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  1. #21
    markbarendt's Avatar
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    Quote Originally Posted by Rudeofus View Post
    Once I got the exposure nailed I can deal with color casts (in the worst case in a hybrid work flow
    This is the rub, you are dealing with three exposures not one; one for the Red layer, one for Green, one for Blue. Any layer that isn't exposed well will also have little or no detail. This isn't just a color cast issue it's a detail issue. If one layer is overexposed, one is normal, and one is underexposed, you only really have one layer that has decent detail and the color is wacky. Hybrid or Analog makes no difference here.

    Quote Originally Posted by Rudeofus View Post
    , my scanner does much much better with slides than negs). Right now I look at pics with bright white mountains in front of white sky and dim star trails on light grey sky.
    I think what you are seeing here is the lack of contrast that existed in the original scene. The SBR is very low and expansion development (pushing) would probably address some of that issue.

    Quote Originally Posted by Rudeofus View Post
    I was not aware that scene contrast would be narrow, in my experience I had to battle excessive contrast as soon as artificial lighting exists in small parts of the view. Moon light should yield similar contrast levels to sun light.
    I'm sure you know this but I'm going to state the obvious here, the moon is moving.

    If you are after detail in the moon your exposure will need to be quite short and yes close to daylight settings. In that situation the rest of the scene's exposure just falls wherever it falls, the moon is the subject that matters. The only other choices in a single exposure are a- using a tracking mount but then the land/cityscape would blur if included or b- picking a day and time where the landscape and the moon are at similar EV's.

    When the moon is included but detail isn't important, then the moon, like the stars, can be treated as point sources and a trail can be expected.

    Similar thought on artificial light sources, just no trail. They can be treated as point sources too.

    If you take the point sources out of the exposure calculation for a given shot, a night scene's subject brightness range can be very, very narrow.

    I was at a workshop a week ago and we were all shooting a landscape scene late afternoon and over cast, the total SBR was about 3 stops when we arrived even shooting toward the horizon and measured by a variety of spot meters. That dropped to as little as 1 stop SBR before we left and it wasn't even dark yet.

    Excluding point sources a night landscape may have an SBR well under 0.5. This is where I think your white mountain gray sky issue is rooted.
    Mark Barendt, Beaverton, OR

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

  2. #22

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    Quote Originally Posted by markbarendt View Post
    I was at a workshop a week ago and we were all shooting a landscape scene late afternoon and over cast, the total SBR was about 3 stops when we arrived even shooting toward the horizon and measured by a variety of spot meters. That dropped to as little as 1 stop SBR before we left and it wasn't even dark yet.

    Excluding point sources a night landscape may have an SBR well under 0.5. This is where I think your white mountain gray sky issue is rooted.
    Could you go into more detail as to how you made these measurements?
    Kirk

    For up from the ashes, up from the ashes, grow the roses of success!

  3. #23
    markbarendt's Avatar
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    Quote Originally Posted by Kirk Keyes View Post
    Could you go into more detail as to how you made these measurements?
    Kirk,

    I actually use and N90s with a longish lens that I spot with. Darkest shadow with detail, brightest highlight with detail.

    About half of the participants had some form of hand held 1-3 degree spot meter and there was a solid consensus.

    It was a really tough afternoon for shooting.
    Mark Barendt, Beaverton, OR

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

  4. #24
    benjiboy's Avatar
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    The answer to the O.Ps original question is, nobody.
    Ben

  5. #25

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    I understand what you are trying to do because I am about to venture into the astrophotography realm as well. As for shooting slides I can give you no guidance other then what I have read. Shoot Provia only because it doesn't block out as much of the red wavelengths as other films. Also What are you going for? Star trails or whole swaths of the sky? I think this will make a difference. That device more or less tells you the "quality" of the sky light.

    Meaning if there is less "Sky glow" you have a higher quality of sky light. Ultimately your best bet is to try to find a very very very dark area only if you are trying to shoot photos of large expanses of the sky. The whole idea for this is for the people with there dobsonian and newtonian telescopes. How well will you be able to pick out details from deep sky DARK objects.

