Polarizing Polarizer Filter

Polarizing Polarizer Filter

The Truth About Neutral Density Filters

This week one of my loyal customers asked me a brilliant question about Neutral Density filters. It was so good I just had to answer it via this article. Youâ€™ll most likely appreciate this digital photography tip as much as he will.

â€œA question, I want to get a graduated filter, however, all the one's I see are graduated grey, are they still ND and will not affect the colour? Very best regards, Pete.â€

What Peteâ€™s digital photography question is all about is the common confusion of photography equipment looking like something different to what we first expect.

When choosing a filter for our digital photography its best to first look at them as tools. Firstly in order to maintain clarity about ND filters, firstly think about what you need then work your way from there. Peteâ€™s a fantastic photographer and is ready to move to the next level with his digital photography equipment choices, which is where I come in.

The answer to Petes digital photography question is yes, they are still ND, but like all filters, the colour will be affected. Iâ€™ll explain.

ND filters are predominately used to darken a bright sky so that both the sky and subject can be properly exposed. Graduated ND filters have varying degrees of â€œgraduated grey.â€ The Graduated ND filter comes in a few different types, but can really be broken down into two main categories. They are; hard edge and soft edge.

As the name suggested a Hard Edge is mainly applied when there is a sudden difference in the luminance of the digital photo, such as an overexposed sky over a landscape. The soft edge filter is mainly applied to a digital photo that has less distinct over and under exposed areas such as the same landscape but perhaps taken at approaching dusk when the light is not do hard. A soft filter just gently tones down harder areas of light. Itâ€™s less dramatic and can often be used very well in black and white photography to give the digital photo a â€œboostâ€ of the dramatic.

You can have a variety of ND filters that go from a weak graduated grey to quite a strong graduated grey. The â€œintensityâ€ of graduated grey is described by numbers. So for example a weak graduated grey ND filter is known as â€œND2Xâ€. And the strongest is â€œND8Xâ€.

All filters affect digital photography colour whether subtly or dramatically. You can have an ND filter thatâ€™s quite soft but still darkens an area of the digital photography image. Even though itâ€™s subtle, anything you put onto that lense will be affected. But it depends what we mean by â€œaffected.â€

If we mean the colours disappear and change completelyâ€¦well a lot depends on that such as the intensity of grey, the colour at the time of day, the seasons etc. If you are using a Full graduation from top to bottom then your colours will most definitely change. They will become darker. However if you are using a less intense ND filter, then youâ€™ll notice the change in colour is not as apparent. Youâ€˜ll notice that the lighter ND filters will have more of a polarizing affect, the darker areas being at the top and not so much shading at the bottom.

Graduated ND filters are brilliant in times of excessive brightness coming from the top of the sky for example. You can use an ND filter to darken an overly bright sky and keep the main subjectâ€™s luminance the same. It has a terrific influence over evening up unbalanced light. It can effectively tone down over exposed areas in your digital photography.

Happy Shooting,

Amy Renfrey

About the Author

Amy Renfrey is the author of two major successful ebooks â€œDigital Photography Successâ€ and â€œAdvanced Digital Photographyâ€. She is a photographer and also teaches digital photography. Sheâ€™s photographed many things from famous musicians to portraits of babies. Amy also teaches photography online to her students which can be found at www.DigitalPhotographySuccess.com

Polarization (of Light) Problem...Please Help?

Unpolarized light of intensity 20.0 W/cm^2 is incident on two polarizing filters. The axis of the first filter is at an angle of 25.0° counterclockwise from the vertical (viewed in the direction of the light is traveling) and the axis of the second filter is at 62.0° counterclockwise from the vertical. What is the intensity of the light after it has passed through the second polarizer?

Intensity of unpolarized light is multiplied by 0.5 by the 1st polarizer. Subsequent polarizers multiply intensity by cos(theta)^2, where theta is the angle between previous and current polarizer.
Thus I = 20*0.5*cos(37d)^2 = 6.378 W/cm^2.

Screen test 16mm kinor with polarizing filter Kodak Vision2

Tiffen 58MM Circular Polarizer Glass Filter
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