So I've become pretty adept at making my own FS mirrors by paint stripping the backing of regular house mirrors, and they are clearly capable of making a bright reflection. I've been practicing this because I will soon need multiple FS mirrors for my upcoming project and unfortunately I will also have to cut them to very specific sizes (which means I may break a few).

My question is whether I'll be missing out as far as mirror transmission goes as compared to the more expensive FS mirrors you can purchase? I have no need for UV blocking or heat resistance, as I know they have specially made mirrors for that, but I am concerned with light transmission. My assumption though is that bare silver is bare silver, though perhaps there's more transmissive grades of silver?

I'd appreciate anyone's insight into this.

Yes, they do differ, but the gains per dollar get nailed by the law of diminishing returns like everything else.

It also appears to depend on just where in your light path you "turn" the image.

Planarity precision is important and is measured in wavelengths (lambda/#). The flatter the better but they get really expensive.

My LL mirror has obvious coating flaws when viewed in a darkened room with a bright backlight yet my eye sees a beautiful image when I utilized it in my projector.

elken2004 has gone into some details regarding the various FS mirrors available and also has stripped some on his own. You may want to review his datumisms.

I'd ultimately like to do some experimenting of my own - seeing is believing after all - but for now I'd say the ebay dude some have been using is a good place to get a FS mirror for starters.

Edit: They're not necessarily silver. There are Al and Au coatings too. I'm sure others as well but maybe they're really more exotic and not what we'd want for the visible light spectrum. Protected/hardened Al costs more but is prolly worth the $$$'s???

Check Edmund Scientific for some info.

Flatter is better makes sense. I guess I have some research to do. Anyone know a good source for a highly transmissive FS mirror (even if expensive)?