Graduated Neutral Density Filters

This is how I saw Pedersen Glacier in Kenai Fjords National Park, Alaska.  But with out a graduated neutral density filter or a similar tool, my camera would have not been able to capture the photo.

Our eyes have an amazing ability to see a very large dynamic range.  We can see detail in the shadows along with detail in sun lite areas at the same time.  Unfortunately, film and digital cameras can’t begin to come close to matching what we see with our eyes.  Here is a perfect example.  With my eyes, I can see the warm, first light of sunrise lighting up the glacier off in the distance.  At the same time, I can clearly see the colorful field of fireweed in the dark shadows.  The camera can’t capture what I see.

I was able to properly expose the sunlit glacier by using shutter speed of 1/13 with an aperture of f/22, but as you can see I lost all detail in the foreground.

By increasing my exposure by about 3 stops to .6 of a second at f/22, I was able to capture the detail in the foreground, but I have now blown out the glacier.  Here is where a graduated neutral density filter saved the day.

These filters are clear on one half, and dark on the other.  The dark portion cuts the amount of light by a set amount, you can purchase them in increments of 1 stop up to 5.  The one stop filter reduces the amount of light in the dark portion of the filter by one stop.  I used a three stop filter in this scene which decreased the dynamic range to something my camera could capture.

In addition to blocking varying amounts of light, these filters can be purchased with either a hard edge or soft edge.  The terms hard or soft edge are used to describe the transition between the dark portion of the filter, and the clear portion.  The hard edge is a sudden transition, perfect when you have a nice defined change in light, I used a hard edge filter in the top photo.  A soft edge is a more gradual transition.

Here is a photo of a 3 stop hard edge on the left, and a 2 stop soft edge on the right, I think this gives you a good idea what this filter is about.  I use Singh-Ray filters developed originally by the late Galen Rowell.  These are supposedly the most neutral, meaning they cause very little shift in color.  Like most things associated with photography, they aren’t cheap for a piece of plastic.  Each filter cost about $100.  There are cheaper options, but most can cause an undesirable shift in colors.  The 2 stop soft and 3 stop hard would be a good starting set.

Now that I have described how I captured the photo, you can go back and look at the original, or this bigger version and I think you can see where the filter was placed.  I had the dark edge begin right at the leading shore of the lake because the reflected light in the lake was so bright.  If you look close, you can see the gravel moraine areas on the left and right side of the lake are extra dark because of the filter.  This is unfortunate, but typically goes unnoticed by viewers.  If I pulled the filter up higher, I could have avoided having dark dirt, but then a portion of the lake would be overly bright – this is something that doesn’t look natural and would be noticed by viewers.

You can get a holder which screws onto the front of your lens and allows for precise placement of the filter.  If you have a depth of field preview button, this can be very helpful when positioning the filter.  It is much easier to see the transition when the preview button is held down.  I usually just hand hold my filter in front of the lens and will typically take a few exposures in order to make sure at least one has proper placement.

I use these filters all the time, they are one trick of the trade I couldn’t do without. There is a new way of dealing with extreme dynamic range called HDR photography that involves combining images of different exposures with special software on the computer later.  The advantage of HDR photography is that you are not limited to preset transitions as you are with filters.  In this example, HDR photography would have allowed me to avoid the dark dirt areas.  I have started using this method recently, and will write about it in a future blog.  I am tempted to go back and rework this photo and others, because I believe this new process may help them.