Some Simple Q's - Aperture vs. shutter

The more I learn the more I realize how much I have to learn. Sigh.

I have a Q that is basic but could use some opinions on...

When shooting a photo do you choose Aperture or Shutter Speed? I shoot mainly candid portraits and I have the Rebel XT and usually shoot with my f2.8 18-50mm (although I just got the f2.8 70-200mm).

I sometimes think - I want this to be a high shutter speed shot to freeze the action (especially of kids) - but then it sets the aperture so high that I lose the detail. Other times I think - I want everything in focus so I'll set the aperture but then the shutter speed is so slow I lose it again. I do play around with ISO but I have it in my head I should keep it as low as possible for best print results. I try manual mode but then I spend so long adjusting the moment is gone.

I do have a flash - shoudl I be using that more? That could help freeze the moment I guess. I just love natural light. If I set teh flash in ETTL will it set the shutter speed taking into consideration the flash?

Sorry for teh basic Q's but I just feel I'm spending way too long determining Aperture, shutter speed, ISO - any words of advice from the wise? (If this is discussed elsewhere I apologize - I'm new to forums and still figuring it out!)

I think most use Av.
Here is how I approach the subject. If my main goal is to control DOF, then I shoot in Av. I increase ISO to increase shutter speed (to freeze motion or what not).

If I'm trying to control motion by panning, I'll be in Tv mode and pick a slow shutter speed for panning. If I need to get more or less light, then I"ll adjust the ISO.

Good luck

I am very new to photography. I started in June of last year. Since then I have tried to soak up as much information as possible. I would encourage any novice photographer to read "Understanding Exposure: How to Shoot Great Photographs with a Film or Digital Camera" by Bryan Peterson. If you read it from top-to-bottom and then read it again, you won't be disappointed.

Answer is 'It depends'! You should Aperture first if primary importance is control of Depth of Field in the shot and motion control is secondary. You choose Shutter first if motion control is of primary importance and Depth of Field is secondary. That is what you already know and have been trying, but you then discover that there are ALWAYS TWO parameters in photoshooting that go hand in hand to making an exposure, so choosing one often hurts the other! So that is when thing like supplemental lighting enters the picture (so to speak) or gets taken away!!!

>>If I set teh flash in ETTL will it set the shutter speed taking into consideration the flash? <<

Yes, if you are in P or Av. If you are in Tv or M, the set shutter speed remains in effect, no matter if it is a good choice or a bad one!

Krista, the mode is just the means you use to arrive at a given aperture/shutter speed combination. Both are displayed in the view finder,and you need to pay attention to both. The only difference you will see in using one mode or the other is when using exposure compensation. If you are in aperture priority and use EC the camera will adjust the shutter speed and try to keep the aperture you have set (the set aperture is first priority) . But again, both values are displayed for your acceptance or change. Using shutter priority will have the opposite result The camera will hold the shutter speed you select. If you use flash there will be a slighty different set of parameters to learn.

I started with canon back in the 60's with an FT and lived though the Av - Tv wars, was really funny. Anyway I use the P mode and then use the wheel to select the settings I think will work best with what I have in mind for the picture. It makes no real difference if you use M, Tv , Av or P if you understand the relationship between the two numbers.

The best way is to be experienced with the settings. after a while, you will get the hang of it. When using the flash light, remember to bounce the light, it will give you a gentler even light.

I remember that also. Heh.

Av and Tv is exactly like M - except the camera picks one of the two values for you as a baseline exposure. You adjust from there. At that point, you might as well be in M. If you bump either the aperture or the shutter speed in any one direction, you have to bump the other the same amount the other way to maintain the same exposure. That is, if you stop down (smaller aperture) you have to increase the exposure (longer amount of time) and vice versa...

If the lighting will remain pretty close throughout a shooting situation I usually leave it on M. If the lighting changes more frequently, I'll use Av or Tv to get a little speed.