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Using White Balance With RAW, Resetting a Photo's Date, Understanding Crops, and More

Dave answers questions about RAW format, polarizing filters, emptying a memory card, and more.

Have a question about digital photography? Send it to me. I reply to as many as I can--though given the quantity of e-mails that I get, I can’t promise a personal reply to each one. I round up the most interesting questions about once a month here in Digital Focus.

For more frequently asked questions, read my newsletters from December, January, and February.

Does RAW Format Use the Camera's White Balance?

I seem to be getting mixed messages about color balance and RAW. I thought a RAW capture was merely a recording of the levels of light from each pixel, so color balance set in the camera should not affect the resulting RAW file. However, I've seen it recommended that you should set the color balance manually to match the lighting environment even when capturing in RAW. I can see the merits of doing this if I am recording in JPEG, but not in RAW. Am I mistaken? --Brian Palmer, Whitby, Ontario

You're right: Your camera's RAW format doesn't factor in the camera's white balance setting when it captures a photo. This is one of many ways that the RAW format is far more flexible than the JPEG format; you can completely change the color balance of a photo on your PC without degrading the image quality.

But there's a little more to the story. When you take a photo in RAW mode, your camera records the white balance setting in metadata. When you open a RAW image on your PC, most photo editors display the image at that white balance setting by default. This gives you a decent starting position, which you can then tweak to your heart's content. So it's a real time-saver to set the white balance properly when you take the photo, or else you'll have to make a large correction to the color balance every time you open a RAW photo on your PC.

Simulating a Polarizer

I am aware that you can use a polarizing filter on a camera to "see through" otherwise opaque water. If I have a photo taken without such a filter, is it possible to edit or process it on a computer afterwards to achieve the same effect?--Marv Keefer, Colorado City, Colorado

You're right that a polarizing filter has the almost magical ability to let you see into water by dramatically reducing the glare caused by sunlight reflecting on the surface. It can only do this at specific angles, so you need to stage such photos very carefully to achieve this effect.

One of the reasons I recommend that serious photographers buy a polarizer is that this is one of the few effects that is impossible to achieve with software filters after the photo is taken.

Will some magical software technique be invented in a few years that can replicate the effect of a polarizer in as program like Adobe Photoshop? Sure, I suppose it's possible, in the same way that I've been amazed by some of the almost supernaturally effective "content aware" features in the newest version of Photoshop. But armed with a few semesters of college physics, I'll wager that it's pretty darned unlikely. The bottom line is that this is something you'll almost certainly never be able to do without a filter screwed onto your camera.

Changing the Metadata

I was recently in Europe and took over 500 pictures, but I forgot to set the date until just before I returned. I would like to be able to correct the dates on these pictures but I can't figure out how to do it.--Ron Shanbrom, Las Vegas

It's easy to change the "date taken" metadata of your photos, and you can do it painlessly with a free program from Microsoft--Windows Live Photos Gallery, which is a part of the Windows Live Essentials suite. Just find the photos you want to change in Photo Gallery, select one or more of them, and then choose Adjust Time from the Edit tab in the ribbon at the top of the program window.

Crop Factors and Sensor Sizes

I was interested to read your recent article about megapixels and megabytes. That ties into the article you wrote about camera lens crop factors. Several of us in our camera club are still in disagreement, though. Some say that, everything being equal, there is little difference between an image made by a APS-C sensor and a full frame. While the smaller sensor seems to have enlarged the image by a factor of 1.5, in fact the image is actually just cropped from a potentially bigger image. So the image has not really been enlarged, it only seems to have been. You are just seeing less of the same view. That is, you cannot really see further with a APS-C sensor--it only seems like it. Likewise, if a APS-C sensor enlarges an image by 1.5, why would you ever buy a full-frame sensor camera if you can buy a 300mm lens and get the results of a 450mm lens for a great deal less money? --Richard Finn, Livermore, California

The folks at your camera club are right; the 1.5x crop factor in APS-C cameras is only an apparent zoom or enlargement. What's really happening is that the smaller sensor in an APS-C camera doesn't capture the "full frame" visible by the lens--it captures a smaller part of the frame. In other words, the APS-C lens gives you an effective focal length that's larger than what the focal length would be on a full-frame camera, but only because you're only taking a square out of the middle and "blowing it up" to a larger size.

So yes, APS-C cameras do give you more bang for the buck with a telephoto lens than a full-frame camera, but as I've mentioned many times before, you pay for that with terrible wide-angle performance. Want to take a really wide angle photo? Your APS-C camera makes your wide-angle lens 1.5X less wide, meaning that wide-angle aficionados have to buy a really wide-angle lens to get even moderately wide results. And if you think that telephoto lenses are expensive, try shopping for a very-wide-angle lens. They cost a fortune.

Do Memory Cards Get Erased Automatically?

I am an artist who has been using 35mm cameras and slide projectors to do my paintings for 35 years. I have just bought a digital camera and will be buying a digital projector in the near future. When you download the photos to the computer, do the original images on the memory card get deleted automatically? I would like to view the images on the computer to choose one for a painting subject, then insert the memory card into the digital projector to trace onto my illustration board.--Joe Russ, via the Internet

Generally, Joe, photos stay put until you intentionally delete them. Your camera's memory card is no different than your PC's hard drive in this regard; If you copy a file from your hard drive to another device, it stays on your hard drive afterwards.

You should watch out for the "fine print," though. Some programs that transfer photos from your camera to the computer might try to make your life easier by deleting the photos from your camera as they're copied to the PC. You can test how your software works by taking some unimportant photos and using your transfer software to copy them to the PC. Then check your camera to see if they're still there. Or check the settings for your software and look for a check box that says something like "Delete photos from my camera after they're copied to the computer." If you see that, clear the check box.

Hot Pic of the Week

Get published, get famous! Each week, we select our favorite reader-submitted photo based on creativity, originality, and technique.

Great news! For a limited time (from March 1 till August 31, 2012), Hot Pic of the Week winners will receive one free downloadable copy of Corel PaintShop Pro X4.

Here's how to enter: Send us your photograph in JPEG format, at a resolution no higher than 800 by 600 pixels. Entries at higher resolutions will be immediately disqualified. If necessary, use an image editing program to reduce the file size of your image before e-mailing it to us. Include the title of your photo along with a short description and how you photographed it. Don't forget to send your name, e-mail address, and postal address. Before entering, please read the full description of the contest rules and regulations.

This week's Hot Pic: "Ground Zero" by Harvey Whitmire, Stroudsburg, Pennsylvania

Harvey says: "I took this photo on a trip to the World Trade Center in 2008. I used a Panasonic DMC-FZ8 and shot from the 50th floor of WTC7. At that time there were no offices or walls on the floor so it provided a 360-degree view around New York. However, it also meant shooting through structural reflective glass, which presented some problems, even when using a polarizing filter."

This week's runner-up: "Boom" by Michael Maluk, Daytona Beach, Florida

Michael says: "I was bored one night and decided to go for a night-time hike and take some pictures. I set up by the side of a road where the lights from traffic gave the scene some life. I used a Kodak Z981 in manual mode, with a 15-second shutter speed and an ISO of 64.

To see last month's winners, visit our February Hot Pics slide show. Visit the Hot Pics Flickr gallery to browse past winners.

Have a digital photo question? E-mail me your comments, questions, and suggestions about the newsletter itself. And be sure to sign up to have Digital Focus e-mailed to you each week.

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