What are the factors that affect imaging quality?
Why do images presented by a lens have optical aberrations?
A. Distortion
Distortion will cause real objects to be straight lines, but in photos tobe non-straight lines, to be curved lines.
a) barrel
b) pincushion
c) complex/wavy
Types of lenses prone to distortion: usually zoom lensesand wide-angle lenses.
B. Field curvature
For plane objects in reality, after imaging, thereal image surface is curved, and most actual sensors are also flat, which willcause the center field of view and the edge field of view to be unable topresent clear images at the same time.
Lens types prone to field curvature: usuallywide-angle lenses and large aperture lenses.
C. Vignetting
a) Vignetting-----Light Falloff
Uneven brightness Light Falloff, the exposure ofthe center field of view and the edge field of view are different, resulting ininconsistent brightness between the center and edge of the picture, which iswhat we often call thecamera vignetting problem.
b) Vignetting-----Color Cast
Usually there is a color difference between theedges of the picture (especially the corners) and the center area. It is notentirely caused by lens aberration, filters and sensors will also have acertain impact.
Types of lenses prone to vignetting: usually large
There are many factors that cause optical aberration inlenses, some of which have been shared above:
1)distortion
2) field curvature
3) Vignetting ---Light Falloff
4) Vignetting ---Color Cast
In fact, there are someother influencing factors:
1) Focus Shift
When you reduce the aperture size, the best focusplane will move to the front or back. That is, the aperture size will affectthe best focus plane position, which is what we call focus shift.
Common lenses that are prone to focus shift: largeaperture lenses. When adjusting the aperture, the focus usually needs to bere-adjusted.
2) Onion ring bokeh
There are some out-of-focus circular rays of lightin the optical path of the lens, which is generally caused by a defective lens.
Common lenses that are prone to "onionrings": Some large aperture lenses often use aspherical lenses because ofthe flatness of the surface involved during processing.
3) Flare-Ghosting
When there are some abnormal colored patches inthe presented image, usually like colored circles or colored blocks of specificshapes, we become ghost images.
Common ghost images: zoom lenses, lenses with alarge number of lenses, and large-diameter lenses. During processing, try toreduce the aperture as much as possible, or use post-image processing.
4) Flare-Internal Reflections
Generally speaking, highly reflective objectsinside the lens, such as structural parts with too high reflectivity, or dirtylenses in the optical path, etc. In most cases it is caused by workmanshipissues.
Common internal reflection stray light lenses:especially large aperture lenses, during the production process, you can try toeliminate light, cut off light, block stray light, increase transmittance, andreduce the aperture as much as possible when conditions permit.
