| Canon EF 300mm f/2.8 L IS USM Specifications | |
| Frame Coverage | 35mm |
| Lens Construction (groups) | 13 |
| Lens Construction (elements) | 17 |
| No. of Diaphragm Blades | 8 |
| Minimum Aperture | 32 |
| Closest Focusing Distance | 2.5m (98.4") |
| Maximum Magnifcation | .13x |
| Filter Diameter | 52mm (rear gelatin filter) |
| Maximum Diameter x Length | 128mm x 252mm (5" x 9.9") |
| Weight | 1190g (89.9oz) |
Reviews
Source
AstroPix.com
In my opinion, these lenses are not usable for high-quality long-exposure deep-sky astrophotography when used wide open unless the photographer is willing to clip a significant amount of highlight detail in the stars.
Luminous-Landscape.com
My own more pragmatic tests show that this lens is usable wide-open without any hesitation. Stopping down only increases resolution and micro contrast very slightly. When you pay for f/2.8 with this lens, you get an f/2.8 that is every bit as usable as any other aperture. That's what one is paying for.
The-Digital-Picture.com
The Canon EF 300mm f/4 L IS USM Lens differs from the Canon EF 300mm f/2.8 L IS USM Lens in title by only one f-stop, but there are more differences. The f/2.8 is sharper at f/2.8 than the f/4 is at f/4 and remains sharper at all comparable apertures. The f/2.8 costs significantly more and is significantly larger/heavier than the f/4.
