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Sigma 50/1.4A: Color Correction and LOCA, Implications
Sigma discusses axial (longitudinal) chromatic aberration:
For axial chromatic aberration that is hard to correct even during the image processing, SLD (Special Low Dispersion) glass elements are incorporated, ensuring high image quality throughout the entire focusing range. The lens achieves sharp and high contrast image rendering.
Other than spherical aberration which is generally well controlled by aspheric element(s), the dominant contrast-degrading aberration for fast lenses at wide apertures is longitudinal chromatic aberration (LOCA).
LOCA is responsible for the dreaded violet fringing, but that violet halo effect is only made obvious with some subject matter. It can look awful in backlighting, but for many images it simply will not be seen.
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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.
