Mech just PM'd me with something else that probably should be mentioned, and it has been elsewhere on this forum but still is a valid comment that people really need to understand...
That comment is- A person is going to see little to no difference between a gray that is N8.25 and N8.5. Most people will likely will see a difference between an N8 and an N9 and that is where a step gray can come into play, but doing a step gray between that is playing the laws of diminishing gains, and most people will not see a difference between N8.25 and an N8.5, but they may see a difference between N8 and N8.5. Even with commercial screens we don't see this granular of steps for gray screens. Typically it's a light gray, medium gray, and then jumps to dark gray. Again back to D65, some say it's not important, but 50% or more of the commercial screens we've reviewed and tested fall within the D65 'target', and to me that is significant. The better the screen, the closer it is to D65. (Reference the last post and quote from Sound and Vision as to why this is important)
The key really is in the color balance, or more accurately stated, the lack of 'color'. Neutral isn't a color at all, and that can be confusing. What this thread is discussing is variances on paint batches from one company to another, as well as from can to can. Yes, we are saying there will be a variance, but it is a small one unless the store has a problem with their equipment or paint staff. For an OTS (Off The Shelf) gray, the identified grays mentioned throughout this forum will serve anyone well. There really is no need for a list of hundreds of grays that are 'close' when we have many manufacturers supplying D65 grays right off the shelf.
As projectors continue to get better and better, the tolerances of screens will become less important, but the concept of sticking to D65 still remains as far as getting the best and most accurate image reproduction. The closer your screen is to D65, whether it is a commercial screen or DIY screen, the easier it will be to calibrate your projector, and the better the color reproduction will be. Efficiency has also been mentioned, and a D65 screen will also be more efficient at color reproduction, and therefore also be slightly brighter and more vivid than a screen that you have to compensate for at the projector. Keep in mind, any compensation you have to do, be it keystoning, lens shifting, zoom settings, or color adjustments all have an impact on your image. Why mess with a screen that requires compensation? That is our goal and what we are constantly talking about... the best and making it easy as well. Like my signature... things don't need to be complicated at all. Even the 'advanced' screen we are working on and hope to have unveiled next month as a final application is still very easy to do.
How dramatic of a difference are we talking about?
This...
...these...
and this...
It really does look like a 'veil' was lifted from the screen and is even a more dramatic difference in person than anything captured from any screen shoot. (Keep in mind, this is an N7 or darker screen compared with an N8 and N8.5 shade gray screen and it holds its own better than anything I have personally seen be it commercial or DIY)
And what we are talking about is $30 and anyone that can paint a room can paint this screen, no special or complicated methods needed at all, no special rolling methods, no 'hotdog' rollers... just a good quality low nap roller and anyone can do this. How did we get here? By testing and measurements of course. We're currently looking at those tolerances and variances that mech mentioned to determine the best base color and company that ensures a consistent application. Right now, my personal recommendation is if you have a Lowes nearby, check them out and talk to their paint department. They can color match anything within the tolerances we are talking about as well as do perfect matches to any other manufacturer out there, including Behr and Glidden.