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Pentax-A 120mm f/4

This page shows how the Pentax-A 120mm f/4 performs on the demanding mosaic target.

I took an immediate liking to the Pentax 120mm f/4. I used a loaner from a reader. It’s solidly built, and it uses an old-style focusing helicoid with plenty of “throw” for fine focus adjustments, all the way to 1:1 on a 44 X 33mm sensor.

I haven’t tried the autofocus FA version, but I doubt that it will compare favorably for manual focus, because AF lenses are usually a compromise in ergonomics, lacking a focusing helicoid.

Using the AF focus assist on the 645D consistently results in front focus and thus a blurred subject. This is true with the 120/4, and with other lenses I tried. Caution advised, and use of fine focus adjust feature might help (not yet tested).

For this test, I focused manually with 3 trials. Not all attempts were as good as the one shown here.

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Since 2006, Diglloyd Advanced Photography is the authoritative review and reference for DSLRs and their lenses: Canon and Nikon primarily, but also Pentax and some medium format. Reviews of key DSLRs are included, but the primary focus is on lens performance. Also included is a wealth of technique and workflow approaches.

DAP includes thousands of pages of exclusive coverage and high resolution Retina-grade examples detailing Canon and Nikon DSLR bodies and their lenses, with in-depth analysis of sharpness and contrast, color, bokeh, vignetting, distortion, MTF, and flare, behavioral and practical usage.

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