How To Expose (Your Picture) Properly, For Photography Beginners - The Practical
On your power user camera, there should be, on the mode dial, these modes: P; Av; Tv or Sv for some manufacturers; M. These are what you are going to use to override the camera settings for the exposure. Have your camera ready for some hands-on.
M is for Manual. It hands total control of the camera over to you - you have control over everything from aperture; shutter speed; ISO independently to things like white balance; flash compensation etc. which for the purposes of this article are not so important.
From the theory you already know, give the settings a twirl. (Most cameras should do it using some sort of dial, refer to your user manual for the exact method.) Most digital cameras with LCD screens should have exposure simulation functions to show you, in real time, the effects of the changed settings on the picture luminosity. Otherwise, just take a shot and compare.
Change the aperture. You will notice as how I mentioned earlier, the picture goes dimmer as your f-number gets smaller (Try f/5.6 to f/18). Compensate for this by upping the ISO or the shutter speed and you will slowly see your picture, from being under-exposed, to having a proper normal exposure again - that is to say, looks just bright enough - like human vision. Some cameras have a meter to help objectively guide for you to the correct, normal exposure. Take a shot and zoom in on the picture. Do you see the increased noise with higher ISOs and how difficult it is for a steady shot at longer shutter speeds? Do you see that regions out of the point of focus get blurrer as your aperture gets wider because of the decreased DOF? There you have it, you have observed what you learnt from theory.
Now try to take a picture. A normal picture. Take a picture of the clock on the wall in a well-lit room, for instance. Then, go to somewhere dark and take a shot, adjusting for exposure if necessary. Then, go back to the room and take a shot of a chair or something else. Now repeat the process five times, or until you get tired of it.
Now how long did you take? Do you think you'd be faster on automatic mode? Starting to miss the usual automatic mode on your camera now and appreciate the hard work your camera is doing without your knowledge all the time? Ah, but you have already been sold on the shortcomings of full automatic. Would you not wish to have like... A semi-auto mode for you to just tweak the important things as needed?
That is what Av (Aperture Priority); Tv (Shutter Speed Priority) and P (Program) modes were designed for. Aperture priority lets you just adjust the aperture value and ISO (Most cameras allow you to leave ISO at Auto so that you don't need to worry as well), and the camera will take care of the shutter speed. This is useful when you want to force a low-noise shot of a stationary subject, and lighting is a challenge so you want as much light to be picked up as possible with the smallest effects on camera shake. Shutter speed priority is similar - you adjust the shutter speed and ISO, and the camera will take care of the rest. Such is excellent for sports scenes e.g. a soccer kick when you can force the camera to snap fast, minimizing blur, and not have to spend precious seconds manually adjusting for exposure. By the time you would have done it, the special moment to take the shot is already past e.g. ball past the goal. Program mode is mainly just ISO adjustment, and the camera takes care of the rest, though actually throughout all these modes, white balance (colour temperature) and other variables not necessarily affecting exposure directly can be set by you - these can be done automatically for you as well if desired.
Play around your camera a little while. Getting the hang of it?
You may notice that you cannot go beyond certain values - for instance, the widest aperture is f/2.8 or lesser, and it decreases in size as you zoom, or that ISO 3200 is the maximum you can go. All these are hardware limitations; you get what you pay for. In fact, now that you have learnt, for example, the effect aperture has on the exposure, you might consider getting a camera with a better aperture next time if you realize that now, your low light shots are not exactly ideal. In fact, a common problem you may in fact face is that your night pictures come out grainy in automatic mode. This is explained by the fact that your camera aperture is not wide enough to allow you to capture the shot with enough exposure. To allow more light in "naturally", it has to allow the shutter to stay open longer, which isn't good lest the camera is on a tripod, for you are going to face blur due to camera shakes. Hence, it raises the ISO in order for it to still get a usable picture and there you have it, all the grain and lack of detail caused by the confluence of factors.
There Is No Rule, But There Are Guidelines
The next section will give you some examples of settings to use with some shots. Remember - there are actually no hard and fast rules for what settings to use for what kind of scene, there are only guidelines! Let nothing inhibit your creative urge!
Always think - what is the desired effect? Then, break it down into photography jargon, translating it to fast or slow shutter speeds etc. This is where your understanding of theory will come into play.
What do you want?
For static, wide scenes, you probably want everything to be in focus, because you want detail. You want to be overwhelmed and go like - wow. It's a day shot, so lighting is not an issue.
Maximum focus should lead you to think, maximum DOF. What do you need for maximum DOF? A narrow aperture. For maximum detail and clarity, minimum ISO.
Go into aperture priority mode and set a small f-number and low ISO. Letting the camera take care of the shutter speed, hold steady and go. Voila!
If you have trouble with camera shake, you can experiment with increasing the ISO slowly, to avoid having a negative impact on image noise.
What do you want?
Someone is running. If you don't freeze the shot fast, no one is going to be able to tell what your subject was from a bad blurry image.
Shutter speed priority. Fast shutter and go. ISO adjustment... Optional, I would say, if you have the time. ISO 80 or 100 if you are really concerned about noise. This picture was apparently taken with a 1/800 shutter; f/4.5; ISO 100.
Night Fast Traffic
What do you want?
This one's a challenge. You have fast cars, and low light. You do not want a blurred image caused either by camera shake or subject movement.
Low shutter speed, and widest aperture for the dim light - to do both you need manual mode. Ideally of course, ISO should be as low as possible but this could be a "worst case scenario" - there is simply not enough light for your camera. Crank up the ISO, or leave it at Auto and live with the noise. You would rather a degraded picture than a near-black picture. Take the shot.
But with the low light comes a creative opportunity. Interestingly, you can choose either to freeze, or make use of a long shutter to create a rather nice aesthetic effect from the car backlights - look at the orange streaks on the picture to the right. That was done with a long shutter of a few seconds, either on a tripod or with super-stable hands.
Long shutter not only helps you with the streaking effect, but also allows for a greater exposure without resorting to high ISO tweaks. Thus it's a win-win situation. Creativity, plus quality.
What do you want?
Waterfalls are again another interesting creative opportunity. Do you want to freeze the water, to be able to see splashes; droplets? Or do you want to create a misty, flowing look? For the former, fast shutter; the latter, long shutter. Pictures for comparison below from fastest shutter speed on the left to the longest on the right.
You know the drill already, I guess - Tv mode, and tweak according to your desires. Congratulations! You are now properly acquainted with your camera's exposure abilities!
There will be many different scenarios, many different needs you will attempt with your camera. More importantly, is your sense of creativity that is the difference between you and your camera processor - and it is also why you paid higher prices for your PASM camera in the first place, to gain control.
But in the end, as our earlier experiment showed, do you want to spend minutes composing the shot each time you take a picture? Unlikely. My personal preference is to leave the PASM for scenes where the camera fails me, and fall back on Auto mode mostly. Unless I really need full Manual mode, I will usually use only either Av or Tv mode to compose the shot.
Remember though, it is not about the camera or the f-stop or anything in the end. Ultimately it is about the photographer, and the content he or she has. When you chance upon the golden moment, whip out your camera and just point, and shoot! Story and opportunity first, then technique if you have the time to afford it.