"F. Craig Callahan" schrieb: > > Norman Chappell wrote: > > > It is a means of accurately ensuring the correct point of focus and > > aperture when a specific depth of field range is required. The reason Canon > > don't provide a "shift" capability is that it would basically defeat the > > entire purpose that the mode is meant to be used for. > > Exactly. If you want more or less DOF change your DEP 1 and DEP 2 points of > focus. >
You seem to think about DOF a little different than I do. Namely as an invariaby fix zone, that depends on aperture and focusing distance only. DOF is a little more complicated, because it also depends on your definition what you think is "sharp". Canon thinks a part of the image is "sharp", when the circle(s) of confusion are smaller than 0.035mm. Now, this is just Canons definition and not a physical law carved in stone. And personally, I find this definition just doesn't meet my expectations. If you ever enlarge to 8x12 inch or larger, you'll find that 0.035mm on the neg means 0.28mm (or more) on the final print. And you'll likely find that doesn't really look all that sharp. And so what you'll be looking for is not a larger area that should appear sharp (=more DOF), but you want the same area to look "sharper". Now, in practice, this is not *much* of a difference, but there still is one. If I have to guesstimate by choosing appropriate points of focus, DEP 3 and DEP 4 so to say, to get DOF (according to my definition, say CoC size=0.025mm) from DEP 1 to DEP 2, this negates the concept of DEP mode somewhat, IMHO. Where do I focus to get this CoC size of 0.025mm if I would get 0.035mm focusing on DEP 1 and DEP 2? Isn't DEP mode there in order to NOT have to "guesstimate"? If I wanted to guesstimate (which is not too hard BTW and I do it most of the time anyway), I'd avoid DEP mode alltogether and use AV or M. Thomas Bantel * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
