Depth of field — it’s more than just aperture!

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Depth of field photo

We all know that the aperture value controls the depth of field, but I am shocked how many intermediate photographers have never learned what other factors also impact depth of field (how much is sharp and how much of the photo is blurred).  In fact, these other factors have as much impact on depth of field as the aperture does.

The first “other” factor that controls the depth of field is the focal length.  Assuming all else is equal, the longer the lens, the shallower the depth of field.  This is yet another reason why I advocate so strongly that landscape photographers buy an actual wide-angle lens rather than just the 18mm kit lens.  A true wide angle lens has terrific depth of field for wide landscapes.

The second factor is the subject-to-lens distance. The closer you get to your subject, the shallower the depth of field.  I always get a laugh when I see flickr comments on a macro shot that say something like, “Wow!  Great creative use of depth of field!”  I laugh because it is almost impossible NOT to have shallow depth of field for macro (close-up) shots because the lens is so close to the subject.  Knowledgeable macro photographers usually put forth every effort possible to INCREASE the depth of field by using a high aperture value.

The last factor is the distance between the subject and the background.  If you're taking a photo of a newborn baby, you might as well give up on trying to use depth of field.  Newborn babies are always lying down, so nothing you do can make the blanket behind the baby's head blurry.  It is so close to the focus point on the baby's face that it is not possible to make it blurry.

What do these three factors teach you?  If you're disappointed with your lens not being able to get a sufficiently shallow depth of field, choose the lowest aperture, stand close to the subject, increase the distance between the subject and the background, and zoom in as far as you can.  This technique also works on point and shoots when you want to blur out the background!

If you're a beginning photographer, you might consider purchasing my book “Improve Your Photography: How Budding Photographers Can Get Pro Results” for just $5.99.  After payment via paypal, you can read the digital book right on your computer.  No special software necessary.

8 thoughts on “Depth of field — it’s more than just aperture!”

  1. You bring up a really good point with respect to depth of field. Thank you for clarifying the other factors affecting DOF other than aperture settings.

  2. I’m looking to upgrade my camera I feel I want a more professional camera. I have a cannon xti rebel now. I’m looking for I truss the term is better depth of field. I want to have pictures where the person is in focus at a greater distance away. Is it the camera or a wide angle lens or do I need a 85mm lens

  3. Billy is absolutely right – depth of field DOES NOT CHANGE because of focal length. In fact, in a way, you could also say it does not change due to distance from subject either – it is only affected by the COMBINATION of those things. I know that sounds contradictory – but what I mean is, depth of field is ultimately affected by the APPARENT distance of the subject. That is to say, from 30 metres away from a subject with a 20mm lens, there will be all but NO depth of field effect, i.e. everything behind them will be in focus. But that is because a subject from that distance at 20mm will take up almost none of the frame, and appear distant. However, a 400mm lens will make it a different story. With a 400mm lens, you will be basically taking a ‘classic portrait’ of say, an adult human. And now they are taking up a decent part of the frame, there will be some blurry background effect. So you the distance they are away from you isn’t the issue, but rather how close they APPEAR due to the lens you are using.
    Also your last factor, about the distance behind the subject… sorry but that’s also technically incorrect. It gets the point though, at least for portrait applications and such – but hang on, you did not mention sensor size?
    In fact, sorry but this article kind of misses the mark a fair bit.:-/

  4. hello, good article!
    i’d like to add that another factor that affects dof is (in digital photography) the size of the sensor, a 35 mm sensor will make a more shallow dof than an aps-c, I think this happens because of the crop factor that obligates the use of smaller focal lengths to achieve the focal length as on a 35 mm type sensor.
    Best wishes.

  5. Lauren Mellinga

    I have a bit of a creative bent that most would not approve of…but, never one to let that hold me back I have decided to go with it. I have had some fabulous results with LANDSCAPES and my TELEPHOTO lens. The knack is to find part of the landscape with layers in it already, and , be a distance from it. It compresses the scene into something unique.
    As you have guessed it my problem though can be keeping crisp images. The focal length is short, I increase the focal area to wide and increase the depth of field with higher value apertures and sometimes stack a couple together and try hard to minimize that drift you get with a heavy lens and wind on the mountain. Please could someone do a lesson on this for me??? Or advice??? Thank you

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