading reply quoted above.

Jerry
01-16-2007, 10:54 PM   #14
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QuoteOriginally posted by Sailor Quote
Today, I finally got around to tryng my K28/2 on the K10D that Amazon delivered at the end of November. After "permitting" the camera to recognize lens openings from an aperature ring, I mounted the lens, set the camera to M and MF and, aimed, pressed the green button and . . . . . . got a wildly overexposed shot. I've seen this issue mentioned, but I don't recall if the consensus is that the problem is a firmware related or something requiring adjustment. Has anybody followed this subject closer than I have?

I have a bag full of legacy lenses dating back to the late '70's, including the 28, an FA 50/1.4, an A* 85/1.4 and a K300/4. Since I bought a DS2 a little over a year ago, I've updated my collection with a number of DA lenses and an FA 32/2, and I use the K lenses far too infrequently (read: virtually not at all) to send the camera back for repair simply for this problem alone. Even so, it would be nice if this defect could be corrected by a future firmware update.

I'd appreciate any info. Maybe I ought to email Pentax tech service, as well; I've never tried that and it would be an interesting experiment.

Thanks,

Jerry
Full answer here:

K Mount Metering & Exposure Bases - A Technical Brief

Hope this helps (a long read, though)
01-17-2007, 05:07 PM   #15
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QuoteOriginally posted by RiceHigh Quote
Full answer here:

K Mount Metering & Exposure Bases - A Technical Brief

Hope this helps (a long read, though)
Thanks, RH. An enjoyable read.

Jerry
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