I don't want to give the whole lighting class here on the G - but here is a preview.
NOTE: Thanks, Mike for posting this- and my comments are not a criticism on the offer, lamps, or directed at Mike for posting this - just an analysis of info for comparison.
In the last example that Mike posted - there is a chart of specifications that is very useful.
An average MR16 lamp is a 50 watt EXN. The "brightness" of a lamp is expressed in lumens. The more lumens per watt, the more efficient the lamp.
Most lamp manufacturers do not publish lumen output ratings for MR16 lamps or other reflectorized lamps in their catalogs. Instead, they publish beam angle and CBCP, which provide more accurate information about the performance characteristics of the lamp. NLPIP tested several 50-watt MR16 samples of the same type (EXN) to determine their lumen output, which ranged between 560 lumens to 710 lumens, and averaged 625 lumens.
So an average 50 watt MR16 puts out 625 lumens or 12.5 lumens per watt.
The 1.05 watt LED replacements in Mike's post have an output of 25 lumens or 23.81 lumens per watt. Much more efficient but quite a bit dimmer and in my estimate, not bright enough to be practical by themselves.
One would have to run 25 LED replacements to get the same "brightness" - but the wattage used would only be 26.26 watts, or about half the number used for one MR16 lamp being replaced.
Beam angle and center beam candlepower (CBCP) are performance parameters that characterize the beam appearance and the maximum beam intensity of a directional lamp. According to manufacturers' catalogs, the beam angles of MR16 lamps range from 7 to 60 degrees, and their CBCP may range from about 500 up to 15,000 candelas, depending on different wattage and beam angle combinations.
Mike's example shows CBCP at 10,000 to 12,000 MCD so they are a pretty bright spot. Comparing them to an EXN MR16 might not be very fair since an EXN is a much wider beam spread. The only way to truly tell if they will work is to try them out. And for the price it is hard to resist. I may have to pick some up to demo for the class.
Other things to consider are actual color temperature (not just "white"). If someone says "white" matboard to you, you know what I mean.
That is why the lighting lab at the WCAF will be so useful. We will have color charts colored fabrics and art examples lit by Halogen, CFL, and LED lamps so you can see the difference in output.