350D/XT dynamic range

There seems to be a number of ways in which dynamic range can be measured, and that is a problem. The 7-stop chart may be useful from a printing point of view, but how much brighter is a light bulb compared to pure black in terms of stops? How about the sun? Photography hasn't the ablility to light beyond pure white, and printing can only go as white as the paper allows.

Of course, the dynamic range of the camera can go beyond those extremes if it can allow recover of detail from shadows beyond those which are seen on the screen, or pull down blown (or almost blown) highlights to reveal details in the high-to-over exposed portions of the image. And that's what the dynamic range is about - the ability to move the exposure around a bit after-the-fact to show that parts of the image that may be hidden at the extremes. Remember that all that end-to-end detail still needs to be squeezed into the narrower dynamic range in which the monitor or printer/paper can display.
This can be a fascinating subject.

Tom makes several good points. The contrast range of a scene can easily exceed 10000:1 (more than 13 stops) and go up to 100000:1 or more. OTOH, that much contrast is pretty taxing to the human visual system, which, I read somewhere, can only comfortably process at most 10000:1 contrast range. That's different from the sensitivity of the human visual system, which perceive everything from starlight to the sunlight, which is easily a difference of 100000000:1, just not all at once.

Movick you have made several massively wrong assumtions and plain obvious mistakes in your argument.I won't go into detail,it's not worth the effort.The previous posters have mentioned the main mistakes.
I'd advise some serious study into this subject.Starting with the EV scale would be a good first step

hey guys before we go on super technical details, please help me. The main reason I post this is because I'm suspecting my XT has a problem in its dynamic range, I think it's to narrow. normally I use partial metering since that's the only mode available on XT closest to spot metering (I think). I notice that bright areas on a scene gets washed out easily even if the camera measures only about 2 2/3 stops of dynamic range. for example, in Av mode partial metering, i get a 1sec for the dark areas and 1/8sec on bright areas. that's just about 3 stops right, when I set the camera to expose the scene for 1 sec, the bright area gets washed out but the dark area is exposed just right. is this normal? please help because I want to be sure before taking my camera to a service center.
Thanks you very much.

Post a couple of sample photos, pref straight from the camera, or even better put RAW files on a web server and post the links.

Yes, that's normal. 1 sec. to 1/8 sec. is a 3-stop difference, putting anything that should have been exposed at 1/8 on the very bright part of the "spectrum" (i.e. looks washed out) when exposed at 1 sec.

If the dark area is supposed to be very dark, then the exposure for that part should be given less exposure than recommended by the camera because the meter always wants to make everything mid-gray in tone. Like-wise, the bright areas needs to be given more exposure then recommended for the same reason. If you had taken the shot with, say, 1/2 or 1/4 sec, then both the dark area and the bright area would probably have come out looking more properly exposed.

PacAce wrote:
Yes, that's normal. 1 sec. to 1/8 sec. is a 3-stop difference, putting anything that should have been exposed at 1/8 on the very bright part of the "spectrum" (i.e. looks washed out) when exposed at 1 sec.

If the dark area is supposed to be very dark, then the exposure for that part should be given less exposure than recommended by the camera because the meter always wants to make everything mid-gray in tone. Like-wise, the bright areas needs to be given more exposure then recommended for the same reason. If you had taken the shot with, say, 1/2 or 1/4 sec, then both the dark area and the bright area would probably have come out looking more properly exposed.

Yeah, I tried stepping the exposure compensation down to -1 and the image looks much better. thanks everyone! still much more to learn

-randal