The moon tracks across the sky by its own diameter in approximately 90 seconds. So from that, you can figure out the max allowable exposure duration from whatever print size / sharpness criterion you have. Personally, I would go no more than 3-5 seconds even with a small-appearing moon. And with an exposure that long, the moon is going to be hugely (like 7+ stops) over-exposed because...
Originally Posted by Michael R 1974
The moon (with no clouds obscuring it) is in full sunlight and therefore requires about Sunny-11 exposure, e.g. f/11 1/100s for EI100. So if your total exposure for the foreground needs 20-30s at 22:00, I would highly recommend you do a double exposure:
- take a 20s exposure or whatever you require BEFORE the moon is up, then
- take a very short lunar exposure once the moon is where you want it.
The second exposure is hundreds of times less than the first one, so nothing in the scenery will even show up at all. If you wanted to really push your luck, change to your longest lens between the exposures so you get a huge moon; just be careful where in the frame you put it so that it doesn't overlap some scenery.
To give you an example of this (no lens-changing though):
That was shot on Acros at f/11. One 4s exposure for the buildings (and the very-bright moon on the tower) then a sequence of 1/125 exposures at 3 minute intervals for all the properly-exposed moons. If you took that approach but did the first exposure without the moon visible, obviously you'd not get that one huge bloomed moon.
Edit: IMHO double exposures are fair game to balance light levels, especially if you don't move the camera between them. Multiple negs in a print or reloading rolls after shooting many moons, not so much.
Last edited by polyglot; 06-16-2011 at 09:54 PM. Click to view previous post history.