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.

Shutter/Aperture Priority

Some cameras have modes called shutter priority and aperture priority. These are not available in the basic point-and-shoot models but in some of the more advanced models. These modes are usually represented in the mode dial by S or Tv for shutter priority and A or Av depending on the manufacturers wish.

Shutter and Aperture priority modes are a sort of semi-automatic modes. In the fully-automatic mode, the camera will choose the shutter speed and the aperture value automatically depending on the exposure. These automatically chosen values cannot be changed or can be modified using a 'program-shift' feature that some cameras provide.

But now, in these modes, you have the option of choosing the shutter speed or the aperture value on your own and the camera will adjust the other parameter depending on the light and required exposure. For example, suppose the automatic setting requires an aperture of F/5.0 and shutter speed of 1/200s. Now, in the aperture priority mode, I set the aperture to F/2.8. Now the amount of light has increased because of the wider aperture. So correspondingly the shutter speed will be decreased to about, say 1/500s, by the camera, since it is in the aperture priority mode.

Similarly in the shutter priority mode, you are allowed to change the shutter speed value and the camera automatically chooses the best aperture value for a good exposure.

This might not sound very interesting during normal photography, but it makes for very simple shooting when shooting some creative photos.

Exposure

Loosely an exposure is defined as the process of light entering the camera and forming an image on the lens/film.

Exposure is a term that is used widely in photography. An exposure is something which indicates that light is passing into the camera through the lens. Usually exposure is quantified by an other term depending on the quality of the photograph.

For example, one of the usages of exposure is in qualifying the image. Consider the set of photos below. Assuming that the photo in the center is how we want our image to look like, you can easily make out that the photo on the left is darker than desired and the photo on the right is brighter than desired. This means that less light than necessary entered the camera to form the image in the left case. Hence the photo was not exposed correctly, in this case the photo is 'under'-exposed. Similarly in the right photo, too much light found its was into the camera and hence the photo is 'over'-exposed. Since the photo in the center is what we need, we would say that this photo is exposed correctly.


So we have now come across the different exposure qualities. Lets say we consider the under-exposed photo. Why is the photo under-exposed? It could be because the shutter speed was too fast, or the aperture was too small or a combination of both. Similarly the over-exposed image was a result of the shutter speed being too slow, or the aperture being too wide or a combination of both. From either cases we realize that exposure is a resultant of the shutter speed and aperture. Exposure is directly proportional to aperture and inversely proportional to shutter speeds. This is the mathematical definition of exposure.

Mathematically,
Exposure = Aperture / Shutter Speed.
[Note: There might be other factors affecting exposure, but this is the relation of exposure with aperture and shutter speed]

To achieve good exposure one must choose an ideal combination of aperture and shutter speed. In the point-and-shoot mode, the camera itself has an automatic control mechanism where it would choose the aperture and shutter settings for correct exposure. In little more advanced cameras there is a shift mechanism whereby you can set an increase in shutter speed and corresponding decrease in aperture or a decrease in shutter speed and corresponding increase in aperture. You might wonder where is the necessity to modify the automatically chosen shutter and aperture settings. This part we will cover in the posts on how to get creative with aperture and shutter. For now its important to understand the relation of Exposure to Aperture and Shutter-speed.

The other usage of exposure is 'long'-exposure and 'short'-exposure. Long-exposure refers to taking a photo keeping a longer shutter speed duration while short-exposure is one where the shutter speed is very high. The reasons for long and short exposures will be looked at in the posts that deal with creativity.

Shutter Speed

Whenever an amateur photographer wishes to break out of his shell and get into some serious photography then he would have to start learning about 2 important features of the camera. The shutter and the aperture. In this post we will have a look at the shutter of the camera.

So, what is this shutter?
The shutter is something which covers the opening to the sensor of the camera. If the shutter is closed then there will be no light going to the camera and if the shutter is open then the light will reach the camera and it will be able to capture the image of the object that you are pointing the camera at. You can think of the shutter as something similar to your eye lid. When you open your eye lids, light enters and you are able to see. When you close your eye lids, no light enters and you are hence not able to see anything.

Shutter Speeds:
So, what can you do with the shutter to influence the photos that you take? You can set a parameter in the camera called shutter speed. The shutter speed dictates the duration for which the shutter will remain open hence allowing light into the sensor/film of the camera. Shutter speed is measured in seconds. If you set the shutter speed value as 1s, then that means the shutter will be open for 1 full second. If you set it to 1/500s, then that means the shutter will be open only for 1/500th of a second.

How do you think the shutter speed can influence the image formed? Think of when you were a kid and you used to burn leaves/paper using a magnifying glass. You had to focus the rays of the sun onto the paper for a good number of seconds before the paper caught fire. If you had held it for just a few seconds then it wouldn't have made a difference to the paper. If you had held it a little longer then you would have noticed that the paper start to get charred. What I am trying to say is that the intensity of light that the paper receives, is directly proportional to the amount of time for which light falls upon its surface. Similarly, if the shutter is open for a short duration then less light enters the camera, than if the shutter is open for a longer duration.

Usually shutter speeds are not mentioned anywhere on the body of the camera as a major specification. This is very much unlike the other parameters of the camera like aperture, zoom, megapixels etc. This is because not many people look for the shutter speeds when buying a camera. Usually the compact cameras have a fastest shutter speed of 1/2000s, larger(and costlier) ones have it at about 1/4000s. Semi-pro SLRs have much faster shutter speeds at 1/8000s. On the other hand the slowest shutter speeds can range from 2s in some compacts, to 8s in the majority of the compacts. Some more advanced compacts have slowest shutter speeds in the range of 30s - imagine the amount of light entering the camera at this setting. SLRs have a mode called bulb mode, where the shutter is open for an indefinite time till a pre-defined button is pressed.

We shall see how to be more creative at taking photographs using the shutter speeds in a later post. For now this is all you would need to know about shutters in cameras.