I'm not bad at finding notes on the fretboard; I estimate it takes me less than a second for any string.

But if I have the guitar tuned to anything other than standard, I'm lost.

I balk at the thought of having to learn it when downtuned to C# or D. I don't use any tunings where the strings are at relatively different intervals from standard, but I imagine learning those would be even harder.

So, for those who use alternate tunings, is your knowledge of the fretboard as good as it is for standard? If so, how long did it take?
I don't know the fretboard as well as you, it takes me a few seconds rather than less than one for any note... But I can still tell you that it will come with practice, just dabble with different tunings and it will sink in, everyone's different, it may come to you quickly or it may take a little longer... It's not really one of those things you can force into your head so easily

Good luck
I can just assure you, that even my guitar teacher is lost when i downtune my guitar. It just take some time and practice and you will get it right.
you know the fretboard in standard, so if tuned in D, just shift the entire pattern 2 frets up. it takes a while to get used to it but it's quite easy really..

in standard, the 8th fret on the E string is C, 10th fret is D, ...
in D , the 10th fret on the E string is C, 12th fret is D, ...
Quote by psyks
You are filthy.
you know the fretboard in standard, so if tuned in D, just shift the entire pattern 2 frets up.

One thing you can do if your in Drop C/C# after getting used to in D, first name the note as it would be if it was in C, then move the letter lower based on the tuning. ie.

in Drop C (low C string) on the 5th fret

In drop D it's a G(whole step down from standard), then you moveanother whole step down because of the tuning and BOOM! it's an F! It's easier that way rather than trying to re-memorize for every different drop tuning you do. at first that will seem annoying, but in the long run it's better. In my opinion at least.