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Canon 28mm f/1.8
Canon EF 28mm f/1.8. I got this one here. Here and here are also great places I would use personally. It helps me keep adding to this site when you get yours from these links, too. Back to where you were in the main Canon 28mm f/1.8 Review Back to the top of the Canon 28mm f/1.8 Review July 2007 SHARPNESS and COMA back to Performance or back to Introduction. It's very sharp, as expected. Also, as expected for a wide lens with a fast aperture, it's a little soft wide open. Even at f/1.8 it's great for hand-held low-light shooting, but if you're shooting test charts or astronomy, stop down to f/2.8 or spend $1,000 on an L lens like the 24mm /1.4L, 35mm f/1.4L or the Nikon 28mm f/1.4 on a Nikon if you need perfect sharpness wide open. For regular photography, don't worry: it looks great at every aperture, and if you want perfect test sharpness, shoot at f/2.8 or smaller. The low contrast wide open comes from spherical aberration, which means that there is always a sharp image, but a veiling haze appears over it wide open. Stopped down to f/2.8 it's fine for astronomy, too. Here are stars in the moonlit sky.
Resort by Moonlight. Canon 28mm f/1.8 at f/2.8, Canon 5D at ISO 800, 8 seconds. Here's a complete guide image from my full-frame Canon 5D, from which I will show you crops.
Full image, Canon 28mm f/1.8, full-frame Canon 5D. Center Here are crops from the center of the above image at 100%. Remember, the complete image printed at this same magnification would be 44" (1.1m) wide:
Canon 28mm f/1.8 at f/1.8, crop from center of 100% image. See the slight veiling? That's what happens if you're dumb enough to shoot at f/1.8 in broad daylight. In dark situations where you'd really use f/1.8 hand-held, it looks fine. This is normal and the sort of thing you'd probably never notice until you owned the lens 5 years, then if you saw it for the first time you might worry. Not to worry; this is what this lens does.
Canon 28mm f/1.8 at f/2, crop from center of 100% image. Even stopping down 1/3 stop to f/2 improves the image.
Canon 28mm f/1.8 at f/2.8, crop from center of 100% image. By f/2.8 the center of the image is perfectly sharp, so long as your subject is within the small depth of field at f/2.8.
Canon 28mm f/1.8 at f/4, crop from center of 100% image. This shot's for free: the image is as sharp as it's going to get by f/2.8 in the center, so f/4 looks the same. Diffraction will start to soften the image at f/11 and smaller, as it does on all lenses. Top Right Corner, Full-Frame Here are crops from the top right corner of a full-frame image at 100%. Like all wide lenses, performance gets worse as one gets further away from the center, so the corner of a full-frame image is the toughest test. It will be better on a 1.3x (1D Mk III) and much better on a 1.6x (Rebel and 30D) image.
Canon 28mm f/1.8 at f/1.8, crop from top right of 100% image. This is softer due to the veiling of the spherical aberration, but notice that there is a sharp core as well. The details are here, hiding behind lower contrast. It's also a bit darker in the corner due to the slight falloff.
Canon 28mm f/1.8 at f/2, crop from top right of 100% image. Stopping down a third of a stop to f/2 is an improvement, both in improving falloff and sharpness.
Canon 28mm f/1.8 at f/2.8, crop from top right of 100% image. f/2.8 is much better than f/2, but since we're in a far corner, still not as sharp as in the center at f/2.8.
Canon 28mm f/1.8 at f/4, crop from top right of 100% image. By f/4 even the corners are great. f/2.8 is all you need for perfect sharpness, but if you're looking at it with a microscope like this, then stop down to f/4.
Coma is what makes points of light in the corners look like blobs or comas instead of points. If a lens has coma, it's visible at only the widest apertures. Coma is caused by spherical aberration. The Canon 28mm f/1.8 has pronounced coma at f/1.8 and f/2, and it goes away at f/2.8.
Full-frame image, Canon 28mm f/1.8 at f/1.8 for 6 seconds, 5D at ISO 200. See what looks like Saturn in the upper left along the top edge? It's actually Jupiter, and should look like a point, not a blob. The huge bright thing is a 12 day old moon (3/4 full). The blobs at the bottom left and right also are not as we'd like them. These blobs are coma.
Full-frame image, Canon 28mm f/1.8 at f/2 for 8 seconds, 5D at ISO 200. Stopping down a third of a stop to f/2 is a small improvement.
Full-frame image, Canon 28mm f/1.8 at f/2.8 for 16 seconds, 5D at ISO 200. By f/2.8 the coma is gone, hooray!
Full-frame image, Canon 28mm f/1.8 at f/4 for 32 seconds, 5D at ISO 200. f/4 is even a little better, and as you can see under Sunstars, the little points of light are starting to grow points. Jupiter now looks a little bit elongated, but that's due to Earth movement making it appear to move towards the lower right, This longer 32 second exposure brings that out. Back to where you were in the main Canon 28mm f/1.8 Review. Back to the top of the Canon 28mm f/1.8 Review.
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