Does anyone use the "light source" reality check? Is it reliable?

The light source reality check is where you check to see where the light in the room is coming from. Has anyone used this? Is it good?

IMO a good RC should be super fast to perform, with a generally unambiguous result, and available to do wherever you are, based on nothing external to yourself: so that means, for example, nose pinch and hand check. Nose pinch gets the vote for best possible RC because you can also do it in the dark.

I only usually have vague notions of lighting: most often, bright daylight, dim twilight, vague indoor lighting. If I'm aware enough to check for a light source to see if I'm dreaming then I'm basically already lucid :).

I have never heard of this RC before. However, I have stared at the sun in an LD, which makes me think it is possible to find a source of light in many dreams. I've tried the classic light switch RC, but have easily turned on the lights a few times, so I don't use that one either. :p

p.s. I've used a light switch once in my memory in a non-lucid, and it worked just fine…

i recently incorporated the light source into my arsenal...funny you mentioned this....i was giving this one thought the other day,.....my average lucid dreams are about 5 minutes long....and during these times i have never wondered where any light was coming from...and im usually in a well lit room........
i can only remember becoming lucid OUTSIDE, outdoors maybe twice......i want to become lucid at night in a dream....lol

I wouldn't call this reliable, but if it works for you...
nose plug RC is the only RC that has like 95 % success rate for me. I highly recommend it :) and nothing else.