Easy Exposure
This write-up is primarily for beginners and the less experienced, but others may also find it helpful.
In this feature for photography beginners, Rohinton Mehta shows some sure-shot tips to get the exposures right
One of the questions that I am often asked relates to exposures. It goes something like this: “There are several metering modes and exposure modes on my camera. Which one should I use?” “Which is the easiest-to-use exposure mode?” And so on.
Let’s start with the ‘exposure’, ‘exposure meter’ and ‘exposure modes’ within our cameras. An ‘exposure’ is a combination of the correct ISO (film/ sensor sensitivity), aperture and shutter speed – the three fundamental settings in using our cameras. The ‘exposure meter’ reads the brightness of the light and helps us in setting the proper exposure. Our cameras offer a couple of exposure metering modes — Evaluative/ Matrix, Centre-weighted, Spot, Highlight-weighted and in the case of Canon cameras, also Partial metering. Since we want to keep this simple, we will not go into how the different exposure meters work (you may check our earlier issues; this is a topic that is often covered).
Let’s first see which exposure modes are available to us and how they work. We have: A (Aperture Priority, pic 1); S (Shutter Priority, pic 2); P (Program, pic 3) and M (Manual, pic 4).
Note: Canon prefers to call Aperture Priority as Aperture Value (Av) and Shutter Priority as Time Value (Tv).
How do they work?
The first thing you need to do for any kind of exposure mode is to set the sensitivity (ISO). This, most often is ISO 100.
Aperture Priority: You set the aperture of your choice (depending on the depth of field you desire) and the camera automatically picks up what it considers as the appropriate shutter speed. Note: For greater depth of field, you set a narrow aperture (like f/11 or f/16) and for shallow depth of field, you set a wider aperture (like f/4 or f/2.8 etc.)
Shutter Priority: You set the shutter speed of your choice (depending on whether you want to freeze the action or create a sense of movement in your picture) and the camera automatically picks up what it thinks is the appropriate aperture.
Note: To freeze subject movement, you select a fast shutter speed (like 1/500sec1/4000sec, mostly depending on how fast the subject is moving) and to create a sense of movement, you select a slower shutter speed (like 1/15 sec – 1sec, just as an example). Different shutter speeds will create a different ‘look’ to your photo.
Program: In this mode, the camera automatically selects the aperture as well as the shutter speed. Hence I would consider this to be the easiestto-use mode of exposure. However, since this is an ‘Auto’ mode, in my opinion, it does not allow a newcomer to learn about exposures.
Manual: This mode requires that you set the aperture as well as the shutter speed. There is an ‘exposure meter’ within the camera that tells you when the exposure is correct. You can first set the aperture and find the corresponding shutter speed, or you can first set the shutter speed and find the corresponding
aperture. Since this mode requires that you set two parameters, it takes a bit longer to do that.
So, which exposure mode should you use?
That is your choice. For the majority of my photos, I use Aperture Priority.
Note 1: Whichever exposure mode you prefer to use, I suggest that you keep using that mode till you get comfortable with it. Once you are comfortable with a particular exposure mode and want to experiment further, that is your choice.
Note 2: When using any exposure mode, you must keep an eye on the camera selected parameter (within the Viewfinder, you will see the aperture/ shutter speed/ISO etc). For example, when using Aperture Priority mode, you must keep an eye on the shutter speed that the camera selects. If the shutter speed is too low for hand-held camera shots (which could get you a shaky picture), you may consider using a wider aperture, or consider increasing the ISO sensitivity. If you look at it another way, Aperture Priority also works like Shutter Priority – you can adjust the aperture till you get your required shutter speed!
What could you do if the photo on the camera LCD appears too bright or too dark?
First, keep in mind that the LCD at the rear of your camera is not perfect. Almost every camera LCD shows the captured photo brighter than it actually is.
If the photo appears too bright, use the Exposure Compensation button (see pic above right), shown with red arrow provide a minus compensation and take the shot again.
If the photo appears too dark, use the Exposure Compensation button, provide a plus compensation and take the shot again.
Note: Exposure compensation may not work if you are in Manual exposure mode. It is as simple as that!
Two Helping Hands
If you want to take things further (and you should), consider taking the help of the two helping hands: the Histogram and the Overexposure Warning.
A histogram is a graph that shows us the distribution of tones in an image. It also gives us an idea of the brightness level of the different pixels in the image. Though there is no such thing as a perfect histogram, the following gives us an idea about the different tonalities in our image.
a) If the histogram is bundled to the left, it tells us that some pixels are very dark. (See Screenshot above)
b) If the histogram is bundled to the right, it tells us that some pixels are too bright. ( See Screenshot above)
c) If the histogram has a dip in the centre, but is high at the sides, it indicates that the image has a lot of contrast. (See Screenshot below)
d) Generally, we want a histogram that is neither touching the left vertical side nor the right vertical side, but one that is spread out as close to the vertical sides, without touching them.
The ‘overexposure warning’, if set, draws our attention to any area of the photo that is overexposed. It does so by blinking the overexposed areas. (Overexposed areas have no detail in them, and very often, there is nothing we can do to get back the lost details. Hence we must ensure that highlights are not overexposed).
As long as you follow the basic guidelines mentioned above, you should be able to create perfectly exposed images that will be loved by you and your viewers. Good luck!