September 14th, 2009

flock

new camera puzzlement

OK, so there we are at DMRF with a bright shiny--OK, a flat black new camera, a Canon EOS Rebel Xsi, looking forward to taking even better pictures with our better hardware...

...until we realized we were getting fuzzy images, without a single F. fuzzy Holloway in sight. (Darn it. When I first read the book, I so wished that they actually existed... but that's not important right now.) What the heck? We pushed the button halfway down, and watched the little red LEDs light up where it said it had focused, or is that focussed, and then pushed the button the rest of the way down. Reviews say that the Xsi latches on to focus very quickly indeed, and I bellieve them.

So, we went to the images themselves, and right clicked and asked for "Properties", and then we saw.

Exposure time: 1/24 sec.
Exposure time: 1/19 sec.
...

From what I've read, the longest exposure time that will avoid problems with wobbly humans moving the camera is 1/60 sec. Ah, apparently it's a little more complicated than that. There's a "Reciprocal of the Focal Length" rule: for X mm focal length, exposure better be shorter than 1/X seconds. (That takes care of wobbly photographers--there's also the question of wobbly subjects.)  We're using a zoom lens with focal length ranging from 18 to 55 mm, so maybe the camera is honoring that rule--but if it is, and the rule works, why are we getting fuzzy images?

So--the question is, why is it that our spiffy new Canon EOS Xsi picks such long exposure times in full automatic mode? We will experiment (maybe turning off the Image Stabilization will make it more conservative), and we will go talk to the folks at Christian Photo from whom we bought the camera.

UPDATE: A fellow on amazon.com says the fix for claimed autofocus problems on the Xsi is, don't do full auto; choose one of the other modes and pick exactly ONE of those nine points as the one that autofocus should pay attention to. We'll give that a try, too.

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