Exposure Compensation and DSLR Camera Program Modes

See that button on your camera? I bet you didn’t know what it’s for…until now!

See that button on your camera? I bet you didn’t know what it’s for…until now!


I like to think of photography as a journey. We start out eager with a camera in hand and images in our imagination, but at the beginning, we lack the depth of skills and technical knowledge to fully achieve our vision; we don’t yet grasp the “craft” of photography sufficiently enough yet to operate in full Manual mode and build the images we dream of.

On your way to Manual, there’s no better place to spend some quality time than in your camera’s Program modes. These are the letters on your Mode Dial, “P,” “Av or A”, “Tv or S” (Av/Tv = Canon, A/S = Nikon and Sony).

How do these work? Each of the Program modes offers us a deepening level of image and exposure control. Let’s start with P, in a scenario where we have the Exposure Compensation set to “0”.

Program Mode (P)

P stands for Program. How does our camera work in this mode? I like to think of it as “Phone +.” If “AUTO” mode (which is also on the mode dial) turns our camera into a Phone camera, which is basically a camera with no controls at all, and simply a shutter button, then P mode does that but adds one very significant extra feature - we can control the brightness or darkness of our exposure via the Exposure Compensation button (+/-).

This means that the camera reads the exposure of our frame (remember this means brightness level) , and chooses the camera settings of Aperture and Shutter Speed to create a balanced exposure. A balanced exposure occurs when our histogram or light meter are in the middle, not too bright, not too dark - at “0.”

The EC (+/-) button allows us to move that up (brighter) or down (darker) to suit our taste. How does this happen? The camera will adjust the aperture and/or shutter “in the background” to deliver a different exposure that is skewed in whichever direction you sent the compensation - “-” (to the left) is darker, “+” (to the right) is brighter. You have ZERO control over what changes are being made to Aperture and Shutter Speed - the camera does this.

So to recap = “P” mode is AUTO, but you can adjust the exposure Brighter or Darker.

Av / A - Aperture Priority

Av Mode (A on Nikon and Sony) stands for Aperture priority. This allows the photographer to set the camera’s aperture, and the camera will read (meter) the exposure and automatically set the shutter speed to deliver the exposure you specify with the EC button.

Stop for a minute and think about this - YOU pick the Aperture, and the camera picks the Shutter Speed. If you have the EC set to 0, the exposure will be perfectly balanced - not too bright, not to dark - with no parts overexposed and no parts underexposed. If you have the EC set to -3, the camera will pick a shutter speed to make the image very dark. If you have the EC set to +3, the camera will pick a shutter speed to make the image very bright.

Why would you pick the aperture? To set the “Depth of Field” and control one important aspect of what your photo looks like. Depth of Field (DOF) is “how much of my photo is in focus.” Wide apertures (lower numbers…f/2.8, f/4) mean shallow DOF, and less in focus. Narrower apertures (bigger numbers…f/16, f/22) mean deeper DOF, with more in focus.

Why would you do this? Portraits are a great example - shooting a picture where a person is close to the camera and they are in focus and the far background is not. At the opposite end of the aperture range (your f/16 to f/22 values) are your landscape photos are made - because landscape photographers typically want photos where the close nearground, middleground, and far background are all in sharp focus.

In a nutshell - select Aperture Priority mode to specify the aperture of the photo, and thus how much of it is in focus, or how much Depth of Field it has.

Tv (or S on Nikon and Sony) - Shutter Priority Mode

In this mode, you specify the Shutter Speed, and the camera picks the aperture. Shutter speed controls not only exposure, but also how motion looks in our photographs. Slower shutter speeds (bigger fractions of time) will show water as silky and smooth instead of stuck in time. Faster shutter speeds record shorter moments of time, showing moving objects frozen in the frame.

We choose Shutter Priority Mode when we want to control how motion looks in our photographs. Choose faster shutter speeds (smaller fractions; 1/2000th) to freeze moving objects, choose slower shutter speeds (larger fractions; 1/6th of a second, or 2 seconds) to show moving objects as blurry.

And again - whatever we have the EC button set to (remember that is a range from -3 to 0 to + 3) will dictate how the camera chooses the OTHER variable than whatever mode you are in, to deliver an image with that specified exposure.

ISO

I have glossed over one very important point until now - what about ISO? If you have it set to Auto, the camera will also pick this variable, or if you don’t it will use whatever value you have it set to - ISO400 is a good value for average daytime situations.

Phew! That’s a LOT of information. I just want to take awesome pictures!

Yes, yes it is, I know you do, and you will get there, trust me! Learning and mastering photographic exposure is challenging, and will take some time and considerable effort on your part. You have to go out and shoot, and do it wrong A LOT, and think critically about why things look the way they do. Eventually ya light bulb will go off if you stick with it and you will get it.

Let’s recap:

  • Program modes offer control over Exposure (bright versus dark) as well as how our photos look by letting us isolate and control just one of three variables at a time

  • Whatever the Exposure Compensation is set to (-3 to 0 to +3) is what level of exposure the camera will deliver, regardless of the mode

  • In P mode, the camera settings of aperture and shutter are automatic, but we can make the exposure brighter (“+”) or darker (“-”)

  • In Av (A) mode, we set the Aperture and the camera chooses the shutter speed

  • In Tv mode (S), we set the Shutter Speed, and the camera chooses the Aperture

  • Regardless of which mode we are in, after we set the variable, we can use the EC button to make the image brighter or darker (and the camera will change settings for us)

Give these modes a try, try them one at a time, and slow down and look at the images and what settings they were taken at. Eventually over time, with enough trial and error, you will begin to develop the understanding of exposure needed to craft together any image you can dream up!

Tips to remember:

  • Slow down!

  • When you switch modes (Av to Tv) to change what you are learning, set the EC to Zero right away

  • Try Auto ISO so you don’t also have to think of that exposure variable

  • In an effort to not overly complicate things, I avoided talking about the different metering modes, which allow a camera to examine the whole frame, a center weighted average of the whole frame, or a small spot on the frame. I’ll do a separate post on that in the future.

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Homework Assignment:

  • To learn Shutter (Tv or S) - take pictures of moving cars with your camera on a tripod at every shutter speed your camera has, and look at the image on a computer

  • To learn Aperture (Av or A) - take pictures of a still life (bowl of fruit) about one foot from your camera on your kitchen counter. Focus on the fruit. Vary the aperture across the range your camera has, and look at the images on your computer.