Fairly recently, I upgraded from the Tamron 90/2.5 to the Zuiko 90/2. The main
motivation for this was to improve the wide-open performance for portrait-style
shots of rock-climbers (ie focus distance 2-10m). Generally the light is crummy
and the Tamron's performance was nothing special in these situations.
When I got the Zuiko I expected this to be the only situation where I found a
marked difference, in fact I expected the macro performance to be worse, if
anything, but I ran a few tests anyhow...
First, the zuiko did what I hoped - the extra 2/3rds of a stop was useful, and
I could rely on it to come up with the goods wide open. In fact, its clearly
the sharpest lens I own. As ever though, once you can't blame the gear, the
limitations of your own technique become more obvious... at f2 it is very
difficult to keep a moving (albeit slowly) subject sharp. I get a lot of shots
where the focus isn't on the eyes as I'd hoped. No doubt this factor had
previously been blamed on the tamron... However, unlike with the tamron, the
zuiko always gives me a razor-sharp line of focus through the guys shoulder or
elbow to show me how far out i was...
I think the 'looser' focussing action of the zuiko may be partly to blame for
this - if out, the focus is always just behind the subject, consistent with a
slight twist of the focus barrel caused by pressing the shutter. As others have
reported, the focus helicoid is sufficiently loose that it unwinds by itself
when pointed straight down - a pain for macro work.
I did a few tests at 1:2 (minimum focus) of a banknote, lit with a T28 to see
how they compared. First, the Tamron is slightly shorter - at 1:2 it needs to
be ~3mm closer but shows a smidgeon bigger view. Sharpness - both were easily
acceptable, but the zuiko was better, especially at the widest apertures.
The acid test? I haven't used the tamron since, whereas the zuiko is my most
used lens. If you want to buy a tamron 90, mine is for sale ;-)
Adam
www.adamlong.co.uk
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