Good Exposure is Like Pie. Or a Pantry. Hmmm.

(Are you trying to figure out your new camera?  Or do you need a quick refresher on the relationship between aperture, shutter speed and ISO in getting good exposure?  Here are some silly musings that have crossed through my mind as I practice shooting in manual.)

Think of good exposure like a full pantry.  It doesn’t matter what amount of peas vs. carrots vs. bread you have – full is full.  But if you eat some carrots, you have to replace them – you can replace them with peas or carrots or bread, as long as your pantry is full again.

For good exposure, your light needs to be “full.”  If you let in less light through a smaller aperture, you need to have more light through a longer shutter speed or higher ISO sensitivity.

The proportions don’t matter so much, as long as you have 100% of the light you need.  If you aren’t bringing in enough light, your picture is underexposed and your pantry isn’t full.  Increase your aperture size, shutter speed and/or ISO.  If you let in too much light, you picture is overexposed.  Reduce any combination of aperture size, shutter speed and/or ISO.  And donate some food from your pantry to goodwill.)

For those more visually minded, I’ve made pie charts to illustrate.  Note how each pie below is 100% full.  The proportions of the ingredients (aperture, shutter speed and ISO) are different, however.  If a piece of pie were missing, you’d have low light and an underexposed photo.  An overexposed photo, on the other hand, has way too much light coming in – think of the pie that overflowed and made a big mess on the bottom of your oven.

I shot a series of pictures all at the same exposure using a variety of settings to hit that exposure.  The pictures are all boringly the same, right?  But the camera settings are drastically different.  Click on them if you want to see the detail, or hover over each image to display the aperture, shutter speed and ISO.  On the pie charts under the pix, aperture is blue, shutter speed red and ISO green.  I used my 50mm f/1.4 on a tripod for these shots.

So Do the Settings Matter if the Exposure is Right?

According to my camera, the exposure was “right” in each of these shots.  They’re actually a little dark for my taste, but that’s another post.  As long as the camera says my settings are in balance, do I really care what the individual numbers are?  Yes.

Depending on your current shooting conditions, one of these settings will be more important than the others.  You might need a super short shutter speed to get good focus on moving kids like the shot at the top.

(Someone told me on Clickin’ Moms this week that her rule of thumb is keep the denominator of her shutter speed below twice the focal length of her lens when shooting without a tripod.  So with a 50mm, your shutter speed shouldn’t be longer than 1/100th of a second.)

Or you might want to use aperture to produce a bokeh effect to emphasize part of your image.

Or use a small aperture to make sure that there is even focus across your image.

Shooting in low light?  I prefer to keep ISO as low as I possibly can while keeping aperture and shutter speed reasonable for the situation.

So whether you are thinking of shooting in manual or just trying to figure out how your camera works, remember to start with what you want the most control over – aperture, shutter speed or ISO – and use the other settings to balance the exposure.

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