View Single Post
  #12 (permalink)  
Old 03-30-2013, 11:16 PM
FenceFurniture's Avatar
FenceFurniture FenceFurniture is offline
Member
 
Join Date: Sep 2012
Location: Close as dammit to Sydney, Oz
Posts: 137
Default DEPTH OF FIELD (how much of the subject is in focus relative to the distance from the

....the last word in the title is "camera"

There are four things that affect DOF:

  1. The focal length of the lens (shorter focal length gives larger DOF)
  2. The aperture used (smaller aperture, or bigger number gives larger DOF)
  3. The distance of the field from the camera – the greater the distance away the greater the DOF)
  4. The size of the format (i.e. how big the sensor is) – and this relates back to the focal length

Given that it’s only immature technology/production cost that keeps digital sensors small, I’m not going to discuss the last of those four points. One day in the not too distant future all/most camera will have a proper 35mm sized sensor. Suffice to say that in film cameras the same focal length and aperture combination will give a very different result from one format size to another.

The notes that I have put after each point above are really all that you need to know about each of them. I did read in the other thread that someone was saying that there is a sweet spot of aperture for the best performance of any given lens, and that’s true. It’s usually around three stops smaller than the maximum aperture of the lens, but specialist lenses can be exceptions to this. For example, the Canon 85mm f1.2L Portrait lens has been designed to be used at f1.2 so that the DOF is miniscule, and focuses our attention on the all important eyes, where a macro lens is better at the narrower apertures because DOF is already restricted by the closeness of the subject to the camera and so smaller apertures are required to get any DOF. Even then there is an exception to this – the Canon 200mm Macro lens has magnificent out-of-focus characteristics where the background is just a smear of colour, and this is particularly useful shooting wildflowers et al where there a sticks and other nasties in the background that just get obliterated by these characteristics.

However, to say that you’ll get a poorer result from stopping right down or opening right up is not necessarily correct, especially with a good quality lens. You will still get a slightly better result from using a middle aperture, but I’d have to say that I don’t think I’ve ever really seen a noticeable difference from any of my Canon or Mamiya lenses.

Remember – everything in photography is a trade off – if you gain one characteristic then you will have lost something else, without fail.



Very helpful post by a reader:
I use a great little App to occasionally work out the DOF.
It's called DOFMaster.

For example; on that shot, with the 400D, 39 mm focal length lens, f5 (all obtained from the EXIF data), assuming a half metre away from subject, DOFMaster says that about a depth of 4.6 cm will be in focus.

Doubling the f number will ~ double the DOF, so f10 will make a depth focus about 9.2 cm, f16 will make a DOF of ~ 15 cm which should cover the full width of the plane.

The App also determines the hyperfocal distance (minimum focusing distance for which everything beyond that to infinity will be in focus).
At f16 for that setup above it's 3.2m. The final DOF would be 1.6m to infinity.






__________________
Please sign my Petition to get decent Saw Files made...it takes a few seconds - help us get a result!

Last edited by FenceFurniture; 03-30-2013 at 11:18 PM.
Reply With Quote