« on: September 08, 2013, 08:41:15 PM »
I usually crank up the ISO. If ISO 6400 and 30 seconds deliver the exposure I intended, I lower the ISO to 3200 and expose for 60 seconds. Or ISO 1600 and 120 seconds... You get the idea.
Just use a very high ISO and then calculate the necessary shutter speed for getting the same exposure with a lower ISO.
This is what i do also. i don't know what camera your using, but on the 5dmk3 when in bulb mode the top LCD counts the seconds you've had the shutter open. Actually, for all i know all canons have had this feature for a while, or not, i just don't know. anyway, sometimes useful. i used to use a kitchen timer, and still do when the camera is positioned in such a way that i can't see the LCD. unfortunately even doing this, you will probably need to just check the LCD and disregard the camera"s meter. it's just not designed for this stuff.