The DNG's confirm it. No visible "amp glow" in a 60 second exposure using an SX50.
Nice.
FWIW if darkframe subtraction is active (as it is by default for long exposures without CHDK overrides), it will take care of most of the amp glow, at the expense of making each shot take 2x as long as the requested exposure time.
That said, it appears Canon has greatly reduced the amount of amp glow in recent cameras, my elph130 and sx160 both show very little in exposures of a couple minutes. A dark frame is still desirable to get rid of hot pixels normal dark current.
Some examples
https://app.box.com/s/sjj9a6kiyx95qeda9ixubxpkmuhuol3u3992 is 4 minutes, 3993 is 2 minutes, elph130. Canon DFS was off.
From comparison, 3724 is a 64 second exposure with D10 (note the exif in the canon jpeg says 15 sec but it's wrong
) Fuzzy green spot is comet C/2014 Q2 (Lovejoy)
For both cameras, the CRW_*.jpg files are processed in raw therapee, using a separately created dark frame as described in
http://chdk.setepontos.com/index.php?topic=10159.msg101969#msg101969Edit:
Interestingly, someone complained about what appeared to be bad amp glow or something similar on sx50hs in
http://chdk.setepontos.com/index.php?topic=11062.0
