Av mode always underexposed

[caspertodd]

On my Canon Xt, it always seems that when I take photos in Av mode my photos are underexposed. Doing some test shots in manual mode, I set my aperture to 5.6 and shutter at 800, and the photo was perfectly exposed. I switch to Av mode and set my aperture to 5.6, and the shutter speed that is chosen is 2000, and the picture ends up being underexposed. Am I missing something here? I am using spot metering, and metering directly of the subject on the same spot each time. Any ideas?

Thanks!

 

[Rachelsne]

in av mode your camera is using its brain and being mechanical its not going to get perfect results-your eye and brain is better than the camera's brain which is why I think that your camera is better in M

 

[NateWagner]

I would assume this isn't the case, but you could also check and make sure that you don't have it set to a negative exposure compensation, perhaps -2.5 or so. This would also accomplish it. I personally have a problem with my XT but, I can usually edit the exposure compensation to make it work right (for me though it tends to over expose).

 

[Overread]

Most DSLRs tend to underexpose as a default - its part of the beast. I suppose its because the camera is making a choice for the photographer and it is safer to underexpose (and thus save details) rather than to mistake and overexpose - thus possibly blowing out details which can't be recovered

If you know enough and have time I would sit in Manual mode - however I do like to stay in AV mode as I don't have to worry as much about changing lighting when taking a shot (and as its often something fast moving I don't have time to play with the exposure in maual mode to get it right.

Shooting RAW can also help if you find it to be underexposing a lot more than you want it to

 

[NateWagner]

yeah, but the camera shouldn't be off by 1.5 stops (appx the difference between 800 and 2000). I mean, cameras will default one way or the other, but, that seems to be kind of extreme by itself.

 

[caspertodd]

I checked the exposure compensation, and it is still at default. If I change this, it will affect manual mode too right? Or does it just affect automatic modes? Could the quality of lens have something to do with it, or does that not generally affect the light meter on the camera?

I would shoot in manual mode all the time, but that is not practical for me on days when the light is changing rapidly, as overread had said.

 

[mrodgers]

Cameras use the same meter no matter what the mode used is, right?

So, if you have it at 0 exposure compensation for any of the semi-auto modes, or you set the manual settings up so that your meter is reading centered I would think the shot should be the same.

Can you set the metering different in the different modes with dSLRs in general or the XT specifically? For example, can you have spot metering set in Aperture priority but have average or matrix or whatever it is called set in manual? I can't in my camera, the metering mode is the same no matter what the shooting mode is, but I don't know about dSLR cameras.

I checked the exposure compensation, and it is still at default. If I change this, it will affect manual mode too right? Or does it just affect automatic modes?

To answer this specific question.... No, exposure compensation does not affect manual mode. With manual mode, you manually selecting the settings is the exposure. To compensate for exposure in manual, you have to be the one who decides and changes the settings (aperture or shutter).

 

[Josh66]

Can you set the metering different in the different modes with dSLRs in general or the XT specifically? For example, can you have spot metering set in Aperture priority but have average or matrix or whatever it is called set in manual? I can't in my camera, the metering mode is the same no matter what the shooting mode is, but I don't know about dSLR cameras.

I know my 10s (35mm) does this, M defaults on spot metering, everything else defaults on evaluative. I don't think the 350D does that though, pretty sure it stays the same no matter what mode you're in.

 

[RyanLilly]

Exposure comp should not effect exposure in M, because you compensate by manually increasing or decreasing the exposure, your meter just reads normally.

 

[KD5NRH]

On my Canon Xt, it always seems that when I take photos in Av mode my photos are underexposed.

What does it do in other modes?

 

[Tiberius47]

Try resetting the camera to factory defaults. I had to do that on occasion, worked fine.

 

[caspertodd]

What does it do in other modes?

I haven't noticed it with Tv mode, but I haven't been using it much. In full automatic mode it is fine. I may try reseting to factory default as Tiberius suggested since I do not remember having this problem before.

 

[caspertodd]

Well, resetting it to factory defaults seems to have fixed it! So that says that I changed something while learning the settings on my camera. I'm bad about doing that sometimes, but it's how I learn. I just wish I knew what I changed. I'm sure I will do it again though since I'm not scared to go into and change all the settings when I'm trying to learn them. I would have definitely thought that changing the exposure settings would have affected other modes, but it makes sense now that it would not affect manual mode. So at least I learned that. Thanks to everyone for the help.

 

[KD5NRH]

It wouldn't necessarily take much to get things mixed up; I've seen a lot of weird behavior from electronics in low-voltage conditions as the logic starts getting goofy signals. If your battery ran down just a bit too far one day, I could see it getting stuck on -2EV and staying there after charging.

At least it was digital; nothing spoils a good shoot like realizing a major setting problem after you develop the film from a once-in-a-lifetime opportunity.

 

[manaheim]

You might consider playing with your metering mode as well... the Nikons have (I'm using the wrong terms here, but) ...

• Spot: Metering done exactly on your focus point.
• "Slightly bigger spot": Metering done at the focus point and at a small area around it.
• Full Frame: Metering done on the entire image that you see.

The spot and bigger spot modes are going to more ensure that your subject will be properly exposed, but can cause problems if you are trying to take a picture of more of a scene than a subject.

In any case, the wrong mode can totally do what you are describing...

Say, for example, you have the classic problem of the not so well lit person with a bright source of light behind them. In full frame mode, the camera will wind up giving you a silohette of the person... not useful unless thats what you were going for. If you put it on spot mode and put the focus point on the person, it will totally blow out the window, but the person will be more appropriately focused. (There will be other issues, here, but at least you'll get that part right.)

In spot mode, you could be taking a picture of a scene and inadvertantly have your focus point on a significantly darker or brighter area in the frame somewhere, thus making your camera (respectively) over or underexpose the shot.

As Rachelsne said, your best weapon in these cases is your own brain and Manual mode, but being aware of the different metering modes will help you significantly.

A good example of a really tough scene for metering is this one...

This is, in fact, the place I learned about this problem. I tried spot metering with this, and got all kinds of horrible results. I tried full-frame with it, and got generally "ok" results, but the sky wound up being washed out too much because the area was overall on the dark side.

In the end, I used my brain and manual mode... I looked up at the sky with the cam, metered that, then looked down at the darker spots and metered those... I put it about 1/3 of the way up from the recommended exposure of the darker areas, and this was the result.

Anyway... hopefully this helps.