Super long expsures (we're talkin' 6 hours here) and light tripods.

[PhotographicBlack]

I have a Bogen carbon fiber tripod rated to 25.4 lbs. and a Bogen 3028 rated to 11.1 lbs.. I've done daytime work with this set up and it works fine. Would anyone conjecture me to have problems with camera shake and this set up with a long exposure?

-R

[Alan Davenport]

Six hours is a bloody long time for any camera/tripod system. With most LF cameras, you're also at risk of bellows shake if the wind picks up. (I guess I'm assuming you'll be outdoors.)

OTOH, if the tripod simply stays put, and the adjustments don't slip, then any shaking over a 6 hour period probably won't even register on the film.

[PhotographicBlack]

"OTOH?" What's that mean?

Yea... I'll be doing star trails. I'm hoping that there is no wind! I'll be a lucky man to have no problems. I've a lot of prep work to do...

[JW Dewdney]

OTOH = on the other hand.

I'd expect some camera shake. You might even be surprised to find out that one of the standards or part of your tripod is very slowly dropping, too. You never know. One of the biggest concerns I'd have apart from this - is that, unless you're aiming to deliberately heavily overexpose, I'd think that you're going to have next to zero shadow detail - due to reciprocity failure.

[PhotographicBlack]

Ah... I've been at night for many years now and I have been come somewhat of a wiz at it. My last three shows have consisted of night photography and I've done testing on both Velvia 100F and Provia 100F and know their reciprocity characteristics fairly well. Plus, I was going to go on a new moon, but double expose the scene in the shot initially during dusk to achieve detail in my shadows.

[Walter Calahan]

if it is windy, you could rig up a wind block

also hook weights, such as light stand sandbags, to the tripod

you may want to set up a second tripod and clamp it to the first for added support

finally hope you done have an earthquake (HA!)

[Mark Sampson]

Be sure you're on solid ground, too. Buildings, even huge ones, shake a little. I've seen it in short exposures, when the resulting image is magnified.

[Ralph W. Lambrecht]

You must have some pretty dark sky (no light pollution) for this to work. The background illumination is usually too high to support a 6-hour star exposure. I hope better luck and skies than I did. 1/2 hour was about my limit.

[Alan Davenport]

Ralph's right; a six hour exposure may offer unexpected rewards.

Here's an example (below) of what you might get with a one-hour exposure (note the star trails.) IIRC, it's one hour at f/8 on ISO200 negative.



And it was taken from midnight until one A.M.

[A.C.]

PhotographicBlack
I'm sure that more than just I would be interested in your reciprocity corrections for such long exposures. Velvia 50 correction is widely known up to the half minute mark, but Velvia 100F and Provia 100F corrections at much longer times would be very, very interesting - how do you feel about sharing some guidelines?