Looks like plain and simple flare to me. You've shown us the wide
open crop, but I wonder how the one and two stop down versions look.
How well baffled are the inner walls of this lens, and how clean is
the glass, any filminess? The sharpness looks reasonable for a 100%
selection but it's eaten away by flare giving the overall impression
of softness, and it'll prevent the lens from resolving low contrast
details. AFAIK, Adaptall lenses are all full frame, so you could
explore deepening the lenshood or putting a format shaped mask in the
hood opening (but not if it rotates). Shooting backlit fine details
like this will always bring out the worst in a lens.
regards, Anthony
"Of what use is lens and light
to those who lack in mind and sight"
(Anon)
2009/7/4 Francis <fran...@islandlight.ca>:
> Hi Pentaxians
> Do you know if Tamron's SP 300mm f2.8 (60B) is compatible with Pentax DSLRs
> or not?
> I bought one of these lenses this spring to use for wildlife photography on
> my Pentax K20D and when it arrived (looking almost new) it seemed to have
> sharpness issue which I was not familiar with. The images are very soft (in
> an odd way) and "fringy" when the lens is used wide open and only become
> sharp after about F6 or F8. I have uploaded a sample photo at:
> http://www.islandlight.ca/fm087749-100-crop.jpg it is a 100% crop at f2.8 on
> a tripod.
>
> I sent the lens in to Tamron Canada who didn't fix (or find) the problem,
> but fixed the mount instead. They said that if there was a problem that they
> had missed (the technician hadn't actually tested it because they had no
> adaptall mount on hand to test it with :( ) that no one would fix it because
> it was discontinued, but indicated that the problem was just that it wasn't
> designed for digital media.
>
> Do you know anyone who has used one of these lenses on a Pentax digital?
> Should I invest in sending it to Tamron USA (who said they could likely fix
> it) or is it just not going to work with a digital SLR.
>
> Thanks for your help,
> Francis
>
>
> --------------------------------
> Island Light Photography
> www.islandlight.ca
>
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