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08-06-2010, 12:32 PM   #1
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invisible blue?

So today i was playing some computer game and i decided to point my k20d with 50 mm f1.4 on the wall and take a photo. so i focused on the lamp in front of it and shot.....
i got the lamp... but the background baby bluish color was actually white!
i was confused so i shot it wihtout my ir filter... same result. so i pointed the opposite direction and shot, this time the blue came out.
can anyone explain y this is happeninng?
btw the first location was right next to the wall and light is shown on the wall from the window diagnoly
the second location the light shines straight to it...
someone plz solve the mystery..

08-06-2010, 12:36 PM   #2
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It's either due to incorrect white balance, overexposure, or the fact that your lamp was illuminating the wall.

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08-06-2010, 12:38 PM   #3
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white balance was good, no illumination from lamp....
i just tryied it with faster shutter and it worked!
haha man i am a newb...
08-06-2010, 12:48 PM   #4
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QuoteOriginally posted by jolee1990 Quote
white balance was good, no illumination from lamp....
i just tryied it with faster shutter and it worked!
haha man i am a newb...
Then it was overexposed. Remember that little lesson when taking photos containing the Sky.



08-07-2010, 12:49 PM   #5
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jeffffff actually it wasnt over exposure! it was 1/30th! there isnt much light in here... it doesnt make sense............................
i went from 1/30th to 1/90th and still it has the gray background
the blue just isnt there...
08-07-2010, 01:09 PM   #6
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I guess you're just going to have to show us the picture then. A lot of times, with one of the auto exposure modes (Av or Tv) just changing one thing doesn't change anything. The other will adjust automatically. When I'm having trouble getting what I want, I'll go to M, Spot metering, and then adjust both shutter speed and aperture (ISO always stays at 100) for best overall exposure.

08-07-2010, 05:50 PM   #7
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the thing is that i always leave it on M mode, so it was all in manual. i tried 2 diff lenses ect... i swear it has something to do wiht that light that was coming in or the color of the blue wiht the light just like a green screen u know?
08-07-2010, 06:14 PM   #8
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Still would be useful to see a photo but the only thing I can think of, if it wasn't originally over-exposed, is a mixed light source (Tungsten and daylight for instance, or florescent)..



08-07-2010, 06:57 PM   #9
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QuoteOriginally posted by jolee1990 Quote
the thing is that i always leave it on M mode, so it was all in manual. i tried 2 diff lenses ect... i swear it has something to do wiht that light that was coming in or the color of the blue wiht the light just like a green screen u know?
Take a breath, then post the shots :-)
08-07-2010, 11:37 PM   #10
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Is the lamp using a florescent bulb?
08-10-2010, 09:09 PM   #11
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What makes you say it's *not* a white balance issue? If you were using auto WB, then it was just doing it's job - looking at th scene and trying to remove any color casts it saw. Normally, the color cast removed is due to the color of the light, but it has no way of knowing whether than wall was white with blue light shining on it or if it was actually painted blue. So it's completely normal that it might guess wrong and think you had blue light and you wanted that color cast removed. Set WB to the actual type of lighting you are using to avoid that (or else fix WB in PP, although that's usually easier when shooting RAW).
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