Field Reference Card Pack — FocalMath

A printable, personal-use PDF built for the moments a phone screen is the wrong tool — cold weather draining your battery, harsh glare washing out the display, or simply wanting one less thing to fumble with while your hands are full of gear. Print it, fold it, keep it in your bag.

What's Inside

• Four hyperfocal-distance tables, one per common sensor format (full frame, APS-C, Micro Four Thirds, 1" type), each covering 8 focal lengths across 5 apertures, so you can check a hyperfocal distance without pulling out a phone.
• Two astro quick-reference tables (full frame and APS-C) showing both the 500 rule and the more accurate NPF rule side by side across common focal lengths and wide apertures, for planning a Milky Way or star shoot at a glance.
• An exposure-compensation cheat sheet: an ND-filter shutter-speed conversion table (ND2 through ND32000, twelve metered speeds) and a full-stop equivalent-exposure ladder for trading aperture, shutter speed and ISO against each other.
• A formulas page listing the exact math behind every table, so you can verify or extend any number by hand.

Why a Printed Reference Still Matters

Every calculator on this site works better than a static table for computing a specific result — but a phone has real limitations in the field that a piece of paper doesn't. Cold weather drains batteries fast, and a dead phone means no calculator at all. Bright sunlight can make a screen nearly unreadable at exactly the moment you need to check a number quickly. And some photographers simply prefer not adding another screen check to a workflow that's already screen-heavy through the camera's own menus and playback. A printed card sidesteps all of that.

Delivery

The PDF is delivered by email within 24 hours of purchase, for personal, non-commercial use. It's sized to print on standard letter or A4 paper and fold to fit a typical camera bag pocket. If you'd rather laminate it for durability in wet or humid shooting conditions, the layout is designed to survive that process without losing legibility at typical laminate thicknesses.

Who This Is For

Landscape and astro photographers who shoot in remote locations with limited phone signal or battery access get the most direct value, since those are exactly the conditions where a phone-based calculator is least reliable. It's also useful as a teaching aid for anyone introducing someone else to manual exposure and depth-of-field concepts, since having the numbers on paper in front of both people makes the underlying relationships easier to point at and discuss than passing a phone back and forth. And for anyone who simply prefers a physical reference over another app, it's a genuinely useful item to keep in a bag long-term rather than a novelty purchased once and forgotten in a drawer.