sumpra wrote in post #14849239
I'm looking at canon 28 1.8.
Is 28 2.8 better?
Better for what? The 2.8 has the following advantages over the 1.8. It is smaller, lighter, less expensive, and uses smaller filters.
Otherwise the 1.8 is a much nicer lens and generally easier to use with its fast ring USM focus, faster aperture, seven blade diaphragm, closer min focusing distance etc.
The 2.8 has a strongly curved plane of best focus. It is even more pronounced with a full frame camera. The lens looks great in test labs like the glowing review at SLR Gear. Their results show that it is very sharp corner to corner from f/2.8 - f/22 on full frame. Reviewers refocus for each part of the image for maximum sharpness so that the slight field curvature in most lenses doesn't affect the results. It isn't slight in this lens however. Real pictures are taken with the lens at a single focus distance. The sides, and even more so the corners, come into focus further away than the center. This lens would work great for photographing the surface of a beach ball. Photographing a flat wall, up close, at larger apertures, with the focus taken at the center will have blurry corners. If you focus for the corners, the middle will be blurry.
You can overcome this with practice and understanding. Taking pictures of flat things up close requires small apertures to avoid looking soft in the corners. Distant shots where almost everything is in focus should use one of the side focus points to avoid going much beyond infinity at the corners, using the depth of field to give reasonable results throughout the frame. Close-up wide open shots can actually work fine if the subject is near the middle. The rest of the picture will blur nicely.
The 2.8 can take some great pictures and used copies can be very inexpensive. It is very sharp in the center from wide open, and the lens gets very sharp when stopped down. It is supported in Canon DPP for lens corrections such as distortion and CA. I use DxO Optics Pro and this is one of their supported lenses. The curved field will cause trouble sometimes if you aren't aware and compensate accordingly. Other times it might help the shot. It took me quite a while when I first got the 2.8 to figure out why I got some great shots and some awful ones. I finally directly observed the focus plane curvature and how the focus gets further away the farther you are out from the center.
If you can afford the 1.8, you will probably like it better.
. I'm assuming you're using natural light? Why not get a medium gray background (Adorama is selling a 10x24 right now for $54) and use that for extractions/composites instead? Just Google "compositing with gray background" and you'll see what I mean. Also, grey is pretty versatile in that you can gel it to get whatever color, but you can also overexpose it to get white or underexpose it to get black.
