EXCERPT page containing first few paragraphs. 2018-09-23 04:17:04
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This page assesses the Sigma 105mm f/1.4 DG HSM Art for focus shift at a distance of approximately 1.5 meters.
One might think that a “small” amount of focus shift is acceptable. But it is not—I think I at first unfairly blamed the Nikon D850 for focusing errors in the f/4 and f/5.6 images. It might well be a factor, but the dominant error is the zone of sharp focus being too deep, e.g., centered inside the eyeball instead of centered on the iris of the eye. This series explores that possibility
Picnic table wooden surface
The entire frame aperture series is shown below. A casual glance show a hint of a focus shift issue, but it’s not very obvious.
As to correction for secondary color, it is outstanding. There is no obvious secondary color in either the foreground or background only the sparest hints of it—truly outstanding, world class performance.
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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 28 megapixels filling up to 5K display, 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.