Double Exposure

Practical uses for Double Exposure by Brenda Hartshorn

When people think of photo manipulation these days, their mind probably goes straight to the idea that it was created in Photoshop.  However, photographers have been using tricks to manipulate their photos ranging from exposure techniques, processing methods, and printing methods.  I was lucky to have attended college for photography right on the cusp that digital photography was only starting to taking over.  I was able to get the experience that I needed from digital while still learning film techniques since digital had not become the standard.  Having a background in film has made pay close attention to everything that I'm doing to create the desired images the first time around.

Notable Old School Methods

More is... More Better

Double exposure is probably among the most well know method as it has been used to trick people into believing images of ghosts and UFOs.

Double exposure is not just for fun, there are actually practical uses for the technique.  possibly best used in architecture photography.  When considering that color photography cannot make use of the Zone system by exposing for the detail in the shadows and developing for texture in the highlights (color hue and contrast would shift horribly with this method) photographers can take multiple exposures over a period of time by first taking a photo of the sky, wait for the sun to set then take a photo of the lights inside the building, then turn the lights off and take an exposure for the exterior of the building.

The featured photo this week is of the LA skyline from  Koreatown. To do this, it is best to set up in a place that you don't have to worry about the tripod moving at all.  We were using Toyo 4x5 studio cameras in our giant Manfrotto tripods.  Slight rumbling of the tripod with sheet film would have been devastating.  If the film moved at all, the exposure of the sky would no longer match the edge of the buildings.  I do not recommend attempting to do this from a parking structure as those are designed to give and move a bit when the weight of a car rolls by.  

Do what I say, not what I do. This photo was actually shot from a parking structure with much resistance.. but resistance is futile.  

Low Risk Rationalization:

  • Structure was pretty empty and did not appear to get regular use

  • View was good

  • This was not for a client

  • There was time to reshoot for the assignment if needed

Technical Info

Desired exposure to get everything in focus from the tree in the foreground to the skyscrapers in the distance was a small aperture. To be honest, I can't remember the exact exposure, but it was somewhere between f/22 and f/64.  Iā€™m inclined to say that I probably shot this at f/22, to reduce the length of time that the shutter would have to be open for the second exposure of the buildings.  Once you get past exposure times of a second long, you run into a fun thing called reciprocity.  Basically, when the shutter is open longer, the film becomes less responsive to the light.  So you have to increase the length of the exposure even more.

Materials:

  • Manual Camera of Choice: As long as you have a bulb setting and can take an exposure without having to advance the film, the camera should work
  • Light Meter:  Needs to have accurate reflective readings.  Doing incident readings only will not work for this process.  I'm a big fan of my Sekonic L-558, which is about 10 years old now but still working great.
  • Shutter release: You don't want to be clumsy and bump you camera.
  • Heavy Tripod: Stay!
  • Sandbag(s): I said, STAY!
  • 3-way Bubble Level: Don't want that horizon slanted.  Might as well take a couple minutes to double check that things are good for that 3 hour photo you're about to take.
  • Watch/Timer: Because counting "One Mississippi..." isn't always good enough.
  • Partner in Crime: You have expensive equipment just sitting there waiting for someone to take it off your hands.  Safety in numbers.  You're less likely to be messed with if you have someone else with you.
  • Extreme Patience: You will be waiting around for HOURS.

Basic Procedure:

  1. Once you have set everything up (with camera facing west) you will need to wait til the choice* peak of sunset that appeals to you.  Did you notice the asterisk there next to choice?  Good, you also need to make sure that the buildings are going to be complete silhouette.  That means no exposure from the buildings can burn into the film, you only want the sky to expose.  You have your trusty reflective meter so you can meter the buildings and sky value differences.  Desirable difference would be probably be around 5 stops to get nice color in the sky.  Remember that your light meter is metering for 18% grey.  So you're going to want to underexpose the sky from the reading that you're getting from the meter.  If you're not shooting large format, you will need to use a low ISO, smallest possible aperture to increase the length of the exposure as much as possible. You may want to consider getting some neutral density filters to be able to achieve this.  
    Important!  I keep saying bulb for a reason.  Once you take the 1st exposure, you cannot change the settings on your camera without risking the second exposure from being slightly shifted.
  2. Then wait til the sun goes down and there isn't color left in the sky.  Once you think you're done waiting, do a meter reading on the concrete of the building and street lights.  Then wait some more because it's nowhere near where you need to be.  What you're looking for is a sky that meter reads as black (3+ stops under), street lights that are no more than 3 stops over normal, and the concrete in the concrete jungle to meter at normal (in-between the street lights and the night sky.)
    Ratio example of what the meter would read:
    • Sky is f/22 at 16 seconds?
      Compensate for 18% grey to black, exposure is really 4 seconds.
    • Lights is f/22 at 1 second?
      Compensate for 18% grey to white, exposure is really 4 seconds.
    • Concrete: f/22 at 4 seconds.
      No exposure compensation needed if it is standard sidewalk grey.
  3. Once you have compensated the exposures, do they match?  Amazing.  
    Note: If the stops are more than 5, that's still ok.  Key factor in finding the length of the exposure will be to make sure that the ratio between your street lights and the concrete isn't more than 3 stops.  It's ok to let the street lights blow out a little bit.
  4. Make sure to also meter those sky scrapers and make sure that they are within a stop of your meter reading for the concrete.
  5. So, you found balance?  Did you factor for reciprocity failure?  You with the large format, bellows compensation?  Great, take that final exposure and go home!  The local security is probably getting pretty annoyed by this time that they are still babysitting you.