Exposure and resolution of fine art images goes beyond the exposing process with light. D max of ink jet film gets iffy below 10% tonal values, same for CTS Ink Jets. The hardness scale helps with making sure the screen receives a certain quantity of light, but the effect of real film d-max vs ink jet d-max is dramatic in halftone formation at the same hardness value. Solid areas and mid to upper tonal values of ink jet are similar to real film. In CTS systems wax vs inkjet is similar to real film vs ink jet in opacity. Nothing wrong at all with CTS systems or Ink Jet, you can slightly under expose and capture lower tonal values, but what happens to the printability of the dot in underexposure? The side walls get affected. Wider openings on the squeegee side are typical with underexposure and the result is dot gain. The sharpness of the dot also gets affected and in upper 1/4 tone values underexposure can effect halftone reproduction and cause 85%+ dots to disappear due to angled side walls. Printing is subjective. We can all make decent prints, but at some point there are companies who master the printed dot better due to better films, exposure units, dialing in proper exposure time, and in choice of emulsions, or adding a face coat to get a sharper emulsion shoulder to prevent dot gain. Achieving 1:1 reproduction of the tonal art at full exposure is a sign of a good emulsion. Note, 'full exposure'. If you have to underexpose emulsion to image the dot it could be part of the emulsion's properties, your light source, your EOM. Sure I sell Murakami, and for a very good reason, my best prints came from Murakami Aquasol TS, which has been taken over by Aquasol HVP in sales due to shops wanting more viscosity, but TS will make better tones and have excellent emulsion strength. A hard 7 on emulsion A at full exposure may have difficulty with dots below 10% and need underexposure at a lower hardness. A hard 7 on Emulsion B (TS or HVP) will image 2-10% tonals better with full exposure. In today's print market of waterbase, discharge, and HSA inks this full exposure is crucial to get a screen that holds a good tonal ramp capture and more importantly, stands up to these harsher inks. 1:1 screen imagery at full exposure equals good production yields with less downtime and less headaches with breakdown. Full Exposure of high quality emulsions allows higher line counts to image 65-85 lines in plastisol or index printing that makes an image glow with smooth tonals and sharper imagery. Taken a step further, hybrid screens of 65lpi with stochaistic in the 10-4% dot yields even finer tonal rerproduction that avoids vignette moire which can be imaged with a RIP like Wasatch.
The hardness scale serves another important function. It monitors your lamp strength. If you expose with light units this issue is compensated, but with seconds or timed exposures suddenly your emulsion can't hit a hard 7 and more time has to be added, and then more time, showing the need for a new bulb. Of all the tools for exposing emulsion well, the bulb is often replaced grudgingly to squeeze every penny out of the bulb while downtime on press is blamed on emulsions. Hmmm, maybe swapping it out early and keeping the old one as back up could keep the shop running at full speed. 90% percent of my tech calls get solved with good light. The hardness scale is a great tool to prove your light system is in great shape. Underexposing should never be the first option for tonal capture, your emulsion and quality light are the winning combination for 1:1 image reproduction.
