Absolutely. Most bulbs send out light equally in all directions. At the very least you want to redirect that light in a downward direction or the half going up is wasted before you start. A better reflector is essential if you are using a light more than a few inches from your plants. A good reflector will get about 80% of the light onto your plants.

parabolic reflectors are great. also if they are dimpled even better. octoganal reflectors are great too

My HID light was designed by Hydrofarm. You can follow the links to learn more about some of the features they design into their reflectors.

Super T8 or T5HO fluorescent fixtures are the most efficient at directing light. Efficiencies over 90% are not uncommon, and is one of the reasons metal halide and other HID is "old technology" compared to the best fluorescents.

Most of your good quality reflectors should reflect down almost all light on the "back" of the bulb. Around 90% or better. Hydrofarm's Radiant reflector is probably among the best "mainstream" reflectors, and Sunlight Supply has a good one as well.

Look at that. Someone calling HID "old technology" and I let it slide :)

Fittings for both fluorescent and HID lamps are available with better than 90% efficiency. This means that over 90% of the lumens created by the bulb emerge from the fitting in a downward direction. 95% is considered the benchmark and you really can't get better than that without some fairly fancy, and temperamental, technology.

The main reason that HID is "old technology" is that twenty-year-old HID fittings, ballasts, and bulbs don't compare to brand new fluorescent fittings. Duhh!! Brand new HID lamps do compare and the decision on which technology to use must be based on particular situations.

Absolutely, It is true. We have to give more importance about the light reflection.

Here is a link that might be useful: reflector design