Proper exposure for stars, no moon?
Hi guys, does anyone know how to shoot starts, with no trails, for maximum "starry night" effect? I imagine a pretty short exposure is required because otherwise the stars would move and start showing up as lines instead of dots. I'm envisioning using a very wide lens and getting the equivalent of what we see with our eyes-- tons of stars over a dark landscape. Any exposure tips?
Cheers to all,
~cj
Re: Proper exposure for stars, no moon?
oh hell, I meant STARS, not starts...!
Re: Proper exposure for stars, no moon?
Re: Proper exposure for stars, no moon?
hi chris
i have a black cat exposure guide that is kind of helpful ... but not exact ...
for example it suggests asa100 ( or 125) film at f4 it will be about a 1minute exposure
for a landscape and a quarter moon in the sky .. it didn't list starry night that was
the closest match to your "scene" that i could find ...
you might have to bracket a bit ( or use a digital camera as a metering tool + test exposures )
good luck!
john
Re: Proper exposure for stars, no moon?
A motorized equatorial mount used in astrophotography would be the best, and probably the only way to get good results with film. As the mount "follows" the stars, you can give them enough exposure without streaking. For an idea of the possibilties in the hands of a art photographer, see: http://davidelivaughn.com/
Otherwise the easy way is to use digital, and the maximum possible exposure, which is maximum or near-maximum ISO, white open (preferably f2.8 or less), and 30s or less. With their sharp wide-angle lenses and great high-iso capabilities, Nikons would probably yield superior results, but on Canon, the 24/1.4 shouldn't be too bad. This will not yield by far the level of quality of equatorial mount images.
Re: Proper exposure for stars, no moon?
It's useless to give him advice about f2.8 or f4... Stars being point light sources depend on the actual aperture opening dimension in their effects on the film. (a f4 on a 300mm lens is not the same as f4 on a 65mm lens, for a point light source.) Very few LF lenses, if any, have such an actual aperture opening diameter that they could yield the demanded "starry night" effect on 50 -100Asa films.
More studies on his side (there are plenty of good web sites for it) will be more useful and can give him all the info he needs than this fishing for useful info.
Re: Proper exposure for stars, no moon?
not much help here. but i shot some stars on my last trip to utah. i was trying to get them moving. i do remember that even with very short exposures i still had some movement in the star. i got plenty of movement at 15 min. i am going to guess that even down near 2-3 min they showed movements (my memory refuses to function well on info that old...)
Re: Proper exposure for stars, no moon?
The star trailing movement on the film depends on the focal length of the lens, among other elements. Short focal lengths are less prone to it but have smaller actual aperture dimension than longer lenses etc...
Re: Proper exposure for stars, no moon?
You get two choices:
A) tonnes of stars with a blurry landscape using a tracking system like QT mentioned, or,
B) star trails with a possibly sharp landscape using a regular tripod mount for the camera.
Or, you can composite the landscape from Option B with the stars from Option A and make a photoillustration.
Look up "The Backyard Astronomers Guide" by Dickinson and Dyer.
Re: Proper exposure for stars, no moon?
1/film speed at f8 or wider should do it.
p.s. the earth rotates 1 deg every 4 minutes. You can work out how much rotation is acceptable for you.
Just remember that the image angle of view on film is what you are measuring the movement across so with a 150mm lens on 4x5 film you are looking at approx 43deg of view. Then decide what percentage of the circle of confusion is acceptable as movement and calculate from there. Also the bigger the enlargement you want, then the smaller the acceptable coc will be. And the longer the lens focal length, the narrower the field of view and therefore the faster the star will move across the film.