As an iPhone user and Pentax photographer, I like the concept of having some photo related applications in my pocket to help me in a pinch. However, I have to admit, I'm not often in a pinch.
Besides geotagging, there doesn't seem to be any calculation problem that needs solving or iPhone assisted extra note-taking in my average photo routines, because I'm not usually doing expensive macro photography with manual Medium Format cameras. And I'm really not interested in the cheesy photo editing apps or any that upload iPhone snaps to blogs.
But some of you might feel differently, especially if you're new to manual photography or have enjoyed applications like these in other incarnations for Palm or Windows Mobile. The potential for a really great iPhone Photo application is out there, because a number of the available apps have basic features that serve real purposes, not just whimsy: they can help you figure out when the golden hour is for your current location, they can calculate depth of field for a given lens and aperture, and they can help determine exposure compensations.
Here are 5 iPhone photo applications that are starting to show some potential.
PhotoBuddy ($1.99) by Frank Bauer
This has the handy calculators for Sunrise/Sunset using your current location, finding depth of field for a given lens and aperture, and it also can use the iPhone's own camera to calculate exposure for your manual camera (a very rough approximation, but it works). It even has features to help with white balance, but for that you'd have to trust the iPhone's color calibration (which I don't). Graphically, it looks pretty nice, and the price is just cheap enough to be worth a test drive.
iMarkMySpot ($0.99) by iCloseBy.com
Photojot ($2.99) by Shaila Klosterman
This application is not only for Geocode note-taking, it has calculators (Sunrise/Sunset, DOF, Flash, email support), and the bonus of voice message recording. A good package that mixes the features of PhotoBuddy and iMarkMySpot into one application. However, it's also the same price as if you bought the other two separately.
PhotoCalc ($2.99) by Adair Systems
The basic tools for the old school photographer: Exposure reciprocity calculator, a flash calculator, as well as a camera glossary. Like Photo Buddy and Photojot, this application also uses your current location to find Sunrise/Sunset and moon phase times.
Visual Depth of Field Calculator ($0.99) by Jun Chen
This one has a really simple and good GUI. You just enter the lens focal length and the subject distance to get a little graphic representation of the measurements. Cute and cheap.
For any application to have more usefulness, the iPhone needs more integration with cameras. Ideally, it should be tethered wirelessly (bluetooth or WiFi) to the camera, or at least be able to read and write to your camera's SD memory card through an adaptor. Since that can't happen yet, the iPhone applications are limited to serving basic information based on calculating measurements or logging your location. Hopefully, though, someone will come up with a breakthrough and get working on a third party app (hello, Eye-Fi?) to take us all to the next level.