The IRIS OPENING (or APERTURE) determines the amount of light you let pass through the lens. This factor is usually expressed in intervals called F/stops. The higher the number – as in F/16 – means that the IRIS is smaller, allowing less light in. In some cameras you will not actually encounter these numbers; you will perhaps only see something like a toggle or lever marked with a PLUS or MINUS that will allow you to increase or decrease the IRIS opening.
Use your PREVIEW SCREEN to get an idea as to how dark or light your photo will be. Pay attention that your BRIGHT AREAS are not too BLOWN-OUT (meaning there is no detail at all, just bright white). If the subject’s face is over-exposed, then you must decrease the IRIS opening. If the BLOWN-OUT area is of little importance – like the sky – then go with it. The same is true of the DARK AREAS being completely BLACK with no detail.
Make your IRIS adjustments according to your best judgment and then, if possible, take a couple of backup shots of different IRIS settings and choose the best later on your computer.
If you cannot get your IRIS opening to open any further, then look at your SHUTTER SPEED to see if you can lower it and thus get more light to the CHIP. (See below as how slow you want to go with SHUTTER SPEED.)
Remember, however – and this is very important – that IRIS and SHUTTER SPEED operate like a see-saw. They are connected. When one goes up, the other must go down in order to maintain a proper exposure.
You can also resort to increasing the ISO (in other words, make the camera more sensitive to light or FASTER). You can also, as I said early earlier, choose to just slip the camera into AUTO.
Turning AUTO-IRIS off is especially useful in VIDEO. Imagine a situation where your subject is on the other side of the street and there is auto traffic in between. In AUTO-IRIS, the exposure will change constantly as lighter and darker cars go by. It won’t look good. So turn off AUTO-IRIS and set your exposure for the subject and let the passing cars be as dark or bright as they in fact are.
One advantage of manual control of the SHUTTER SPEED is that choosing a lower shutter speed might be better than increasing the ISO. Usually, going below a SHUTTER SPEED of 45 will increase the possibility of a blurred image (from your hand movement). Using a tripod, or steadying yourself against a tree, or resting the camera on a rock, will allow you to shoot even below a 45 SHUTTER SPEED.
In fact, maybe your camera (or lens) has a STABILIZATION function that will cancel out your hand movements. With landscapes you can even drop into time-lapse zone, perhaps seconds at a time. But remember that if your subject is moving, time-lapse will create a blur in whatever part of the scene has movement. This might be acceptable, however, or even totally desirable. So take a few shots to see what the effect will be. You should be able to see this in your PREVIEW SCREEN and make a decision accordingly.
Most cameras now have AUTO-FOCUS, and it is a most useful tool. But sometimes it can work against you and you will want to turn it off now and then. Let’s say you want your subject to be near the edge of the frame. With AUTO-FOCUS, the camera will try to focus on whatever is at screen-center. Turning off AUTO-FOCUS, you simply point at the subject, manually FOCUS on the subject, and then reframe the shot with the subject near the frame’s edge.
AUTO FOCUS is certainly most useful in VIDEO – particularly as you PAN from one subject to another at varying distances from the camera. But in VIDEO, turning it OFF is most advantageous when capturing a scene where there may be people or cars passing between you and the subject. In such a situation, AUTO-FOCUS will go crazy every time a foreground object comes into view. It is better to turn it OFF and simply focus on the subject and let the extraneous FOREGROUND movement stay out of focus.