One of the most interesting features of your camera is controlled by this button which generally sits near where your right thumb would be when clicking.
Its called the Auto-Exposure lock by Nikon and is denoted by a * button in Canon. It can lock 2 things, exposure and focus. In this part of the blog I will be covering the Exposure part only.
The function of this button is to lock the metering once you press this button. What does this mean?
It means that if your camera has the following exposure value for something
Shutter : 1/1000
Aperture : f/8
ISO : 400
Once you press this button, the camera will not change these values even if the light conditions change.
Why would the light conditions change? Well, maybe you decided to move the camera but why?
There are a lot of situations where this might be needed.
For e.g. lets say you have gone to a show/drama and the speaker is always lit by a spot-light. You would inevitably end up using spot metering as the default, because everything else is completely dark right? Good, so once you decide to use spot metering you encounter another issue especially with Canon.
In Canon cameras (all except the 1Dx and 1DxMark2) the Spot Metering is not linked with the AF point unlike Nikons.
So does that mean that all Canon guys will have to keep the subject in the centre?
No not at all. It just means that the Canon guys will first keep the speaker in the centre, let the camera take the exposure reading from there, then press the AE-L/* button so that the camera locks it and then they are free to recompose and click.
Does it make it useless for Nikon guys then? Well not really.
- Imagine that you want an image which is rim-lit. How do you do the exposure for it? The easiest way is to point your camera towards the source of light, and then once the exposure reading is done, lock the settings and recompose to shoot your subject.
- Silhouette : Either achieved by underexposing or easier still, aim the camera at the brightest area in the scene, lock the exposure reading and then recompose and shoot.
I like this way of doing rim-lit and silhouette more than exposure compensation as it does not need to be reset. It automatically unlocks so I don’t have to worry about the future images going dark/bright because of this.
Go ahead give it a try guys