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Hi all. Our photoshop at work is doing something to one image that it doesn’t do to others. It’s version 7.0.1 on a big windows 2000 machine.
We use the ‘white point set dropper’ in ‘adjust levels’ in order to change the ‘white balance’ of an image for on-the-fly camera illumination
correction on a research microscope.
Basically, we shoot a featureless ‘background’ image on the microscope (which looks like an off-white frame that is brighter in the middle, but not white, and fades toward the edges (like a light bulb at a distance seen through frosted glass), then move it into photoshop, and after a gaussian blur, we white-point-set it at the brightest central point, at
which time the middle of the image turns white, and the edges fade out to the real color of the illumination impurity, because of the math.
Then we reload that into the scope camera, and our subsequent images are evenly illuminated using that correction. But that’s not the problem –
This one lady is shooting a gold film surface that is coppery brown in color, to get her illumination frame, which is then coppery in the middle and fading to brown at the edges. When we use the white point set dropper in the middle of this, it doesn’t turn the middle white, like every other image we’ve done – it turns it pure yellow.
It’s like it brings the red and green to 255 as usual, but completely ignores or zeros the blue when it expands the histograms. So we get an image with that perfect yellow in the middle instead of white. This is not a soft error, it does this repeatedly with this one image even after a reboot.
Any idea what is happening, and how we can fix it? We need this coppery image adjusted so the brightest point is white, and fading toward the edges – if we don’t we will get an anti-yellow image (cyan?) from the camera! Is this explanation making sense?
Any help vastly appreciated! -cmb, microscopy guy
We use the ‘white point set dropper’ in ‘adjust levels’ in order to change the ‘white balance’ of an image for on-the-fly camera illumination
correction on a research microscope.
Basically, we shoot a featureless ‘background’ image on the microscope (which looks like an off-white frame that is brighter in the middle, but not white, and fades toward the edges (like a light bulb at a distance seen through frosted glass), then move it into photoshop, and after a gaussian blur, we white-point-set it at the brightest central point, at
which time the middle of the image turns white, and the edges fade out to the real color of the illumination impurity, because of the math.
Then we reload that into the scope camera, and our subsequent images are evenly illuminated using that correction. But that’s not the problem –
This one lady is shooting a gold film surface that is coppery brown in color, to get her illumination frame, which is then coppery in the middle and fading to brown at the edges. When we use the white point set dropper in the middle of this, it doesn’t turn the middle white, like every other image we’ve done – it turns it pure yellow.
It’s like it brings the red and green to 255 as usual, but completely ignores or zeros the blue when it expands the histograms. So we get an image with that perfect yellow in the middle instead of white. This is not a soft error, it does this repeatedly with this one image even after a reboot.
Any idea what is happening, and how we can fix it? We need this coppery image adjusted so the brightest point is white, and fading toward the edges – if we don’t we will get an anti-yellow image (cyan?) from the camera! Is this explanation making sense?
Any help vastly appreciated! -cmb, microscopy guy
How to Master Sharpening in Photoshop
Give your photos a professional finish with sharpening in Photoshop. Learn to enhance details, create contrast, and prepare your images for print, web, and social media.
