autofocus accuracy revisited

While measuring autofocus speed is no mean feat, measuring autofocus accuracy is quite straightforward with the ol' Nikon D70 Focus Chart. I did this once with the 300D, and now it's time to see what, if any, improvements we find with the new AF system of the 450D.

Two years ago I tested all the lenses I had with narrow enough DoF to make the test meaningful: the Canon EF 50mm f/1.4 USM, Canon EF 85mm f/1.8 USM, and Canon EF 70-300mm f/4-5.6 IS USM. Today I ran the same test on those same lenses, as well as the EF-S 17-55mm f/2.8 IS USM, with the 450D. Here's the results:

EF 50mm f/1.4 USM
300D: 5-10mm front focus
450D: 4mm front focus every time

EF 85mm f/1.8 USM
300D: 0-1mm front focus
450D: 2mm front focus every time

EF 70-300mm f/4-5.6 IS USM
300D (190mm f/5.0, starting at MFD): 2-6mm front focus
300D (190mm f/5.0, starting at infinity): within DoF
450D (300mm f/5.6, starting at MFD): 2mm front focus
450D (300mm f/5.6, starting at infinity): within DoF

EF-S 17-55mm f/2.8 IS USM
300D: untested, but no problems in practice
450D: within DoF every time

Lessons learned:

• 450D autofocus accuracy is highly consistent, more so than 300D
• when either of my Rebels misfocus, it's always front focus
• my 50mm f/1.4 is now a reliable tool, but still not perfect
• Live View kicks ass:

450D with EF 70-300mm f/4-5.6 IS USM
@ 300mm f/5.6, IS off, tripod, mirror lockup, AF

450D with EF 70-300mm f/4-5.6 IS USM
@ 300mm f/5.6, IS off, tripod, Live View, MF