From: ka1gt@cbnewsm.cb.att.com (robert.m.atkins)
Subject: EF 75-300 (was Re: Elan Telephoto Zoom Lenses)
Organization: AT&T
Distribution: na
Date: Thu, 21 Jan 1993 18:09:20 GMT

In article <1993Jan20.173344.7992@cbnewsm.cb.att.com>, ka1gt@cbnewsm.cb.att.com (robert.m.atkins) writes:
> In article <TJWU.93Jan19224507@w20-575-76.mit.edu>, tjwu@athena.mit.edu (Thomas J Wu) writes:
> > In article <1993Jan19.232316.3762@cbnewsm.cb.att.com> ka1gt@cbnewsm.cb.att.com (robert.m.atkins) writes:
> > >
> > >  Where does the (often quoted) opinion that the 75-300 has poor optics come
> > >  from? Is it just because it is cheap, or is there hard data to back up the
> > 
> > Popular Photography, April '92.
> > 
> 
> Look at the hard data in that report, and compare it with hard data on
> similar lenses (such as the Minolta 100-300 zoom in the same issue). Then
> tell me if the 75-300 has poor optics. By "hard data" I mean the charts
> and tables rather than the "opinions of the experts", which often seem
> to contradict (or at least conflict with) the numerical data. I'm not
> saying the 75-300 is the worlds best lens, just that it is not to be
> dismissed on the basis of poor optics. It isn't a fast focusser and it
> feels quite "plastic", but it has a 4:1 zoom range and it is inexpensive.
> 

Let me add some numbers. Comparing here the Canon EF75-300, The Sigma 75-300,
the Sigma 75-300 APO and the Tamron 90-300 (all from Pop Photog tests).

First SQFs at 8x enlargement (8x10)

           Canon        Sigma     Sigma APO     Tamron
300mm
f5.6       94.4         94.2      93.9          90.7
f8         95.0         94.2      94.7          92.3
f11        94.7         95.6      96.5          94.4
f16        93.6         95.4      96.0          95.0

Wide open the EF75-300 is the BEST of the bunch, better than the Sigam APO
lens. It still wins stopped down to f8! 300mm lenses are almost always used
wide open to get a fast shutter speed, so wide open sharpness is where things
count. It does start to lose out when stopped down to f11 or slower, but not
by enough to matter very much.

200mm
f5         95.6         96.8       97.2         94.8
f5.6       96.4         96.6       97.1         95.5
f8         97.4         97.4       98.2         95.9
f11        97.3         97.3       98.0         96.9

75mm (90 for Tamron)
f4         95.4         98.0       98.4          94.3
f5.6       98.1         98.0       98.6          95.6
f8         98.7         98.4       99.0          97.7
f11        98.6         98.6       98.6          98.2

Wide open the Canon is very slightly softer than the Sigmas (remember, SQFs
above 95 are A+, i.e. excellent). By 5.6 at 75mm the Canon is better than
the non APO sigma and real close to the APO.

Now lets look at aperture accuracy:
Canon EF75-300 "Extremely accurate" within +/- 0.1 stops everywhere.
Sigma 75-300 "Generally accurate" but only to +/- 0.5 stops
Sigma 75-300 APO "Acceptable" +/- 1/2 stop at 300mm

+/- 0.5 stops is what I usually bracket at with slide film! It is not
"acceptable" to me....

How about field curvature and astigmatism:
Canon EF 75-300. OK at 75mm, good at 200 and 300mm
Sigma 75-300. OK at 75 and 300mm, good at 200mm
Sigma 75-300 APO Very good at 75 and 300mm, good at 200mm

No problems with the Canon lens there

How about Macro performance:
Canon EF75-300. Average performance with little distortion
Sigma 75-300. Average performance with very noticable distortion
Sigma 75-300 APO. Average performance with slight distortion.

Still no problems with the Canon lens as far as I can see.

How about flare then?
Canon 75-300. 300mm "eliminated by f11"
Sigma 75-300. 300mm "noticable even at f32"
Sigma 75-300 APO. 300mm "evident above f22"

Looks like the Canon is the best here.

I could go on, but I think the point should have been made by now. The next
time someone dismisses the Canon EF75-300 zoom as a poor performer ask them
what the basis is for their comments. In many ways it outperforms the
Sigma 75-300 (which is regarded as an OK lens), the Sigma 75-300 APO (which
is regarded as a good lens) and the Tamron 90-300 (which I have heard no
critical comments about). I did not include the Minolta 100-300(i?) zoom
which was tested in the same Pop Photog issue as the Canon lens because
it did so poorly, especially at 300mm.

So all you guys who knocked the 75-300 Canon, what do you have to say now?
It may not be the world's best lens, it may be made of plastic, it may
not have distance markings or IR marks, it may not have internal focussing
and the front element might rotate, but don't forget it is inexpensive and
you can draw your own conclusions about it's optics from the Pop Photog
data. I have used this lens myself and I can believe the Pop Photog
numbers.

===============================================================
Bob Atkins  AT&T Bell Labs  email (direct)  att!clockwise!rma
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