SL2 Backfocussing Question

HNY (well almost). My wife’s SL2 back-focusses enough to be noticeable compared to the same pic through live view. This with the standard 18-55 lens. I have the opportunity to exchange it or send it in to have it examined by Canon Canada. My question is does anyone have experience having their camera serviced for that reason or if they got a replacement what are the odds of the same problem on the new body. I have read that the tolerances are not that strict when manufactured and recall DPR noting a back focus problem when reviewing the t6i I recall.

jbent1 wrote:

HNY (well almost).

HNY back at ya! I hope it brings good luck too (camera-wise).

My wife’s SL2 back-focusses enough to be noticeable compared to the same pic through live view. This with the standard 18-55 lens. I have the opportunity to exchange it or send it in to have it examined by Canon Canada. My question is does anyone have experience having their camera serviced for that reason or if they got a replacement what are the odds of the same problem on the new body. I have read that the tolerances are not that strict when manufactured and recall DPR noting a back focus problem when reviewing the t6i I recall.

If you have the choice, just exchange it (if you're certain it's acting up).

FF/BF issues with bodies are rare. It's almost always the fault of the lens. I have 2 problematic lenses (one FF's, and one BF's). I need to apply autofocus micro-adjustment for both (with my 70D).

If you have a chance, test another lens to be sure (wide-aperture primes will be most telling). Makes sure that the camera isn't set to Auto Mode or all AF points (AF can get really screwy). Always use a single AF point when shooting (anything)!

Best of luck to you!

R2

Thank you R2D2. Your advice is always thoughtful. Tried the Center cross type point only and it is a closer match to the live view pic. Too bad the sl2 was shackled with the 9 point focussing but sports good live view focussing. Why not the 19 point of the previous t6i? Could not be that much more expensive. Canon makes some quirky decisions yet floods the market with  many models. Nikon makes more sense with their model line, but their live view, oh well. Just my rant. Thanks again.

jbent1 wrote:

Thank you R2D2. Your advice is always thoughtful. Tried the Center cross type point only and it is a closer match to the live view pic. Too bad the sl2 was shackled with the 9 point focussing but sports good live view focussing. Why not the 19 point of the previous t6i? Could not be that much more expensive. Canon makes some quirky decisions yet floods the market with many models. Nikon makes more sense with their model line, but their live view, oh well. Just my rant. Thanks again.

Thanks.  Glad to hear it has improved.  Do a bit more testing to be sure.

Keep in mind too that the camera’s actual autofocus area is about twice the size of the individual AF box in the viewfinder (twice the height and width).  This can work to pull the focus to unintended objects that are outside of the AF box (but within that larger AF area), even when using a single AF point.

Also explain to your DW that the (viewfinder) autofocus is programmed to focus on the closest object with sufficient contrast that’s within the autofocus area (note that I said ‘area’ and not ‘box’), since again the area is a bit bigger than the box itself.

That said, on occasion the AF can be drawn to a very contrasty object in the background, if part of it is within the AF area.  Think chain link fence, or branches, or striped clothing, etc.

The camera’s AF (both the viewfinder AF and the Live View ‘LCD’ AF) is also more sensitive to vertical contrast than horizontal, even though you might be using a cross type sensor.  In fact, the Live View AF cannot focus at all on a purely horizontal line!  If you ever do run into this situation, just tilt the camera to one side a bit to acquire focus, then recompose and take the picture.  Not a common occurrence at all, but something to remain aware of.

I know this sounds like a lot of doom and gloom, but in reality the SL2’s AF is truly excellent.  It just doesn’t have all of the options that its big brothers have.

So advise your DW to keep using that single AF point!  It’ll provide the best chance for success.

Happy shooting, and Happy New Year to you and yours!

R2