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04-30-2009, 05:28 PM   #1
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Should K20D overexpose with M lenses?

I'm in a bit of a bind here. My autofocus lenses are far away from me right now, and I'm trying to determine if a K20D is metering properly. I have two M lenses with me right now, and the K20D is overexposing by at least two full stops with either lens. When shooting really luminous whites (white rose in direct sunlight), it clips quite a bit. The rose shots I took (in both JPEG and raw formats) all have very blown highlights.

I tried the same rose shots with a Canon XSi, and it retained all of the detail in the whites. I tried to match the cameras up as equally as I could. Both cameras had a fast 50mm lens, were recording in raw, were using evaluative or spot metering (I tried both), and had no exposure compensation applied. Regardless of which aperture I tried, the K20D was always choosing a much slower shutter speed than the Canon.

I'm trying to get a hold of an F or FA lens to see if the K20D meters properly with that. But what I'd like to know in the meantime is if the K20D has metering issues with M lenses in general.

Many thanks.

04-30-2009, 05:36 PM   #2
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The short answer is "Yes". Both the k20d and k10d have metering issues with non - A lenses. I have just received an LL-60 screen (meant for *istD) and it seems to be better with the manual lenses. It will be a week or so before I've run all the tests, but it is looking pretty good right now. Depending on the aperture you set with the stock focusing screen, the non-A lens might over or under expose.

In the mean time, work your way up the apertures in M mode and find out where the best metering aperture is. Shooting Av, you will find that the camera will only operate wide open. Shooting M the aperture will stop down to your selected aperture. There are two metering philosophies for these lenses. Set the aperture and press the Green Button. The camera will stop the lens down, meter, and set the shutter speed. The other option is with the on/off switch last position set to optical preview, holding the dof position will bring up the exposure scale in your viewfinder. Turning the front e-dial while watching will allow you to set your preferred aperture and shutter speed.
04-30-2009, 05:51 PM   #3
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Many thanks for the reply! So maybe this camera's meter is OK after all. I was beginning to worry that it had a faulty meter.

I'm not following your second method of metering. The second method sounds to me like a way to choose my shutter speed manually (after having already set the aperture manually, of course). How is there any metering involved in that method?
04-30-2009, 06:22 PM   #4
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Based on your post, you haven't tried center-weighted metering. And you're using Manual mode and the green button, right?

04-30-2009, 06:28 PM   #5
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QuoteOriginally posted by asdf Quote
Based on your post, you haven't tried center-weighted metering. And you're using Manual mode and the green button, right?
Sorry, I did try center-weighted as well. Yes, manual mode and the green button.
04-30-2009, 06:38 PM   #6
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What aperture were you shooting? Try F4 and see how it works. My K10D does the same thing with manual lenses, anything above F4, and I get overexposure. At F4 it seems to meter very well. The higher the aperture number, the more it overexposes. And below F4, it seems to UNDERexpose. Or, you could go old school, and get a hand held meter, and use it to set your exposure.
04-30-2009, 07:04 PM   #7
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QuoteOriginally posted by Stratman Quote
What aperture were you shooting? Try F4 and see how it works. My K10D does the same thing with manual lenses, anything above F4, and I get overexposure. At F4 it seems to meter very well. The higher the aperture number, the more it overexposes. And below F4, it seems to UNDERexpose. Or, you could go old school, and get a hand held meter, and use it to set your exposure.
OK, I just tried f/4, checking it against the XSi. At f/4, the K20D overexposes by one full stop.
04-30-2009, 07:33 PM   #8
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Maybe I just shoot more contemplatively than others. But when I am in M mode and I see an overexposed frame, I stop it down and chimp until I get one I like. Isn't this what M is all about?

04-30-2009, 07:38 PM   #9
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QuoteOriginally posted by Timarete Quote
OK, I just tried f/4, checking it against the XSi. At f/4, the K20D overexposes by one full stop.
Or the XSi is underexposing by one full stop. Take your pick.

