Large format star trail experience?

Discussion in 'Large Format Cameras and Accessories' started by kurt765, Apr 25, 2011.

  1. kurt765

    kurt765 Member

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    Can anyone share experiences with shooting large format film star trail shots? I'm planning for a shot that involves star trails as one component and I'm planning on shooting with large format film (or possibly 6x17 as an alternative). I've been told that over time temperature changes can cause the film to move through the exposure? I have a dew not that I was planning to use to heat the lens to keep dew off. Do I need to extend this to the film back as well somehow?

    Any help will be greatly appreciated.
     
  2. DanielStone

    DanielStone Member

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    where will you be shooting? If its in a cold, slightly damp environment, then you'll have a higher chance of "fogging" up the lens, and possibly condensation on the film.

    what about throwing a few dessicant packets(you know those little "sacks" in shoe boxes) into the bellows, tuck them down in the folds so they don't interfere with the light path?

    depending on which film you'll be using(b+w, color, which emulsion?), different films have different reciprocity characteristics, so you might want to choose depending on what you like. Provia 100F is known for its great ability on long exposures, and IIRC, the T64(Tungsten balanced) films(Kodak if you can find any anymore, T64 from Fuji now, only in 35mm/120) have almost NO reciprocity failure.

    I did star trails in Joshua Tree 2 years back, and I used T64(120 sized), and the shots came out ok, but I should have chosen my framing more carefully. Its kind of a crapshoot(at least it was for me), I guess if you do star trails or long exposures all the time, you gain some sort of intuition as to how long to expose the film, but I just framed my shot at sunset, and waited until 8pm or so, and left the shutter open until 4am or so, so 8hrs total exposure time. Only enough for 1 frame/night.

    if you want to shoot sheet film, you might try putting a few small pieces of tape, rolled into a reverse tube(so the sticky stuff is pointing outwards), and put that in your film holder, so the film is literally "held down" by it, film can flex/bend due to atmospheric/humidity changes quite easily.

    -Dan
     
  3. kurt765

    kurt765 Member

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    I'm shooting Provia 100F. I've been doing test exposures with my twin Mamiya 645 cameras. The shot will be between 12000 and 13000 feet in the Sierras in August or September (weather depending). Temps will dip to around freezing at night, hence the concern for dew. With so much snow in the sierras this year, it may be that there is snow around where I'll be.
    Are you talking about silica gel packets? That seems like a cool idea. Are there special film holders that I could look into renting that hold the film in place more? I've got awhile to figure things out, though the time is going to fly right by.

    -K
     
  4. ntenny

    ntenny Member

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    ...and leave them there for a while before the temperature changes start, because the idea is to guarantee that the air inside the bellows is as dry as possible. I'm not sure that a large-format camera is really airtight enough for this to work well, though; you might just get new, humid air circulating in as fast as the moisture gets sucked out by the desiccant.

    From telescopic experience, I think the biggest dewing problem will be on the front element of the lens. Heaters work reasonably well at preventing that problem.

    I haven't shot a lot of star trails, but it seems like the exposure is pretty forgiving. (The effective exposure is determined more by the rate of motion of the star images on the film plane than by how long you leave the shutter open, so this makes sense. Because of this, the wider-angle the lens, the brighter your image will be!) My biggest problem has been skyglow---that lovely dark sky gets blown out on film pretty quickly if there's some light pollution. The astronomical folks have skyglow filters that should help, but I haven't gotten around to experimenting with them yet.

    -NT
     
  5. David William White

    David William White Member

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    This past summer I made this with a 90mm on my 4x5, HP5. I focused on the moon, then waited until it went down. As you say, dew was a problem on my first trial -- I came out to retrieve about 2am and the lens had condensation all over it. This was from the next night, when luckily there was a gentle breeze to keep everything dry. I don't know what to suggest for condensation except maybe a fan, if that's possible.

    Exposure was at f/8 for about 1.5h and pushed substantially in D-76.
     

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  6. kurt765

    kurt765 Member

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    I'm getting close to my magic formula. Still a ways to go. Here is one of my tests:

    [​IMG]
    4.5 hours at the Devil's Golf Course by Kurt Lawson, on Flickr

    I wonder if heating the whole camera would help? I could get an extra large heater strip to put onto the Dew Not controller I have and maybe wrap it around the back of the camera? Maybe silica gel inside, heater on the lens and the film holder? Hmm. I'm planning on shooting with my 5D2 as a digital backup and probably a Mamya 7II as a film backup, with either 6x17 or 4x5 film being the primary goal.

    -K
     
  7. ntenny

    ntenny Member

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    That's really nice. I don't remember seeing a wide-angle set of star trails centred on the equator before---it seems like people prefer to point at the poles to get obviously circular arcs, and the diverging ones here really grabbed my eye!

    It seems like humidity in the Sierras actually should be pretty low under those circumstances, so you might not encounter a lot of dew problems. (And the colder the better, right? If all the water is frozen into snowflakes and lying on the ground...) That won't help with the possibility of film shifting, though---I think the tape suggested by DanielStone above seems like a good idea.

    -NT
     
  8. TheFlyingCamera

    TheFlyingCamera Membership Council Council

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    At 13000 feet, there will be some snow pack all year round. To avoid the dew issue, take the lens out in a ziplock bag and let it acclimate to the temperature before mounting it. Let the camera sit, open, for a good hour or so also so it can acclimate without condensation forming.
     
  9. kurt765

    kurt765 Member

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    Thanks. Yeah there will be some snow around, though in this particular location there won't necessarily be a lot of it. At least I'm hoping there's not too much snow because that will force me to wait a year before trying this again. I don't want to wait that long! Heh.

    Double sided tape to hold the film in place? Hmm.

    -K
     
  10. konakoa

    konakoa Member

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  11. Vaughn

    Vaughn Subscriber

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    My LF star trail experience...I had a real nice image set-up in the bottom of the Grand Canyon -- the north star was directly over one of the "temples". But I fell asleep and did not wake up until after the sky started to get light.

    Nice dry air -- might have been a nice one. Still have a nice image of it my mind's eye, some 25 or so years later...

    Vaughn
     
  12. kurt765

    kurt765 Member

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    Maybe I should build one of those. Hmm. Thanks for the link. I think a Mamiya 7 or 7 II with the 43mm will be my backup film camera. It's possible I will scratch plans for the 4x5 and just shoot a couple of Mamiya 7s. I don't know yet. So much to figure out, but at least I have a few months before August to figure it out.

    -K
     
  13. pgomena

    pgomena Member

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    Double-sided tape works just fine for holding film in place for long exposures. A little piece about 1/2-inch long is plenty. Touch the side of the tape that faces your film a few times to decrease the stickiness or it can be difficult to remove the exposed film.

    Peter Gomena