Tried my First Long Exposure

[Pfiltz]

last night in an effort to get star trails. Was a beautiful night. Weather has cooled down toward the end of the week. Not that it's been terribly hot anyway.

I was using Foma 100 4x5 film. I placed the camera in a small field around 8:00 to get focusing. I walked back out at 9:00 to cock the shutter, and pull the black slide out. Walked back at 10:15 to closed the shutter, only to find out that the front of the lens was covered in moisture.

Kind of bummed out on that moisture part.

Any ideas on how to shoot something like that? I have NO light pollution here in the sticks.

[Jim Jones]

This is a problem that has long plagued astronomers. This link explains the problem and some solutions: http://www.astronomy-education.com/index.php?page=188. I improvised a heated dew shield from a rectangular tin can, a resister from a box of radio junk parts, and old filter rings to mount it on the camera. It takes only a very few watts of power to eliminate dew on night-long exposures. Mine is a 120 volt model, but one powered by rechargeable batteries should be practical for remote locations.

[Corran]

To be fair, with the abysmal reciprocity failure of that Foma, I doubt you'd have gotten anything on film anyway. I've had limited success with T-Max 100 and long exposure and it has better reciprocity.

I've never had dew on my lens, except when I would come out of a cool car into hot humid evening, at least here in the Deep South.

[Pfiltz]

To be fair, with the abysmal reciprocity failure of that Foma, I doubt you'd have gotten anything on film anyway. I've had limited success with T-Max 100 and long exposure and it has better reciprocity.

I've never had dew on my lens, except when I would come out of a cool car into hot humid evening, at least here in the Deep South.

Well, how do they shoot it then, or are you saying you can't shoot star trails with LF film?

[Jody_S]

I did most of mine in winter, at -20 degrees. The air was dry enough that no frost formed on the glass.

[Greg Miller]

last night in an effort to get star trails. Was a beautiful night. Weather has cooled down toward the end of the week. Not that it's been terribly hot anyway.

I was using Foma 100 4x5 film. I placed the camera in a small field around 8:00 to get focusing. I walked back out at 9:00 to cock the shutter, and pull the black slide out. Walked back at 10:15 to closed the shutter, only to find out that the front of the lens was covered in moisture.

Kind of bummed out on that moisture part.

Any ideas on how to shoot something like that? I have NO light pollution here in the sticks.

Just hang by the camera and check the lens periodically. Wipe the lens if a bit of dew has formed. It only takes a couple of seconds so will not affect the photo. Take a stool, sleeping bag, or blanket and listen to photo podcasts to kill the time.

Also, keep the lens at ambient air temperature before shooting. Check the weather forecast to see where the dew point is relative to the actual temperature. Clear nights allow for a lot of cooling of the air which in turn raises the risk of condensation on the lens as warm moist air cools to the dew point.

[Jim Noel]

If you want star trails you need to think of exposures longer than one hour. The stars only move 15 degrees per hour.

[Corran]

No, I'm not saying that, I'm saying that you need to use an appropriate film for the task. Having used some Foma 100 in 120 that stuff would lose the shadows even for a 2-second exposure, so if the "correct" exposure was 1 hour, you'd probably have to give it 4-5 before it was even close to being exposed enough, and might never get there. Acros or Provia would be a much better choice, or any number of films with better reciprocity.

I've done a lot of startrail stuff with digital and film, and it's a challenge, and you have to experiment and learn and really practice it. Haven't gotten to do any in almost a year because of poor weather, but here's a shot on Provia that I believe was about an hour exposure, taken with a 35mm Fisheye / Pentax 67 (edit: that jpeg looks terrible after resizing, oh well):



I saw a lovely image of the New River Gorge Bridge up in West Virginia a couple years ago, taken on 4x5 with TMX I think (65mm lens). I don't remember the photographer but it was really great and I think it was a 4-5 hour exposure.

With respect to Jim, the amount of "apparent" movement in the stars depends greatly on which direction you are looking. The closer to the poles, the less they'll move, the further from them, the more they will move. Yes, 15 degrees per hour, but different size "circles."

[Jac@stafford.net]

This is a problem that has long plagued astronomers. [... snip good article ...]

I don't know if they are still available, but I got a couple heated aerial camera-port windows from www.surplusshed.com.

[Pfiltz]

Appreciate it guys..

Don't know much about film or foam's reciprocity characteristics. Haven't shot much film to be honest. Just started around 9 months ago.

I may have some other films in the freezer I can consider as well.