OUCH....this is a mess.

Until I learn to edit html I suggest you look up his posting on www.dejanews.com. Search for colson1@compuserve.com.

What follows is Olson's jumbled article

I recently did some analysis on the use of "Equivalent Focal Length" (EFL) in
a 35mm camera to describe the imaging in CCD digital cameras.  The equivalence
depends entirely on the actual size of the image on the CCD.  If they give the
EFL and you can find out the actual lens focal length (AFL) then you can
compute the image diagonal (DIA") very simply, and you can gain an insight
into the camera design.
In the two systems, equivalence requires the angles at the lens rear principal
points subtended by the two frame diagonals to be identical.  We know the 24mm
by 36mm frame in a 35mm camera has a 43.267mm diagonal, so the relationship
takes the form (solver statement for HP17BII calculator):
             EQUIV.35MM.F.L:EFL=AFL*43.267/DIA"/25.4
This produces key labeling in the "CALC" mode of EFL, AFL, and DIA", and after
inputting any two values, pressing the remaining key gives the third.
For a little more insight, the following calculates the pixel pitch in microns
(PPUM) for 4:3 aspect ratio pictures, given the image diagonal (DIA") and the
pixel count in the long direction (LPIX):
             PIXEL.PITCH:PPUM=DIA"*0.8/LPIX/30.37*1E6
Calculating the above for a few of the most interesting cameras produces the
following listing in order of decreasing image size:
 MFGR      MODEL       EFL     AFL     DIAG"   LPIX    PPUM
Fujifilm  DS-300      35-105  9-27     .438    1280    6.95
Olympus   D-600L      37-110  9.2-28   .423    1280    6.72
Fujifilm  MX-700      35      7.6      .370    1280    5.87
Canon     PRO-70      28-70   6-15     .365    1536    4.83
Kodak     DC-120      38-114  7-21     .314    850     7.51
Olympus   D-500L      50-150  9.2-28   .313    1024    6.21
Ricoh     RDC-4300    35-105  5.6-16.8 .273    1280    4.33
Olympus   D-340L      36      5.5      .260    1280    4.13
Nikon     Coolpix 900 38-115  5.8-17.4 .260    1280    4.13
Kodak     DC-210      29-58   4.4-8.8  .258    1152    4.55
Olympus   D-320L      36      5.0      .237    1024    4.70
Olympus   D-220L      36      5.0      .237    640     7.52
Ricoh     RDC-2       35,55   3.7,5.6  .180    768     4.76
Sony      FD-7        40-400  4.2-42   .179    640     5.68
I couldn't get the AFL on the Agfa ePhoto 1280, but I remember a posting that
suggested Agfa might be using thesame CCD as the Olympus D-320L.  Also I
suspect that both the D-340L and the Coolpix 900 might be using the new low
cost, low power, high resolution CCD sensor that NEC announced on 2/4/98,
(Nikon and NEC both tout 30 frame/sec color image output for LCD display.)
Chuck Olson W6PKP

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