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03-10-2009, 01:33 AM   #1
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what's causing this weird yellow tint ?

I was playing with my FA 50mm/1.4 this evening and noticed something strange.

Some shots of a kitchen cabinet door show this weird horizontal band of yellow tint.

Here it is around the upper middle of the camera:



This is pretty much the same shot, but now it's on the lower edge of the camera:



The next two shots of the same cabinet door don't have the problem, or to a much smaller degree (less tinting):





Here it is on the lower half of the camera:



Again, but to a smaller degree:



Here it is on the lower edge of the camera, after I've flipped the camera upside down:



Does anyone have a clue what's causing this ? I'm stumped.

03-10-2009, 02:08 AM   #2
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Strange indeed. Only happens with the 50/1,4? In which case, it's likely in the lens itself... can you remove the lens and look inside? Perhaps one of the elements came loose???

If it happens with other lenses, then it's clearly an issue with the body, and probably something to do with the sensor and/or firmware.
03-10-2009, 02:10 AM   #3
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Weird

...but did you have a filter mounted? I wasn't thinking of a yellow gradual filter , but rather speculating (wildly!) if e.g. a polarizer used in ambient light could cause effects like this.
03-10-2009, 02:25 AM   #4
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QuoteOriginally posted by RawheaD Quote
Strange indeed. Only happens with the 50/1,4? In which case, it's likely in the lens itself... can you remove the lens and look inside? Perhaps one of the elements came loose???

If it happens with other lenses, then it's clearly an issue with the body, and probably something to do with the sensor and/or firmware.
I don't see anything inside it. Nothing obviously loose. If I wiggle it, I do hear a little sound, but I don't see anything moving. Not sure if this is normal or not. I haven't really tested it with another lens yet as this it he first time I've noticed it.

QuoteOriginally posted by gazonk Quote
...but did you have a filter mounted? I wasn't thinking of a yellow gradual filter , but rather speculating (wildly!) if e.g. a polarizer used in ambient light could cause effects like this.
No filter mounted--well, except for a hoya uv/protector.

03-10-2009, 02:40 AM   #5
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Remove the filter and snap a similar shot to see if the yellow cast is still there. If so, send it in.
03-10-2009, 02:53 AM   #6
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why complain? I think the door looks a lot more nice with the yellow line
03-10-2009, 03:31 AM   #7
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what is the light source?

While I didn't believe it at first, (I thought the phosphours coating on bulbs eliminated the flicker and color shifts, I was told by other forum members that depending on shutter speed, you could see large color shifts on flourescent bulbs. I took a shot of a tube and ou could see different colors along the legth as the slit of the shutter moved across the frame
03-10-2009, 03:39 AM   #8
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QuoteOriginally posted by felixkh Quote
Remove the filter and snap a similar shot to see if the yellow cast is still there. If so, send it in.
Ok, so it still has that problem without the uv protector. What's strange is, if I turn on the flash, the problem goes away. Also tried it with my 18-55 kit lens at a similar focal length, and there's no problem there. Weird..


50/1.4 with flash


18-55 kit lens

QuoteOriginally posted by losecontrol Quote
why complain? I think the door looks a lot more nice with the yellow line
Lol

03-10-2009, 03:40 AM   #9
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QuoteOriginally posted by Lowell Goudge Quote
what is the light source?

While I didn't believe it at first, (I thought the phosphours coating on bulbs eliminated the flicker and color shifts, I was told by other forum members that depending on shutter speed, you could see large color shifts on flourescent bulbs. I took a shot of a tube and ou could see different colors along the legth as the slit of the shutter moved across the frame
Oooh... the light source is from flourescent tubes directly overhead. Let me try a different shutter speed..
03-10-2009, 04:15 AM   #10
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Is your White Balance set to Auto?? It looks like a White Balance problem.
03-10-2009, 04:23 AM   #11
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QuoteOriginally posted by chiem Quote
Oooh... the light source is from flourescent tubes directly overhead. Let me try a different shutter speed..
Lowell, you're my hero. The flourescent flickering is exactly the problem.

For the curious, here are some shots at different shutter speeds:


50mm 1/160s


50mm 1/200s


50mm 1/250s


50mm 1/320s


50mm 1/400s


50mm 1/500s


50mm 1/640s


50mm 1/800s


50mm 1/1000s


50mm 1/1250s


50mm 1/1600s

The reason why flash wasn't affected should be obvious. The kit lens shot was at f5.6 1/60s. I learned something new tonight--I should never shoot faster than 1/160s around flourescent lighting.
03-10-2009, 09:44 AM   #12
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QuoteOriginally posted by Lowell Goudge Quote
what is the light source?

While I didn't believe it at first, (I thought the phosphours coating on bulbs eliminated the flicker and color shifts, I was told by other forum members that depending on shutter speed, you could see large color shifts on flourescent bulbs. I took a shot of a tube and ou could see different colors along the legth as the slit of the shutter moved across the frame
This is what I'm betting on as well. Try duplicating the shot but use a slow shutter speed. I'll be surprised if it shows up at 1/30th of a second or slower.
03-10-2009, 01:42 PM   #13
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QuoteOriginally posted by Parallax Quote
This is what I'm betting on as well. Try duplicating the shot but use a slow shutter speed. I'll be surprised if it shows up at 1/30th of a second or slower.
Yup, I'd bet a dollar that's the case.

If you're shooting in mixed light (natural light from the outdoors plus light from an artificial flickering warmer light source like some fluorescents) you can get results like these. The reason it only shows up on part of the picture is because the shutter mechanism takes some time to complete its travel -- and it moves vertically across the sensor, as your photos show. So the electric light is going from bright to dark or vice versa as the shutter does its thing, and you get yellow on part of your photo as the electric light is in its "bright" phase.

I have never seen this phenomenon quite so pronounced -- but still, I bet it's perfectly normal.
03-10-2009, 04:31 PM   #14
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Well now I learned something today! Very interesting and something to watch for.
03-10-2009, 05:06 PM   #15
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1/160 it is!
I hope I'll remeber this as a rule of thumb....
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