Equal and Opposite Reactions and Camera Settings

Know The Reactions When Changing Camera Settings

Things that happen when changing your camera settings

No matter what settings or modes you use, there is always only one “perfect” exposure and this can be captured with either;

A slow shutter speed (long exposure/more light…30th/sec, 15th/sec, 1 second etc) and small aperture in the lens (small hole/less light…f8, f11, f16 etc)

A fast shutter speed (short exposure/less light…125th/sec, 250th) and large aperture in the lens (big hole/more light) and so on…there is still just one perfect exposure. How you capture it is up to you and the effect you desire.

A fast shutter speed (less light), small aperture (less light) and high ISO (400, 800, 1600…) to compensate for the lack of light from the other two.

A slow shutter speed (more light), a wide aperture (more light) and a low ISO (200, 100, 50) to make the sensor less sensitive due to the larger amount of light let in by the other two.

Note: Imagine a set of scales with three trays, one for ISO, one for Shutter Speeds and one for Apertures. These always need to be balanced. Any change in one settings needs to be compensated with another.

For example, let’s say you are taking a landscape photo and your camera gives you a correct exposure meter reading of:

Shutter speed – 125th/sec, Aperture – F5.6, ISO – 100

This will give you a perfect exposure but if you change/increase the shutter speed to 250th/sec (faster by one stop as there is fast movement that you wish to capture) you are letting less light in and are in danger of underexposing the image.

Therefore, you need to adjust either the aperture or ISO by one stop to compensate and give that light back.

So this would give you an aperture of F2.8 (wider by one stop to let more light in) or an ISO of 200 (more sensitive by one stop to let more light in).

OR, if you changed the aperture to F8 to increase the depth of field (this allows more of the photo to be in focus…F2.8, F4 means not much will be in focus), again you need to compensate as you are decreasing the amount of light coming in with a smaller aperture.

So, you now need to either change the shutter speed to a slower 60th/sec (one stop increase to let more light in) or set the ISO to 200 (to make the sensor one stop more sensitive).

Your turn! Grab your camera and try this.

Go outside (if weather is ok), set your camera up on a tripod if you have one and place an object, any object, about 4 feet from the lens.

Set your camera to manual exposure and manual focus and focus on the object using 50mm focal length on the lens (whether it is a fixed lens such as the 50mm 1.8 or a zoom such as the 18-55mm…set it to 50mm.

Set a shutter speed of 125th/sec, set the aperture to f8 and set the ISO to 100

These are the settings most likely to give a correct exposure on an overcast day. They may change if it is sunny where you are.

Look at the light meter through the camera or on the LCD and if it is currently over or underexposed, adjust either the shutter or aperture (or both) until you have the correct exposure. (This will give you a kick start for trying manual).

Let’s assume you have the same reading…125th, f8, ISO 100. Now, take a photo.

Next, change the aperture and shut it down to f16…the meter should now show you will underexpose if you take a shot.

Change (decrease) the shutter speed to get the correct exposure, bear in mind it could be quite slow, hence the tripod. You should get between 15th/sec and 60th/sec…take a shot.

Now change the aperture to as wide as it will go, for many of you this will be f5.6 but if you can, go to f2.8 or wider (f1.4, f1.8) and change the shutter speed accordingly. It should now speed up to between 200th/sec and 500th/sec or faster…take a shot.

Either use the rear screen or load to your computer to look at all three images in turn, they should all be correctly exposed but look at how much is in focus at f16 compared to wide open (f2.8 etc). This illustrates depth of field and the need to counter one action with another to keep the correct exposure. It also illustrates how much control you have depending on whether you want to blow out the background or keep it in focus with the subject.

You can also practice this with the ISO to see what effect it has…it is all about practice!