Some thoughts:
- “Better” cameras won’t necessarily produce “better” images.
1a. Having greater control over shutter speed, aperture, lens, etc. may help, but also may not produce much better results than learning to control the capture device one already has. Indeed, capturing at higher resolution can create adtl. problems with moiré especially. Which is all to say: if you have a phone app that allows you to control shutter speed, you quite possibly can capture decent images with just a phone, with some practice/experimentation. That being said, the extremely wide angle of most phone lenses can be a hindrance, depending on what you are trying to achieve.
1b. Personally, I think one should consider the capture device as part of the signal chain (rather than a neutral observer of a monitor – or whatever image one’s eye sees). You’re already planning to further translate the image into screenprinting, so I would encourage experimentation with capturing as well. “Honor thy error as hidden intention.”
- I don’t suspect there are any good ways to directly expose screenprinting screens (or even a transparency from which one can make a screenprinting screen) from a CRT (without a precise lens set-up that basically equals a camera anyway). But there are many possibilities for taking photography of a CRT and translating it into a screenprint.
2a. CMYK color separations are the most obvious perhaps
2b. Building a series of monochrome images into separations (similar to how Phil Baljeu created RGB oscillographic images by capturing 3 passes of b&w Rutt Etra images). But the separations could be mapped to any color you want – not replicating the colors seen on the CRT but creating something new.
2c. One can create custom separations from a full color image by isolating certain dominant colors in Photoshop (or similar graphics programs). Especially since the RGB color gamut of a CRT is so much wider than CYMK, this may help produce more vivid results.