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Hi,

I'm shooting with a Canon 400D and I'm getting the feeling that the camera regularly underexposes by (up to) a stop. I've uploaded an example shot to flickr. When I adjust the exposure correction (see next photo in stream), the photo looks better.

I'm wondering if this is something of the environment or the camera or if I'm missing something completely different here.

Thanks,

flag	asked Feb 7 at 19:07 David Schmitt 115●5

	If you look at the RGB histogram for your example image I think you will find that the Red channel is either blown out or very close to it. Remember that the camera is trying to set the average exposure for the overall scene to match that of a neutral gray. Reds always tend to be brighter and will blow out before the other channels. In this case because your image is so dominated by red, the other channels will appear to be underexposed but if you increase the exposure then you will really start to lose the reds. – Sean Phillips Feb 7 at 21:23
	@sean: your're right. looking at the EV+1 shot, there are already places where the red is lacking details. Still, this is not the first picture where I had the impression of underexposure. Many neutral shots I do have room at the bright end of the histogram. – David Schmitt Feb 7 at 22:09
	@david: I'm sure you're right, but I'm not sure that this is actually a problem. For people shooting in jpg mode blown highlights are a disaster, so cameras will often meter to protect those highlights. For Raw shooters it doesn't matter as much because you can easily adjust in post. In my mind the real key is to know your camera well enough to be able to compensate in most situations. The gift that the LCD and histogram provide is that you can very quickly adapt to almost any situation! – Sean Phillips Feb 8 at 17:16

John Cavan · Accepted Answer · 2010-02-07 20:41:02Z UTC

A quick Google search shows there to be a lot of people complaining about this issue. I did find a discussion on DP Review that indicated that the Digic processor was a little too aggressive on the gamma curves. The author adjusted the gamma to .7 of the original 1 and felt that it was then correct in comparison to other shots of the same scene with different cameras.

In either case, I don't think the problem is you. The number of hits to "Canon 400d underexposure" is pretty hefty... You may want to see if Canon has a firmware update that addresses the issue. Otherwise, for certain, shoot in RAW and give yourself more control over the "developing" process.

Sean Phillips · Answer 2 · 2010-02-07 21:17:43Z UTC

In my experience every camera / lens system is a little bit different and you need to adjust your exposure appropriately for the system. My previous two cameras tended to underexpose by about 2/3 of a stop, but my newest camera is only out by around 1/3.

Of course the lighting conditions and the subject will dramatically impact the metered exposure, so this is more of a general impression or an overall average than an absolute. For example, if you are shooting snow or relatively small subjects against bright backgrounds the camera will always underexpose by anywhere from 1 to 2 stops. The opposite would be true for dark subjects.

The good news is that these cameras all have an LCD on the back so you can see right away how the exposure looks. combine that by using the histogram and you have a very powerful tool for getting the exact exposure you want!

systematic underexposure with canon 400d

2 Answers