Using a Shutter Release Switch

Interstate 5

San Diego, California, United States

Canon 5D Mark II

Focal Length 24

Aperture 22

Shutter 62 sec.

ISO 50

So here's a great chance to talk about a Shutter Release Switch.  The purpose of a manual switch is to hold open the shutter for an indefinite length of time, allowing the film/file to obtain the proper exposure.  For this instance I needed to manually hold the shutter open longer than the camera would allow normally (30 seconds) because I had set the ISO (Exposure) and the Aperture at the lower extremes of the cameras functionality.  Since the Exposure and the Aperture were set at their absolute minimum the only way to let in more light was to extend the shutter time.  Conversely, if I wanted I could set the shutter for 30 sec. and left the ISO at 50 and adjusted the Aperture.  If I had done that, I would likely have had to stop the shutter somewhere around F14.  

      - or - 

I could have left the Shutter at 30, and the Aperture at 22, but I would have had to bump the ISO up to over 1000 which would have sacrificed the quality of the image.  This is where the Shutter Switch shines.  With a shutter release you don't have to sacrifice either the Aperture or the ISO (Exposure).  Even when those (Aperture/ISO) were set at their minimum (F22 (for this lens) and ISO 50) you could lock the cameras shutter open for as long as needed to sync up with them.  To properly expose your shots you will need to use all of these (Aperture/Shutter Speed/Exposure (ISO)) in conjunction.

Also, for this picture I shot with a black card.  When I manually locked open the shutter for 62 seconds to capture only the light trails of the cars I was able to place a black card (many other black objects may do as well, but a card is easiest in my opinion) during the time that no traffic was present and omit those periods.  

The shutter length is deceiving for this picture however.  Even though the shutter was locked open for 62 seconds, it was likely only recording light for 40-45 seconds of that, because some of the time a black card was blocking any light from coming in which would have further exposed the film.  So, to properly expose your photo it may be good to take a reading/metering of the scene with the cameras light meter and keep that number in your head as the amount of time that will be needed without the black card in front of the camera.  Personally, I find it much easier to simply take a few shots of differing shutter periods.  

Also, sometimes at smaller (larger numbered) apertures the shutter won't coincide with the aperture at the same degree of accuracy as it would at lower numbered (larger) apertures.  If you are shooting at larger numbered apertures (above F14) it is important to take several shots.  I think four shots would be safe.  Shoot one at where the light meter suggests and shoot three additional shots at either one F stop (Aperture stop) lower (lower numbered - ex. 20, 18, 16) or drop the shutter down slower (to a longer interval ex. 37, 49, 66 sec.) or bump up the ISO to a higher number (ex. 100, 135, 160).  These are all hypotheticals, but after reading this you should have a good idea of how these three elements of the camera work in conjunction with each other.

Moving the ISO to a higher number - Letting more light in.

Moving the Aperture (F stop) to a Lower number - Letting more light in.

Moving the Shutter to a slower (longer time period) setting - Letting more light in.

For this shot a Graduated Neutral Density Filter would have helped tremendously since the bright white church in the background was so much brighter than the highway below.  Here you would have put the dark/shaded section of the filter over the brighter church and the transparent/clear section of the filter over the traffic lanes.  When this is done the lanes are exposing at their normal rate as where the top of the filter that is covering the church is exposing at a slower rate (ex. 75% of, 60% of, 40% of, etc...) depending on the strength of the filter.  

This was part of the reason for using the black card.  Since I was only exposing during periods where the black card was absent I tried to maximize the amount of light that was coming in from the lanes of traffic.  There is more light when exposing off traffic on the road than exposing off of the road when there is no traffic.  Here, without the filter it was extremely difficult, even when using the black card to maximize the intensity of the light, to properly expose the church and the freeway.

Below is the original file (which I also slightly rotated).  Here you can see how dark the freeway originally was.  To correct this I used the "shadows" and the "exposure" adjustments in Aperture 2.0.  These functions are also available in Adobe Photoshop under the same headings.  I also adjusted the definition (Aperture 2.0), adjusted the luminosity of certain colors, namely yellow and red, independently by isolating their color channels, and slightly adjusted the contrast of the image.  A Graduated Neutral Density Filter would have greatly reduced the need for such drastic post production.