jerry2 Posted December 7, 2002 Share Posted December 7, 2002 Sorry this part got garbled in the post.... 177.6 inches near DOF to maintain desired cc 180.0 Inches, point of exact focus. 182.5 inches, far DOF to maintain desired cc Link to comment Share on other sites More sharing options...
robert_a._zeichner1 Posted December 7, 2002 Share Posted December 7, 2002 Bill, I have at least three texts that diagram the "one third in front, two thirds behind" Depth of Field concept. The most common of these volumes is "The Amateur Photographer's Handbook" 8th edition, by Aaaron Sussman. Pages 86 & 87 are where you'll find it. More importantly, I've observed this first hand in doing many hundreds of ground glass alignment tests. Such a test procedure is described in my 1997 (Nov/Dec issue) View Camera magazine article along with instructions for building a home made version. Link to comment Share on other sites More sharing options...
scott_fleming1 Posted December 8, 2002 Share Posted December 8, 2002 You wrote: ****It really *did* seem like it happened overnight. (I went to two large camera stores yesterday to buy a spanner wrench, and both of them looked at me like I had three eyes, when I asked for that tool). At that point, it *did* hit me; "Holy shit, everything *IS* different; nobody even knows what a spanner wrench is, let alone do they stock it any more." I sort of slinked out of the store, feeling old and hunchbacked, while all the Christmas shoppers stood three deep in line for the latest greatest digital snapper, wiping the drool from their mouths.**** Well brace yourself. You will probably be 'discovered' any day now. The glitterati will think you are a genius. When the public sees some of your stuff it will look like the freshest thing ever after being soaked in over saturated color and buried under instant photographia everything. It's innovators like yourself that will never let film die. Hey, as per my post above, how and with what did you shoot 'dog' in lynchberg? Regards, Scott River Run Ranch Texas Link to comment Share on other sites More sharing options...
squareframe Posted December 8, 2002 Share Posted December 8, 2002 > Was your comment about the spherical holder a joke? not a joke. I have been experimenting with it and haven't quite decided how and if I should proceed. Link to comment Share on other sites More sharing options...
jerry2 Posted December 9, 2002 Share Posted December 9, 2002 I investigated Robs comments about DOF being 1/3, 2/3 in front of and behind the psf. After further review of the standard DOF formula, I made an interesting disovery that I never realized before. Both myself and Rob were right about this! It's amazing how tricky and deceving these formulas can be unless you run them.... the bottom line is, at closer distances, the split is almost exactly 50/50, (DOF in front of psf / DOF behind psf) yet at further focus distances the split move is dramatically altered, such as 10/90 ! Here is two examples..... Depth of field (non macro) 150 focal length mm, f11, 0.0333 cc mm, 10 ft - focus distance 114.3 " DOF Near, 126.3 " DOF far 11.9 inches total DOF 48% In front of focus distance (psf) 52% Behind focus distance (psf) So focussing at 10 ft (definetly not macro) the DOF split is almost exactly 50/50 Now lets focus at 150 ft. 150mm fl, f11, 0.0333 mm cc, 150 ft focus distance 86.0 ft DOF N, 586.7 DOF F 500.7 DOF ft total 13% In front of focus distance (psf) 87% Behind focus distance (psf) Focussing at 150 ft, the DOF split is close to 10/90! (even way more than 1/3, 2/3) So bottom line, based on the variables in the DOF formula, I have found the DOF in front of the "point of exact focus" can vary from .1% to 50%, while the DOF behind the "point of exact focus" can vary from 50% to 99.9%! So there is no fixed % of DOF in front of or behind the point of exact focus (psf). Link to comment Share on other sites More sharing options...
robert_a._zeichner1 Posted December 9, 2002 Share Posted December 9, 2002 Bill L., thanks for your dilligence in tracking this down. Just when you think you understand all this stuff, someone goes and actually USES one of these formulas to remind us all of how much we take for granted. Just another example of how valuable this forum and it's participants contributions can be to our passion. Link to comment Share on other sites More sharing options...
emmanuel_bigler Posted December 10, 2002 Share Posted December 10, 2002 Schneider has on catalog and improved 4"x5" film holder system. It is compatible with International 9x12-4"x5" backs. If your wallet is brave ;-), follow this discussion : Schneider Hi End Camera Back http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=0039Aj Link to comment Share on other sites More sharing options...
arne_croell Posted December 10, 2002 Share Posted December 10, 2002 As far as I know, Schneiders Hi-End camera back was discontinued last year or earlier. It is also no longer listed on their web sites. Link to comment Share on other sites More sharing options...
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