i do not understand the lingo ....what does 'aim for printing lights of around 20 for Double-X and......Vision3....aim for printing lights of around 27-32 (green channel) mean
Printer lights are the method by which you control exposure and color on a contact print from motion picture film. It's similar to darkroom printing in stills.
With motion picture printing, the processed negative and a fresh roll of print stock are pressed into contact together and fed through the printer. This is done in total darkness. When both pieces of film pass thru the gate area, they are exposed to a controlled amount of light that passes thru colored filters. Those filters produce precise amounts of red,green, and blue light on the print stock.
If the negative is dense, then you need more light to pass thru it and expose the print stock. And if the negative is thin, you need less. You can also vary the amount of RGB light, and thus affect the color balance of the print. The printer lights are generally calibrated (or trimmed) to a scale of 0-50, with 0 being no light, and 50 being the maximum. One stop of exposure is usually either 6 or 8 printer points depending on the lab, so you can think of each printer point as 1/6 to 1/8 of a stop of exposure difference. A 'normally' exposed negative should print around the 25-25-25 range.
Because there are color biases in the negative stock, this is never exactly the case. But you can use these numbers to judge how dense the negative is, and if you are in the right range of exposure. Most people like to print in the mid to low-30s just to be safe. This produces rich blacks, tight grain, and more color saturation. Once you go below the 20s with color neg, the blacks start to look thin and lifted, there's more grain, the color is thinner, and you might start to see some color in the blacks.