From: JesseWest@cup.portal.com (jesse c newcomb)
Newsgroups: rec.photo
Subject: Tamron review: 35-105 f2.8
Date: Mon, 27 Jul 92 17:51:56 PDT
Organization: The Portal System (TM)
Distribution: world

I have recently bought and tested the new Tamron 35-105 f2.8 ASL. If
you're interested in this lens, read on...

Testing was conducted with the manual focus version mounted on a
Canon F1n, using Velvia. Unfortunately, the Adaptall FD mount was
damaged and proved to be unreliable, which rendered some of the tests
inconclusive. (The problem was a bent stop-down lever. Some slides
were badly over-exposed.)

Instead of listing the individual tests performed, I will give an
overall analysis of the lens:

The lens is solidly built. The big pieces are all metal, and only a
few things are plastic, like the aperture ring. The filter size is 67
mm. Focus and zoom are both on a one-touch ring, covered with a
smooth rubber/plastic grip. To zoom out to 35 mm, the grip is pulled
towards the camera body. This shortens the lens. Zooming is fairly
stiff. This is one lens that won't slip out of the set focal length
by itself. Travel on the zoom ring is fairly short, apx 3 cm from min
to max focal length. Focusing does rotate the filter ring. To focus
to infinity, the grip is rotated CCW from the operator's perspective.

The maximum aperture of f2.8 is maintained throughout the zoom range.
In a lens this small, that's quite remarkable. The lens will also
"focus" to 1 meter at all focal lengths. There is no special
close-focusing setting, it's continuous from one end to the other.
These specs are made possible by the aspheric surfaces in the lens.
Shutterbug says there's one asphere in the front, but I find more by
inspection. The rear element is definitely aspheric - you can tell
just by looking at a reflection in it. Then there's a likely asphere
about 1 or 2 surfaces in from the front. There may be more, but it's
hard to tell for sure. Anyway - it's obvious that this lens was
designed by computer.

I say it "focuses" to 1 meter because the job it does is a poor
excuse for focusing at this distance. At the 105 mm focal length,
focusing to 1 m creates really bad flaring and loss of contrast. At
f2.8, it's bad enough to cloud newspaper text in the finder but still
have it easily read. The effect is decreased by using smaller
openings, but you'll still notice it at f5.6 if you compare to a true
macro. So you're not going to count whiskers on a frame-filled face
in low light, but in a pinch you can certainly make the shot.

To fix the close-up focusing problems, you can do any of three
things: Zoom out, move away, and reduce the aperture. The problem
waits until the extreme conditions outlined above before it's
apparent. Zooming out very quickly reduces the problem. If you move
away to 2 m, that's about the threshold (for 105 mm). Reducing the
aperture helps, too, but only as much as you'd expect (f2.8 is bad,
f4 is about half as bad, etc). My preference is to just not use the
105 mm setting for closer than 2 m. Again - no frame-filling
portraits unless it's necessary!

The lens exhibits a fair amount of light falloff at the fastest
openings. Most of it's at the 35 mm end, as expected. It's fairly
even and not as bad as some fixed-length lenses I've seen, but it's
still there. Closing to f4 very quickly reduces this problem, and
probably eliminates it in most circumstances. Really, you'd only
notice the falloff on evenly-toned subjects, like sky.

Outside of the above problems, I find this lens to be quite good.
Contrast and color rendition are good, it's small for a quality
35-105, it'll take you down to f2.8 at any length, and it's solid.

Conclusion:
You get what you pay for. As zooms go, this one's worth about 500$.
If you want to do close-ups, get a macro instead. If you want to
maximize image quality and take no chances, get fixed-length lenses
instead but be prepared to carry more stuff. For a good,
multi-purpose workhorse zoom that can stay mounted, this one will do
just fine. Best application: photojournalism.



- Jesse

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The views and opinions expressed herein are mine and do represent
those of my employer, whether they know it or not.

Jesse Newcomb, Mountain View, CA     415 965-2868
jessewest@cup.portal.com
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Newsgroups: rec.photo