White Balance And RAW
* Do You Need White Balance With RAW?
* Protective Filters
* Reboot For Performance
Do You Need White Balance With RAW?
Q) Since I got my digital SLR, I’ve really enjoyed the flexibility that comes with shooting RAW. While this “digital negative” has been fun, I do wonder about bothering with setting white balance. Since I can adjust the white balance to whatever I want when converting the RAW file, I’ve just been ignoring the white-balance setting. Am I missing something here?
A) Before I get into your white balance question, I’d like to respond to the term “digital negative.” It’s true that this is a convenient term and has been made even more popular since the introduction of Adobe’s DNG format. But to try to use it as an analogy between film-based photography and sensor-based photography is a little misplaced. A more closely matched term would be “latent image” rather than “negative.” Just like the latent image on exposed but unprocessed film, the RAW file is invisible until it’s processed in some manner.
The analogy goes even further: There are different processing methods to “develop” the “film” or RAW image (you can’t reprocess a negative, though you can print it differently). Just as a photographer might develop black-and-white film in different ways with various developing chemicals, a photographer might “develop” the digital latent image using Adobe Camera Raw, Raw Shooter, Capture One or the RAW image processor that came with the camera, and each one will result in a slightly different version of that RAW file.
Now, on to white balance. It’s true that the white-balance setting can be adjusted during RAW processing. This is because the white-balance camera setting is just a bit of metadata stored in the RAW file. It doesn’t affect the sensor data until you start processing the file.
While you can ignore white balance during shooting, you’ll only delay your adjustment. There are several problems to this approach:
1. You’ll need to do a basic white-balance correction for all of a group’s shots before you get to any other processing adjustments or else colors will be difficult to match. This adds more work to your processing.
2. If the white balance is far off, your initial image viewing might be distracting—you might concentrate on the image’s color problems rather than looking at other aspects. This can be especially tricky when you’re dealing with a large number of images.
3. If you’re shooting with auto white balance, and your composition changes (say, from zooming in or out on your subject), you can find your white balance changes from shot to shot. Then you’ll have to try to match them, plus you won’t know which one is more accurate.
4. On a more philosophical note, ignoring white balance can lead photographers to start ignoring other camera settings. I’ve heard some say that they don’t have to worry about exposure or they don’t have to bracket anymore because of the miracle of RAW format. Though it’s true that you may “get an image” from a marginally exposed shot with RAW, there’s no substitute for good exposure.
Q) I got into a heated discussion with a friend about whether I should use a “protective” filter on my lens or keep it bare. I won’t tell you which one of us is on which side, but there’s a polarizing filter riding on your answer.
New York, New York
A) For those of you not familiar with this discussion, the reasoning goes like this: You’ve just spent a lot of money on a lens for your camera. You should spend a little more and always keep a “protective filter”-usually a UV filter-screwed on the front of the lens. This way, if you do something that might scratch or damage your lens, the filter will take the damage. And, so it goes, the filter is a lot cheaper to replace than the lens.
At face value, that logic makes sense, but it always reminds me of one of my childhood neighbors. Whenever my friends and I went over to this neighbor’s house, we always giggled as we entered the living room. While the room was nicely decorated, all of the furniture had clear plastic slipcovers.
How does a protective filter remind me of a slipcover? Just as the designer of that sofa spent time and effort to create a beautiful piece of furniture, lens manufacturers spend time and effort to create an efficient and high-quality optical system. They use exotic formulations of glass and high-tech coatings to minimize reflections, diffractions and aberrations. All of this science is working to create an ideal optical path for the light that will be traveling to your camera’s image sensor.
While there are excellent UV filters, no piece of glass is perfect. Adding a filter to the front of the lens can add reflections, glare and other anomalies to the optical path. All of that can degrade your final picture. So, you could change the reasoning of the original argument to: You’ve spent all that money on the lens—why lessen the optical quality?
If you need to use a specific filter for a specific reason (such as a polarizing filter to remove reflections from glass or darken a sky), by all means, use it. If you shoot in a harsh environment (like a place with blowing sand), you may want to use a protective filter. But if you want to protect your lens for normal shooting, I suggest the following methods:
• Always use a lens shade to protect the front of the lens, even when you don’t think you need it.
• Always use a lens cap when not shooting, and don’t forget to use end caps if you take the lens off the camera.
• Follow your lens manufacturer’s instructions for cleaning your lens. In particular, use a manual blower to remove dirt from the lens before using any type of cleaning system.
Reboot For Performance
Q) My question deals with “USB Effects” in the March/April 2006 issue. In your answer to the question about getting maximum performance from a computer, you stated, “I reboot my computer and start up only my image-editing application.” How is this done?
A) Simply reboot the computer and then start only the image-editing program. In other words, don’t first check e-mail, listen to music or run some other application if you want to get maximum performance out of your computer. I don’t even start these applications and then quit them—that’s why I say to reboot and then start the image editor.
I’m the first to admit that I do this infrequently—usually when I’m working with large images that stress system resources such as a panorama with several images all coming from 16-bit RAW files, or if I’m printing a large picture.
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