Moonlight film

**Kirk Gittings** · 30-Nov-2005, 12:06

A good friend of mine (and a very accomplished large fromat photographer) William Stone has a unique problem. He needs to document a lunar archeo-astronomy site where a shaft of moonlight hits a petroglyph. He needs this in color and he needs relatively short exposures (like maximum 2 minutes). This is more for a scientific purpose than art. You can see his work at:

http://www.williamstonephoto.com/

I have not been of much help. I suggested that he turn the flash off (haha) and use a high speed color negative film.

What would you do?

**Steve J Murray** · 30-Nov-2005, 12:17

Astronomical photographers "hyper" their film, which I think is exposing it to hydrogen gas, which increases the sensitivty quite a bit. Here's a link to an outfit that sells hypered film:

http://www.lumicon.com/hyf.htm

**george jiri loun** · 30-Nov-2005, 13:48

Hypered film is used for very long star skies exposures (tens of minutes). What's his problem exactly? Using normal films (100 - 400 ASA) with exposure up to 2 minutes is no problem with moonlight.

**Steve Feldman** · 30-Nov-2005, 13:58

Maybe I'm crazy (as an LFer I guess that's a given) but doesn't the earth move during a 2 minute exposure? And the moon moves also. I've been told that even a 10 second exposure of the moon itself will cause a movement blur. Seems to me that shaft of light would move around during a 2 minute exposure.

**Scott Davis** · 30-Nov-2005, 13:59

He might want to try a tungsten-balanced film with a tungsten-daylight filter, to help out with the reciprocity and color-shifting issues. It is my understanding that most tungsten-balanced films have a much greater reciprocity tolerance and much less color-shift at a longer shutter speed than do daylight balanced films. Some daylight films need correction with anything slower than 1/10th of a second.

The other really arcane way of dealing with this is to shoot it as b/w color separations, then make carbro prints. That solves the color shifting due to reciprocity.

**John Berry ( Roadkill )** · 30-Nov-2005, 14:11

You might contact this guy.
http://www.auroradude.com/indexb.html

**Kirk Gittings** · 30-Nov-2005, 14:32

"Using normal films (100 - 400 ASA) with exposure up to 2 minutes is no problem with moonlight." His testing suggests that an 100 asa film would require a 15 imute exposure.

"Seems to me that shaft of light would move around during a 2 minute exposure." It is simply a question of how muchmovement is acceptable and he thinks two minutes is acceptable.

I do not think that extreme color accuracy is a necessity. Has anyone out there experimented with pushing color negatve film?

**george jiri loun** · 30-Nov-2005, 14:54

What does he want to photograph? The moon? The petroglyphs in the moonlight? Both? A full moon, a quarter moon?

**Paul Butzi** · 30-Nov-2005, 15:02

It sounds to me like this is a problem of photographing by moonlight.

If I recall correctly, the moon is magnitude -13 and the sun is magnitude -26, so that illumination from the moon is something like 17 or 18 stops dimmer than illumination from the sun.

The rule for sunlight is (1/iso) at f/16.

So if you multiply that exposure by 2^17 or 2^18, you'll be in the ballpark. That gives you a range of (262144/iso) at f/16 to (131072/iso) at f/16.

If you're using ISO 1600 speed film (or a digital camera like the EOS 5d set to 1600) that gives you roughly 164 seconds to 82 seconds, not allowing for reciprocity. Two minutes falls neatly between those two values, so I'd guess that two minutes at f/16 with ISO 1600 film would be about right.

You can open up a couple of stops and cut the time some, or use slower film. That is, 800 speed film, 2 minutes at f/11, 400 speed film 2 minutes at f/8.

I'd suggest that checking my math might be in order before using those numbers.

Sounds like an interesting task - photographing the petroglyph by moonlight to show the alignment. That's pretty cool.

**Nathaniel Paust** · 30-Nov-2005, 15:15

For long exposures, I usually go for Astia. I've done long-exposure astrophotography up to about 15 minutes with it unhypered and it has really nice reciprocity characteristics.

A few other things...
1) The moon is going to move about 1-moon-diameter in 2 minutes, so he'll want to either make sure that doesn't matter in the picture or chose a wide enough lens that it can't really be seen.
2) Polaroid film has horrible reciprocity, so he shouldn't expect to be able to proof the scene beforehand.