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Coastal Optics
60mm f/4 UV-VIS-IR APO macro

MTF

The Coastal 60/4 shows some weakness at the edges and corners until f/8. This is easily observed on very high resolution cameras cameras like the Nikon D800 or Sony A7R.

According to lens designer Brian Caldwell:

The coma and oblique spherical disappear quickly on stopping down, which is why performance in the extreme corner suddenly gets great at f/8.

If the problem were truly field curvature then the improvement would be much more gradual.

The latter statement is true, but field shots suggests a very mild field curvature at inifinity focus which “piles on” its subtle effects when shooting the 60/4 at infinity. Use of f/8 is strongly advised for peak quality on high-resolution digital.

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Diglloyd DAP is DSLR-oriented, but also contains workflow and other topics. Much of the focus is on Canon and Nikon but also Pentax and Pentax medium format.

Special emphasis is placed on lens evaluation, focusing on Canon and Nikon and Sigma lenses, but with a few others like Rokinon/Samyang.

  • Make better images by learning how to get the best results right away.
  • Save money by choosing the right lens for your needs the first time, particularly some of the new Sigma Art lenses vs Nikon and Canon.
  • Workflow discusses image organization, raw conversion and post processing. Many examples show processing parameters for direct insight into how the image was converted.
  • Jaw-dropping image quality found nowhere else utilizing Retina-grade images up to full camera resolution, plus large crops [past 2 years or so].
  • Real world examples with insights found nowhere else. Make sharper images just by understanding lens behavior you won’t read about elsewhere.
  • 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.

Want a preview? Click on any page below to see an excerpt as well as extensive blog coverage, for example on Nikon or on Canon or on Pentax.

MTF at infinity, visible light

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