Focus-Exposure Lock

Before I start off, let me tell you that this is one of the things that I find very irritating when a friends says that he/she doesn't know what it is and how to use it. Come on, if you call yourself a photographer or are even trying to be a decent photographer, then you ought to know how to use this feature of the camera.

What it is
So... focus-lock is also referred to as half-press, exposure-lock and so on. In most of the cases, unless your camera has a dedicated button for focus-lock or exposure-lock, this button is the shutter press button. Or, in other words, the same button that you click to take your photographs. Let us call this button the shutter-release from now on so that we have a consistent naming convention across this post.

The feel of this button
Now this is what it is. Unless you have a really cheap or feature-less camera then your shutter-release will have two steps of clicks as you press it. Most importantly you have to realize the feel of this button before knowing what it does. Unless you are able to press it correctly, there is no point knowing what is its use. So pick up your camera and bring it to the computer. There is no need of switching it on as this is a mechanical button and will work the same whether your camera is on or off. If your camera is really old and you have been monstering your way through that button, then it might have become soft and you wont realize the feel, and it might well be harder for you. I have seen this happen in only one camera till now - a friends Sony DSC-H1, where after less than a years use the button lost its half-press sensitivity and the functionality was totally lost.

So, now that you have your camera with you, take position and press the shutter. Give a slow/soft/slight pressure with your finger(I do hope you use your index finger to click. You can use other fingers of course, but the index finger is most responsive to touch/pressure and you are most likely to find the half-press point with this finger) and push the shutter down. Some cameras might have a hard shutter and this might need a harder push with your finger. Nevertheless, keep a constant pressure on the shutter and maintain that pressure as you push the shutter down. Feel the shutter as you push it down. At one point the shutter will stop and you will feel as if it has been pressed down fully. Of course, if it is your first time then you might well have pushed it all the way down. ;)

Keep trying this till you get that mild jerk/feedback as you slowly(really sl-o-o-o-w) push the shutter-release down. You will know that you have reached the half-press point if you get the feedback but you can still press the button all the way down. That is exactly what this half-press button is. If you press it half-way(till the click or feedback point) it does some functionality without taking the photo and if you push it all the way down, then it actually takes the photo. Try this again and again till you are able to get the half-press point every time. Increase the speed of the shutter-release, by giving more pressure each time, till you get really comfortable with this process.

Seeing it in action
OK, its great that you were able to find the 'sweet spot' on the shutter-release. Now the interesting part. You actually have to hold it at that point for about half a second to one second. Again this duration is dependent on the camera. If you press it completely by mistake or release it a little bit then the effect, and effort, is lost. Let us now see this feature working so that you know whether you are holding it at the spot correctly or are releasing it prematurely.

So switch on your digital cameras and keep it in the shooting mode, ready to take pictures. You will see a small square in the center of your LCD screen. This is how it is in most of the point-and-shoot cameras. In case of other more advanced cameras, when you look through your viewfinder(Optical or EVF depending on whether you are using an SLR or an ultra zoom camera) or the LCD screen, you will see a square, multiple squares, a dot, or small squares/rectangles with dots or cross-hairs in them. Whatever it is, these are the focusing points on your camera.

Now when you half-press the shutter-release button, while attempting to shoot an image, you will notice one or many of the following things.
1) The focusing point(square or cross-hair, or dot) changes color or flickers with a different color. i.e in some cases the square turns red, in some cases the dot within the square turns red and so on. You will notice a marked change in the focus indicator.
2) There is a green/red circular spot that appears on the screen. Mostly in the top area.
3) The screen flickers and shows an exposure change. An exposure change means the image on the screen becomes brighter or darker or just flickers.
4) The image blurs and then becomes sharp again. This indicates that the camera is focusing.

This is the half-press point. To confirm that you are pressing it correctly, you can check that the indications mentioned above happen just once. Once the indication happens, it continues to remain that way on the screen, i.e screen doesn't keep flickering, the green spot stays continuously on the screen and so on.

If you release the shutter-release button then the indication disappears or if you press it completely by mistake then the photo gets taken. Try holding it at this point for a few seconds so that you are comfortable with the amount of pressure to keep on the button. Once you are comfortable holding it at this point for long time, depress it completely. You will find that the image is taken. Try to take the image as you would do normally - completely pressing the button at once and notice the behaviour of the camera. Then try to hold at half-press point for 2 seconds and then take the image and notice the behaviour of the camera. Try and compare these two ways to take a photo and note down the differences and try to find out what is happening.

In the next post we will take a detailed look at what functionality this offers and how it will improve your photo taking skills.