DoF calculation question
Posted 30 December 2007 - 03:02 PM
Posted 30 December 2007 - 04:02 PM
Depth of field is subjective anyway, and really needs to take into account the display as well. What looks acceptably sharp in a small QT window can look really soft on a 65" screen, and vice-versa.
Posted 30 December 2007 - 08:04 PM
Posted 30 December 2007 - 11:02 PM
Edited by Chris Keth, 30 December 2007 - 11:05 PM.
Posted 31 December 2007 - 12:14 PM
Posted 31 December 2007 - 04:20 PM
thanks for all of the input. any suggestions/advice on the best way to do the harp test? also, should i test each lens while i'm at it?
Just being pragmatic, but if your adapter softens the image (creates a larger CoC) then using the original CoC for the camera system would actually give you more of a margin of error for focus. You're safer using the more critical CoC anyway, and if you're trying to buzz he BG as much as possible then set your focus just slightly closer than the subject.
Posted 01 January 2008 - 02:43 AM
If you want to be right on, here is how to do a good harp test:
Get a piece of styrofoam. Old crappy beadboard is perfect. Set it on a table about 6 feet from your camera, such that the top of the beadboard is about level with the lens.
Now lay your tape measure out on the beadboard and stick playing cards into the foam (standing up, vertical) every inch, with the intricate back designs toward camera. You have to be able to see every one of the cards from your camera position. The purpose of this is to give you something every inch that will be easy to see if it is in or out of focus. Choose a card right about in the middle and put a tab of tape on it. This is the card you will actually focus on. Number the other cards so that the cards farther from the tabbed one go 1, 2, 3, 4, etc. and the closer ones go -1, -2, -3, etc. When you shoot this and project it, you will be able to see what is and is not in focus. The numbering system will give you a range of distances that defines your depth of field at whatever lens, stop, and focus distance you used.