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Messages - CBGoodBuddy

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Nightly Builds / Re: Nightly Builds - try the very latest stuff here
« on: April 11, 2019, 03:34:38 PM »
Any reason the nightly builds have been stuck since July 2018?

General Development Discussion / Re: 5DII as scientific instrument
« on: October 25, 2013, 05:44:44 PM »
No need for color callibration, I have a bandpass filter where only the fluorescent signal can pass.
Linear respons and 16384 discrete levels instead of 256 are important.

Wavelength calibration is only one issue.  There are others.

The 5DII has a Bayer pattern filter, which is how red green and blue colors are measured.  Depending on the wavelength of interest, you will probably want to only use pixels of the same color as your fluorescent light.  For example if your light is 550 nm, then only include 50% of the green pixels and exclude the 25% red and 25% blue pixels.

In video mode, there is also line-skipping, unless you can go into crop mode, so consider that.

Each individual pixel might have a different response than the others.  You need a way to normalize that out.  In my field of work we call that flat-fielding.  At the very least you need to be able to recognize dead or hot pixels and exclude them.  Really there are two effects: pixel sensitivity (flat field effects) and dark current.   Pixel sensitivity produces varying output samples in different pixels under the same light stimulus.  Dark current produces different output samples in dark conditions (due to varying leakage current in the sensor elements).

In short, if laboratory accuracy is important, you should spend some time characterizing your instrument in dark and in uniform lighting conditions, and also understanding the spatial sampling you lose due to Bayer and line-skipping.


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