Pi-Camera pink tinted center

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I have "daylight" Pi camera as a webcam at capturing images every 30
seconds at 960 x 540 using python script and the picamera python
module.

There is subtle red tinted area in the central area of the image.
Normally visible on clouds:

http://www.howhill.com/weather/webcam/camera-1.jpg

It's not the LED as I've turned that off and at night with it on the
reflection is quite obvious on the left hand side.
  
Is a subtle central red tint a known problem with PiCameras?

Is it a function of only capturing a 960x540 image rather than full
Pi Camera resolution? I can resize later when I add the text.

--  
Cheers
Dave.




Re: Pi-Camera pink tinted center
On Friday, June 27, 2014 11:48:57 AM UTC-4, Dave Liquorice wrote:
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Looking around the net with Google purple/red/pink tints to such cameras ar
e common. You'll see a number of posts about HTC phones, Android devices an
d such with the same basic camera and tint problems. You could recolor thin
gs with software but your problem seems to be only in part of the image, wh
ich will make that more difficult. If the whole picture was tinted that's m
uch easier to correct, but it still could be done. It would just take very  
specialized software setup for that one camera ;(

Re: Pi-Camera pink tinted center
On Mon, 30 Jun 2014 07:45:07 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

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Thanks for that, not surprised it is after all a cheap comodity
camera module.

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The patch is more or less consistent in area but it doesn't always
appear to be there. On the 30 sec frame interval time lapse movies
it's sometimes obvious other times not. Maybe it's an exposure
function, I'm currently using "matrix".

--  
Cheers
Dave.




Re: Pi-Camera pink tinted center
On Mon, 30 Jun 2014 20:58:41 +0100 (BST)

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Might it be internal reflection?  I'd try fitting a hood to the lens.


Re: Pi-Camera pink tinted center
On Tue, 1 Jul 2014 01:02:24 +0100, Rob Morley wrote:

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It looks far too diffuse. I'm caputuring 960 x 540 and the affected
patch is more or less full height, circular and centred.

It's not a refracted highlight, not well enough defined and it's
visible when there is no point source (aka the sun) shining into the
lens. It doesn't move either. It could be a more general lens flare
but they tend  
to just lift the whole image uniformally and without a colour tint.

The module is tapped to the glass of a double glazed window so it
could be an out of focus reflection of the lens, the tint coming from
some interaction of glass/lens coatings.  

--  
Cheers
Dave.




Re: Pi-Camera pink tinted center
On Tue, 01 Jul 2014 08:06:26 +0100 (BST)

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I wonder if it might be worth trying a polarising filter.


Re: Pi-Camera pink tinted center
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Could it be ligt leaking into the camera? see if shining light on the
camera or shading it has any effect.




--  
umop apisdn


Re: Pi-Camera pink tinted center
On 1 Jul 2014 07:10:23 GMT, Jasen Betts wrote:

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I'd expect that to be a streak from a small source or a broad streak
from a more linear source. This a diffuse pinkish tinted circular
area centerd in the frame.

--  
Cheers
Dave.




Re: Pi-Camera pink tinted center


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I would say it's a function of cheap plastic lenses at curtain angles within  
the lens and wave lengths of light. Try another lens - if you can ?

Another Dave ...  


Re: Pi-Camera pink tinted center

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 "curtain angles" seems to be a misspelling for "certain angles". My
search for this term, to make sure it wasn't simply one I was unfamiar
with rather than the misspeling I suspected it was, led me to a wiki
article on the subject of cameras which held my attention for an
enjoyable 20 minutes or so.
  
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 Good idea, but as you pointed out, only if it's possible to fit
another lens that can be adjusted to compensate for varaition in focal
length.

 Such cheap miniature cameras use a lens mounted in a small tube that
is threaded onto the body, typically with thick silicone grease so it
can be screwed in the required amount to satisfy the focussing
condition with the silicone grease acting as 'locking compound' to
hold the adjustment.

 I'm not sure but there's probably a limited number of standard thread
mounting sizes used in this class of camera so it might not be quite
so hard to find another lens (usually canabalised from a scrapped
miniature camera or else borrowed off another working camera) If the
camera manufacturer offers a choice between wide angle and 'Fish Eye'
lenses you may even be able to opt for a higher spec lens.
--  
J B Good

Re: Pi-Camera pink tinted center


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Yes, I should pay attention to auto spell check !. One thing that would  
almost certainly check to see if it's the lens, is to remove the lens and  
place a piece of white paper over the hole and eliminate it from behind and  
see then if is it still has a pink tinge in the centre then.

  


Re: Pi-Camera pink tinted center

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 Disable that damn spell checker[1] :-\ _______^^^^^^
  
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 An excellent idea! (why didn't _I_ think of that?). At least you'll
know whether a replacement lens will be worth trying or not _before_
spending any more money and/or time on a more permanent fix.

[1] I figured you meant to type 'illuminate'. I'll happily accept
another 'auto spell check cockup' excuse for this one ("Once is an
accident, twice is a coincidence...") :-)
--  
J B Good

Re: Pi-Camera pink tinted center
On Fri, 4 Jul 2014 09:38:02 +0100, Dave wrote:


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Probably bugger the camera. This a Pi camera module, if you are
really careful it might be possible to unstick the lens but it's a
bit risky.

--  
Cheers
Dave.




Re: Pi-Camera pink tinted center
On Fri, 04 Jul 2014 16:10:37 +0100, Dave Liquorice wrote:

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Might be worth attaching a (small) piece of paper so its sitting on the  
front of the lens, putting it where its lit by bright, diffuse daylight  
and seeing it it still shows the pink patch. At least that should tell  
you if the problem is external or internal to the camera.


--  
martin@   | Martin Gregorie
gregorie. | Essex, UK
We've slightly trimmed the long signature. Click to see the full one.
Re: Pi-Camera pink tinted center

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And if you do find a pink tinge on the white paper when you eliminate
from behind, do see a doctor. It could be something serious.

--  
--------------------------------------+------------------------------------
Mike Brown: mjb[-at-]signal11.org.uk  |    http://www.signal11.org.uk

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