Why is this photo dark?

Nimai

I had a friend come back from vacation with his new Canon Rebel XTi and tell me that he felt his shots were on the dark side. He gave me this as a sample, shot in Landscape mode which chose F/11 1/320 in this case:


I couldn't see any hot spots that would have caused the camera to under expose the rest of the image. Here's the histo's from Photoshop:



My only thought is that the brightness of the sky (the majority of the photo) is what did it. I recommended always eye-ing the histogram on the camera, and if it's not what you want, adjust using Exposure Comp.
A quicky Auto-Contrast in Photoshop make a big difference. (I could have gotten into HDR with him, but that's a whole other topic!)

Any ideas why the camera chose to expose this way in this shot?
Thanks!

rwells

I've never used an XTi, so take this with a grain of salt with specifics to that camera.


By default on 30D, 20D, the metering is linked to the active focus point. I don't know if this pic has been cropped, but if not the center is mainly in the clouds. The meter's thinking is to take white and turn it to 18% grey. (generalization)

So, looking at the histogram, it appears that's why the camera pushed the highlights (clouds) toward the middle (18%).


Your advise to him is good. Keep an eye on your histogram and adjust EC as needed.

pathfinder

You did not say what ISO he was shooting at.

If he was shooting at ISO 100, then on a sunlit scene, he should expect an exposure of f11 1/250th from the Sunny 16 rule. 1/320th is about 1/2 stop less than this. Knowing what is the appropriate expected exposure outdoors in sunlight can help you judge the accuracy of your metering



I suspect Randy was right, that the point chosen for light metering was the point chosen for focusing ( the default situation in an xTi) and this point was a cloud. This then resulted in the camera wanting to expose the clouds to a neutral gray, rather than a bright white.

One must remember, if you meter off snow ( or bright clouds ), you must add + exposure compensation - that is, you must increase your exposure about 1 full stop to brighten the snow from gray to white.

Antonio Correia

I don't understand very well why this is considered to be an under-exposed picture.

I can see that the histogram is to the left and it should be more to the right.

I think that - if this photo was mine - I would consider it OK and would make a good picture out of it !

How would I do this ?
I would use 2 layers and would blend them with masks and Shadow/Highlight.

May be the photos were all on the dark side because he was underexposing them un-voluntary.

pathfinder

Antonio Correia wrote:

I don't understand very well why this is considered to be an under-exposed picture.
..............................

May be the photos were all on the dark side because he was underexposing them un-voluntary.

The simple reason I think this picture is under exposed is that the clouds are a dull gray, not a real white. When I measure the pixels in the whitest parts of the clouds I get readings of about 180, 180, 180 - that is not white and the clouds SHOULD be white in a nice sunny sky. Real white is more like 245/245/245 or so. If the image had gotten more exposure, the clouds would read nearer 245,245,245 or so.

As Randy said, the camera metered off the clouds, and set the exposure to make them gray, not white. (That is what reflected meter do - it is built into them ) Just like shooting a picture in the snow with autoexposure, without + EC, Antonio.

Does this explanation help any?

Antonio Correia

Thank you Jim.
I think that an ajustment of the cursor on the right of the histogram, to the left would fix the picture.
Then, masks, Shadow/Hightlight


Have a nice weekend.

pathfinder

You are correct that shifting the white point will correct the luminosity of the image, Antonio. I, too, do that frequently, so I am not saying it is a bad thing to do. But it is necessary, because the original exposure was under exposed a bit. Since the vast majority of the information is in the higher bands of the histogram, some data has been lost, when the slider is slid to the left.

I am not saying you should not do this, I am saying that one can improve good images, even more, by better, more correct, exposure.

I'll quit beating this horse now

:deadhorse :deadhorse