Canon Macro Lens EF 100mm 1:2.8 USM
|Aperture Range [f]||2.8 to 32||Closest Focus||0.31m / 1 ft.|
|Dimensions||119mm x 79mm / 4.7 in. x 3.1 in.||Magnification Ratio||1.0x / 1:1|
|Weight||600g / 1.3 lb||Filter Size||58mm|
Analysis of this lens resolution chart revealed that it is the sharpest at f/8. The image quality on a camera's chip depends on the distance from the center, as shown below, with the average resolution in hundreds of line widths per picture height (LW/PH) given below each chart.
The sharpness is relatively uniform throughout the entire frame, and reaches the theoretical maximum (resolution of "37" is the max. theoretical number in this test) at f/8 for almost half of the frame. It is exceptionally sharp then. Contrast in the center is slightly lower at wide apertures, f/2.8 to 4.
Vignetting is very low. Chromatic aberration is negligible. The size of the circles remain constant trhoughout the frame. The circles have also perfect proportion (no ellipses). The lens has virtually no distortions.
Test macro at magnificaction 1:1. A house fly wing has been placed between two microscopic slides and sealed tightly to flatten it as much as possible. A source of light (flood matte bulb) was placed behind the slide. Two photos on manual focusing (at ISO 50) were made at each f-stop, with mirror locked up, one that placed the wing in the center of the frame and another on the side, approximately 15 mm from the center, as shown below.
Actual magnification ratio:
1.033 : 1
23.28 x 34.84 mm
1 pixel = 6.22 micrometer
The 200x200 pixels cropped images are shown below.
The best sharpness was achieved between f/5.6 and f/8. Chromatic aberration is well visible on the sides. There is significant drop of sharpness on the sides of the image, not expected from the charts made form several feet distance. I would not recommend making photos at above f/11 due to the loss of sharpness. F/2.8 is not particularly sharp either.
This is a good macro lens, but clearly inferior than the Canon 180 mm macro lens. Considering its price, it's a very good buy. The magnification ratio is over 3% higher than described in specifications (a good thing). Works well with the extension tubes and with 2x Canon Extender. With putting both of them on you can achieve 3.8 : 1 magnification ratio.
This is a high quality lens, despite its not "L". Good for macro applications and for portraits. A great buy.
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