DOF FX vs. DX?

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Comments

  • MsmotoMsmoto Posts: 5,396Moderator
    OK, in theory, the lens has only one point, the focal plane, where it is in perfect focus. Practically, however, the resolution of fine points will appear to be fine points at distances both in front of and behind the plane of perfect focus. And, this is what creates DOF.

    However, none of this is very important. What IMO is important is that we recognize the DOF is not fixed, but a subjective decision made on a specific level of resolution. And, when we use lenses with very thin DOF, i.e., 800mm at f/8, what is discovered is the actual DOF is almost zero on a practical basis.

    An example is f/8, 3 meters subject distance, 800mm full frame. Calculates on some DOF calculators as 10mm. Yet, when examined in large sizes, it appears less than this in some examples.

    A good explanation of all this is http://www.cambridgeincolour.com/tutorials/depth-of-field.htm

    And this explains the "circle of confusion" is why we have apparent DOF. EVen though a point may not be in perfect focus, the COC is small enough to be perceived as a single point.

    It is interesting to discuss, and I really think it is about how we define things..the semantics which creates our different opinions. We are all correct as we perceive it.
    Msmoto, mod
  • spraynprayspraynpray Posts: 6,450Moderator
    I agree.
    Always learning.
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