That strange yellow glow...?

[Sian]

Hi everyone,

I am presently conducting some undergraduate research that is heavily based in histology and microscopy. I am having trouble capturing accurate images. For some reason there is always a yellow (sometimes green or blue) "glow" coming from the bottom right of all of my images. This effect is not seen through the eyepiece. It is VERY important I figure out how to fix this. I tried to adjust the white balancing which I thought had solved this problem. The images looked find on the computer hooked up to the microscope-camera, but once loaded onto a flash drive and moved to a different computer the glow is back.

Here is a link to a sample photo taken: http://i638.photobucket.com/albums/uu10 ... 17cfbe.jpg

Any help would be much appreciated!

-Sian

[JimT]

Uneven lighting maybe. Do you use Photoshop? If so experiment with white balance and layer masks for the yellow section. JimT

[gekko]

Hi Sian,
I don't know what the "glow" is, but I strongly suspect that you are so overexposing your image that the white areas appear white because they are blown out. I think I would try reducing the exposure such that the right end of the histogram (if your hardware or software can display one) does not go all the way to the right end of the scale (or the brightest area does not reach the 255 brightness level), or such that the brightest background area is light gray (not quite white). Once you do that, then maybe it will be easier to figure out what the remaining problems (if any) are. In other words, your first problem is the over exposure. There may or may not be other problems.
I hope this helps somewhat.

[The QCC]

The images looked find on the computer hooked up to the microscope-camera, but once loaded onto a flash drive and moved to a different computer the glow is back.

If the image looks good on the computer that took the picture and changes when viewed on a different computer you have a colour balance issue.
If your computer monitors have colour controls, set both monitors to a "Cool" setting. If the monitors have the capability to set the colour space, set them both to the sRGB colour space.

It is VERY important I figure out how to fix this

If it is really important, invest in a colour calibration tool such as the Spyder from Datacolor.

[Oliver]

1. rotate the camera. if the position of the glow stays, then you have a camera issue.
2. remove the camera from the microscope and hold it to an even light sourse. check if the glow remains. aif so, then the problem is with the camera and not the microscope.

I suspect that it might be a problem with the camera because of the different colors of the glow.

Oliver

[gekko]

My additional 2 cents' worth: While the suggestions above are excellent and certainly worth trying, I still think that my first approach would be to fix the over exposure (I took the liberty to download your image and, assuming that the image is "out-of-camera" with no editing or other processing, I estimate that it is overexposed by at least 4 stops). I assume that the microscope illumination is centered and properly adjusted. Below (1st image) you can see the histogram for the whole image area (Adobe Elements 10).


The 2nd image (below) shows the histogram for the white areas only (marked with dashed lines on the image):


As you can see, the median level here is 255 (pure white), so half the pixels in those areas would be above 255 and those will display as pure white ("blown out", or saturated) with no detail or color possible.