4

At any given aperture and focal length, I can still focus on something near or something far away by simply touching the lcd on my dslr. Does that mean that because I may not be focussing at the hyperfocal distance my dof isn't at its premium value?

  • Not necessarily. It is possible that you could select a point at the hyperfocal distance. But don't forget that the hyperfocal distance for a given focal length-aperture-sensor size combination will change depending on the intended display size. – Michael C Dec 29 '14 at 4:59
  • 1
    Everything is never in focus (unless it is all equidistant from the camera). Everything may be within the acceptable blur that we call Depth of Field. – Michael C Dec 31 '14 at 0:10
5

'Hyperfocal distance' is a distance and as such has nothing to do with the method of focussing. It is the shortest distance focussed upon for a given f/stop and lens focal length that gives depth of field to infinity (obviously focusing at infinity will also give depth of field to infinity). It varies with aperture, of course, for a given focal length, and varies with focal length for a given aperture. For example, with a 21mm lens focused at 4 feet, the depth of field may extend to infinity at f/11, but at f/4 it may not. At f/4 it may be necessary to focus at 10 feet for the depth of field to extend to infinity with that 21mm lens. In other words, the 'hyperfocal distance' in the first case (f/11) is 4 feet, but in the second case (f/4) it is 10 feet. The depth of field does extend closer to the camera than the focused-upon distance, but that is irrelevant for the purposes of discussing hyperfocal distance, which is the distance beyond which everything is in focus, and always extends to infinity.

  • 2
    +1 — with the important caveat that the extent of the depth of field is subjective and depends on how much blur you're willing to accept as still in focus. And that also depends on both print size and viewing distance. – mattdm Dec 30 '14 at 19:31
  • Yes, but I didn't want to get into that here. – Ornello Dec 30 '14 at 21:11
  • 1
    But for your answer to be complete it is necessary to include that. – Michael C Dec 31 '14 at 0:04
  • That's too much information for the purpose of answering the question on such a forum. This is not a photography optics course. – Ornello Dec 31 '14 at 14:32
  • 1
    @Ornello mattdm stated it succinctly in two sentences. – Michael C Jan 1 '15 at 4:26
2

Hyperfocal distance applies regardless of manual or automatic focusing. The hyperfocal distance is simply the distance at which (when focused on) everything beyond it is in focus. This is a set point for a given focal length, aperture and cone of confusion. It does not change regardless of if you focus manually or automatically.

  • Everything beyond isn't really in focus, only one distance is in focus. When focused on the hyperfocal distance for a specific focal length, aperture, sensor size, print size, viewing distance, etc. (change any one of these variables and the hyperfocal distance will change) everything beyond is within the acceptable range of blur we refer to as Depth of Field. – Michael C Dec 31 '14 at 0:07
  • If you really want to be technical even "in focus" is only acceptably in focus as we don't have lenses that are photon accurate. – AJ Henderson Dec 31 '14 at 1:02
  • At the purely theoretical level there is one precise distance that is in focus, all other distances are out of focus to one degree or another. I think that saying everything is in focus when one focuses at the hyper-focal distance propagates the misunderstanding that depth of field is some magic line that separates in-focus from out-of-focus in which everything within it is focused to the same degree and everything outside of it is defocused to the same degree. – Michael C Dec 31 '14 at 3:14
  • You don't need lenses that are photon accurate until you have sensors with single photon sized pixel wells and no Bayer masks. – Michael C Dec 31 '14 at 3:15
  • My point is that practically speaking, if something is acceptably sharp, it is in focus. A lens can't perfectly focus though it may be able to focus to sub pixel accuracy, but the again, more than one point in a range will have sub pixel accuracy. You are criticizing my answer on theoretical semantics and the argument doesn't even hold up that well. Yes, I could have been more clear that there is a range of sharpness considered in focus, but it really wasn't necessary for this question as everything beyond the hyperfocal distance will in fact be acceptably in focus of the coc is chosen well. – AJ Henderson Dec 31 '14 at 5:17
1

Yes. The feature in the image that is focused on os the most in-focus distance, with some depth on either side being acceptably sharp. Having the touch-here focus is no different than using an old fashioned split prism: it focuses. Choose a feature to focus on that is in the middle of the intended depth. If you want to be sure, use the eyepiece (not the lcd) and there is a dof preview button. Or, take a photo and analyse it and try again. Or, take it off auto-focus after it focuses, and bracket the focusing a touch closer and farther.

  • This is not true, the hyperfocal point is not in the middle of the filed of focus. It is float and depend of factors Michael explain above. Mostly is 1/3 in front and 2/3 behind the focal point (average) – Romeo Ninov Dec 29 '14 at 11:31
  • 2
    I did not mean exactly 50% in the middle. I meant simply between the near and far. For infinite it's clearly not the arithmeric mean nor 1/3. Also equal sized circles of confusion is not the whole story if the foreground is more interestingnthen the (not blurred but not grabbing attention] background. Use the dof preview or a sample shot. – JDługosz Dec 29 '14 at 19:22
  • Nor watching photo on the liveview screen, nor DoF preview button will give you good overview of real DoF. And before explain me what mean and what not the word middle, please check Oxford Dictionary: oxforddictionaries.com/definition/english/middle – Romeo Ninov Dec 29 '14 at 19:28
  • 1
    In your link, adjective 1.2, and also something like phrase 2. In any case, hyperfocal refers to the focal, point at which everything farther is acceptable, and $(near+far)/3$ does not equal the prime focus distance when $far = \inf $. No percentage between can be correct; only between. – JDługosz Dec 30 '14 at 8:11
  • For a succinct but complete explaination, the OP and anyome interested could refer to this paragraph in Wikipedia. – JDługosz Dec 30 '14 at 8:17

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.