New answers tagged manual-focus
Since you have tested the lens on a T2i, the problem is mostly with the older body. Get it serviced. I guess, there must be some discrepancies with the lens contacts on the XS body.
The current standard kit lens with the SL1 appears to be the STM version which means, among other things, that the camera has to be powered on and ready to shoot (not sleeping) for manual focus to respond. Essentially it's a "focus-by-wire" system, where there isn't a direct physical connection between the focus ring and the actual lens elements, instead ...
If you know the daytime brightness for a properly exposed scene, and the nighttime brightness, you can just calculate how many stops difference between the two you have and set the night aperture accordingly. Say, 2048lux day, 64lux darkness = 5 stops difference. (log2(2048)-log2(64)) I don't know how focus comes into this, though, that wouldn't change ...
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