EXCERPT page containing first few paragraphs. 2021-06-24 14:55:37
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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).
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- In-depth lens evaluations covering behaviors not likely to be found anywhere else, based on real-world field shooting.
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- Aperture series from wide open through stopped down, showing the full range of lens performance and bokeh.
- Optical quality analysis of field curvature, focus shift, sharpness, flare, distortion, and performance in the field.