But seriously, look at the histogram. Is the apex of the hump near the center?
04-30-2009, 08:07 PM   #10
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QuoteOriginally posted by jbinpg Quote
Maybe I just shoot more contemplatively than others. But when I am in M mode and I see an overexposed frame, I stop it down and chimp until I get one I like. Isn't this what M is all about?
I'm actually completely fine with the idea of chimping and fiddling. I'm really just trying to determine whether or not I have a good K20D here. If it's exhibiting normal behavior and the meter is not faulty, I'll be happy just knowing that is the case!

QuoteOriginally posted by asdf Quote
Or the XSi is underexposing by one full stop. Take your pick.

But seriously, look at the histogram. Is the apex of the hump near the center?
I have been looking at the histograms of shots coming from each camera. The K20D is clipping the highlights by a lot, and the XSi is pretty much nailing the exposures. I really wish I had a DA lens here to test on the K20D. Grrrrr. Frustrating. By the way, the meter in my MX agrees with the XSi, not with with the K20D, and that's with the very same M lens mounted.

Last edited by Timarete; 04-30-2009 at 08:18 PM.
04-30-2009, 08:25 PM   #11
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QuoteQuote:
The short answer is "Yes".
Well, actually, the ~correct~ answer to the question "Should K20D overexpose with M lenses?" is ~NO~!

Unfortunately, due to the crippled K-mount, the answer to the question "Does the K20D overexpose with M lenses (or K lenses)?" is indeed YES.

:-(

Last edited by fwcetus; 04-30-2009 at 08:52 PM.
04-30-2009, 09:26 PM   #12
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QuoteOriginally posted by Timarete Quote
OK, I just tried f/4, checking it against the XSi. At f/4, the K20D overexposes by one full stop.
Both my M lenses prefer f/5.6 to f/8 for metering. Don't use a stop specified by anyone else - you don't have the same lens. f/4 probably works for a 50/1.7, but it sure doesn't work for a 100/4 or a 400/5.6. Do the aperture, green button, aperture, green button all the way across the aperture list with the camera on a tripod or bean bag, looking at something average. Then run the histograms and you will find the sweet stop. Use that to meter.
04-30-2009, 09:39 PM   #13
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Mea Culpa.

QuoteOriginally posted by fwcetus Quote
Well, actually, the ~correct~ answer to the question "Should K20D overexpose with M lenses?" is ~NO~!

Unfortunately, due to the crippled K-mount, the answer to the question "Does the K20D overexpose with M lenses (or K lenses)?" is indeed YES.

:-(
I answered the unwritten question. You are indeed 100% correct. They should not expose badly. But they do.
04-30-2009, 09:43 PM   #14
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QuoteOriginally posted by Canada_Rockies Quote
Both my M lenses prefer f/5.6 to f/8 for metering. Don't use a stop specified by anyone else - you don't have the same lens. f/4 probably works for a 50/1.7, but it sure doesn't work for a 100/4 or a 400/5.6. Do the aperture, green button, aperture, green button all the way across the aperture list with the camera on a tripod or bean bag, looking at something average. Then run the histograms and you will find the sweet stop. Use that to meter.
Good advice, thanks. One of the two lenses is a 50/1.7. That's the one I last tested at f/4. It was better at f/4 than at f/8, but was still overexposing. The other lens is a Vivitar 90mm f/2.5, and it likewise seems to be overexposing consistently. I'll run a proper test on a tripod with both lenses to find the happy aperture with each. And I'll just assume that my DA lenses will perform normally on this K20D when they get the chance.
04-30-2009, 09:43 PM   #15
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QuoteOriginally posted by Timarete Quote
Many thanks for the reply! So maybe this camera's meter is OK after all. I was beginning to worry that it had a faulty meter.

I'm not following your second method of metering. The second method sounds to me like a way to choose my shutter speed manually (after having already set the aperture manually, of course). How is there any metering involved in that method?
Pulling the on/off switch into optical preview position stops the lens down and turns on the meter. With the K10 and K20, an exposure scale shows in the viewfinder and the top LCD. You do match needle metering, basically. I prefer it. It also gets around things when you know the meter is going to be underexposing because everything is white. You just add the appropriate set of bars. Think snow. Meter the snow, add two stops of exposure on the scale, and you are set. You don't have to green button, then open up two stops. Try it. You might like it. You might hate it, too, but that's ok by me. Different strokes.
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