james king wrote:
> I found that the tamron 90 2.5 does not work with my Canon 5D. I get a bright
> spot in the centre which intensifies and reduces in diameter as you stop
> down.
This is a not uncommon problem with DSLRs and older MF macro lenses.
It's a result of reflections between flat or close to flat lens element
surface(s), generally the back of the rear element, and the shiny front
surface of the sensor assembly. I've used a Tamron 90/2.5 on my 5D for
macro without the effect you mention. Probably because the elements are
farther away when focused close. Mine is the earlier version with 49mm
filter ring, but I think it and the later, 55m filter version are the
same optically.
> Wide open I find the Canon 100mm macro to be far better although the Canon is
> not cheap and you don't even got a hood or lens case...
>
I did some fairly careful testing of Tamron 90/2.5, Kiron 105/2.8, Zuiko
50/3.5 and new Tamron 90/2.8 Di.
The 50/3.5 clearly won over the old MF Tamron and Kiron at 1:2, not only
with better center and edge resolution, but with much less vignetting. A
really sharp, clear image. At 1:1, the 50/3.5 fell behind a little. The
other two had different image qualities, but were essentially equal to
each other. That makes sense, as the Kiron focuses to 1:1 directly and
the Tamron had a 1:1 adapter made for it, while the 50/3.5 was optimized
for 1:2, with other, true macro, Zuikos designed for greater magnification.
The AF Tamron was the winner at both magnifications over all the other
lenses, although only by a nose over the 50/3.5 at 1:2. I know it's
plastic, and all that, but it clearly benefits from improvements in lens
design materials and technology over the last 2+ decades.
There's been a great change in lens performance over the last several
years that lots of folks don't seem to have picked up on. Many modern
lenses, prime and zoom, have optimum performance at or near wide open.
It's a result of newer optical glasses and aspherical elements.
So, for example, my tests showed the Tamron 90/2.8 to be noticeably
better at f2.8 than f8 for flat subject macro work at 1:1 and 1:2. Pop
Photo's test of the lens in their latest issue shows the same thing. I
find this a mixed blessing for macro, as I usually want a small aperture
for DOF. The old MF macros I tested, as expected, had optimum apertures
around f8-11.
Moose
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