I got $10 Chinese light meter from ebay and made some light measurements with different reflectors and without them.
All measurements were made with new 13 watt 6500K light bulb.
Making measurement turned out to be very un precise: moving light bulb half inch or turning it around axis easily changes values by 10%.
For measurements I used:
Light bulb without reflector positioned vertically;
Light bulb without reflector positioned horizontally;
Homemade light (built from vinyl gutter with pieces of mirror glued in)
Distance from light bulb to meter - 14".
If reflector is used distance is from end of reflector to meter.
Table with results
Thus clear winner is polished work light.
And homemade light tuned out to be almost useless.
(I also tried one year old light bulb with same parameters from the same manufacturer and got same results (may be 15% less, but not more))
Adding clear glass between bulb and light meter takes away about ~5%-10% of light.
Some pictures of process.
Light bulb without reflector positioned vertically directly above meter:
Light bulb without reflector positioned vertically moved 5" to a side:
About to measure with Work Light
All 3 reflectors: