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05-25-2009, 12:33 PM   #16
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QuoteOriginally posted by J2R Quote
Well, I used an M series lens,........
Aha, that adds another element to the equation !

Quite a few of us on here use the old "K" and M series lenses, including Marc and myself.

Now it is a well known fact that the K10 (and K20) will lead to progressively overexposed shots as you stop down. The degree of overexposure is variable depending on the lens in question. I wont go into details as to why, there are hundreds of threads on the subject, and it is caused by the standard focus screen.

The upshot is that you will have to use the histogram more and make adjustments yourself to aperture and/or shutter screen to get the exposure right. Just pressing the green button wont always give you "correct" exposure.

05-25-2009, 01:02 PM   #17
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QuoteOriginally posted by Wheatfield Quote
Center weighted metering includes all of the screen in the metering pattern, it is just biasing the meter somewhat towards what is in the center of the screen.
Yes, you're quite correct, of course. I guess the off-centre sky was not quite bright enough to override the general exposure set from the rest of the scene. I'm just going through a bunch of shots I took today, mainly rather hurriedly, using my SMC-M f2.8 28mm, and trying to learn what I can from their histograms. I will check out the histogram tutorials out there on the web as well! There is a hell of a lot to learn with a DSLR like the K10D, isn't there?
05-25-2009, 01:13 PM   #18
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QuoteOriginally posted by pschlute Quote
Now it is a well known fact that the K10 (and K20) will lead to progressively overexposed shots as you stop down. The degree of overexposure is variable depending on the lens in question. I wont go into details as to why, there are hundreds of threads on the subject, and it is caused by the standard focus screen.
Yes, I discovered this a few days ago and have posted about it elsewhere myself. The reality of the problem is more complex than merely overexposing, as at the wide open end of the range, the K10D tends to underexpose. I've been trying to find out what apertures or aperture ranges each of my M lens will meter correctly at, so I can work things out from there (e.g., if I know it's metering OK at f8, I can go 2 shutter speeds slower and use it safely at f16, ignoring what pressing the green button tells me for the 'out of range' apertures). It seems to be most accurate for my Rikenon 1:2 50mm prime at f5.6, for example. Fortunately the range where it is accurate for my Pentax 300mm seems to be quite wide, which is handy.
05-29-2009, 11:36 PM   #19
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I'll borrow this fine thread for my question.

I had some knowledge of histograms before and have now read some of the mentioned histogram tutorials and I think I've got some idea what's a histogram's about. However, sometimes one sees a histogram where the midtone spikes get clipped vertically. How is that possible? The fact that there are limits to how small an exposure amount in the left/dark end the sensor can detect and how much it can take in the right/bright end before saturating seems clear and reasonable. But what on earth does it mean when the midtones spikes are clipped in "height"? Is it just that the visual presentation has a preset scale and the histogram presentation has in this regard actually nothing to do with the sensor's ability to detect the midtone/mid-bright?

I "borrowed" the picture below from luminous landscape to show what I mean.



05-30-2009, 01:58 AM   #20
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There is no "clipping" in the vertical axis. It is simply that the histogram's vertical scale does not go high enough to register the amount of pixels recording the dark/midtone shades.
05-30-2009, 11:35 AM   #21
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QuoteOriginally posted by Wheatfield Quote
Center weighted metering includes all of the screen in the metering pattern, it is just biasing the meter somewhat towards what is in the center of the screen.
Note also that the centre weighted metering will bias to the bottom of the screen a bit as well as the centre. Centre weighted metering tends to fall down somewhat when taking images in portrait orientation.

If you don't want to clip the sky highlights, one trick is to put the sky in the top half of the screen, press AE-L or use M to hold that exposure, then recompose so that the sky is less than half or more than half, depending on what you were aiming to do.
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