Estimate logarithm quickly

[Csaba Tizedes]

I have a very easy to remember method if I want to sketch log/log or log/lin data with hand:
log2 --> 0.3
log3 --> 0.5
log5 --> 0.7

These values approx equally spaced on the log scale and with log1 and log10 values there are 5 points on one decade.

Csaba