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07-05-2009, 06:33 PM   #16
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QuoteOriginally posted by Steve Beswick Quote
Sorry, but I don't consider the wrong-more-often-than-right metering of the K10 to be working.
I don't think it's terribly impressive either, especially when they make such a big deal out of backwards compatibility. Having said that I just put an LL-60 screen into the Samsung GX20 I'm using and it seems to have pretty much fixed the problem. From my limited testing so far metering is fine with the kit lens lens as well as manual focus K mount and M42, except when the lenses are stopped right down (underexposes).

It was my understanding that the cameras revert from matrix to centre-weighted metering, rather than spot metering as mentioned above?


Last edited by Wayno; 07-05-2009 at 07:03 PM. Reason: Cain't schpell
07-05-2009, 06:59 PM   #17
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QuoteQuote:
Overall, the -60 screen provides a more "even" reading. Still, you will have overexposure and gross underexposure depending on metering "method" since with M42s and Ms it reverts to spot...
QuoteOriginally posted by SOldBear Quote
This is new to me.

I haven't use much M42 lenses recently, but I don't have the problem of underexposure at any aperture with Nikkor lenses, which require stop-down metering.

No problem with PK mount lenses (open-aperture metering) either.
I think he means it defaults to center-weighted, not spot metering. At least that is how the manual reads.

Steve
07-05-2009, 09:09 PM   #18
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QuoteOriginally posted by rawr Quote
Just bracket your shots by 0.5 or 1 EV?

I do that for any of my new or old lenses where the exposure may be tricky.
But the thing is there shouldn't be any need for me to do that in most situations. I've never needed to with my film bodies (all Pentax) so why should I with my dslr? I don't thnk I need to remind anybody that the K10 was top of the line when it hit the market. I personally own two handheld meters, but I feel that a top of the line 2007 model camera should be able to meter properly by itself in most situations.
07-05-2009, 09:54 PM   #19
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QuoteOriginally posted by stevebrot Quote
Generally, I would have to answer:
No, it is not possible
As for your camera not "metering right"...you have a very good point. Blame it on the "crippled" mount, the "optimized" screen design, and the correction factors that are applied to the meter output by the camera to make it work properly with A-contact lenses. If it is any consolation, Pentax is not the only brand with these problems. By report, stop-down metering is broken on both Nikon and Canon as well.

Steve


P.P.S I would give my eye teeth for a dSLR without the <expletive deleted> crippled mount...
What is a crippled mount?

07-06-2009, 03:58 AM   #20
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I find my M42 lenses underexpose by +- 1 stop. For this i compose my shot, press the green button then open up the 1 stop.

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07-06-2009, 04:35 AM   #21
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QuoteOriginally posted by res3567 Quote
What is a crippled mount?
all pentax DSLRs and several of the latest SLRs do not have the mechanical coupling from the aperture ring to the body to tell the camera where manual aperture lenses are set.

this is referred to as a crippled mount.

there is no official designation for it, but many refer to it as the J mount because the lenses that appeared with it are FA-J lenses.

to give pentax credit, the need for this coupling disappeared with the pentax Program cameras of the early 1980's and the KA mount.
07-06-2009, 05:13 AM   #22
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It's only the matrix mode that is unavailable with m42 and PK-m lenses. The camera then reverts to center-weighted. You still can use spot metering if you want, but the default is CW if you're on Matrix.
07-06-2009, 05:20 AM   #23
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QuoteOriginally posted by Steve Beswick Quote
But the thing is there shouldn't be any need for me to do that in most situations. I've never needed to with my film bodies (all Pentax) so why should I with my dslr? I don't thnk I need to remind anybody that the K10 was top of the line when it hit the market. I personally own two handheld meters, but I feel that a top of the line 2007 model camera should be able to meter properly by itself in most situations.
Film has a way better "out-of-camera" dynamic range, and thus can handle quite severe under/overexposure without us noticing... And anyway, it was the minilab that usually corrected exposure problems, so you were never aware of them...

I accidentally overexposed a negative film once, by easily 5Ev (tried some fill-in flash on a beach, around noon, with the lens wide open ...), and there was still something to salvage on the film...

07-06-2009, 05:39 AM   #24
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QuoteOriginally posted by Steve Beswick Quote
But the thing is there shouldn't be any need for me to do that in most situations. I've never needed to with my film bodies (all Pentax) so why should I with my dslr? I don't thnk I need to remind anybody that the K10 was top of the line when it hit the market. I personally own two handheld meters, but I feel that a top of the line 2007 model camera should be able to meter properly by itself in most situations.
I argued this point long and hard with pentax on the K10D. Aside from the metering, the K10D is a fine camera, and I have used it successfully with manual lenses, but I have mapped out how all my lenses perform so I know what to expect in advance.

the metering, which is the same on the K20 is the fundamental reason I skipped the K20. I did not see the new sensor as a sole reason to change an otherwise excellent body and have used it extensively.

