Crop-Factor & Equivalence Converter

How to Read This Result

Two numbers come back, and they answer two genuinely different questions. The field-of-view equivalent tells you what focal length on your comparison format would frame the same scene the same way. The depth-of-field equivalent tells you what f-number on your comparison format would produce roughly the same depth of field, once you're framing identically — and this number is usually different from your actual aperture, which is the single most commonly misunderstood idea in this corner of photography.

The Part Everyone Gets Wrong

A 35mm f/2.8 lens on APS-C is not "really" an f/4.3 lens. Your camera meters, exposes, and lets light through exactly as an f/2.8 lens does — the shutter speed and ISO you need for a correct exposure are identical to what a full-frame camera would need at f/2.8 in the same light. What changes is depth of field: an APS-C body at 35mm f/2.8 already has more depth of field than a full-frame body would at the longer, framing-matched real focal length (about 54mm at this site's 1.5x-labeled, 1.53x-computed APS-C crop) and the same f/2.8 — to get that same field of view AND the same depth of field on full frame, you'd need to stop down to a narrower aperture, about f/4.3, not open up — which is why full frame is often described as having a shallow-depth-of-field advantage, even though exposure itself never changed.

Why This Matters in Practice

If you're comparing a lens across two systems for background blur or portrait work, the depth-of-field equivalent is the number that actually predicts what you'll see. If you're comparing for framing — will this lens capture the same scene on my new camera as it did on my old one — the field-of-view equivalent is what you want. Conflating the two is where most of the confusion around crop factor actually comes from.

A Common Use Case

Photographers switching systems — moving from APS-C to full frame, or the reverse — use this tool most often to figure out which lens in a new system replicates a favorite combination from the old one. Enter your old setup as the source and the new system as the target, and the two results tell you both what focal length reproduces the same framing and what aperture reproduces the same background separation, which are rarely the same lens spec you'd guess by intuition alone.

Reading Direction Matters

Set your CURRENT setup as the source and the system you're CONSIDERING as the target — the calculator is directional, and swapping source and target reverses which sensor's dimensions drive the equivalence math. This matters most when comparing formats with a large size difference, like full frame against Micro Four Thirds, where the two directions produce genuinely different numbers rather than simple inverses of each other.