Very inexperienced person here when it comes to photography and raw processing here. I'm using a Canon SX 60HS camera. No attachments — filter/hood/etc. — of any sort were attached to lens.
After switching to raw+jpeg mode, I started noticing black round corners for some of the images. I had never experienced this while using camera in automatic mode.
After researching, I found out this is called as vignetting and is a limitation or function of lens and some other parameters at the time of taking the snap.
Why does this not happen when taking the picture in auto mode? Even the jpeg images generated in raw+jpeg mode do not show vignetting. Only raw images show it.
If it matters, I'm using Darktable 2.4.1 on Ubuntu. Since I don't have access to Windows PC, I can not test on Canon software.
I understand vignetting can happen. However camera image preview does not show vignetting. Is there any way to detect vignetting in the camera while I'm at scene so that I can adjust parameters and take the picture again. What sort of information I should check for possible vignetting. I tried to find a common pattern, but so far no luck.