Hi! I just joined, thanks to the excellent advice of someone I met on Flickr. Thanks nattylux! I only started writing iPhone apps recently. Objective-C is a pretty neat language, if a bit weird! Thank goodness for Apple's excellent documentation. I've just finished and submitted the third version of my exposure calculator, Expositor 1.2. I describe it in great detail at the Expositor website, and it's available in the App Store as I write this! A free version, Expositor Lite, is in the review queue and will be available soon. Here's a screenshot or four: Moved to a different combination of settings: With exposure compensation: From the documentation: Expositor is a handy slide-rule based exposure calculator for photography. Pick the situation you're shooting, then slide the ruler until your camera's ISO is lined up next to it, and every combination of F-stop and shutter speed to the left will get you close to a perfect exposure. Use it in the field if you don't have a light meter handy, or use it to train your big ol' brain to be its own exposure calculator. Expositor is here to help you shoot great pictures! Simple example, basic settings lookup: Say you're shooting on a sunny day, and your camera is set to ISO 100. First check the list of EVs to find 'Bright sun', EV 15. Next, slide the ruler (touch and drag it) until ISO 100 is lined up next to EV 15. By looking at the two columns to the left of the red line (seen above) you can see all combinations of aperture and shutter speed that will produce a decent exposure, including F8 at 1/500 second, F16 at 1/125 (Sunny 16!), and F32 at 1/30 second. Pick the one that best suits your artistic intent! Advanced example, a creative approach: Say you're shooting a waterfall on an overcast day. To get a soft look, you'd like to use a shallow depth of field, F4, and drag the shutter a bit to blur the water, 1/4 second. Slide the ruler (touch and drag it) until F4 is lined up next to 1/4 second. Notice that there's no ISO value listed next to 'Heavy overcast day'. That's because the scene is much too bright for you choice of aperture and shutter speed, but all is not lost! You can use the exposure compensation slider to calculate the density of the ND filter needed to bring the ambient light down to a workable range. Slide the exposure compensation slider until an ISO supported by your camera (for this example, ISO 100) is next to 'Heavy overcast day'. This should put the slider value at +6 stops, meaning that at ISO 100, F4, and 1/4 seconds, the scene is six stops overexposed. Just grab enough filters to block six stops, put them on your camera, and you're ready to shoot a proper exposure with the look you want! Advanced example, compensating for equipment performance: Sometimes you may be shooting with a camera that's off-spec and is predictably overexposing or underexposing shots, or with modifiers that change its exposure performace, such as filters and extension tubes. Use the exposure compensation slider to correct for these issues! If your camera regularly overexposes by 1/3 stop, set the slider to -1/3 stop. If you know a stack of extension tubes makes your camera underexpose by 2/3 stop, set the slider to +2/3 stops. If you put a 3 stop ND filter on your camera, set the slider to +3 stops. Just tell Expositor how off your equipment is, and it adjusts the slide-rule to automatically calculate the correct expsosure settings, taking your camera's actual performance into account! Once set, use Expositor as you normally would, there's no need for any mental math! ----- I would love to hear your feedback on the app, the website, anything really. Even better if you're a photographer, what do you want me to add?