The iPhone's camera is a great tool for taking spontaneous photos for sharing on sites like Facebook or Flickr, or even as actual prints on paper or in photo books. But just like photographs taken with a point-and-shoot, and even a DSLR, these images aren't necessarily their best when you first capture them. A few tweaks in a photo editor can greatly improve your iPhone photos, whether they were taken with a first-generation iPhone's 2-megapixel camera or the iPhone 4's 5-megapixel camera.
While there’s no single editing formula for producing a good photograph—all problem images have their own issues—there are a few concerns you can regularly expect to find with iPhone images.
The tools First, you’ll need basic image editing software.You don't need to splurge on an expensive editing program. If you already use iPhoto to transfer your images from your iPhone, there’s no reason not to do your editing there. It's true that Photoshop has more image editing power, but since iPhone images don’t have a lot of image editing latitude, the extra power won’t buy you much.
Though we’re focusing on iPhoto, you can make the adjustments I describe in most image editors, and some even in Preview. Alternatively, you can skip the Mac and do a lot of these edits directly on your iPhone using an app like Photoshop.com Mobile, Photogene, or Perfectly Clear. Results will vary based on the application, so experiment with the specific settings to get the best result. (If your editor has a histogram, you can learn how to read it and adjust tones with this histogram primer.)
White balance In general, the iPhone's white balance is very good when shooting in bright daylight, but under other light sources (and sometimes, even in daylight) its white balance can go out of whack. A bad white balance manifests itself as a color cast in your image. Either it's too warm (reddish) or too cool (blueish) or has some other strange overall color tone (usually yellow or orange when shooting in low-light).
Adjusting iPhoto's temperature slider can help correct these problems. If there's something gray in your image, use the white balance dropper to select that neutral gray and see if that corrects your white balance. Keep in mind that not all white balance problems can be fixed, especially when you're working with small JPEGs like the iPhone's.
Dull colors and skin tones The phone often produces images that aren’t as saturated as they could be. While iPhoto has a Saturation slider, you might find that the Temperature slider works better for strengthening the color in your image. If flesh tones are looking a little unsaturated, and the Saturation slider isn’t helping too much, try increasing the temperature, or sliding the Tint slider a tiny bit toward the pink side. Just a little bit of temperature and tint correction is all you need when making a correction to skin tones.
When adjusting color you might feel like iPhoto’s controls aren’t doing as much as they usually seem to do. This is probably true, if you normally adjust images created from a "real" camera. The iPhone’s images don’t pack a lot of dynamic range, and are simply not as data-rich as what you get from a real camera. This means that your adjustments won’t yield as much change, and that they will quickly degrade the image if you push them too far.
Not enough contrast If your image looks a little flat or hazy, or if the darkest thing in the image is a black object that isn’t appearing truly black, then the photo probably has a contrast problem. Move the left-most slider in the Levels control to the right to correct the problem. You can also move the right-most slider to the left to improve contrast, but be careful that highlights don’t overexpose to complete white. You can also simply slide the Contrast slider to the right, but Levels gives you more control as well as the ability to protect bright highlights.
If you shot an image in low-light with the idea that you’d brighten the photo later, you can try increasing the Exposure slider, but again, you’ll want to be careful that your highlights don’t overexpose. You can also try sliding the Shadows slider to the right, but brightening an iPhone image with either of these controls poses the risk of increased noise—splotchy or speckly patterns in your image. The iPhone is a fairly noisy camera to begin with, so you can’t brighten your images very much before it starts to show.
Needs to be sharpened Finally, all iPhone images will need sharpening. Slide the Sharpness slider to the right, but not so far that your image takes on crunchy look or becomes over-sharp. If you start seeing halos around edges, you’ve gone too far. When it comes to sharpening, it’s better to err on the side of not enough than to stray into too much. Even with a good amount of sharpening, your images will still not be as sharp as what you’ll get from a good point-and-shoot camera. This is not a function of megapixels as much as it is the small lens on the iPhone’s camera.
When sharpening, keep an eye on the noise in your image. Sharpening can increase noise, so you want to find a good balance of these two factors. You can try to tackle the noise problem with the Reduce Noise slider, but this will most likely soften your image.
Don't over think Don't spend too much time trying to make your iPhone photos perfect. The iPhone's images are never going to look the same as a photo taken with a DSLR or a good point-and-shoot, and too much editing can actually decrease the quality of your image. Luckily, the photos shot with an iPhone have a recognizable low-fi quality that can be part of their charm, especially if you play it up with an app that imitates film like CameraBag or Hipstamatic.
[Macworld senior contributor Ben Long is the author of Complete Digital Photography, fifth edition (Charles River Media, 2009).]