Z-Stop

Expose for the shadows, develop for the highlights. Z-Stop is an iPhone spot meter true to this Zone System principle. Shoot black-and-white film with the Zone System, no external meter needed. [ Sound familiar? ] - Still guessing exposure by feel? - Wasting expensive film on bad exposures? - Carrying a spot meter for a camera with no meter? - Metered a shadow and got a picture that was too bright? - Forgetting where you metered by the time you develop? For about the price of a roll of black-and-white film, you can leave these behind. Meter one shadow with your iPhone, and Z-Stop shows the shutter and aperture that make it Zone 3, in 1/2-stop steps. With Pro, one tap on "Save" keeps the scene as a record image. [ The Zone System ] Worked out by Ansel Adams and Fred Archer around 1940. It divides tones into 11 steps, from black (Zone 0) to white (Zone 10), one stop apart. Detail is clearest from Zone 3 to Zone 7. Zone 3 : darkest shadow with full texture Zone 4 : foliage and stone in shade Zone 5 : middle gray (18% gray card) Zone 6 : sunlit light skin, light stone Zone 7 : brightest textured areas Expose so the shadow detail stays on the film, then set development so the highlights land where you want them. [ A meter only knows Zone 5 ] Any reflected meter renders what it reads as middle gray (Zone 5). Shoot a shadow at its reading and it turns gray. To place a shadow on Zone 3, give 2 stops less than the reading. That is why spot metering matters: a wide reading mixes one shadow with other tones. [ Why Z-Stop ] Finding a shadow, subtracting 2 stops, converting to real settings, and bracketing by half stops is slow and error-prone. * No spot meter or DSLR required - A reflected spot meter that reads only inside a small circle on screen. * Tells you if a shadow is good for Zone 3 - It checks how even the spot is (deviation): green "Z3 OK" if usable, red "Re-meter" if texture or an edge is mixed in. * No hunting for where to meter - "Find Zone 3" points only to usable spots. - With no Zone 3 it looks for Zone 4; with neither it says "Don't shoot", so you don't waste film. * No mental math - Shows values that match your body's shutter speeds and your lens apertures. - Values you cannot set get a red warning. * Ready for half-stop differences - Five steps in 1/2 stops, from the reading to -2 stops. - "By aperture" (Pro) brackets the aperture for full-stop mechanical shutters. * A steady reference - Exposure locks at the first reading, so up to five spots compare fairly. * No notebook needed (Pro) - The record image keeps the screen, readings, shutter, and aperture, so you can check your Zone 3 spot after developing. * See the gray before you shoot - B&W preview shows what tone a red sign or green awning will become. [ How to use ] 1. Tap a shadow. 2. Tap a green "Z3 OK" box to set the anchor, or press "Find Zone 3" at the lower left. 3. Fix the aperture ("By shutter") or the shutter speed ("By aperture", Pro), and read the five steps. In theory Zone 3 is -2 stops, but the right step shifts by half a stop with film, EI, development, and printing. Choose a main frame and a sub frame. 4. With Pro, press "Save" to keep the record image in the "Z-Stop" album. [ Free and Pro ] Metering, Find Zone 3, the Zone 3 anchor, the five 1/2-stop steps, B&W preview, and settings are free. Pro (in-app purchase, yearly subscription) unlocks By aperture and record saving. Setup : EI, aperture, ND, camera body (35mm, medium format, and more) Privacy : no internet except the subscription check with Apple; no ads or analytics; video stays on your iPhone Terms of Use : https://www.apple.com/legal/internet-services/itunes/dev/stdeula/ * Z-Stop calculates from the brightness of the iPhone's standard (1x) camera. * Development for the highlights is up to you. * Not for important shoots you can't repeat (weddings, trips, paid work) at first. * Test with a roll or two, set it up, and bracket until you know your results.