If youplan to use the camera a lot on manual lenses, you may wish consider putting an *istD screen into it. it does meter a lot better, as my test showed.

note however, if you plan to do a lot of manual focus, a split image may be a better selection, but it won't help the metering issue,
07-06-2009, 07:17 AM   #25
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QuoteOriginally posted by Steve Beswick Quote
But the thing is there shouldn't be any need for me to do that in most situations. I've never needed to with my film bodies (all Pentax) so why should I with my dslr? I don't thnk I need to remind anybody that the K10 was top of the line when it hit the market. I personally own two handheld meters, but I feel that a top of the line 2007 model camera should be able to meter properly by itself in most situations.
Sorry guy

I am with you. Stop-down metering used to be the gold standard for accuracy. Why something so simple should fail on a modern camera is beyond me. There are multiple threads on this site devoted to the problem and possible causes. The consensus is that it has to do with correction factors that are applied to support matrix metering and the xx-80 series of focus screens.

In defense of Pentax; the metering issues are in the manual, though that does not help when the marketing hype claims backward compatibility. As I pointed out above, this is not just a Pentax problem. Nikon users have the same issue with older Nikon glass as do Canon users with the numerous mounts that can be adapted to that brand.

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07-06-2009, 07:21 AM   #26
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QuoteOriginally posted by Lowell Goudge Quote

note however, if you plan to do a lot of manual focus, a split image may be a better selection, but it won't help the metering issue,
...And that is why I have not gone to the xx-60 screen. I use a split-image/microprism so that I can accurately focus. Yes, that is the other "dirty little secret". All focus screens made for Pentax dSLRs suck for manual focus. They "feature" exaggerated DOF such that fine focus is nigh near impossible. Oh, the frustrations of using archaic lenses on modern cameras!

Steve
07-06-2009, 12:08 PM   #27
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QuoteOriginally posted by dlacouture Quote
Film has a way better "out-of-camera" dynamic range, and thus can handle quite severe under/overexposure without us noticing... And anyway, it was the minilab that usually corrected exposure problems, so you were never aware of them...

I accidentally overexposed a negative film once, by easily 5Ev (tried some fill-in flash on a beach, around noon, with the lens wide open ...), and there was still something to salvage on the film...
I often developed my own b&w. Besides, your arguement would only make sense if there were As many exposure errors with modern lenses.
07-07-2009, 12:58 AM   #28
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An update:
I called Pentax USA this morning. I was instructed to change the setting in "green button in M mode" to "Tav shift". While it has not completely cured my issues, it has made a considerable difference. I am going to test it heavily over the next few weeks, but it seems as though it has gone from up to 3EV off to a max of 1EV. The biggest errors now are at the narrowest apertures.
07-07-2009, 05:42 AM   #29
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My K100D has a split prism screen, which aggravates the preset lens metering problem (perhaps because the screen's average central brightness increases strongly as f-stop increases, a geometric optical effect concentrating light in the center.)

Metering is improved if mulitzone metering is used (non-central parts of the screen are also used for metering.) Multizone metering is possible if the camera thinks the lens is an A type.

The camera can be fooled into thinking all lenses are A type by shorting out the A pin on the camera mount. This has the added advantage of making flash work properly with preset lenses.

I used a P&S camera to photograph the viewfinder' appearance for various f-stops with my K100D (brightness graphed with ImageJ):
(some of the vignetting is due to the P&S camera)

The center's relative brightness is much higher for higher f-stops; this may be the root cause of exposure problems with preset lenses. It demonstrates why using multizone metering helps.

Dave in Iowa

PS I'm not recommending you modify anything, just providing info about what might be going on.

Last edited by newarts; 07-07-2009 at 05:56 AM.
07-07-2009, 10:07 PM   #30
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QuoteOriginally posted by Steve Beswick Quote
An update:
I called Pentax USA this morning. I was instructed to change the setting in "green button in M mode" to "Tav shift". While it has not completely cured my issues, it has made a considerable difference. I am going to test it heavily over the next few weeks, but it seems as though it has gone from up to 3EV off to a max of 1EV. The biggest errors now are at the narrowest apertures.
Interesting. What firmware version are you using? I tried to implement this fix, but could not find that option.

As for the error at narrow apertures...this is to be expected. The amount of light reaching the meter at those apertures is often below its sensitivity. What you see is an absolute flattening of response (same shutter speed at f/11, f/16, and f/22 for example).

Steve
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