Ok, it is not discussed in the Arentz book but his approach to testing seems to me would negate the need of the "timer". The only reference I have read refering specifically to the metrolux timer is made in the Weese/Sullivan book. Short of an intergrator I think the metrolux is the best thing, but for that kind of money you can get a NuArc 26-1K with integrator and vaccum frame on E bay. Why dont you check the pre press equipment. I had posted one here about a couple of weeks ago, it went for $243. I got mine on E bay, if you are really looking to control your exposure there is no better way than this plate burner.