Motivating the use of the ‘holy three’
Last two tutorials we talked about exposure and how it works and is ‘made’ with the shutter speed, aperture and ISO. This short tutorial I’ll shortly explain why one would want to choose one over the other in certain situations. In most cases, an ‘average’ works (that is, nothing too extreme, somewhere I would call the middle mode. On a normal, overcast day, you would shoot at ISO 200 an f-stop of about f/4 and a shutter speed of 1/250-1/500 second depending on how harsh the light is. Now this is just an example of a picture that would probably be exposed right. Sometimes, the lighting conditions change, your subject changes and you want to set one (or more) or the holy three accordingly. In the end of course, you’re going to have to compensate by adjusting the other one or two to keep a properly exposed picture.
Shutter speed
Like I explained in last tutorial, shutter speeds are most commonly used to ‘freeze’ the frame; this means that the shutter speed is fast enough for the sensor of your camera to simulate a non-moving subject. The faster the thing moves you photograph, the faster your shutter speed should be to freeze your subject. A running cat wouldn’t need as fast a shutter speed as f-16 jet fighter flying close by at an airshow. Of course the relative distance to your camera matters. When shooting action sports (like many of us probably will at some point) you should use a fast(er) shutter speed (than you would use in an ‘everyday’ situation like taking snaps of random stuffs) to freeze the subject. For sports like skateboarding and skiing anything over 1/1000 is preferred and even faster when possible. By now you should understand that when you want to use a higher shutter speed, you should compensate by using a bigger aperture or a higher ISO or a combination of the two.
In some cases, you want to use a very slow shutter speed to try and capture the movement of something, like a flowing river. If you shoot at 1/4000 second every droplet of water will be frozen in the air, maybe you want to show that the river is flowing. In this case you would use a slower shutter speed so you get motion blur, the blur we talked about in last tutorial where I moved the camera by the NS hat. Other examples from when you want to use a (very) slow shutter speed can be a shot of the ocean to make the water appear silky smooth or of a busy square where people are walking by all the time to simulate how busy it is.
A subject to look into is ‘panning’ your camera. This is moving your camera with your subject, thus making the relative movement from your subject less – you’ll be able to use a slower shutter but still keep your subject sharp. As a result from panning you often get a blurred background, because the background doesn’t move, whereas your camera does. You often see this in motorsports photo’s, where the car/motor is in focus, but the background is blurred; this is a result of panning your camera.
Aperture
Ah. The reason people buy ‘fancy’ camera’s: blurred back- and foregrounds. Like you could see in the second tutorial, using a big aperture (low f-stop) results in a small DoF (Depth of Field) and a small aperture (high f-stop) in a big DoF.
Why would you use a certain f-stop in some situations?
Well, here’s why: depth of field is a great tool to pull the viewers eye to- or from your subject. Our brains are programmed to be more concerned with what’s in focus than out of focus (OOF). Most people love portrait photo’s with a blurred background, because the person (or animal, product etc.) is isolated from the background. Our mind is mostly occupied what’s happening in the focal plane, right where your model is. The blurred background (or foreground) is what we call ‘bokeh’ (bowh-kay. It’s japanese for ‘blur’). It’s a great tool to establish the attention of the viewer on the subject, while leaving other parts, that aren’t important for the composition out.
If for instance you’re taking a shot of a person from the waist up, it really doesn’t matter if the grass or tree in the background is in focus. It would only be distracting of what’s important in the picture: the person. It does work the other way around as well though. In some cases you want your whole composition to be in focus: both the fore- and background add to the composition, so you want to have all in focus. An example could be a tree in the foreground, with a beautiful mountain range and a warm, orange/pink sunset in the back. The lighting is beautiful and as far as the eye can reach, the only thing you see is beauty. Everything adds to the picture, so you want everything to be in focus. It would be very disturbing if either the tree or the background would be out of focus; it would throw the whole photo off.
As we see from the above two examples, in some cases you might want to use a low f-stop (in case of the portrait), while in others you might want to use a high one (in case of the landscape).
ISO
You could say, that to a certain extent ISO is the black sheep of the family of the holy three. It’s very rarely using a high ISO is favorable over using a lower one.
Why of course, would you want noise in your pictures? Sometimes, the artist might want this effect, because it can be ‘artsy’. Think about old black and white (B&W) photography where there’s a lot of grain. Some people think it can add to the picture in some cases.
There’s another reason why you would want to use a high ISO of course. This sort of builds forth on what we discussed in the first tutorial. Compensating one (or two) of the three to keep the others the same. If you shoot with a lens that has a lowest f-stop of f/2 and you want to shoot a portrait while it’s nighttime, you’re going to have to compensate for the lack of light. You can start of by using the lowest f-stop your lens offers: f/2. Now, you probably still don’t have enough light to properly expose your picture. What is the next step? Adjusting shutter speed or ISO. You can only go so slow with your shutter speed before your subject starts blurring (both because the subject moves a little and because your hands shake). Most people start getting blurry images between 1/40 and 1/80, depending on how steady you are. You want a sharp picture, so you can’t shoot at 1/10 of a second; it will blur. You can adjust your ISO to keep a fast shutter speed, to keep your image sharp and not motion blurred.
Most of the time, people crank up their ISO to compensate for lack of light (indoors or when the suns down), but this doesn’t have to be. Be creative and mess around with it! That’s all what photography is about.
Just because most people first adjust their aperture and shutter speed rather than ISO, this doesn’t mean you have to as well!
That wraps up the third (and final) tutorial of the ‘exposure’ series. By now you should understand what certain values ‘mean’, why you use certain values and how they effect your final picture.
Next tutorial? Photography slang!
