It also eliminates the drying step between multiple coats of direct emulsion. A single direct emulsion screen could take up to an HOUR OR TWO to make because of the drying, while a direct film screen may only take 20 to 30 minutes. Another real advantage to direct film is the sharpness of the image edge. Because the film is adhered to the bottom of the screen it gives a very smooth surface. This enables you to reproduce a very sharp print.
Direct film is sold in various film thicknesses.
These range from 15 microns all the way to 84 microns. For general T-Shirt printing a 35 micron works good. If making heat transfers you should use at least a 40 micron and preferrably a 70 to 84 micron just to lay enough ink down for a good print. The mesh count or color doesn't have a bearing on the exposure. If you are looking for consistency then this is it.