Photography: Aperture & Shutter Speed - Part 1

When trying to control the amount of light that comes into your camera there are three things you can adjust; Aperture, Shutter Speed, and the ISO.

Note:  This is an important point I need to make that I did not mention in the previous blog. This entire blog series assumes that you are using your camera in Manual (M) mode. A lot of what I am about to say is valid in all the different modes your camera offers you, but you do not have total control unless you are in Manual (M) mode. If you really want to learn about photography, you must shoot in Manual (M) mode. Once you fully understand what we are about to talk about in the next few blogs, then you can revert to the auto settings if it suits your needs at the time? I don't need more the two hands to count the number of times I have shot in anything other than Manual over the past 25 years.

Adjusting the ISO does not have any direct creative aspects. Simply put, you can adjust the ISO so that if the quantity of light coming into your camera is too low or too high you can adjust the ISO without affecting the creative aspects of your Aperture or Shutter Speed choices. Think of it as a type of multiplier with the ability to double, quadruple, cut in half or quarters the amount of light

But...Aperture and Shutter Speed not only control the quantity of light that comes into your camera, but they both have creative aspects and the choices you make can dramatically change the look of your image, for better or for worse.

In Part 1 of this topic we will focus on controlling the aperture. In Part 2 we will focus on controlling the Shutter Speed.

Aperture

As I discussed in the previous blog, the aperture is the size of your lens opening. The smaller the number, the bigger the lens opening and therefore more light comes in. The bigger the number, the smaller the lens opening, the less light comes in. I know, this sounds completely backwards! It does, and that is how you remember it, because it is the opposite of what you would expect. So, if you want to increase the amount of light that comes into the camera, decrease the aperture. If you want to decrease the amount of light that comes into the camera, increase your aperture or lens opening. Now remember, aperture and shutter speed work together to control the quantity of light that comes into your camera. So this assumes that your shutter speed is staying constant at whatever shutter speed you have chosen (and we will get to shutter speed in the next blog).

Now, I know what you are thinking, "OK Rory, you said that aperture can control the creative aspect of a picture, but all you have talked about is how much light comes into the camera, that is not creative". You are correct. So, let’s continue...

There is a second change that takes place when you change your aperture from low to high or high to low, and that is called the Depth of Field. Depth of Field defines how much of your image is in focus. Meaning, if I am looking down a barb-wired fence and I focus on the third fence post, how much in front and behind the third fence post will also be in focus? If you take a look at the two images below, they were both shot at f4, which means I shot them with a really low depth of field. The subject is in focus, but very little in front and behind the subject is in focus. If you look at the first image, the bottom flower is in focus, the little white flowers above it are a little out of focus, and my niece is really out of focus. The same is true with the second image, Sherylynn is in focus, the sand at the bottom of the image which was closest to me and the waves behind her are completely out of focus, allowing Sherylynn to pop out of the image.

I remember when I first started shooting portfolios for a modeling agency here in L.A. I photographed the first model and turned in the images and the agency seemed genuinely pleased with the results. When I turned in the images from the shoot with the second model, the woman at the agency, who really liked me so she was trying to be tactful, asked me if I could shoot images like the one that was on their wall. She asked if I knew how to put the background out of focus. Up till now I had not been doing that because it never entered my mind to do it. Of course I said, "Sure I can, is that what you are looking for?" Of course that is what she was looking for and I should have been doing that all along because she wants the model to jump out from the background. While driving home I realized I really did know how to do that because I understood depth of field, I just was not applying it. So from that point forward I always shot at a low aperture, usually f4. I know photographers that always shoot at f2.8, but that is a little too much DoF for my taste.

So when I am shooting models and I want a small DoF, I choose a low aperture such as f4 and then find the corresponding shutter speed that will properly expose the image. Now when I am shooting landscapes, I usually want everything in focus so I use a higher aperture such as f11 or f16.

The next blog is going to cover Shutter Speed and its affect on an image. Following that subject, we are going to return to Depth of Field because there are other factors that affect DoF other than Aperture, such as distance and the lens you are using.

If you are interested in seeing more examples of Depth of Field (this is the shameless self-promotion I warned you about), you can go to http://www.westwindmediapub.com/ and purchase a calendar or two as a study aid in DoF, and other aspects of photography. J

Keeping on shooting!