Changing the dial from auto to P, Av or Tv



I'm very much still a beginner, whilst I've taken quite a few photos that I'm proud of, most of them have been taken on auto or on the preset options, with a few taken with slow shutter speeds, light trails and waterfalls. I'd like to ask a couple of questions that will probably seem really stupid, but hopefully I'll get cleared up. I'm wanting to start getting more creative and I quote I read in a magazine was "using a DSLR on auto is like buying a porsche and using it only to do your weekly shopping", so I'm looking to get into the creative zone.

There was an article on street photography in a mag I read, it stated the best way to shoot street candids is to select Tv or Av so you're ready to shoot. My question is, how do you select the shutter speed or aperature when doing this?

Another thing I've heard mentioned is metering, how is this done?

Like I've said, probably really obvious questions, but I'd appreciate help.



Well-known Member
First question is easy - just turn the command dial. In aperture priority this will change the aperture, but it'll also change the shutter speed to balance it (higher aperture value = lower shutter speed and vice-versa). Same thing goes for shutter priority - you pick the shutter speed you need, and you'll see the aperture value adjust to the lighting conditions.

Metering just the camera measuring the light. Mostly you leave in on the default mode, when it just evaluates the whole scene and makes a best guess as to the correct settings. If you've got extremes of light and dark in the image though, the camera can get it wrong. You can override the cameras metered value +/- a certain amount, or use a centre weighted matering mode, or switch to full manual and view the meter reading and set your own shutter/aperture (these days very few people seem to do that though).


Well-known Member
Hi Dave.
I beleive that you own a 350D. Rather than me trying to explain how you should go about using the creative modes, I'd recommend spending some time reading this tutorial. It's catered for the 350D user (or Rebel XT as they call it in the USA) and, like it did with me when I first got my 350D, will greatly help you understand a lot more about your camera. It covers everything from shutter speeds and aperture control to ISO's and metering and more. I also found it very easy to follow. Another recommendation is to get yourself a copy of Understanding Exposure. A fantastic book for anyone starting out in SLR photography as the author explains things in a very simplistic way.


Distinguished Member
Tv (Time Value) = Shutter speed. Here you set the shutter speed and the camera works out what the best aperture and sets it for you (and ISO if set to auto). Shutter speed is primarily used when motion is the most important aspect of a photo - slow shutter speeds cause blur and make photos look dynamic and fully of movement. Fast shutter speeds 'freeze' motion or time. Exactly which one to use depends on many variables and also what you are trying to do creatively.

Av (Aperture Value) = Size of aperture. You set the aperture and the camera works out and sets the shutter speed (and ISO if on auto). Aperture is primarily used to control DoF (depth of field). Big number = small aperture size and wide DoF (objects far and near in focus). Small number = large aperture and narrow DoF. Its a little confusing to begin with - they way i remembered it was by thinking larger number mean larger DoF.

The smaller the aperture is, the slower the shutter speed will need to be. So you cant always have your cake and eat it :) But, there is usually several combinations of Tv, Av and ISO that will get the right exposure - that why full manual is handy when getting really creative. I try to shoot on manual all the time (never even used a dSLR until 2 months ago), unless im in a rush and need Tv ot Av.

Buy Understanding Exposure as mentioned about. It like a kind of rite of passage it would seem to read that book (Bryan Peterson must have made a fortune from that book, written in the 80's and still the most recommended photography book!).

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