Strange metering with a Rebel XT - HELP!

DrDavid

I've recently noticed that when the camera is in Tv or Av vs P the metering is totally different...

For example, if I set the camera to Av mode, and set an aperture of 4.0, it will want a shutter speed of about 0"3!! But, in P mode, with the same ISO, it chooses 1/60 f4.0 all by itself. 0"3 vs 1/60 is a HUGE difference. It was the same photo, same lighting, same everything. The only difference is that when I choose Av or Tv, the other variable is way strange vs. in P mode.

Anyone know why this happens?

David

Richard

DrDavid wrote:

I've recently noticed that when the camera is in Tv or Av vs P the metering is totally different...

For example, if I set the camera to Av mode, and set an aperture of 4.0, it will want a shutter speed of about 0"3!! But, in P mode, with the same ISO, it chooses 1/60 f4.0 all by itself. 0"3 vs 1/60 is a HUGE difference. It was the same photo, same lighting, same everything. The only difference is that when I choose Av or Tv, the other variable is way strange vs. in P mode.

Anyone know why this happens?

David

Are you using the same metering mode in P as in Av and Tv?

Foochar

DrDavid wrote:

I've recently noticed that when the camera is in Tv or Av vs P the metering is totally different...

For example, if I set the camera to Av mode, and set an aperture of 4.0, it will want a shutter speed of about 0"3!! But, in P mode, with the same ISO, it chooses 1/60 f4.0 all by itself. 0"3 vs 1/60 is a HUGE difference. It was the same photo, same lighting, same everything. The only difference is that when I choose Av or Tv, the other variable is way strange vs. in P mode.

Anyone know why this happens?

David

I'm not sure about this, but I'm thinking that in P mode it is deciding on its own to use the flash. In Av and Tv mode it wants you to make the decision to use the flash, and unless you press the flash button it won't use the flash...

aj986s

Have you tried taking the same photo with different settings? Are the resulting photos acceptable? Maybe you can also confirm settings via the pics exif info. Is there any possibility that the camera has inadvertenly been set with an erroneous default EC setting while in AV/TV? Or maybe P has a default adjustment.

DrDavid

I'm shooting with the 580EX flash on the camera. I'm going to take some test shots and upload them so you can see the EXIF, etc.. It's just really strange...

In Av mode, when it wanted 0"3, I switched to M, dialed in f4.0 and 1/60, and the picture was perfect (but the camera was complaining it was going to be underexposed).... Let me post some images later when I get a chance.

Richard

DrDavid wrote:

I'm shooting with the 580EX flash on the camera. I'm going to take some test shots and upload them so you can see the EXIF, etc.. It's just really strange...

In Av mode, when it wanted 0"3, I switched to M, dialed in f4.0 and 1/60, and the picture was perfect (but the camera was complaining it was going to be underexposed).... Let me post some images later when I get a chance.

Ah, you were using a flash. In P mode with a flash, the camera will meter for the subject and pretty much ignore the rest of the scene. It will set the flash to properly expose the subject, and it will almost always choose 1/60 sec. In Av mode, it will meter for the background and use the flash in fill mode for the subject.

BigAl

with Richard. See p96 of the manual - it is one of the more painful lighting implementations on Canon cameras (and the only override is 1/200s on CFn3). I use M for flash photography to get the lighting as I want it.

DrDavid

BigAl wrote:

<img src="https://us.v-cdn.net/6029383/emoji/15524779-Ti.gif&quot; border="0" alt="" > with Richard. See p96 of the manual - it is one of the more painful lighting implementations on Canon cameras (and the only override is 1/200s on CFn3). I use M for flash photography to get the lighting as I want it.

Argh, what a pain.. I've avoided full manual mode because I like(d) being able to get the camera to meter for me and set the other variables.. I guess I just need to bite the bullet and do it for real. I know what I'm doing--it's just a lazyness thing. <sigh>

Thanks for the info -- that clears up a lot of the frustration I was having. Now, to figure out how to work around this issue without too much agrevation. Any good suggestions?

David

DrDavid

Just read the manual.. What a pain.. I wish there was a middle ground with this; I'm guessing that the better camera bodies (30D/40D/etc) don't have this same issue? Or, is it a Canon issue?

David

jdryan3

DrDavid wrote:

Just read the manual.. What a pain.. I wish there was a middle ground with this; I'm guessing that the better camera bodies (30D/40D/etc) don't have this same issue? Or, is it a Canon issue?

David

Canon issue. Try this thread in the Techniques section as a jumping off point.

The resources Pathfinder put together, while lengthy, are well worth the read. They explain what priority each element takes in each shooting mode.

ziggy53

This is not related to just Canon cameras.

Once you understand "how" electronic flash works and how it can factor in to the exposure, you have a choice to make whether the flash is to be the dominant light source (the "Key" light) or a supportive light (a "Fill" light, for instance).

Like anything important in life, it can take some getting used to, but once you learn the technique of proper lighting it gets much easier and faster.

I tend to use either full manual or aperture priority mode and I use the appropriate modifier to achieve the best results according to the situation and the environment. Typically I use a bounce card device for low ceilings and a "scoop" reflector for high or colored ceilings.

I will use direct flash for fill light, but rarely anything else.