Evaluation
of the Canon EF 28mm f/1.8 USM Lens
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The Canon EF 28mm f/1.8 lens was evaluated for use in wide field astrophotography. The following information on resolution and 50% MTF is applicable to all photographic uses of the lens. Astrophotographs demonstrated that the lens gives good performance (minimization of coma and aberrations) if stopped down to f/4. |
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Resolution and 50% MTF Performance
Data
Link
to Methods Used
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Light Drop Off (Vignetting)
The table summarizes how image field illumination evens as aperture is closed.
| Aperture | EF 28mm f/1.8 | EF 24-70mm f/2.8L |
| Wide Open | f/2 Moderate Vignetting |
f/2.8 Moderate Vignetting |
| One Stop Closed | f/2.8 Mild Vignetting |
f/4 Minimal Vignetting |
| Two Stops Closed | f/4 NegligibleVignetting |
f/5.6 NegligibleVignetting |
Corner Image Sharpness with EOS-1Ds Mark II
| Aperture | EF 28mm f/1.8 | EF 24-70mm f/2.8L |
| Wide Open | f/2 Soft |
f/2.8 Mildly soft |
| One Stop Closed | f/2.8 Mildly soft |
f/4 Sharp |
| Two Stops Closed | f/4 Slightly soft |
f/5.6 Sharp |
Center Image Sharpness with EOS-1Ds Mark II
Central image sharpness varied among the lenses tested. There was no central chromatic aberration. Examples below in the table are from the center of this chart.
| Aperture | EF 28mm f/1.8 | EF 24-70mm f/2.8L |
| Wide Open | f/2 Sharp |
f/2.8 Sharp |
| One Stop Closed | f/2.8 Sharp |
f/4 Sharp |
| Two Stops Closed | f/4 Sharp |
f/5.6 Sharp |
Linear Distortion
There is no appreciable linear distortion with the prime. The zoom has very mild barrel distortion at 28mm.
Image Sharpness Comparison of EF 28mm f/1.8 and EF 35mm 1.4L @ f/2.8
| Aperture | EF 28mm f/1.8 @ f/2.8 EOS-1Ds Mark II |
EF 35mm f/1.4 L @ f/2.8 EOS-1Ds (Mark I) |
| Center | Sharp | Sharp |
| Corner | Slightly soft | Slightly soft |
Astrophotograph Comparison of EF
28mm f/1.8 and EF 35mm 1.4L @ f/2.8
Ektachrome 200; Camera
mounted on Kenko Skymemo tracking mount
| Aperture | EF 28mm f/1.8 @ f/2 3 minutes |
EF 28mm f/1.8 @ f/2.8 5 minutes |
EF 28mm f/1.8 @ f/4 10 minutes |
EF 35mm f/1.4 L @ f/2.8 10 minutes |
| Center | Slightly soft | Sharp | Sharp | Sharp |
| Corner | Moderate spherical aberration and coma | Mild spherical aberration and coma | Mild spherical aberration | Slight far corner spherical aberration |
©
2005, William L. Castleman
Initially
posted 1 June, 2005, updated 12 June, 2005