Raspistill image quality looks like rotation dependent

[Zeno]

Since I had to mount the camera upside down, I have to use

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raspistill -rot 180

.

I was quite disappointed with the image quality (too dark), until I realised that this darkness was caused by the rotation itself.

After trying unsucessfully to make it lighter by playing with --brightness and --iso, I opted for taking a unrotated picture and then rotating it by Imagemagick, which unfortunately requires my script to run a little longer.

Did anybody else realised about this problem? Is this something which could be fixed in a newer version of raspistill?

[jamesh]

That's weird. Do 90 and 270 show the same problem?

I'm trying to think of a possible reason this might go wrong, and so far I'm stumped.

[Zeno]

Probably I have found the reason: this seems to happen only when using raspstill -t 1.
Now I left the default time delay and image qualities are the sames.

Strange anyway, I would have expected the quality to be indipendent from --rot.

Concerning the question from Jamesh: --rot 90 and 270 were less affected. --rot 180 was very dark (tolerable by daylight, but unusable by artificial light).

[RaTTuS]

-t 1 is far too short
what does
-vf instead of --rot 180 appear like

[jamesh]

OK, it's an exposure problem. As Rattus says, -t 1 is almost instant, so the system has not had time to get the exposure right. I think you need at least 500-750ms.

Why it's slightly different depending on rotation could be anything, but all bets are off with a -t that short.