Neal, I am not that precise. I use one dry down factor regardless of tonality. Frankly I don't see that much of a visual difference from high to low key. I find that the dry down factor works consistently. I have a Zone VI cold light stabilizer with a dry down meter. I go through the process of making the best print that I can with the dry down meter at zero. Once, I've completed and recorded all adjustements (i.e. burning dodging etc.), I dial in 8% of dry down and make the final print(s). That's it. If I were you, I'd establish my basic dry down factor and start using it. Then, I would fine tune it to fit your application.