Monday, March 31, 2008
May 2008 HelpLine
When New Tech Meets Old Tech
• Being Clear About Filters
• Aspect Respect
-------------Being Clear About Filters
Q) A lot has been written about the amazing things that can be done with plug-ins. PCPhoto has given me a lot of great tips as I've been learning more and more about using layers in order to fine-tune my digital images. I've become fascinated by what I can do with filters when editing my images. So now I'm wondering about whether I even need any filters when I take my digital photographs.
Via the Internet
A) I know what you mean about the magic that can happen with software plug-ins. Only a few pages from this column, Rick Sammon constantly amazes me with his dexterity with Photoshop. But am I ready to take my filters out of my camera bag and leave them on the shelf with my reciprocity charts? No! (Reciprocity? That's for you film shooters out there-you know who you are.)
In my bag, I carry several filters that I always want with me. The polarizing filter can be approximated with some plug-ins with phenomenal results, but they're just simulations. Software can deepen the blue in the sky and enhance the contrast, but reducing or eliminating glare and reflections is a job for a true polarizer in the field.
A group of filters that I rarely leave home without are ND (neutral density) and graduated ND filters. An ND filter reduces the amount of light that enters the lens without adding color to or removing color from the light. A graduated ND filter starts clear and gradually transitions to a light-reducing filter. How quickly the filter transitions to ND is indicated by whether it's a soft or hard ND filter.
Each of these filters has a different use. Let's start with a graduated ND filter. It's often said that High Dynamic Range (HDR) capture-where you take several shots of the same scene at different exposure levels and then combine them in the computer—-makes a graduated ND filter obsolete. I use HDR, but still keep grads in my camera bag, too.
While I don't disagree that HDR can be useful for capturing scenes that involve a high contrast ratio, there are occasions that make grads a great choice (such as when there's motion in the scene or when long exposures are required). If you look at the image in my October 2007 HelpLine column, you'll see a long exposure shot that used a grad filter. (You can view this image online at www.pcphotomag.com/how-to/helpline/october-
If I tried to accomplish this with HDR, it probably would have required three exposures, all of them fairly long. Since I was using the long-exposure noise-reduction system in the camera, each exposure would take twice the time. This means that the moon would have moved position even more, and I would have been going through my batteries quickly. With the grad, once I captured the scene, I was able to see if I got the image I wanted.
While you can argue HDR versus ND grads all day, there are several cases where a standard ND filter is the only way to capture an image. If you want to slow down your shutter speed to capture more movement, many times the only way to get the shutter speed you want is to use an ND filter. For example, the only way I could capture the soft motion in the waterfall was to use an ND filter. I had stopped down the lens as far as I could while keeping the image sharp; I had set my ISO to the lowest setting the camera would go, but I still couldn't get the image I wanted. The only answer was to mount an ND filter on my camera. Then, and only then, could I get this image.
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