In simplified terms:What is the relevance of the two terms depth of field and depth of focus and what is their relationship to one another?
Could someone put this into a bite size nutshell?
-Depth-of-field in normally used to refer to the amount (depth) of the subject that will be rendered "adequately sharp" (refers to object space)
-Depth-of-focus refers to the acceptable amount the sensor/film plane can be "off" and still be "acceptably sharp" (refers to image space).
The values are inversely related in a given situation. For example a 4/0.10 will provide (realtively!) large depth-of-field while it will have very shallow depth-of-focus.
For a more detailed discussion see:
http://www.microscopyu.com/articles/for ... depth.html
Unfortunately the terms are frequently used interchangeably, which can lead to confusion at times.
As mentioned above, somewhat counter intuitively.... your depth-of-focus (image space) is extremely less with a low power objective like a 4X than it is with something like a 40X. This is one reason why photomicrographers will sometimes have a hard time getting a really sharp image from a high quality 2X or 4X objectives with a microscope that is supposedly "parfocal" (eyepieces and camera in focus at the same time). A film/sensor plane "error" that is practically inconsequential with higher power objectives can be very bad with a low power objective. For example... if the system was set up with the "parfocality" established using, say, a 20/0.40 you could be far off with a 4/0.10 which has 30X less depth-of-focus. (Even though the 4X would have about 10X the depth-of-field).