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Natural Science Forum / Physics / Optics / April 2005DSLR - background field colour cast...
My brightfield images always have a pale "salmon coloured" cast to the background. I generally run the lamp at around 6-7V, but the issue persists at 12V too - so I don't think it can be a colour temperature thing(?). Visually, the background looks perfectly white to me. I'm projecting the image directly onto the 10D's CMOS sensor and thought maybe IR was the problem but adding an IR blocking filter just before the condenser made no difference!? Is this just a common issue that's always fixed by later colour and white balance tweaks (which seem to work just fine), or am I missing something at the capture stage? Cheers Beats PS. Scope is a Zeiss ICM 405 inverted with an EOS 10D attached to the front photoport. Light is 12V/100W halogen. Generally, all the sophisticated digital cameras need to be adjusted for the white balance. While some correction can be made via software after the image is made, it is best to do this beforehand. You will need to fill the field of view with a blank portion of the slide and institute the correct procedure for the white balance. Sometimes it is helpful to perform this procedure with the microscope slightly out of focus. Aaron >My brightfield images always have a pale "salmon coloured" cast to the >background. I generally run the lamp at around 6-7V, but the issue [quoted text clipped - 14 lines] >PS. Scope is a Zeiss ICM 405 inverted with an EOS 10D attached to the >front photoport. Light is 12V/100W halogen. >My brightfield images always have a pale "salmon coloured" cast to the >background. I generally run the lamp at around 6-7V, but the issue [quoted text clipped - 14 lines] >PS. Scope is a Zeiss ICM 405 inverted with an EOS 10D attached to the >front photoport. Light is 12V/100W halogen. Check out Extensis Intellihance. This is a plug-in for Photoshop. It will allow simple or aggressive cast removal. Gary Gaugler, Ph.D. Microtechnics, Inc. Granite Bay, CA 95746 916.791.8191 gary@microtechnics dot com >>My brightfield images always have a pale "salmon coloured" cast to the >>background. I generally run the lamp at around 6-7V, but the issue [quoted text clipped - 17 lines] >Check out Extensis Intellihance. This is a plug-in for Photoshop. It >will allow simple or aggressive cast removal. The reason the image is yellow is due to different color temperature. Your camera is probably set for daylight (5000K-6600K) while halogen bulbs are about 2950K. Dedicated microphoto systems fix this by changing the color temp of the light source at the source. Oly uses an LBD filter (others do the same--they are a blue filter) just past the lamp house or above the lower projecting field lens. This brings it much closed to daylight. If your camera supports variable color temp settings, try setting it to 2900K, 3200K, thereabouts. Otherwise, try Incandescent if it has that option. Gary Gaugler, Ph.D. Microtechnics, Inc. Granite Bay, CA 95746 916.791.8191 gary@microtechnics dot com |
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