Re: FED

[T3D john bercovitz <bercov@xxxxxxxxxxx>]

George Themelis writes:
> John B. has done and posted in photo-3d a nice technical
> analysis/review of the camera.  Perhaps he can repost it here
> for the benefit of those who cannot access past digests.
 
I have no idea if this is appropriate for this mailing list.
We're still evolving.  8-)  I wrote this in early '94.  Joel
has forgotten more about FEDs than I'll ever know so it would 
be nice to hear from him.  I don't think John Vala wanted to 
hear philosophy but I'm bothered by the FED's having the same 
blades do duty as shutters and apertures.  Which of my stereo 
cameras do I use the most?  The FED.  It's not that I'm not 
fast with a hand held light meter; I'm just faster without it.  
I hope some day FED has the sense to release a camera where the 
shutter and aperture functions are separate and the aperture is 
somewhat round and these things are located where the chief 
ray crosses the axis of the lens as nature intended.  8-)
 
John B
 
================================================================
 
As a courtesy of Marty Hewes of Kagan and Hewes, I've recently had 
the opportunity to examine a FED 35 mm stereo camera fresh from 
the factory-sealed box.  [See, being the list manager isn't _all_ 
bad.  Anyone want the job?  8-) ]  This camera had not had the 
adjustments which Marty applies to all the cameras he sells.  So 
this is a review of how a camera might behave if you bought it 
from an outfit that did _not_ touch it up before selling it.  
 
I'll mix measurements and impressions and then give my overall 
imnpression.
 
** Small stuff
 
The cell the camera requires is apparently a silver oxide #76.  I 
say this after checking the no load and load voltages of the cell 
supplied by the factory and measuring the cell diameter (.455") 
and thickness (.211").  This cell is sold as a Radio Shack SR44, a 
Burgess 76SO, an Eveready S76, an RCA VS1776, a NEDA 1107SO, a 
Ray-O-Vac RS76, or a Mallory MS76.  Nice to know you don't have to 
try to find an illegal Hg cell.  8-)
 
The viewfinder magnification is approximately 0.5.  The lens cap 
needs to have a flag to cover viewfinder window.  No, I didn't 
shoot any with the lens cap on but I _could_ have.  8-)
 
The metal finish is black paint.  It's not a great paint job, but 
it's certainly a functional paint job.
 
Miscellanea:
 
Hot shoe.  No PC connection.  No range finder.  No bubble level.
Distance setting marked in feet, meters, and pictographs.
Weight 765 +/- 4 gms including strap, lens hoods & lens covers
Case is additional 184 +/- 4 gms
Bulb is at f/2.8 only.
Frame number is fuzzy, small and hard to read.
Rewind button doesn't disengage everything properly.
 
** FED lenses, shutter, gate spacings, dimensions, etc:
 
The lenses are 38 mm f/2.8.  They have a little springiness to 
their mountings so they can be pushed around approximately +/- .12 
mm.  The lenses appear to be on a nominal spacing of 63.30 mm.
 
The film gates are 29.34 mm wide and 23.60 mm high.  They are
64.30 mm on center leaving a space between them of 64.30 - 29.34 
= 34.96 mm (confirmed by measurement).  This means that required 
positioning of the film is decidedly not critical. (29.34 mm image
centered in 34.96 mm space leaves +/- 2.81 mm tolerance.)  It
would have been kind of them to make the film gates a bit wider, 
say 30 or 31 mm, so that there would be a little more mounting 
freedom in a 28 mm-wide mask.
 
There is an identification notch on the inside of the left film 
gate.
 
The distance between the film guide rails is 35.3 mm.  (35 mm film 
is generally about 34.9 mm wide.)  The rails the emulsion side of 
the film lays against are very rough and have rough lead in and 
lead out but they are well away from the image area.  The space 
for the film to travel through is .010S thick.
 
The mechanical shutter reads around 1/20 second at f/2.8 on my 
shutter speed tester.  It reads around 1/23 second at f/5.6.  
Speeds are the same on both shutters within the accuracy of my 
meter.  
 
Flash synch is very good at all apertures.
 
At f/16 it is obvious that the shutter openings are not equal.  At 
all apertures the aperture is a four-sided figure with one of the 
corners being very acute.  The one corner being acute raises a 
little concern about how much power is going into diffraction 
hence decreasing contrast.
 
Checked focus with ground glass against the rails.  I found the 
focus was .0035 behind the rails.  The thickness of the space the 
film travels in is .010.  Kodachrome 25 is .0057 thick.
 
** Resolution test
 
Film: Kodachrome ASA 25
 
At f/16, the exposures of the two images were noticeably 
different.  The left image was lighter.  At f/11 there was still 
some difference but not enough to be noticeable in use.
 
The film was scratched on both sides.  The emulsion-side scratches 
were outside of the image area but the base-side scratches went 
right through the middle of the image area.  However, these 
scratches were narrow and not noticeable in practice.  I could not 
find the cause of the scratches.
 
The resolution chart had line groups with frequencies varying in a 
ratio of approximately 9:8 hence the ratios of the cited 
resolutions below.
 
f/stop      lpmm in the center   lpmm in the corner
 
 5.6              72                 36
 8                64                 45
11                64                 40
16                72                 40
 
The right image was fuzzier than the left image for some unknown 
reason possibly related to lower exposure level and/or to a slight 
defocus.  It was fuzzier by one line pair increment (ratio of 
9:8).
 
For comparison, here are some other resolution tests:
 
Belplasca stereo res test       Film: Kodachrome ASA 
                      radial         circumferential
f/stop   lpmm in      lpmm in        lpmm in the corn
         the center   the corner
 
4           48            54              38
5.6         61            54              54
8           61            61              61
11          61            61              54
16          48            48              48
 
 
Kodak stereo res test     Film: Kodachrome ASA 
                      radial         circumferential
f/stop   lpmm in      lpmm in        lpmm in the corner
         the center   the corner
 
5.6          60            -               -
8            68           24              24
16           60           38              21
 
Note:  Some corners much worse than others.  The lenses must b
misaligned (elements not centered relative to each other, and lens
axes tilted relative to film plane).  What is shown is sort of the
average corner value.
 


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