To accurately control the flow of light through the lens we must be able to measure how much light passes through the aperture. Now, you'd think that would be pretty straight forward. Just measure the diameter of the opening. But the laws of physics don't allow us to do that. You see, the light gathering capability of any lens is controlled not just by the aperture opening but also the focal length of the lens. 

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Creative Exposure

We’re happy to report that we are back from our Greek Islands Photography Tour and it was a smashing success. Many people have worried about the financial and political situation in Greece but we found everything business as usual. The Greek people are wonderful and everyone had a great time. 

More about the trip later. Today we want to share with you some photography tips that will really add a lot to your portfolio.  Since the advent of digital photography the use of filters has been greatly reduced. Color correction is now a menu option and special effects are now done digitally.  One of the few filters that is still recommended is a good polarizing filter.  But there’s another one you’ll want to add to your camera bag - a good Neutral Density (ND) filter.  We packed some Vu filters for our trip to Greece and the results are stunning.

This was shot at ISO 100, f/22, 20 seconds with a 10-stop Neutral Density filter

Neutral Density filters reduce the amount of light that passes through the lens without altering the color of the light.  This provides the photographer a broad range of flexibility in managing their exposure and depth of field.  You can find these filters in a variety of densities. I use VU filters and they provide ND filters in 1, 2, 3 and 10-stop densities as well as a Variable Neutral Density filter that provides up to 7-stops of density.  

So, why do you want to use one? 

When you compose an image, one of the “photographic controls” you can use is shutter speed.  As you know the shutter speed can be uses to show movement - either freezing movement or blurring movement. I love waterfalls shot with long exposures that turn the water into a milky smooth blur.  

Without a filter you’re limited on when you can do this. In bright daylight, if your camera’s slowest ISO is 100, then even at f/22 you’ll be getting a shutter speed too fast to blur the motion. Some people add a polarizing filter which gives you 2 stops of density, allowing you to reduce the shutter speed even more.  But in bright daylight that is still too fast to really blur the water. 

This is when you mount your 10-stop Neutral Density filter.  If your shutter speed without the filter is 1/60th of a second, after you mount the 10-stop ND filter you get a 15 second exposure. Now that will blur the water. 

You can read more about the Vu filters used on their website at VuFilters.com.