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Lens review

Pentax smc FA 77 mm f/1.8 Limited

22 September 2009
Szymon Starczewski

4. Image resolution

The lens’s resolution test was based on the strength of RAW files from a Pentax K20D, developed by the dcraw program, of course without any sharpening. The results in the sense of MTF50 values for the frame center and the frame edge are presented in the graph below.

Pentax smc FA 77 mm f/1.8 Limited - Image resolution

In the frame centre near the maximum aperture i.e. by f/1.8-2.0 the lens reaches the level of 33-35 lpmm so enables to take sharp and fully acceptable shots. This fact makes it stand out very favourably against its Canon and Nikon competitors which fared definitely worse wide open. On stopping down to f/2.8 the Pentax produces images of already excellent quality and by f/4.0 the results are simply on an outstanding level.

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You can have some small reservations about the frame edge performance by f/1.8-2.0 - there the reached level of about 23 lpmm is unacceptable for a lens of this class. Fortunately using f/2.8 aperture you can eliminate all the problems because the sharpness, even in the frame corners, returns to a good level.

The following crops show the situation for JPEG files, saved along with the RAWs.

Pentax smc FA 77 mm f/1.8 Limited - Image resolution