Bug 9741 – Pictures taken with flash have wrong white balancing (green tint) and are too dark.

Bug 9741 - Pictures taken with flash have wrong white balancing (green tint) and are too dark.


Summary:	Pictures taken with flash have wrong white balancing (green tint) and are too...

Status:	RESOLVED DUPLICATE of bug 7060

Product:	Images and Camera
Component:	Camera
Version:	5.0/(3.2010.02-8)
Platform:	All Maemo

Importance:	Unspecified normal (vote)
Target Milestone:	---
Assigned To:	unassigned
QA Contact:	camera-bugs

URL:
Keywords:

Depends on:
Blocks:
	Show dependency tree

Reported:	2010-03-28 00:03 UTC by fileshifter
Modified:	2010-03-28 00:24 UTC (History)
CC List:	2 users (show)

See Also:

Attachments
n900 green and dark picture (701.75 KB, image/jpeg) 2010-03-28 00:04 UTC, fileshifter	Details
n900 screen during taking picture (looks fine) (368.46 KB, image/jpeg) 2010-03-28 00:04 UTC, fileshifter	Details
picture taken with another camera as reference for the colors. (435.03 KB, image/jpeg) 2010-03-28 00:05 UTC, fileshifter	Details
Add an attachment (proposed patch, testcase, etc.)

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Description fileshifter (reporter) 2010-03-28 00:03:55 UTC

SOFTWARE VERSION:
3.2010.02-8

EXACT STEPS LEADING TO PROBLEM: 
1. Take picture in moderately dim light conditions using flash

EXPECTED OUTCOME:
Nice, balanced, bright picture

ACTUAL OUTCOME:
Green, dark, ugly picture

REPRODUCIBILITY:
Always

OTHER COMMENTS:
I tried ALL the different white balancing settings as well as the exposure
settings. All of this doesn't make a difference. My table is brown, not green.
See the 3 attached pictures. n900_too_dark.jpg shows the ugly picutre,
n900_looks_fine.jpg is a picture of the n900's screen while focusing the
subject, which has nice colors and is bright, and sony_should_be.jpg is how the
picture should actually look like (taken with a 4 years old sony pocket)

Comment 1 fileshifter (reporter) 2010-03-28 00:04:20 UTC

Created an attachment (id=2541) [details]
n900 green and dark picture

Comment 2 fileshifter (reporter) 2010-03-28 00:04:54 UTC

Created an attachment (id=2542) [details]
n900 screen during taking picture (looks fine)

Comment 3 fileshifter (reporter) 2010-03-28 00:05:15 UTC

Created an attachment (id=2543) [details]
picture taken with another camera as reference for the colors.

Comment 4 Joerg Reisenweber 2010-03-28 00:08:30 UTC

white balance done in torch mode doesn't fit for flashlight pictures, it seems.
Probably light temperature of the flash LEDs is changing with increased
brightness.

I can reproduce the described bahviour here

Comment 5 Joerg Reisenweber 2010-03-28 00:22:30 UTC

suggested fix:
as the color shift of the flashing LEDs between torch and flash is constant,
the following procedure might fix the issue:
- get picture without LED fillin - calculate brightness.
- get picture with torch mode LED fill-in (autofocus + whitebalance) - get
brightness.
- calculate percentage of LED light in picture from brightness in 1. and 2.
step
- adjust whitebalance to match the constant colorshift of flashmode (vs
torchnode) * percentage of FLASHlight in total light (which is torchlight
percentage * flash/torch constant factor)
- take final picture with flashlight


sidenote: probably it's the yellow flourescent in white flash leds that changes
color (or more precisely efficiency) on higher brightness levels

Comment 6 Venomrush 2010-03-28 00:24:08 UTC


*** This bug has been marked as a duplicate of bug 7060 ***