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  1. #1
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    Question Fixing Camera White Balance Levels

    Is there any way to fix the white balance of the camera?
    I'm processing viewfinder frames obtained from the camera,
    but the camera (or program) seems to be very sensitive to
    the environment in terms of lighting.

    Any way to normalize or somehow fix the white balance of the
    camera so that it is the same no matter what im looking at
    and where i am.

    For example I'm inside , looking at the display (which is showing processed images obtained from the camera). Things are ok, but if I point it towards the outside (through a window) I can see the display sort of dimming. I.e there's a process somewhere I don't have control over, and I want to ...

  2. #2
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    Re: Fixing Camera White Balance Levels

    Hi,

    You might check if CCamera::SetWhiteBalanceL() is supported on your device?

    Also, from your description it sounds like it might be the exposure (SetExposureL) and not the white balance that is the problem. You could experiment with both.

    Sorcery

  3. #3
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    Re: Fixing Camera White Balance Levels

    As far as I know, there is no way of fixing a value of white balance or exposure in the viewFinder images. Several pre-sets can be chosen though, but they only affect the way that the exposure is changing with the frames.

    I have not found a way to have it with a fixed value.

    I think it is kind of annoying when you need to perform analysis of the viewFinder frames...
    --------------------
    Miguel Bordallo
    Machine Vision Group
    University of Oulu

  4. #4
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    Smile Re: Fixing Camera White Balance Levels

    hi you can Check the current White Balance status by...
    CCamera::WhiteBalance();
    if u want to change the WhiteBalance of your device you can do this by..
    SetWhiteBalanceL();
    only if Device support this changing..!!

  5. #5
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    Re: Fixing Camera White Balance Levels

    From the SDK on SetExposureL function:

    Parameters:
    TExposure aExposure The required exposure adjustment.

    So, it means that you can only specify a value depending on TExposure.

    This values are not real values, but just settings.

    ExposureAuto Set exposure automatically. Default, always supported.
    EExposureNight Night-time setting for long exposures.
    EExposureBacklight Backlight setting for bright backgrounds.
    EExposureCenter Centered mode for ignoring surroundings.
    EExposureSport Sport setting for very short exposures.
    EExposureVeryLong Generalised setting for very long exposures.
    EExposureSnow Snow setting for short daylight exposure.
    EExposureBeach Beach setting for short daylight exposure with reflective glare.
    EExposureProgram Programmed exposure setting.
    EExposureAperturePriority Aperture setting is given priority.
    EExposureShutterPriority Shutter speed setting is given priority.
    EExposureManual User selectable exposure value setting.
    So, no affect for individual frames of the viewFinder.

    Am I right?
    --------------------
    Miguel Bordallo
    Machine Vision Group
    University of Oulu

  6. #6
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    Re: Fixing Camera White Balance Levels

    Yes, they are more exposure modes than settings. They all have an "auto" component to them.

    I've posted about this before but the thing to note here is that "exposure" is not an exposure time but a combination of how fast you read the sensor (which has physical hardware limits on the high end and motion distortion limits on the low end) and what gain you use in the sensor. It would be quite hard to convey any meaningful setting for this to a user. A manual setting with a numerical scale might be a good option for the future though.

    I'd suggest for various machine vision issues that the external light level can change anyway and it'd be nice if your algorithms were robust to that too. I agree not at all good for doing controlled experiments though.

    Very high end camera phones do/will have mechanical shutters. That would then make sense to have an actual exposure time as for a good standalone camera.

    Sorcery

  7. #7
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    Re: Fixing Camera White Balance Levels

    Actually, a "Fixed" value will be enough for most of image processing. Something that does't change through frames for a certain sequence. Something like that is not on the public API anyway
    --------------------
    Miguel Bordallo
    Machine Vision Group
    University of Oulu

  8. #8
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    Re: Fixing Camera White Balance Levels

    If I can't 'fix' the white level, can I at least read it off for each frame ? I need a numerical value of white level to incorporate it into my algorithms.

  9. #9
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    Re: Fixing Camera White Balance Levels

    I don't think there's a public API for this but you might be able to partner one from Nokia. It's quite possible it is device specific though.

    Out of interest have you tried the "Manual" white balance or exposure modes? What do they do? (I'm guessing not a lot).

    Sorcery

  10. #10
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    Re: Fixing Camera White Balance Levels

    I have not tried it no, sorry. My project is fast approaching the dead line so I have decided to ignore this. Of course I'm still curious to learn if anyone has tried this approach.

    Thanks for everything guys, you've been extremely helpful.

  11. #11
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    Re: Fixing Camera White Balance Levels

    Hi All,

    I tried SetExposureL( CCamera::EExposureManual ); on N73 and N82 phones and got a KErrNotSupported - it's not supported (see CameraInfo::iExposureModesSupported).

    I need to solve this problem somehow. Also I need to set the Focus to infinite or to lock it. There are references to a class CCameraAdvancedSettings in the documentation. But as far as I know this class is not implemented and there is no support for it.

    I wonder if anybody had/solved these SetExposure and LockFocus problems.

  12. #12
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    Re: Fixing Camera White Balance Levels

    Hi,

    Not supported is what I was expecting - there isn't another function to set an actual level once you've selected manual so what else could it do?

    There are no public APIs for what you want to do and since the built-in camera applications don't have this functionality I'm guessing there aren't any private APIs either. There is probably some level of interface that will allow you more control of the camera but it will vary across devices and platforms - it may even vary between firmware versions. You might be able to partner such an interface from Nokia but then again, maybe not. The only thing I can suggest at this point is that you use a technical support request (which you have to pay for).

    Sorcery

  13. #13
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    Re: Fixing Camera when i click baton

    Hello dear nokia usear.
    i had a serias problem with my n95 normal.before updating frimware verson 30.0... when i use my camera some picture take the camera show first a whait frame then show green fream and third black sceane and show that picture.and that is very comfortable for me.

    and now when i take a picture shot..he sow first whait fream and second black sceane and take photo.
    and that is the problen where is gone Second green fream?

    so..please tell me is there a problem or setting missing?
    and how can i solve ..
    i would to wish my first one...whait..green..and photo..
    my nokia n95..version is..v30.0.015
    15-07-08/rm-159/nokian95(10.01)
    please help...

  14. #14
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    Re: Fixing Camera White Balance Levels

    Sorry, I really don't understand your question - it sounds like an end user query though and this is a developer discussion board. You might have more luck elsewhere (or by taking your phone to a service centre).

    Sorcery

  15. #15
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    Re: Fixing Camera White Balance Levels

    thank`s for reply.i am poor in english languages ,that`s why u do not undurstand my qustion .now i tell my nokia has no hardware problem.it`s all r fine even picture quality is very good.my qustion was how to take picture with camera.
    and when i take picture my camera freme to ur face and then i click the button and take photo.it`s all ok.but problem is when i take ur face picture the capture fream (whait square )and then black and said prosasing and photo.
    now i would to know what is the right way ..

    please another see my previse post..
    Last edited by amzad759; 2008-09-30 at 11:10. Reason: for missing some taxt

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