Page 1 of 3 123 LastLast
Results 1 to 10 of 23

Thread: How to measure and time long exposures at dusk or dawn.

  1. #1

    Join Date
    Apr 2012
    Posts
    16

    How to measure and time long exposures at dusk or dawn.

    Hi,

    I enjoy long exposure photography very much. I do some of it in digital, which is quiet easy. But at changing light and considering Schwarzschild effect, it get's more complicated.

    I use a Sekonic L-758 for metering. Most of the time incident, but sometims spot metering. I am to slow on spot metering, have to practice it more
    Then I use two Android apps to do the compensation. ND Filter Calc to get the compensated time and then Exposure Assistant, which calculates the Schwarschild effect for several film brands and ISOs.

    From the technical point it's straigt forward and clear, although I would wish to have an app, which could somehow take over the metering and do both compensations. But that's another story...

    Where I struggle now is how to compensate for the changing light during dusk and dawn. How do you handle this? Also passing clouds are not that easy to handle. Do you have any rules of thumb how to compensate?

  2. #2

    Join Date
    Apr 2014
    Location
    Edinburgh, Scotland
    Posts
    176

    Re: How to measure and time long exposures at dusk or dawn.

    The easy, expensive, option is to use Fuji films, Acros and Provia both have exceptional reciprocity response and need very little adjustment for very long exposures.

    Alternatively you can not worry too much about it, realise its very hard to over expose once you're into Schwarzschild territory and use a compensating developer to help. If you are scanning you can get away with quite a lot, its not ideal but it is amazing what you can get away with.

  3. #3
    Jac@stafford.net's Avatar
    Join Date
    Dec 2012
    Location
    Winona, Minnesota
    Posts
    5,410

    Re: How to measure and time long exposures at dusk or dawn.

    It is faster to set the lightmeter's ISO to compensate for the ND filter, or any other filter. Those factors will not change, so you need read only once. No conversion necessary. Regarding reciprocity failure, a simple small card giving ranges is adequate, as stevo mentioned.

    Changing light will become easier to compensate with experience. When a huge cloud moves into a significant part of your scene with a very long exposure, just let it be, make the picture and prepare to make another.

  4. #4
    Lachlan 717
    Join Date
    Apr 2007
    Posts
    2,437

    Re: How to measure and time long exposures at dusk or dawn.

    If you have an IPhone, consider Reciprociry Timer app. (Not sure if it's available for Android).
    Lachlan.

    You miss 100% of the shots you never take. -- Wayne Gretzky

  5. #5

    Join Date
    Apr 2012
    Posts
    16

    Re: How to measure and time long exposures at dusk or dawn.

    Thanks for the tips.

    @steveo
    Acros and Provia prices are really hefty! 25 sheets above 80€ compared to 50€ for Deltta 100.... But the advantage is tempting.

    @Jac
    You are right, i also think it's an experience thing. It's a pity, it's that seldom I manage to get out shooting! I really should try to do the iso compensation. It's one step less and there are plent left!

    @Lachlan
    Thanks for the tip, but it's not available for Android. But Exposure Assistant is doing exactly the same. So no problem here.

    In meantime, I also found this very interesting thread: http://www.largeformatphotography.in...t-at-dawn-dusk
    They discuss the same topic and also have some interesting tips.

    Let the brighter sun compensate for the most of Schwarzschild during morning Hours. But there is no tip for me for the evening hours.

  6. #6

    Join Date
    Apr 2012
    Posts
    16

    Re: How to measure and time long exposures at dusk or dawn.

    What I do not fully understand. In my understanding, a compensating developer holds back the light areas and pushes the dark ones resulting an a less contrasty image. Wouldn't this strenghten the Schwarzschild effect, as it tends to underexpose?

  7. #7
    Corran's Avatar
    Join Date
    Apr 2011
    Location
    North GA Mountains
    Posts
    8,407

    Re: How to measure and time long exposures at dusk or dawn.

    I don't know how long of a timed exposure you are doing. But I've done some real long exposures, up to 10-20 minutes in abandoned buildings. I usually pulled the development 10-15% for every extra "stop" I gave the exposure to correct for reciprocity.

    I found some adjusted times online and used them. They worked fine. I don't use silly phone apps, I just remember correction values.

    More importantly than any of this discussion is just trying it out. Shoot a few sheets and see what works for you.
    Bryan | Blog | YouTube | Instagram | Portfolio
    All comments and thoughtful critique welcome

  8. #8

    Join Date
    Sep 2003
    Location
    Hudson Valley, NY
    Posts
    1,691

    Re: How to measure and time long exposures at dusk or dawn.

    Quote Originally Posted by mongole View Post
    Where I struggle now is how to compensate for the changing light during dusk and dawn. How do you handle this? Also passing clouds are not that easy to handle. Do you have any rules of thumb how to compensate?
    The good news is the actual exposure time with long exposures isn't all that critical. For example, if you determine your exposure should be 2 minutes, a full minute underexposure is only 1 stop off, and full minute overexposure is only (about) 1/2 stop off. So for long exposures I just count in my head. I have practiced and I am rarely off by 10 seconds or less, and that amount of time is inconsequential for exposures of a minute or longer. For really long exposures i just look at the time on my phone. The most you are going to be off is one minute (on average it will be 30 seconds) and that is meaningless on a 30 minute exposure.

    As for clouds, if you have the time, meter when the cloud cover is close to what you want for the actual photo. Then wait some more until the clouds get right again and make the photo. This won't work if you happen encounter a unique cloud that you want to photograph, or you are short on time. But it works pretty well most of the time.

  9. #9
    Vaughn's Avatar
    Join Date
    Jan 2007
    Location
    Humboldt County, CA
    Posts
    8,631

    Re: How to measure and time long exposures at dusk or dawn.

    I think the best way is to bracket, keep notes and from the results you'll have hard facts and experience to last you the rest of your days.

    But as starting points, from info by Michael Kenna: For Tmax400 and Tri-X.
    Attached Thumbnails Attached Thumbnails Kenna's Night Exposure Recomendations_Page_1.jpg  
    "Landscapes exist in the material world yet soar in the realms of the spirit..." Tsung Ping, 5th Century China

  10. #10
    Lachlan 717
    Join Date
    Apr 2007
    Posts
    2,437

    Re: How to measure and time long exposures at dusk or dawn.

    Quote Originally Posted by Corran View Post
    I found some adjusted times online... I don't use silly phone apps

    Why is an app "silly", yet "online" is okay?
    Lachlan.

    You miss 100% of the shots you never take. -- Wayne Gretzky

Similar Threads

  1. Killing time during long exposures
    By Ed Richards in forum Darkroom: Film, Processing & Printing
    Replies: 24
    Last Post: 24-Dec-2010, 20:36
  2. Exposure measurement at dawn/dusk
    By Lars Åke Vinberg in forum Style & Technique
    Replies: 24
    Last Post: 25-May-2006, 10:39
  3. How to accurately time long exposures?
    By Bernard Languillier in forum Lenses & Lens Accessories
    Replies: 18
    Last Post: 1-Nov-2004, 22:30
  4. Bracketing for long time exposures ?
    By Bruce Barelly in forum Style & Technique
    Replies: 10
    Last Post: 13-May-2001, 05:28
  5. Polarizing filter ok for long time exposures ??
    By Bruce Barelly in forum Lenses & Lens Accessories
    Replies: 3
    Last Post: 26-Apr-2001, 06:06

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •