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Mark Wallace
Digital Photography 1 on 1, Fundamentals, portraits, Videos 12 Comments

Depth of Field


In this episode I’m talking all about Depth of Field. Three things impact Depth of Field:

  1. Aperture
  2. Focal Length
  3. Distance from subject

After posting this video to YouTube a few people commented that I left out sensor size. Well the truth is that sensor size does not determine depth of field… but it does influence it. Let me explain.

If you have a smaller sensor and a full frame sensor both shooting at the same distance with the same aperture and focal length the DOF will be the same for both. Therefore, sensor size does not determine DOF. The problem is that with a small sensor you’ll need to use a wider angle lens or shoot farther from the subject to get the same scene as a larger sensor – and that will impact DOF because you’ve changed one of the three deciding factors.

So does sensor size impact DOF? No. But it does change how you have to shoot and that in turn does impact DOF. So yes, sensor size ultimately impacts DOF.

Gear used in this video

 

  • MaciekH

    Sorry, but it's not true.
    If I shot with 5D (FF) + 160mm@f/4 and 10m to the subject the DOF is almost twice smaller comparing to 50D (APS-C) + 100mm@f/8 in the same situation. This is not a myth, it's math. Check it out on wiki or simple DOF calculator.

  • http://blog.snapfactory.com SnapFactory

    Exactly right. If you shoot 160mm@f/4 the DOF will much shallower than 100mm@f/8. The sensor isn't causing this, it's the focal length and the aperture. But if you shot the full frame and the APS-C camera with the same settings the DOF will be the same.

    Since a smaller sensor has a crop factor (you see much less in the frame) you'd need a wider angle lens (like the 100mm you mentioned) or you'd need to get farther from the subject.

    The sensor is changing the DOF but it's changing the way you shoot (shorter lens, greater distance from subject) and that is what changes the DOF.

  • MaciekH

    Sorry, I made a mistake in my post. I wanted to write the same setting for the 5D and 50D. Because if I shot both with the same settings DOF is not the same and this is because of the math involved.

  • http://blog.snapfactory.com SnapFactory

    Here's a great article (with lots of math) explaining more about DOF and sensor size. http://www.clarkvision.com/articles/dof_myth/

  • MaciekH

    Yes, the article is impressing and really explaining all issues about DOF and also confirming what I was trying to say. Of course, sensor size doesn't control DOF and I completely agree with that (it's no way to change it's size) but the size ( more specifically the circle of confusion criterion mentioned in the article) has a very big influence on DOF and not only in the way You described in the blog post above.

    And still, If the settings for full frame and asp-c are the same the DOF is different (shallower with full frame) and for example if You want to have the same DOF like in small sensor You have to change the settings (like in linked article).

    But nevertheless I'm a big fan of You and Your work and I was waiting for the new episodes since You posted the first clip about building sets;) I hope You've got something for a bit more experienced photographers;)

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  • Bryan Ford

    So does sensor size impact DOF? No. But it does change how you have
    to shoot and that in turn does impact DOF. So yes, sensor size
    ultimately impacts DOF.

    http://www.proinkscreenprinting.com
     

  • Jeykumar S

    Hello Wallace, I am an amateur. I didn’t get the third factor affecting the DOF. As you move closer to the subject, wont you need to change the focal length, since the old value was set to the subject’s previous position?