Saturday, January 10, 2009

What Causes a Dark Photo?

Photography is the art of recording light. Whether you shoot digital or film, you are recording light. The tricky part comes in when trying to record the right amount of light. Recording the wrong amount of light is the most common cause of dark photographs.

Most of the time if you say your image came out too dark someone in the room will chime in with "use a flash". "You need a flash" is all to glib an answer for such a complex subject. While adding flash to your images will increase the amount of light available, it is not a "cure-all" for dark photographs. Another way to increase recorded light is to use a faster film speed . This will decrease the amount of light needed to record the image.

Beyond the immediate answers of flash and film speed there are several more reasons as to why images may turn out too dark. In general, there was a reason you may have not realized how much light was needed or why you captured the wrong amount of light.

    Causes of Improper Light Recording

  • Incorrect Shutter Speed/Aperture/Film Speed Combination

  • Metering Off of Wrong Spot in Composition

  • Inaccurate Light Meter

  • Old and/or Damaged Film

  • Improper Developing


Incorrect Shutter Speed/Aperture Combination

An incorrect shutter speed/aperture combinations are a major cause of dark images. What shutter speed and apertures you can use in a given situation are dictated by the available light, not by what you need to capture the subject. Even though you may want a 1/1000th of a second shutter and a f22 aperture to capture the action at a football game, it will not properly capture the scene at night. The faster you set your shutter speed, the less time light will have to imprint on the film/sensor. Likewise, if you use a small aperture, less light can move through the lens to reach the film/sensor. In order to ensure a properly exposed image when setting the shutter speed/aperture yourself, it is vital that you use your light meter.


Metering Off of Wrong Spot in Composition

Metering is what it is called when you take a reading with your light meter. Whether you actually see the light meter reading or not, unless you have camera with only one setting (like a disposable or pinhole camera), your camera has a light meter. When you point your camera at an object and press the button part way down, the light meter reads the amount of light reaching the film/sensor.

The vast majority of cameras meter purely off of the exact center of the frame. This means that if the center of the image is brighter than your main subject, your subject will be underexposed. SLR type cameras often allow the photographer to select the type of light reading the meter will use.

  • Center-weighted Average

  • Single Point Selection

  • Multi-segment

This allows the photographer to select a reading method more consistent with his/her own shooting style. Even in cameras that do not allow the photographer to manually select the metering style, some cameras are beginning to use a smart metering algorithm that allows the camera to meter off of the obvious subjects in a frame rather than purely off of the center. This does help but it is important you know WHERE your camera is taking its light reading from.

Once you know where the light meter is taking a reading from you can adjust your shutter speed/aperture setting accordingly, or you can force the meter to take its reading where you want it to by pressing the shutter button halfway down when properly pointing at your selected metering spot. If you meter off of a bright blue sky, the hawk that is your actual subject will be underexposed/dark.


Inaccurate Light Meter

Even if you take a good light meter reading and set your shutter speed/aperture correctly, it is still possible to have a underexposed/dark photograph due to an inaccurate light meter. Next to taking a meter reading off of an incorrect point in your composition, an inaccurate light meter is a major cause of dark images. This is especially easy to see in point and shoot and digital cameras. With film cameras, the lab was often able to correct exposure problems when they developed film and the photographer never saw the problem. Now, we are our own photo labs, and we see the problem!

If you are using a basic point and shoot camera and it is under warranty, get it repaired as there really isn't a good workaround for you on this problem. You will either have to get the meter repaired, purchase a new camera, or continue to try to lighten the image in a digital darkroom program. Even using flash probably will not eliminate the problem as the light meter will adjust to the flash.

If your camera has a manual setting you can easily work around an inaccurate meter. You will need to take some test images to see just how badly inaccurate your meter is. Take several shots of the same subject, adjusting your aperture each time. When you view your images, note what exposure compensation produces the desired image. Note this amount and remember to "overexpose" (at least according to your light meter) your images by that amount each time.


Old and/or Damaged Film

Old film will eventually lose its ability to accurately record light. While film technology has improved drastically since the day of Daguerreotypes, it is still not an eternal medium. Film stored in its original containers under good conditions (room temperature) will generally last at least a couple of years. However, it will eventually go bad. When film goes bad due to age it can produce interesting but unpredictable effects. One roll may produce dark images and another old roll may produce streaked images. There is just no way to predict with certainty what old film will do.

Damaged film, like old film, tends to have unpredictable flaws. Sometimes this flaw is dark photographs.


    Film can be damaged by:

  • Temperature
    Acceptable temperatures vary by manufacturer and film - be sure to check the film package for limits.

  • X-Rays
    Use a lead-lined package that has been airport approved for transport.

  • Water
    This includes condensation - keep your film well sealed and insulated.

  • Light
    If unintended light strikes film before, during, or after the initial exposure it will create image problems. Generally this is more of a problem of overexposure than underexposure but it bears mentioning as a cause of film damage.



Improper Developing

Even if you expose an image perfectly, it is possible for the lab to ruin the image in processing. If you receive a bad photo from a lab, look at your negative. If the negative seems to be properly exposed (not overly light or dark) then try having another lab do another print. Hopefully it was only the print that the lab ruined. If your negatives are completely light or dark the negative is ruined.


    Some of the more common lab errors are:

  • Non C-41 process film developed in C-41 process

  • Light contamination during processing

  • Wrong film brand settings

  • Too long or too slow processing time

  • Old chemicals

  • Contaminated chemicals


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