The gif below gives a sense of the test--same target, same light, same everything for stacks comparing test lens and a known-good lens. Target is laser printed paper pasted to a microscope slide. Images are stacked to avoid influence of focus error or differences in field curvature, which doesn't matter much to focus stackers. There are black margins because the lenses' fields of view differ, and I wanted to show them aligned at center with no cropping.
The above gif is too small for serious evaluation. However, quick takeaways include:
- *At this level of scrutiny, quality of both lenses looks about the same
*The lenses have different centers of view. Dennis' lens points a bit higher and to the left of mine. (This is repeatable, not a testing error. It's also quite normal among objectives.)
*The two lenses have slightly different magnifications. (Also quite normal.)
If the test lens passes the above and time permits, I like to do a quick stack of a real-world subject with the test lens. Some of us call this a pudding shot ("The proof of the pudding is in the eating.") So here is a quick pudding shot with Dennis' lens. Uncropped display of APS-C capture; field of view about 1.2mm wide:
100% crop (field of view about 0.2mm wide)
Dennis' bargain lens looks quite decent to me.
Notes:
- Camera: Nikon D7100 (APS-C sensor)
Macro rig: Bratcam
Lighting: Continuous halogen lights through fiber-optic light guides.
All images acquired as jpegs; stacked with Zerene Stacker, PMax method; stacks saved as Tiff.
Post: Pudding shots had curves adjustment; dust removal; small reduction in color as blue scale was initially rendered more vibrant than seen by my eye; and modest sharpening.
--edited typos