Depth of Field Podcast Transcript
Hello, and thanks for taking a look at this video. In this video I am going to discuss aperture, and a little bit about ISO and shutter speed. The three concepts are closely related; some people call them the “exposure triangle.” To view my complete explanation of this see my article The Definitive Guide to Aperture, ISO, and Shutter Speed – Manual Mode located on my website at http://www.snapshotsbymike.com. The link is also in the description box.
First, I will quickly cover what the terms mean. Aperture refers to the size of the hole in your lens that the light goes through. The ISO is the measure of the cameras sensitivity to light. The shutter speed is how long you allow light to enter into the camera. Depth of field is the amount of the picture, from front to back, that has a nice, sharp focus.
To help demonstrate the concept of depth of field I took some pictures of three cans of soup. I set up the experiment by placing the three cans on a sheet. I placed my camera about a foot away from the first can. My camera was mounted on my tripod, and I touched it as little as possible. I used my remote to trigger the shutter. My camera was in manual, or “M”, mode. My lens was also in manual mode. I did not touch my lens to refocus at any point during the experiment.
In the first picture, you will see that the cans are all quite clear, and it is easy to read the labels. The aperture, or f-stop, was set at f/25 for this shot. Because I wanted to use ISO 100, I had to shot this on a tripod for 2 seconds. Don’t bother trying to handhold any shot longer then about 1/60th of a second because you are going to get blur.
The next aperture I shot at was f/16. This is also called “sunny f/16″ because it is the aperture you will want to use on a nice, sunny day. The ISO here is still 100, but you see that the exposure time dropped from 2 seconds, down to just three quarters of a second. Still too long to hand hold the camera though. The reason for this jump is because I almost doubled the amount of light that I was letting in. This means I was able to halve the time it took to get the shot. As you can see, the labels are still pretty clear, although the back can is now a little bit difficult to read. Not too bad though.
On this next picture is where things start to get interesting. Remember, I am not adjusting my lens. I haven’t changed my focus or anything. The difference in clarity is due to the depth of field. As you can tell, both the front and back cans are loosing focus, but the middle can remains sharp. My aperture was set to f/8 and my exposure a nice, fast, 1/5th of a second. Now that is a number that you can easily handhold. Another bit of trivia, photojournalists apparently favor the f/8 setting. There is a quote I heard once “f/8 and be there.”
Here is my final picture from the series. This one was shot at f/4 for 1/20th of a second. Since there is lots of light available, the shutter speed doesn’t have to be open for very long at all. The tradeoff is that the front can of soup is quite blurry now.
A quick word on the ISO that I chose. I could have chosen a different, faster, ISO and managed to get a pretty good picture. The problem with different ISOs however, is that the faster the ISO, the more grainy the picture becomes. Instead, I adjusted the shutter speed to overcome this issue, and maintain a nice clear photograph.
Thanks for taking a look at my demonstration on depth of field with soup cans. I hope you can put this to good use in your own photography adventures. Please take a look at The Definitive Guide to Aperture, ISO, and Shutter Speed – Manual Mode located on my website at http://www.snapshotsbymike.com for additional information, including some handy charts that you can print out to take with you.
If you have any questions, please feel free to leave a comment and I’ll get back to you.