Frequently Asked Photo Questions for April
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 January, February, and March.
More Questions About DPI
I want to enter a photo contest, and the rules say the following: "Photos should be at least 300 dpi. The canvas size should be about 8 inches by 11 inches." My camera saves pictures automatically as 72 dpi at a resolution of 3456 by 2304 pixels. In contrast, my husband's camera saves photos at 3648 by 2736 pixels and 480 dpi. I read your answer to someone's question that the dpi doesn't really matter, but this contest specifically says that they want 300 dpi. So what do I do?
--Jodee, Lawton, Oklahoma
This topic is made more confusing than it needs to be by ludicrous rules like the ones you cite, Jodee. When I say that dpi doesn't matter, I mean that dpi--dots per inch--has no meaning when you are talking about a digital photo, which is composed only of a grid of points of color and can be displayed at any size. Without getting too metaphysical, a digital photo is nothing but potential, and has no inherent size until you display it or print it somewhere.
The claims that your camera saves photos at 72 dpi and your husband at 480 dpi are there pretty much because the cameras must put something in the dpi field; they can't leave it blank. There's no standard dpi that all camera manufacturers have agreed to use. That's okay, because as I've said, this number really doesn't mean much anyway.
As for the contest, what they're really asking for is a submission that's no less than 300 dots per inch times 8 inches across, or 2400 dots horizontally. In other words, your submission should measure about 2400 by 3300 pixels, because they want a photo that can be made into a high-quality 8-by-11-inch print.
Armed with that knowledge, you can probably take it from there. You can see that both of your family's cameras take photos about the right size with no additional processing; just do some minor cropping (if desired) and submit your winning entry.
Dealing With White Garments
I have a question about shooting in sunlight when someone is wearing white. White clothing seems to really wash out the whole photo. I thought it was a matter of adjusting my ISO, but that seems to have no effect.
--Lori Wells, Wahnapitae, Ontario
Lori, ISO is a measure of the camera's sensitivity to light. That might sound like the right thing to adjust in this case, but taking photos at different ISOs will generally all give you the exact same exposure. The shutter speeds and aperture combinations will differ, but the actual exposure will end up about the same. Instead, you should try using the camera's exposure compensation control, usually abbreviated as Ev. If your photos are getting washed out, underexpose the photo by setting Ev to -1 or -2.
Do Refurbished Cameras Mean the Model Is Bad?
While looking at digital cameras for sale, I've noticed a lot of refurbished models. Is this an indication that these specific cameras tend to break, malfunction, or are unreliable?
--Dennis Westlin, Hollywood, Florida
That's a really good question, Dennis. Some people think you can get a sense of a model's reliability by tracking this sort of thing. In reality, though, it's difficult--if not downright impossible--for average folks to really compare the reliability of camera models or manufacturers by watching for refurbs hitting the resale market. I think a better bet is to read PCWorld and other sites (like dpreview) for their advice. You might want to check out Reliability and Service: The Best Companies to Buy From for more information.
Fading Digital Photos
Some of the photos stored on my hard drive are slowly turning to a solid gray color. I have thousands of photos stored on my hard drive and I run across one every so often. The last one I saw was solid gray from the bottom to about half way up. Next time I see it, it will probably be 100 percent gray. Have you ever heard of anything like this?
--Ponce Esquivel, Trinity, North Carolina
Yes, I've seen this, Ponce. I have good news and bad news for you. The good news is that the photos aren't "fading." They're not slowly turning gray all on their own. I know that's not a big consolation, but it's important to keep this in perspective. Your photos are digital files of 1s and 0s, just like Microsoft Word and Excel files. Your Word files don't slowly lose their adjectives from the bottom up, so it's reasonable to assume that photos aren't changing color, either.
So what is happening? Well, the bad news is that this kind of degradation can happen when there's an error copying a photo, such as when you migrate your files from an old computer to a new one, restore files from a backup, or copy files from one drive to another. It's rare, and I've mostly seen it when there's a large amount of congestion on the drive, such as when copying huge quantities of data at once. So my advice is this: If you are copying or moving a lot of files, inspect them right away to make sure they made it to their destination unscathed.
Metadata at Law
Can metadata help me reliably prove the date when a digital photo was taken? Wouldn't the date be reset by the user each time the camera battery was replaced? Or do digital cameras have some kind of internal timekeeping mechanism that continues even when the battery is dead?
--Doug Leichty, San Diego
No, you can't use metadata to reliably prove anything about a photo, including when it was taken. Not only is the date that's set by the camera subject to being set incorrectly, but any metadata can be changed afterwards anyway. I've explained before how easy it is to change the Date Taken field of your photo using software like the free Windows Live Photo Gallery, for example. And, as you point out, the battery in the camera can die, which might require you to reset the date. If you don't, all new photos will get some default date (like 1984).
Hot Pic of the Week
Get published, get famous! Each week, we select our favorite reader-submitted photo based on creativity, originality, and technique.
Here's how to enter: Send us your photograph in JPEG format, at a resolution no higher than 640 by 480 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: "Down to the Last Drop," by Cindy Graf, Waco, Texas
Cindy says: "I was walking around the ranch looking for something to take pictures of when this little thorny vine caught my eye. I used a water bottle to create some water drops and started shooting. I shot this with my Nikon D70 using a 60 mm macro lens and a flash."
This week's runner-up: "The Good Neighbor," by Nicolette Wain-Lowe, Centralia, Washington
Nicolette says that she took this photo with a Canon Rebel XTi one early one morning after a heavy snow fall, as she watched a man clearing his neighbors' driveway.