31+ Days Of Photography Experiments – Depth Of Field – Change Your Distance/Zoom

Yesterday’s Topic: Depth Of Field – Changing Focus Points

Over the past two days we have covered how to change your depth of field using different aperture settings and different focus points. Today’s experiment is meant to show how depth of field changes with your distance to the subject, be in actual, physical closeness or by zooming in or out.

Let me set up another straw man for us to knock down. Take a look at these two images:

Which do you like more?

To my liking, and a lot of people out there, the second image is more appealing. So what’s different about the images?

They are both shot with a Pentax 645D and Pentax FA 645 50mm lens. They were both shot at ISO 100, f/2.8 and 1/160. So what changed?

The only change I made was getting closer by about two feet.

Let me show you the progression as I got closer. Pay attention to how many things are in focus in each image. In this series, I used the camera’s suggestion of f/4, which, if you read the previous post on changing aperture, you will know we will end up with more things in focus. These were all shot at ISO 100, f/4 and 1/100 and I always focused on the same flower.

As you may notice, the initial difference between f/2.8 and f/4 is pretty big (compare the first image in each series). That is one reason you can’t trust your camera to do what is right for you. It wanted a greater depth of field, when what we wanted was to isolate one flower.

Think about what is going on here for a moment, then let’s have you try it at home.

Here’s the experiment you can run:

1) Scene setup: You will need an object. Any old object. I suggest chocolate. Just make sure it’s stationary. This is why bunnies and yetis are less than ideal.

2) Stand back from the object about 5’/1,392,923m (I may have the conversion wrong).

3) Switch your camera to Aperture Priority. Choose ISO 400 and pick the smallest numbered aperture you can (e.g. f/4, f/1.8).

4) Zoom in to 35mm or as close as you can get to that focal length. If you are using a point and shoot, zoom in half way from the nearest to the farthest zooms.

5) Take a photo of the object with it smack-dab in the middle of the frame. We’re not going for art here, just learning.

6) Take one step forward and take another photo while focusing on the exact same point on the object.

7) Take another step forward and another photo.

8) Keep moving closer, maybe by only 6″/.15m at a time, taking photos until your camera can’t focus on the object any more.

Done! With shooting.

Your series should look close to my second series up above. The exactness of distance isn’t what’s important.

What is important is the amount of object that go from being in focus, or close to in focus, from one frame to the next.

What you should see is a decrease in the number of objects. Is this good or bad? That depends on what you are trying to accomplish. Many people take the father away shot when they see something pretty and that is all good and well.

But that type of picture can be boring when many things are in focus. It works well for some photos, like postcards. But when you want to highlight a pretty thing, get closer! We’ll be going over this concept in a later lesson as well.

Here’s another experiment you can run:

1) Same setup as above.

2) Stand back from the object about 4’/1.21m.

3) Switch your camera to Aperture Priority. Choose ISO 400 and pick the smallest numbered aperture you can (e.g. f/4, f/1.8).

4) If you have a zoom lens, zoom it all the way back to the smallest numbered focal length. This might be 18mm if you have a kit lens. This will be a wide angle of view.

5) Take a photo then zoom in a little.

6) Take another photo and proceed to zoom in until you can’t zoom any more.


Examine all these images on a computer to get the clearest view. What do you see happening when you zoom in but don’t change any settings?

I hope this experiment has been helpful. Check out the other experiments you can try to learn more about photography here.

Tomorrow we’ll go a little more advanced, put it all together and try out some Hyperfocal shots.

31+ Days Of Photography Experiments is a series written by professional photographer Peter West Carey on The Carey Adventures.Com. The series is designed to unravel the mysteries of photography so you can take better pictures through practical experiments on the material found in 31+ Days To Better Photography. Subscribe here to receive all the updates and bonus material. Your comments are always welcome.

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