Photography becomes a balancing act between Depth of Field, Aperture and Shutter Speed, with you, the photographer choosing which aspect to give the most priority to, according to what you’re photographing at the time and how you think it will look best.
So, if your main concern is controlling Depth of Field, then you give priority to your Aperture setting, because that’s the bit that controls Depth of Field. You choose Aperture Value Priority mode (AV mode) and select the best f/stop for the amount of Depth of Field you want. Your camera will then work to get the exposure right by choosing the right shutter speed for it.
Likewise, if your main priority is the exposure speed, (like if you were photographing fast-moving subjects) then you go to Time Value Priority mode (TV mode), choose the appropriate shutter speed, and your camera will select the right Aperture setting for you.
I think it’s time to throw in one of photography’s rules because you’re ready for it now: Whenever you half the size of your aperture hole you have to double the exposure time. And vice versa.
Is there anything being left out here?
Yes, of course there is.
Imagine you want to take a photo of a fast-moving critter hopping around in the weak light just after sunrise.
So you choose a fast shutter speed, like 1,000th second, to freeze the action.
At 1,000th of a second your camera might not have enough time to capture enough photons of that weak early-morning light. Wouldn’t it be nice if you could somehow make your camera more sensitive, so that it does its job with less light?
Well you can.
Back in the old film days, we used fast film for low-light situations. The same rules apply with digital.
By increasing your camera’s ISO setting you will increase the sensitivity of your sensor. Which means suddenly your camera is getting enough light again.
I haven’t discussed ISO until now because I figured you had enough to think about, and I won’t say too much more about it right now for the same reason. But here are a few things about ISO:
1 - By default, your camera should be taking care of its ISO settings automatically
2 - Increasing your ISO settings will allow high shutter speeds, or small apertures, in less light
3 - The down side of high ISO settings is that they tend to create more noise in your pictures. By that, I mean that the photos tend to be speckled with incorrectly-tinted pixels, especially in the shadow areas where the poor light issue is at its worst. Still, you might find that you can take your camera’s ISO settings up a bit without too much loss of image quality, and the pros often do exactly that.
All the other rules still apply, but just understand for now that higher ISO allows you to work in weaker light.
To learn how to crank up your ISO you might need to glance at your camera’s manual. But you must be wary of maxing out your ISO settings, or else you might get some unusable images.
There are lots of variables in photography and I could go on and on about them. For example, a telephoto lens (one with a very long focal length) will give a smaller Depth of Field than a wide angle lens at the same f/stop. But the same general rules about Depth of Field, Aperture and Shutter Speed apply.
What next?
So you’ve made it through the basic concepts behind camera exposure. How you apply this is the trick behind using your SLR camera and that is surprisingly straightforward. I want you to be nice and clear about what we’ve already learned. It’s at the heart of knowing when to choose things like Aperture Value Priority (AV) mode or Time Value Priority (TV) mode as you step outside to take your shots.
And the easiest way to make sense of it all and help you remember it, is by talking about some different situations out in the real world. You’ll see how we’re using this stuff to make decisions which drive your SLR camera towards much better photography. |