Canon 55-250 Focus Accuracy


The Canon 55-250 lens does not have a USM focus system, so the front of the barrel rotates & extends, plus it's not super fast. However, at least on my Canon 40D, it's darn accurate, especially as you zoom in. To test this, I used Moire' Interference Patterns at various focal lengths and here are full-size center crops using the auto-focus, and then doing "best" possible with Live View. The 40D was tripod mounted about eight feet away for the 250 and 200 shots - about six feet away for the 55 and 90 pictures. Timed shooting was used to minimize any camera shake and aperture was maximum possible with ISO 800 - shutter speeds were 1/60 to 1/160.

Note the fuzziness at full wide at 55mm - this was repeatable and is slightly back-focused, although it may be due to the fact that the test image isn't large for super-precise focus since if I moved to the minimum focusing distance, it was then dead on. I'll do some real-world testing when I have a chance, especially since this just tests close-in focusing.

Auto Focus at 250

canon 55-250 250 auto focus

Live View at 250

canon 55-250 250 live view

Auto Focus at 200

canon 55-250 200 auto focus

Live View at 200

canon 55-250 200 live view

Auto Focus at 90

canon 55-250 90 auto focus

Live View at 90

canon 55-250 90 live view

Auto Focus at 55 - slight back-focus

canon 55-250 55 auto focus

Live View at 55

canon 55-250 55 live view

Auto Focus at 55 at 3.6 feet

canon 55-250 55 auto focus close

Auto Focus at 55 at 3.6 feet

canon 55-250 55 live view close

Funky Colors due to Anti-Alias Filter on 40D (not unexpected)

Re-sized

canon 55-250 55 colors 1

Fuzzy Center crop

canon 55-250 55 colors 2

Sharp Outside Inner Circle

canon 55-250 55 colors 3



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