Dear all,
I heard it is possible to disable R, G, and B channels in a computer monitor, leaving only the pure grayscale. Does anyone know how can I do that? Thanks!
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Please explain what you aim to achieve. Obviously you can draw grayscale images, so you would get “pure grayscale” but i assume that’s not what you meant.
Grayscale is created by engaging the red green and blue channels at the same time, so your question as it stands doesn’t make direct sense. Could you try to briefly explain what you want to achieve?
Hi @dcnieho and @mariokleiner,
We are doing simultaneous visual stimulation and in vivo 2-photon imaging in mouse. Recently, we came across a light leakage problem from the stimulus monitor to the photomultiplier tube (PMT) of the 2-photon microscope. We tried to optimize an ambient light shield installed on the objective of the microscope but that was still not good enough. In a recent article published on Neuron (https://doi.org/10.1016/j.neuron.2020.04.026), the authors stated that “during two-photon imaging, the red channel of the monitors was switched off to reduce light contamination in the red fluorescence channel”. This triggered my question in this post as I wonder if it is possible to turn off color channels in a monitor. Any comments or suggestions are greatly appreciated! I thought maybe it’s trivial but if their statement doesn’t make sense to the experts here, I’ll go approach the authors of that paper for clarification. Thanks for your time!
Hi @bli
The statement in itself sounds a bit funky, but depending on display technology used, it makes sense:
For self-luminant displays like CRT or OLED, one can simply not use the red channel by using only RGB values with R set to 0. For LCD, there is always a backlight, and then a layer which opacity can be modulated, so red can almost completely be switched off. A very little light (depending on screen, read some detailed reviews) will leak through.
Importantly, sending gray scale images does not achieve what you want. To create different scales of gray, all three color channels need to be active.
In the end, it is probably best to approach the authors and ask how they did that.
Cheers,
Dee
What @dcnieho said. Maybe there are some special light filters that block out only the red spectrum / long wavelengths for LCD’s? Other than that, just drawing pictures without red / red intensity 0.
In PTB, using Screen('Blendfunction', window, [], [], [0 1 1 1]); would make sure that drawing commands into the given window would not draw into the red color channel, so if you chose a background color with red == 0 in the 'OpenWindow' call, that should keep the red channel off for many typical stimulation scenarios.
-mario