In no way is the use of a 1/8" 2nd surface mirror EVER responsible for creating a unfocused image in and of itself. Only a few have gone so far as to state such, but NO ONE has ever actually produced any conflicting data that alludes to such a thing occuring. It's always "IMO" or "It seems like it would...."
The whole idea of it happening is silly. It originated with a few people expressing the belief that a noticable image shift would occur across the 1/8" gap. That didn't wash then, and it remains a unwashed piece of linen today. And even if such did occur, (...which it does not...) at a viewing distance of over 8' from a large screen where such was happening, virtually nobody's eyes could see the difference. If a 1/8" difference occured on a 32" monitor, perhaps. 8' +? No way.
Now as far as using any Mirror with 1/4" or more of a gap? Perhaps so, but since that thickness has never been reccomended for use, it's irrelevant.
If there is one bit of correct information to be gleaned from that misconception, it's that if the correct amount of paint is not applied to a 2nd Surface Mirror, the returning light can make the surface image on the "too thin Top Coat" fuzzy and indistinct due to being washed out by too much light.
Light Fusion denotes the "re-utilization" of absorbed light through reflection and re-combination. But it isn't as if the returning image is creating a singularly seperate image footprint. Instead, the two major happenings are:
1 The "Gap" between the painted Surface and the reflective surface is infused with light. This light however is markedly down in luminence from having some of it's energy lost in passing through the painted surface, and still more is lost via the reflecting off the Mirror. So the light that makes it back is darker, colors are more distinct, and the effect is that the image has more of a depth as relates to the subtile contrast that defines curvature or shadow detail. Unfortunately, the original MMud Mix was found wanting as far as being able to boost the perceived Black levels, so a few dismissed LF as being defficent for that reason alone.
2. The absorbtion of light, and the return of darker light thereof effectively reduces the appearence of SDE (screen door effect ) and other bothersome screen artifacts. These usually are already "Darker" & "Weaker wavelengths of light that are unable to effectively return to show up if they are trapped or muted to non visible levels.
First Surface Mirror? That's a tricky application, one fraught wilth potential failure. At least with the "old Whitey" MMud. Over 2 years ago I acquired a "Freebee" from Plaskolite Mfg. ; a 4' x8' FS Mirror. ($495.00 otherwise!!!
For a week, I tried to get the application to work. FS Mirror's have a special coating on top to protect the Aluminum coating, and it didn't bode well as far as accepting the MMud mixture I was using. And the overt reflectivity of the effecent FS Mirror made getting enough paint on top so as to prevent bleedthrough gave me fits. Lastly, even with what appeared to be the right amount of paint, up close, tiny spaklies made themselves apparent. It was that damnable coating shining through.
Three times I tried, and three times I wiped the Mirror clean. The forth time, I spray applied 6 VERY THIN COATS and nailed it. The resulting screen shots were the best most had ever seen on any Forum anywhere....or at least that was the general consensus. Considering the fact that the PJ being used was a DLP w/1700:1 CR and 1280x720 resolution on a 4' x 8' screen area, the correctness of color and the deffinition was something heretofore not seen this side of a CRT. (See Images below)
But I never went so far as to advocate it as a viable application because of the expense and difficulty involved, and therefore, the rush toward Aluminized Mylar and other Highly Reflective films and Paints began.
Since then, precious few have duplicated the feat no matter what material or paint was used. Mylar isn't an easy material to work with, and to get to lay flat. But it has been done, and when accomplished, one deffinately knows it.
So Light Fusion has remained the next best application, with it's 1/8" Gap, to get the "next best Thing" to a 1st Surface application.
Now however, I have access to 1/16" Mirrors. That's as close to 1st Surface as I feel anybody needs to get as far as a "Mirror" is concerned. Talk about flexible!
Highly polished Aluminum panels, Silver Metallic coated panels, and Brushed Aluminum panels all have potential. And with the newer "Darker" Ambient Light mixes, coverage is more easy to obtain while maintaining a thinness that will alow the substrate underneath to affect the overlaying image.
But good "whites" and "frosted" surfaces have something to offer as well. Much of what made Light Fusion desirable was the need to ramp up the image of PJs that were obviously lacking in lumens, as well as in Contrast. Nowadays, many "out of the Box" PJs sport 2000:1+ CRs, and in excess of 1000 lumens, so there are different paths that are available to explore.
Your post prompted this reiteration of previously posted info (...OK, so did yours too Ericglow....) but it still serves to clarify the Light Fusion equation once again. 99% of all screens I make are 2nd Surface LFs, and 100% of the end results are more than is expected by the end user.
Now, with Black Flame being as easy a mix to apply as there ever was, and rolling such has become a reality, there stands the chance for many more Noobs to attempt the application that ever before. I myself will be applying BF & BF-Lite to several different 1st Surface materials in the very near future. Add to that the potential to use any of many other applicable substrates, and there should be some type of LF out there for just about anybody to try.
Why, there are even some other DIY paints you can try as well. How'd that happen?????
So keep looking............,
....and I'll keep my eye out for your next post.