May 2008 HelpLine

This Article Features Photo Zoom

While software filters can do a remarkable job of emulating traditional filters, for some applications, there’s no digital  substitute. The soft waterfall effect seen here required a neutral-density (ND) filter to block enough light so that, shooting at my smallest aperture, I could get a slow enough shutter speed.

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.

Jacob K.
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

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.

Aspect Respect
Q) I’ve been considering changing from a CRT to an LCD display. Having a wide LCD TV, I know that it can display an image in its proper 1:1 aspect ratio or distort it to fill the screen. I was allowed to try a widescreen LCD at home (no manual), and an image in Photoshop looked like it was stretched horizontally, regardless of its overall display magnification. I set the selection marquee to a 1:1 Fixed Ratio and, sure enough, I got a rectangle. That doesn’t go! My question is, can one expect widescreen LCD monitors to have settings to switch between displaying the image in its proper 1:1 aspect ratio, as opposed to stretching it to fill the screen, and at a true 1:1 image aspect ratio, are the sides of the screen black and useless, or available for parking toolboxes?

Lew Diehl
Houston, Ohio

A) Before I answer your question, I need to clarify some things about displays. With the advent of digital television (DTV), more and more people have high-definition video displays in their living rooms, great rooms, home theaters and home offices. One of the biggest changes that these displays bring is a different aspect ratio.

The old television system has an aspect ratio of 4:3 (width to height). High definition has an aspect ratio of 16:9. Since there’s still a great deal of programming that has been produced at 4:3, there needs to be a way to deal with differences in aspect ratios. (Even though I’m talking about television programs, this also affects digital photography. HD sets have video inputs that allow you to connect your camera so you can present your images on a high-definition display. The latest and greatest sets even have card reader slots. All you need to do to display your images is insert your memory card.)

There are several options that can address the 4:3 “shortcoming.” The first is to stretch out the image so it fills the screen. This method doesn’t respect the original aspect ratio and it makes everything look
wider. (If you thought it was difficult to answer the question, Does this dress make me look fat?, you might want to avoid this setting.)

A second option respects the original aspect ratio of the image. Your image fills the display top to bottom, but the left and right sides of the screen will have black or gray boxes, or pillars. This is known as pillar boxing. This is the most accurate way to display your image—it respects the aspect ratio of the original image.

There’s a third option, which keeps the original aspect ratio of the image, but zooms in on it to eliminate the black bars at the left and right of the image. While many people are distracted by the black bars and prefer this method, it crops the top and bottom of the image, so you lose parts of your original composition.

I think, however, that Lew’s question deals with widescreen monitors that are connected to a computer. In this case, a specific standard doesn’t lock us into a display like our television system does. When you hook up a widescreen display to your computer, you want your video card to output the number of pixels that can be displayed on the LCD. For example, if your display is 1440 x 900, then your video card should output 1440 x 900. It should create a desktop with that format. There’s no reason for the LCD to “stretch the pixels” unless your card won’t support the resolution, nor is there any reason for black bars on the left and right.

And, as Lew pointed out, distorting the desktop changes squares into rectangles-and makes all the people in your pictures look fat. And do you really want to go there?

If you have questions, please send them to HelpLine, PCPhoto Magazine, 12121 Wilshire Blvd., Ste. 1200, Los Angeles, CA 90025 or [email protected].

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