I always perform my own sharpness tests on every lens I buy. I take a JPEG at each full aperture the lens is capable of, as well as minimum and maximum apertures. If the lens is a zoom, I repeat the steps for every focal length marked on the barrel. I rate the center and corner sharpness on a scale of 1-10. Anything under 5 I consider useless. 6-7 is acceptable, 8-9 is great, and 10 (which I rarely give out) is a point where I doubt any improvement can be made. I have finished my test of the 150-600 this evening. The results:
The 'sweet spot' is centered on f/11 across all focal lengths. In most cases, there's very little difference in sharpness from f/8 to f/16. On a minor improvement at f/11. At all focal lengths, diffraction starts to rear its ugly head at f/22, and literally renders the lens useless by f/32. Only at 500mm did I find f/40 marginally acceptable.
On my 1-10 scale, about half of the test points are 7 - 8. A few 6's, mostly in the corners.
At 150mm, the lens performed quite evenly between f/5.0 and f/16.
From 200-300mm, maximum aperture suffers a bit, but f/8 to f/16 is best.
Starting at 350mm, the lens gets a bit softer, but this is to be expected. Not by much, but just enough to notice. However, even up through f/16 there isn't much more IQ in this focal length range.
At 500-600mm, it gets a bit softer still at maximum aperture. But then again, this is normal. However, I didn't see any appreciable softening between these FLs and 300-450 in the f/8 to f/16 range. In other words, between 350mm and 600mm, the lens is a very consistent performer in the f/8 to f/16 range.
While the lens does improve sharpness at f/32 or f/40 at the longer focal lengths, it still doesn't improve enough for me to even consider using that aperture setting.
So the upshot is this: Shoot f/11 if at all possible, but f/8 and f/16 will be just as good throughout the FL range. You'll only lose a little IQ if you need to shoot wide open, And avoid f/22 and smaller at all costs. All my f/32 and f/40 shots are, at best, 5 on my scale, with 200mm having 3 in the center and 2 in the corner. I would rank that a 'dismal'.
So if your DSLR has decent ISO noise capabilities, then don't be afraid to up it to 400 or 800 or even 1600 (depending on your camera) and use that to drive up your shutter speed to stop the action if needed. If you have an entry-level DSLR, you can still shoot wide open with minimal IQ loss. So don't feel bad about 'shooting wide open'. With this lens, there's very little penalty for that!
Since this is a variable-aperture lens, I thought I'd throw out the numbers here:
150mm is f/5 through f/32.
200mm is f/5.3 through f/36.
250 and 300mm are f/5.6 through 46.
350mm is f/5.6 through f/40.
400 and 450mm is f/6.0 through f/40.
500 and 600mm are f/6.3 through f/40.
One oddity I did take note of. Unlike many of my other zooms, the Tamron tends to 'round off' the focal length reported to the camera. For instance, zooming from 350mm to 400mm, it will only record 350, 360, 380 and 400mm in the EXIF data. It doesn't report precise FL, such as 373 or 392. Not that this is a defect, nor does it affect IQ. It's just a quirk I noticed and thought I'd pass along.
I gotta give Tamon credit. Although this lens probably can't compete side-by-side with top-shelf glass, it must be remembered that it's most likely not intended to. Especially considering the price point! If IQ is the sole driving metric for your lens selection, you'll probably be better served coughing up $5,000+ for a Canon-L or Nikkor prime. For the rest of us 'unwashed masses', this lens is a godsend. I have no doubt there's a lot of DSLR owners who have dreamt of getting into the over 300mm arena, but budget reasons would prevent it. Sure, there's cheaper 500mm+ lenses out there, but they're usually mirror lenses, or cheap imports that starts out with a max. aperture of f/16 (with manual aperture control just to kick you in the azz!) We see 'em all the time on ebay for $99 or $159 or $199.
If you've ever been tempted to buy one of those, save your money and look at the Tamron instead. You'll be much happier. And grateful you don't have a $200 glass-filled doorstop.
Oh yeah, those cheapies don't have VR/IS/OS/VC!
The 'sweet spot' is centered on f/11 across all focal lengths. In most cases, there's very little difference in sharpness from f/8 to f/16. On a minor improvement at f/11. At all focal lengths, diffraction starts to rear its ugly head at f/22, and literally renders the lens useless by f/32. Only at 500mm did I find f/40 marginally acceptable.
On my 1-10 scale, about half of the test points are 7 - 8. A few 6's, mostly in the corners.
At 150mm, the lens performed quite evenly between f/5.0 and f/16.
From 200-300mm, maximum aperture suffers a bit, but f/8 to f/16 is best.
Starting at 350mm, the lens gets a bit softer, but this is to be expected. Not by much, but just enough to notice. However, even up through f/16 there isn't much more IQ in this focal length range.
At 500-600mm, it gets a bit softer still at maximum aperture. But then again, this is normal. However, I didn't see any appreciable softening between these FLs and 300-450 in the f/8 to f/16 range. In other words, between 350mm and 600mm, the lens is a very consistent performer in the f/8 to f/16 range.
While the lens does improve sharpness at f/32 or f/40 at the longer focal lengths, it still doesn't improve enough for me to even consider using that aperture setting.
So the upshot is this: Shoot f/11 if at all possible, but f/8 and f/16 will be just as good throughout the FL range. You'll only lose a little IQ if you need to shoot wide open, And avoid f/22 and smaller at all costs. All my f/32 and f/40 shots are, at best, 5 on my scale, with 200mm having 3 in the center and 2 in the corner. I would rank that a 'dismal'.
So if your DSLR has decent ISO noise capabilities, then don't be afraid to up it to 400 or 800 or even 1600 (depending on your camera) and use that to drive up your shutter speed to stop the action if needed. If you have an entry-level DSLR, you can still shoot wide open with minimal IQ loss. So don't feel bad about 'shooting wide open'. With this lens, there's very little penalty for that!
Since this is a variable-aperture lens, I thought I'd throw out the numbers here:
150mm is f/5 through f/32.
200mm is f/5.3 through f/36.
250 and 300mm are f/5.6 through 46.
350mm is f/5.6 through f/40.
400 and 450mm is f/6.0 through f/40.
500 and 600mm are f/6.3 through f/40.
One oddity I did take note of. Unlike many of my other zooms, the Tamron tends to 'round off' the focal length reported to the camera. For instance, zooming from 350mm to 400mm, it will only record 350, 360, 380 and 400mm in the EXIF data. It doesn't report precise FL, such as 373 or 392. Not that this is a defect, nor does it affect IQ. It's just a quirk I noticed and thought I'd pass along.
I gotta give Tamon credit. Although this lens probably can't compete side-by-side with top-shelf glass, it must be remembered that it's most likely not intended to. Especially considering the price point! If IQ is the sole driving metric for your lens selection, you'll probably be better served coughing up $5,000+ for a Canon-L or Nikkor prime. For the rest of us 'unwashed masses', this lens is a godsend. I have no doubt there's a lot of DSLR owners who have dreamt of getting into the over 300mm arena, but budget reasons would prevent it. Sure, there's cheaper 500mm+ lenses out there, but they're usually mirror lenses, or cheap imports that starts out with a max. aperture of f/16 (with manual aperture control just to kick you in the azz!) We see 'em all the time on ebay for $99 or $159 or $199.
If you've ever been tempted to buy one of those, save your money and look at the Tamron instead. You'll be much happier. And grateful you don't have a $200 glass-filled doorstop.
Oh yeah, those cheapies don't have VR/IS/OS/VC!
