Youāre right, and I didnāt take attention to that.
I made the following test: put a 18% greycard on the floor, near a well lit glass wall (sunny day outside, but no direct sunlight into the scene), set up the dial to āPā, checked that the camera was accepting speed/aperture settings and shoot 0, +1/3, +2/3, +1 EV exposures.
In Darktable, the histogram for each raw are:
0EV:
+1/3 EV
+2/3 EV
+1 EV
It seems thereās a light metering issue with the camera, isnāt it?
To tease apart your assertion, what specific thing about these histograms say that to you? Right now, all I see is some clump of image data, moving as I would expect for EV compensationā¦
Post the raw, thatāll helpā¦
I expected to see the histogram spike in the middle when there was no exposure compensation, since Iām aiming a 18% grey subject.
Here they go:
0EV
IMG_4236.CR2 (10.4 MB)
+1/3 EV
IMG_4237.CR2 (10.4 MB)
+2/3 EV
IMG_4238.CR2 (10.4 MB)
+1 EV
IMG_4239.CR2 (10.5 MB)
Out grocery shopping with wife, will look when we get homeā¦
Thanks!
Hi again!
Which metering mode do you use:
evaluative, center-weighted, partial, spot?
Have fun!
Claes in Lund, Sweden
I used evaluative for the grey card shots.
EDIT: Changed to spot and took a grey card shot again and the histogram is a bit more underexposed:
Iām sorry about this, but the previous histogram images are considering a base curve applied to the image.
Turning it off, the 0 EV histogram is like this:
and the +1 EV
Could you redo your raw files with spot metering (and the typical grey card shot considerations)?
Also, +2/3 EV and +1 EV have both ā1/15ā marked on the histogramā¦ EXIF error?
Would the 0 EV be enough?
_MG_4250.CR2 (10.4 MB)
What would they be?
Donāt have a clue. On Digikam it shows the same way.
@gadolf, the camera metering works under the assumption that illumination of pixels in a typical normal photograph averages out to middle grey.
Therefore, if you take a photo of a grey card with camera suggested exposure, its histogram will be bunched in the middle. So your cameraās metering is working as expected.
If you take a photo of a white card, the output should be a grey card and the histogram will be the same!
ā¦ but it doesnāt, right?
Take a look at the last histogram I showed (with base curve turned off). I shot that one without any exposure compensation (0 EV), with the camera suggested exposure. Shouldnāt the histogram be in the middle?
Every camera have certain tendencies. The manufacturer likes to give some signature so to speak. Your camera seem to be underexposing a stop. This does not mean malfunction. Once you know this, and if you donāt like it, then you can correct it manually.
Also, I think that you should apply the base curve to the photo for the histogram evaluation. Because the expected output is a jpeg for manufacturers. Thus the exposure is also computed with basic adjustments in mind.
If you say so, then, Iāll accept that.
In fact, my previous experience with digital cameras is almost non-existent. Before this one, thereās my powershot, and before that, a 4MP Nikon point and shoot.
The strange thing is that if I compensate, say, 2/3 stops, depending on the subject, the resulting image gets really overexposed. Itās like itās not a constant deviation.
18% grey subject.
I really do not want to make things more complicated, but are you sure your grey subject is reflecting 18%???
@agriggioās link covers that. Fortunately, you donāt need RawDigger to examine your raw files.
I wouldnāt do that if I were examining the raw file. And as I and then others have indicated, I wouldnāt process with the base curve most of the time, esp. if you are using filmic.
Other remarks
1. It is entirely possible that your metering is broken. It is not unusual but donāt assume it is so right away.
2. Metering is tied to focusing (and possibly WB). You can separate the two for composing if you prefer a feature like back button focus, etc.
3. Metering is tied to the histogram (or the live view), which is unfortunately the case for all cameras tied to the JPG preview, not the raw file.
4. Due to point 3, your metering would be off say about 1-1.5 EV if your goal is to do ETTR. We call that headroom. For less technical photographers, the headroom actually protects them from overexposure; it is a good thing unless you know what you are doing.
5. Use Manual mode. That way, you get full control over your settings. The are many settings to turn off if you want your live preview to reflect the raw output as much as possible.
6. I had other things to say but I forgetā¦ 
The problem is evaluative metering, you canāt really count on it as a base for personalized exposure. If you need to be precise measuring the light then youāll have to resort to center-weighted or spot metering.