Re: color calibration of microscopic images

From: Aaron (nghy_at_comcast.net)
Date: 09/13/04

  • Next message: Gordon Couger: "Re: Would like advice on microscope purchase" 
    Date: 13 Sep 2004 15:16:03 -0500

    >So, if I understand you, you prefer a tristimulus colorimeter because:
    >1 - I would have directly color coordinates in a CIELab or similar
    >space.

    That is correct. If this meter cannot provide directly in the
    coordinates that you want the coordinates should be convertible to
    others. This unit comes with Software and cables to hook up to a
    computer. I have seen the software on the web for trial examination..

    >2 - since the colorimeter has his own illumination source (if I
    >understand correctly), I would not have to rely on the microscope
    >light source whose characteristics are not well known.

    This colorimeter does not have a light source of its own. I
    envisioned that it could be attached to the microscope to substitute
    for the camera.. This colorimeter is dsigned to read luminous sources
    like traffic lights or other colored illumination. You would
    calibrate this instrument just as you would perform a white balance
    with the camera.

     You could also imcorporate this instrument onto a copy stand which
    might provide the lighting.

    >About the first point, couldn't I just convert my RGB readings to
    >CIELab values (which is what I was planning to do after calibration)
    >without necessarily using a colorimeter?

    The colorimeter is desinged for this work. For the camera yours is

    Each digital color device has a gamut of col9ors it can produce and
    that gamut is not consistent from one device to another. I think you
    will be asking far more of the camera system than it was designed to
    provide. The use of the colorimeter will avoid a complex analysis of
    the camera performance which may ultimately show the camera's
    shortcommings in this non standard application. .

    >What is not clear to me is whether such colorimeters make
    >spatially-resolved measurements. If not, then I can't use them.

    The meter reads the colors directly and provides the numbers. I am
    afraid you will never be able to obtain the same measurements using
    the camera and making calculations. You will have to investigate the
    specifications of any colorimeter that you might consider to see if
    that instrument provides the measurments that you require.. The
    CS-100a is not the only instrument availble. .

    >Please correct me if I am wrong.

    Again I repeat that I an not using this colorimeter presently and it
    has been some years since I was involved in color work. At that time
    I learned that workers, even experienced workers. had trouble
    remerbering colors or understanding how the colors changed with the
    addition of the colorants. I obtained a Hunter Colorimeter to study
    the colors and how small changes in the colorants changed the end
    product. Untimately the colorimeter was used in the quality control
    area to make recommendations on the additives. While this did not
    lead to perfect color matches by eye, the range of colors produced
    became much smaller and had a random statistical variation that was
    far more acceptable.

    I do not know if this particular colorimeter is the one for you. It
    seemed to have characteristics that would be very useful for your
    application.. However, I am at the limit of what I can offer as help.
    You need to contact vendors and see if you can borrow some units to
    determin if this is an avenue.for you..

    Good Luck
    Aaron
    >
    >
    >Beatrice

  • Next message: Gordon Couger: "Re: Would like advice on microscope purchase"

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