Have a question about digital photography? Send it to me. I reply to as many as I canthough given the quantity of email that I receive, I cant promise a personal reply to each one. I round up the most interesting questions about once a month here in Digital Focus.
Shooting Gray Instead of White, Part II
Dave, recently you gave some advice about how to ensure that you get a white background in a product photo. I was once told to overexpose snow and underexpose a black bear in a coal mine because most digital cameras do not capture pure white or black properly in auto mode. Might that have been the ladys problem? Can you comment on what I was told?Gordon Totty, Plymouth, Michigan
You're absolutely right, Gordon. Snow, for example, is about two stops brighter than neutral gray, so when you let a camera set the exposure automatically, it underexposes the scene, and the snow comes out gray. An easy fix is to overexpose the shot by about two stops. (You can be sure I'll explain this again sometime in the winter to help everyone with their outdoor holiday photos.)
But the situation Kaya Atli asked about last month is subtly different. For her eBay product shots, the easiest solution is to set the camera's exposure for the product and to throw enough light on the white background so that the backdrop blows outthe result is a properly exposed subject, and a clean white background.
Improving on Ansel Adams
Ive been trying to get a handle on how to enhance black-and-white photos that I find online. For example, the National Archives has hundreds of Ansel Adams photos free for download. But how do I enhance them without washing out much of the detail?Jim Rems, Irvine, California
My first reaction, Jim, is to ask how much you expect to enhance photos that Ansel Adams took. Adams was a master photographer whose Zone technique brought out every bit of detail and contrast in his photosif you're not having much luck optimizing old black-and-whites, it might be because you've chosen Ansel Adams as your subject matter. That's akin to trying to make chocolate taste more chocolaty.
But let's suppose you have a vintage photo that wasn't a product of the greatest black-and-white artist of the 20th century. I suggest that you try optimizing the photo's contrast by stretching the histogram. I've explained how to do so a few times; check out, for example, "Punch Up Photos With the Histogram." Essentially, through this technique you move the white and black point markers in the histogram to make the best possible use of the light that was available in the scene; it will give you the enhancement you're looking for, and it won't wash out any detail.
I have a point-and-shoot camera, and I have noticed that I get perspective distortion in many of the shots. I can make adjustments using my photo-editing program, but I am wondering what causes this in the first place. Can I eliminate this distortion when I take the picture?Harvey Whitmire, Stroudsburg, Pennsylvania
What you're describing, Harvey, is a distortion effect that is inevitable and unavoidable with most cameras. It's just a matter of geometry: When you photograph a tall building, vertical lines (such as the opposing walls) appear to converge off in the distance, which makes the building look somewhat askew. The closer you are to the building when you take the photo, the more pronounced the effect will be.
Consider this photo that Harvey provided:
It doesn't look bad, but if you inspect it closely, you'll see that the walls of the building are not parallel. That isn't because Harvey's camera is malfunctioning; all cameras do this. Compare it with the photo below, which Corel Paint Shop Pro's perspective correction tool digitally adjusted:
Notice that the walls are now parallel, and that the building looks correct.
The only real in-the-lens solution to this problem is to use a specialized, expensive tilt lens. Generally, such lenses are available only for equally expensive professional cameras. Architecture photographers routinely use themdue to the costs, however, pretty much no one else does. But as shown here, Paint Shop Pro and other photo editors can fix this sort of distortion pretty easily.
A Debate About Enlargement Performance
In 1998, a friend asked me to help him enlarge a Polaroid snapshot. We used Windows 95, a cheap scanner, and Adobe Photoshop 2. We digitally enlarged a cropped segment of the tiny 3.5-inch Polaroid to 12 by 14, and it was just as clear as the original! It had no distortion, as you get with current enlargements (because today's enlargements magnify the picture instead of digitally reproducing the image). So, can you tell me why we no longer can have digitally enlarged images in modern editions of Photoshop? I have purchased many programs in an attempt to find just one that would digitally enlarge instead of magnify, and I've had to return all of them. How was this possible then, but not now?JL, via the Internet
Thanks for the letter, JL. This is a really interesting question, and worth discussing. I must admit that I fundamentally disagree with your premise. You assert that 1995-era Photoshop was able to enlarge a minuscule 3-inch photo to 12 inches with perfect sharpness. I suspect that you might remember that project as turning out better than it objectively did.
For starters, those early versions of Photoshop were no better at enlarging images than their modern equivalents, and were in fact probably worse. Moreover, a small Polaroid simply doesn't have enough visual detail to make a high-quality oversize print, so the enlargement is unlikely to have been as pretty as you remember.
Certainly, it could not have been "as sharp as the original." In order to enlarge a photo and keep it as sharp as the smaller original, the software would have had to invent information that didn't exist in order to maintain sharpness as the photo got bigger. In general, that's impossible.
That said, you can find specialized programs designed to approximate visual information using sophisticated algorithms to make high-quality enlargements. These programs can't create perfectly sharp enlargements that are as good as the original, but they definitely can make something better than a straight pixel enlargement. Check out the free SmillaEnlarger, for example, which I wrote about in "Enlarge Your Photos Without Sacrificing Quality." Using a utility such as SmillaEnlarger, you can conceivably take a high-quality scan of a Polaroid and turn it into an oversize print. In fact, JL, you might have used a '90s-era equivalent of this program to produce the results you describe.
Ideal Scanner Resolution
Recently, you answered a question about scanning negatives. Can you please expand your answer? Specifically, I am interested in knowing what kind of resolution I should choose when scanning slides and negatives, especially as it relates to the optimum balance between file size and resolution. For example, there's no benefit to scanning at excessive resolution, but there is a distinct time penalty. I'm always torn between the two, not sure which is better. I notice that some of my old color slides are deteriorating, and need to be scanned and archived soon.--Stan Hutchings, Concord, North Carolina
This question deserves an entire Digital Focus of its own, Stan, and I promise to do that soon. In the meantime, I can give you some general guidelines that should steer you in the right direction.
My general advice is to scan slides and negatives at the highest optical resolution that your scanner supports, especially if you are serious about your photos. That's because you never know when you might want to make a large print from a cropped section of a photo. If you scan the image at a relatively low resolution, you're stuck; you won't have any pixels to spare to "zoom in" on a better composition.
As a general rule, scanning slides and negatives at 2000 dpi should give you the equivalent of a 6-megapixel photo, which is satisfactory for most standard print sizes. Many scanners go up to about 4000 dpi, and the higher resolution is a lifesaver if you're intent on making high-quality prints from cropped photos. If all you care about is sharing photos online (such as on Facebook), then you can make do with a much lower resolution, such as 800 dpi.
Hot Pic of the Week
This week's Hot Pic: "Nature's Dried Flowers Arrangement" by Paul Bild, Vancouver, British Columbia
Paul writes: "I took this photo with my Canon Power Shot G12 as the late-afternoon light left a golden tone on the vegetation. This is a macro shot of hydrangea flowers in late fall at the Vandusen Botanical Garden in Vancouver."
This week's runner-up: "Tree Top Eagle" by Karl Rudlaff, Waterford, Michigan
Karl took this photo with a Nikon D200 using a 70-200mm zoom lens. He says that he took it handheld, while sitting on a small boat.
Visit the Hot Pics Flickr gallery to browse past winners.