    I have some experience with shooting photos of the night sky but I must admit they are all with my DSLR. I have produced great photos of the moon, of constellations and of subjects with constellations in the background. The key is knowing what you are trying to take a photo of because the advice for exposure is going to be different for the different types of shots.

    Ultimately you are going to have stack photo's together (regardless of photo exposure length) if you want to get all of the possible details and colors from film. http://www.skyandtelescope.com/howto/astrophotography

    That link might help.
    ~mike
    Last edited by mr. mohaupt; 12-19-2009 at 12:21 PM. Click to view previous post history. Reason: forgot to proof it, found an error

  6. #26
    Rudeofus's Avatar
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    Quote Originally Posted by mr. mohaupt View Post
    Also What are you going for? Star trails or whole swaths of the sky?
    Both. Initially I'd like to integrate night landscape with star trails, but by adding and EQ5 mount I could also go for larger stellar structures (Orion nebulas, Andromeda, patches of milky way, ...)
    Quote Originally Posted by mr. mohaupt View Post
    I think this will make a difference. That device more or less tells you the "quality" of the sky light.

    Meaning if there is less "Sky glow" you have a higher quality of sky light.
    Well, what it supposedly does is it tells me the brightness of the sky background, and according to the marketing material it does that very accurately. My aim was to derive a maximum exposure length from that before the sky turns grey in my slides.
    Quote Originally Posted by mr. mohaupt View Post
    Ultimately you are going to have stack photo's together (regardless of photo exposure length) if you want to get all of the possible details and colors from film.
    The funny thing is I didn't need any of that (well, at least for my lowly standards) when I used negative film. Even with Portra 800 I just pointed my camera in the right direction, opened the shutter and closed it when I got tired of it, sometimes after 20 minutes, sometimes after 1 1/2 hours. It just worked.

    Maybe I just shouldn't be doing night shots this with slide film ...

  7. #27

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    I just found an old book I have "Practical Astrophotography," I know there is a section on slide film in there. When I get home I will take a look at it and see what it says. Overall the book is pretty good and talks about a lot of different things.

    You don't need an EQ5 mount to shoot photos of constellations, google a barn door tracker or a "scotch mount." They have become as fancy as a double arm mount which is surprisingly accurate.

    My computer is about to die, I will post more later
    ~m

  8. #28
    bobwysiwyg's Avatar
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    Mr.,

    Interesting, thanks. I had never heard of these devices. In case anyone else is interested;

    http://en.wikipedia.org/wiki/Barn_door_tracker
    WYSIWYG - At least that's my goal.

    Portfolio-http://apug.org/forums/portfolios.php?u=25518

  9. #29

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    bobwysiwyg,
    I guess I should have linked that for the group here but my computer was about dead.

    As for shooting slides of the night sky the only thing that the book talked about was "Hypering" film or subjecting it to hydrogen under a vacuum for a period of time. This apparently increased the sensitivity of the film at the risk of fogging it. ( http://www.amazon.com/Practical-Astr.../dp/1852330236 ) The book has some good starting point or reference exposure times in the back, I will copy some of them down here for you.

    Some things to think about. With a 135mm lens M31 Andromeda will be a faint, small dusty star. Your tracking will have to be really accurate but is possible.

    I would love to see some of your stuff with the Portra film. I would suspect that the sky fogging was less would be do to the latitude and maybe even printing technic?

    If your interested in exchanging information about this send me a PM with your email. I am working on some clear plans for a double arm "Trott" mount that should allow you to shoot photos up to an hour long.

  10. #30

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    Quote Originally Posted by bobwysiwyg View Post
    Mr.,

    Interesting, thanks. I had never heard of these devices. In case anyone else is interested;

    http://en.wikipedia.org/wiki/Barn_door_tracker
    I've built one and added a stepper motor to it to automate the turning of screw. They work well for exposures up to about 10 minutes or so and you need to be very careful aligning them to north otherwise you will get drift in the stars.

    It's a very good thing to start out with and very simple to make.
    Kirk

    For up from the ashes, up from the ashes, grow the roses of success!

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