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Photo Friday – Exposure

February 15, 2013

From Wikipedia, the definition of exposure is:  In photographyexposure is the amount of light allowed to fall on each area unit of a photographic medium (photographic film or image sensor) during the process of taking a photograph.

If you let too much light in, your photograph will be overexposed, like this:

Image

If you don’t let enough light in, your photography will be underexposed, like this:

Image

If you let the right amount of light in, your photograph is properly exposed, like this:

Image

Proper exposure is determined by the right combination of aperture (how wide open your lens is) and shutter speed (how fast the curtain opens) for the particular situation you’re trying to photograph.

If your photograph is overexposed, too much light has hit the sensor.  you need to change the settings to let less light in.  There are two ways you can do this (well, two that we’re going to talk about).

The first way is by increasing the f-stop (aperture) so that the opening of your lens is smaller.  So, if your photograph was exposed with an f-stop of 2.0, and a shutter speed of 1/200 (this would show as 200 on your camera), then you can keep the shutter speed the same and increase the f-stop to 4.0 for a properly exposed photograph.

The second thing you can do is increase your shutter speed.  So, if you took a photo at f-2.0 and a shutter speed of 1/200, you can keep your aperture the same and increase your shutter speed to 1/400 which will keep the shutter (curtain) open for half as long.  This will result in less light coming in, and a properly exposed photograph with settings of f-2.0 and shutter speed of 1/400.  {This assumes that your original photograph was overexposed by one stop}

For an underexposed photograph, the idea is the same, you just decrease aperture or decrease shutter speed to let less light in.

If you’re shooting on an automatic mode (either fully automatic, aperture priority – av for Canon users, or shutter priority – tv for Canon users), and you find that you’re consistently unhappy with the settings your camera chooses (maybe your photographs always seem underexposed to you when you use an automatic mode), you can change the exposure compensation.  This means that your camera will meter the scene and decide which aperture and shutter speed setting is appropriate, then it will overexpose from those settings in an increment that you can decide (generally each tick is 1/3 of a stop).  Here’s a great video I found explaining exposure compensation for a Canon rebel.  You can do the same with a Nikon, you may just need to look it up in your manual to see how to get to the right menu.  (By the way, Lynda.com is an excellent source for online classes to learn photography, photoshop, illustrator, etc…  Maybe this year you should treat yourself to an annual membership?)

ASSIGNMENT FOR THIS WEEK:  Put your camera on fully automatic mode.  Take a picture.  Look at the Info to see what settings the picture was taken at (you may want to write them down).  Switch your camera to Manual mode (don’t be scared).  Set your settings to the same ones your camera chose.  Take the picture again.  It should look the same as the one you just took.  If it doesn’t, be sure your ISO is at the same setting as it was in Manual mode.  If you don’t know how to set your ISO, look at your instruction manual.  Now that you have it set the same way it was in automatic, play around.  Increase the shutter speed by 1 stop (3 clicks) and take the picture.  Does it look darker?  Now decrease the shutter speed by 2 stops (6 clicks) and take the picture.  Does it look lighter?  Put the settings back to what they were originally.  Now play with the aperture.  Increase the aperture by one stop (3 clicks) and take the picture.  Does it look darker?  Decrease the aperture by two stops (6 clicks) and take the picture.  Does it look lighter?  Keep playing around with it until you have a better understanding of how changes to the aperture and shutter speed affect your exposure.  Happy photographing this week!

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One Comment leave one →
  1. February 18, 2013 8:42 pm

    I so need this…I just need to play b/c I don’t.get.it. I don’t take time to understand and I want to! Thanks for writing it down for me and I like that photo class idea 🙂

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