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p.1 #13 · p.1 #13 · BIG image warning!Bokeh rendering sample of Tamron 85mm & 70-200mm F2.8 usm ii..questions.. | |
rscheffler wrote:
This is part of the learning process for each lens. For example, I have the Leica 50/1.4 Summilux-M ASPH., which is considered one of the smoothest background rendering 50s available (Otus 55 is similar, as are a couple other lenses). That said, at certain camera to subject to background ratios, the background can rendering in a very jittery manner. It's possible you're landing in a similar suboptimal ratio with the 85/1.8 in these specific test images. It's a reason to test lenses and shoot with them in a variety of situations, to get a better feel of how they perform. It's also typical for very fast lenses to have nervous bokeh quality wide open with smoother performance often achieved 1-2 stops down.
Looking at the Tamron crops, I'd be inclined to say the rendering is due in part to significant divergence of sagittal and tangential performance, but Tamron's MTFs indicate sagittal and tangential performance should remain very close over much of the frame.... It makes me a bit suspicious about this particular copy and I would be inclined to try another one as a comparison.
What areas of the frame the two sets of crops are from? Center and a corner? Please confirm with perhaps a single uncropped frame (at a reasonable size) to give us an idea of the overall scene.
Also wondering what role Tamron's image stabilization system might play in this? Was it on or off? Tripod mounted camera? For example, Leica with their new SL camera recommend that for highest image quality with the 24-90 zoom, that IS be disabled. I don't think Canon typically recommends this for general photography, but it could be dependent on lens design, IS mechanism capability, etc...
The quality of the 85's bokeh in this example might just be the way it is... but its character also reminds me of my own examples shot with decentered lenses. For example the Leica 50/1.4 again... I've had some trouble with it 'loosening up' physically, which resulted in some play in the lens body that was enough to degrade image quality. Images shot wide open had non-normal wide open rendering but by f/2-2.8 the lens looked normal again......Show more →
Did you check my other sample of the small house (pony express) and the foliage behind it?
That is centered and I dont like it.
this is the Sony A mount version so no IS from the lens, only my camera which is the same IBIS that is in use for all my other lenses.
Perhaps it is indeed a bad copy.
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