Exposure and Camera Modes

I already presented some words about exposure in Exposure and Stops. Just in case here you have some more!

By Fredrik Silverglimth in Lighting, Photography, Photography Basics | May 4, 2008

The exposure is the combined factors of how long time the sensor is exposed to light, how much light comes through and how sensitive the sensor is to light. It’s based on three things, Aperture size, Shutter speed and ISO.

Exposure

There are 3 parts of exposure that you should understand. The following examples ought to illustrate how these 3 components of exposure interact with one another.

Example 1
You take a photograph with the following settings: ƒ/8, 1/250s and ISO 100
But let’s say you want to freeze the object more, which requires a faster shutter speed, you can either change the ISO or the Aperture. First of all let’s change the shutter speed 1 stop faster, 1/500s — now only half the amount of light will reach the sensor. To compensate for this and keep the exposure the same you can change the aperture size 1 f-stop larger, ƒ/5.6.
So ƒ/5.6, 1/500s and ISO 100 will give you the same exposure as ƒ/8, 1/250s and ISO 100 (but now the shutter speed is faster which allows you to freeze your object in a different way).

Example 2
You’re indoors with bad light conditions which makes your current setting too slow and are unable to hold the camera steady enough. The settings are: ƒ/5.6, 1/60s and ISO 100. Your lens’ largest aperture is ƒ/4 which is 1 f-stop larger, changing your shutter speed 1 stop faster will result in: ƒ/4, 1/125s and ISO 100. The shutter speed is still too slow and the result is blurry due to camera shake. Since you can’t change the aperture anymore you will have to change the ISO setting, 1 stop will result in ISO 200, you now have: ƒ/4, 1/250s and ISO 200 which should be enough to get a sharp photograph.

As you hopefully can see from these examples all three parts of the exposure are related to each other. If you just change one of them the result will be either an underexposed or an overexposed photograph, but if you change both you can keep the balance.

55mm, f/5.6, 1/60s, ISO 100

300mm, f/5.6, 1/800, ISO 400

50mm, f/5, 1/320, ISO 400

Overexposure

Overexposure happens when the sensor is exposed to more than enough light, resulting in white images or at least white areas in the images around the light source(s). Sometimes it’s impossible to expose the photograph correctly without getting some overexposed areas. Overexposure can be used as an effect, but most of the time it’s unwanted and avoidable.

Underexposure

Underexposure is the opposite of overexposure, and is the result of the sensor not getting enough light, the photo is dark. Underexposure can be used artistically but just like overexposure it can be unwanted and hard to avoid.

To Underexpose, or Overexpose? That – is the question

With digital cameras it’s much easier to bring back the light and colors from underexposed areas than it is to bring back shades into overexposed areas. If you’re photographing in RAW you might want to consider to underexpose your images on purpose to avoid loosing details in overexposed areas and then use a digital lightroom to bring back the light from the underexposed areas if needed. This depends on the light conditions, and indoors it can be a good idea to overexpose instead.

I personally always underexpose my outdoor photographs 2/3 of an f-stop for this reason, and have found the results much more pleasing than a “correct” exposure.

Exposure Lock

Exposure Lock is a great feature that’s available on most cameras. It’s rather easy to understand what it does, it locks the exposure so that it doesn’t re-calculate the exposure if you move your camera around. Try to find a neutrally exposed part of your object, not the light source nor the shadows but something in between, and press the exposure lock button — recompose your photograph and take the picture.

Camera modes

MANUAL MODES:

• M — Manual mode; this gives you full control over both aperture and shutter speed.
• Av or A — Aperture priority; you control the aperture and the camera calculates the shutter speed for best exposure
• Tv or S — Shutter priority; you control the shutter speed and the camera calculates the aperture
• P — Program mode; a more advanced form of an auto mode. The camera calculates both the aperture and shutter speed, but doesn’t affect settings like ISO or flash.

AUTOMATIC MODES:

• Auto — everything is on auto, including ISO, flash and image quality
• Portrait — uses a large aperture to shorten the depth of field
• Landscape — uses a small aperture to gain more depth of field
• Sport — uses higher ISO to use faster shutter speeds
• Night portrait — uses long exposures to capture the entire scene, often combined with built in flash
• Macro — uses a large aperture to great a softer background

Just Say NO! to Automatic Modes

There is no reason what so ever to use the automatic modes. After you’ve read through this series of articles about photography you should have enough knowledge to control the camera on manual modes — which will result in better photographs.

The Program mode (P) is fine to use, this way you will have the aperture and shutter automatic but still be in control over everything else. Most photographers find a mode that they like and maybe switches between two different modes, this is personal preferences and let me just tell you that far from every professional photographers uses only the fully Manual setting.

I personally use M and Av most of the time, depending on the situation. Av for the situations where I don’t have enough time to set the correct exposure between every shot and then M for the rest.

Note from JaviZ: I usually shoot (perhaps about 80% of my photos) in the Av mode since I use only RAW and I can do some PP if my camera picked a bad shutter speed… and since I have a Canon 40D that’s not the frequent case! Anyway, If I find myself compensating (EV +/-) exposure too often, then I change to M … And I agree with Fredrick, you need the Av mode if you can’t corrext exposure between every shot, for example if you are taking photographies of (wild) children!

Did you think this cute girl of two years old would wait for me to prepare the perfect shot? I think these shots took me about 2 hours!