Phototools opens straight to the calculators — no sign-in, nothing to load. Here's when I reach for each one.
Depth of Field
Give it your sensor, focal length, aperture, and focus distance, and it returns the near and far limits of acceptable sharpness, the total depth between them, and the hyperfocal distance. Use it when you need a specific zone sharp — a portrait's eyes but not the background, or a landscape front-to-back. The hyperfocal figure is the one to remember: focus there and everything from half that distance to infinity holds.
Crop Factor
Compare a lens across sensor sizes. It gives the equivalent focal length, the field of view, and the equivalent aperture — the last one matters because crop changes depth of field, not just framing. It also runs backwards: tell it the full-frame look you want and it names the real focal length to get there on your body.
ND Filter
For long exposures. Feed it your base exposure and the filter you're stacking and it gives the corrected shutter time; or tell it the shutter time you want and it tells you the ND strength to buy. It speaks all three dialects — stops, ND number, and density — so it doesn't matter how your filters are labelled.
The ND and exposure tools overlap on purpose: one thinks in filters, the other in the exposure triangle. Reach for whichever matches how the problem showed up.
Exposure Calculator
The general solver. Set a priority — aperture, shutter, program, or fully automatic — hold what you care about fixed, and it balances the rest, with ND compensation folded in. Everything snaps to the standard one-third-stop scale, and when a setting would run off the end of what's possible, it says so instead of quietly lying.
Middle Focal Length
The specialist. Between two marked focal lengths — say 35 and 85 — the visual middle isn't the average, because framing scales by ratio. This finds the geometric middle, and can space several steps evenly between two ends. It's the newest tool and still being verified, so treat its answers as a strong guide rather than gospel for now.
A note on formats
Every tool works from real sensor sizes: full frame, APS-C in both the 1.5 and 1.6 crops, Micro Four Thirds, one-inch, and medium format. Pick yours once and the numbers follow. It's all client-side, so it works the same on the phone in your pocket as on the desktop.