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Tamron Adaptall-2 SP 400mm f/4 LD IF - 65B
Latest Review Posted Tamron Adaptall-2 SP 400mm f/4 LD IF - 65B
I recently acquired this lens, so this represents my initial impressions after a couple weeks of use. The only lens I can compare it to with regard to focal length is the Sigma 50-500mm Bigma, so I'll make those comparisons when I can, but unfortunately I can't compare it with any of the Pentax or Sigma fast super-telephotos...

Wide open, the lens is quite sharp in the center, probably comparable to the Bigma wide open (I didn't do any head to head comparisons though). The, the advantage of course is that you are 1.7 stops faster than the Bigma is at 400mm. Corner performance is weaker than in the center, but the application of sharpening in post processing makes even corner crops crisp.

Stopping down, improves sharpness across the board, with the corners at f/5.6 matching the center at f/4, and sharpness appearing uniform (and still slightly improved) by f/8.

Even using the Adaptall-2 1.4x tele-converter (#140F) for the equivalent of 560mm f/5.6 the center sharpness holds up fairly well, and while may be slightly softer wide open than the Bigma @500mm, only 1:1 pixel peeping would tell it, and I think the difference would be slight. The application of sharpening (USM) in post processing makes even the corners (on APS-C) usably sharp wide open, even with the 1.4x TC.

Colors, Contrast and Bokeh:
Colors and contrast are very good at all apertures, though the slight softness at f/4 is visible as a slight loss of contrast on a small scale. It might...

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