Thanks for the link to adaptall-2.org!!! I thought it was gone.
It's interesting that the Tamron 17 beat pretty much everything, including zeiss, in the corner at f/8 in the old modern photo tests. edsawyer.com/lenstests I think Center wasn't that hot, but even sharpness across the frame is nothing to sneeze at.
Focus is tough without live view. Ee-s screen is supposed to help, though. Thanks for putting up this test.
cogitech wrote:
[Regarding your comparison to the Tokina, it seems to be the exception, rather than the rule. Nearly every other comparison I have seen puts the Tamron ahead. Look again at the Modern Photo test results on Adaptall-2.org. The Tamron easily competes with (and convincingly beats some) OEM lenses at similar focal lengths. The description of performance on Adaptall-2.org is exactly what one should expect from a properly functioning Tamron 17/3.5. Sample variation is significant with this lens, so I am not surprised that one sample of the AT-X beat one sample of the SP.
At this level, copy variation is high. A good copy of any one of these lenses is a value.
I ran another test over the weekend at a longer distance and was surprised by the results. Again the Tokina was sharper than the Tamron in the center wide open; by f8 they were pretty much the same. The Tamron corner sharpness never really reached acceptable whereas the Tokina improved with each stop. I'm not sure what to make of this; if it was an adapter issue as suggested before would the center and corners to be so drastically different in terms of sharpness? Can an poor quality adapter give the impression of decentering?
The scene (note the vignetting from the Tokina at f3.5)
Center unedited 100% crops
Corner unedited 100% crops (wide open frames appear darking due to vignetting)
From the samples you've posted Paul, I'd agree. I guess the question is, which is more likely the cause for these unusual results: an adapter issue or sample variation?
dfresh wrote:
From the samples you've posted Paul, I'd agree. I guess the question is, which is more likely the cause for these unusual results: an adapter issue or sample variation?
I really can't say, but I think it is worth it to try a different adapter and/or Adaptall-2 mount combination.
I'm not sure whether it was due to sample variation or adapter quality, but when I tested a copy of the Tamron 17/3.5 (1st edition) against the Tokina 17/3.5 (SL), the Tamron was sharper in the center at f/3.5 and f/5.6. At f/8 and beyond though, the Tokina was sharper across the frame with less purple fringing and higher contrast.
dfresh wrote:
I ran another test over the weekend at a longer distance and was surprised by the results. Again the Tokina was sharper than the Tamron in the center wide open; by f8 they were pretty much the same. The Tamron corner sharpness never really reached acceptable whereas the Tokina improved with each stop. I'm not sure what to make of this; if it was an adapter issue as suggested before would the center and corners to be so drastically different in terms of sharpness? Can an poor quality adapter give the impression of decentering?
I wouldn't think an adapter could affect sharpness in any way whatsoever. If the lens can focus there then it can and that's that. Now if the makers were so lame as to have the mount face at a tilt then I suppose it could cause some troubles but the way these things are made I'm going to guess that's just about impossible. You can tell by using a small bubble level if you're interested. So I would guess the only thing is length and a snug fit. It those are right then there shouldn't be any blur things happening due to adaptation.
Now I do notice that some adapters are pretty shiny and barely even black. This can add "ghost and flare" phenomena that occur due to reflection inside a lens (slash adapter) barrel or camera. It can also reduce general contrast too. The [user] cure for that is flocking the inside of your adapter. I know a few people who do this and claim that it's very helpful. I haven't tried it yet - simply because I'm still mulling over the cheapest and best way to achieve it. I think they must be right too because a great number of lenses are internally flocked and probably the majority of lenses I've had in my hand were flocked out the rear exit pupil even if not internally! Many mirror-boxes are flocked as well.
Here's a pic just for kicks. This is flocking applied by the manufacturer of the Canon FD 200mm f/4 S.S.C.:
