Does sensor size affect depth of field?
Yes, but the direction depends entirely on what you're holding fixed, and this is the single most commonly reversed idea in this topic. At the identical real focal length, aperture and subject distance, a smaller sensor actually gives LESS depth of field, not more — its smaller circle of confusion is a stricter sharpness threshold that narrows the acceptable range on its own. The popular claim that smaller sensors are 'more forgiving' only holds when comparing the same framed shot, which needs a shorter real focal length on the smaller sensor.
Two Different Comparisons, Two Different Answers
Same real focal length, same aperture, same distance: a Micro Four Thirds camera at 24mm f/8 has meaningfully LESS depth of field than a full-frame camera at 24mm f/8, because Micro Four Thirds' circle of confusion (0.0144mm) is stricter than full frame's (0.0288mm), and a stricter threshold narrows the sharp range at any fixed real focal length. Same framed shot instead: matching a full-frame 24mm composition on Micro Four Thirds needs roughly a 12mm lens, and that dramatically shorter real focal length widens depth of field far more than the stricter circle of confusion narrows it — the net result is that Micro Four Thirds ends up MORE forgiving once you're comparing the actual photograph you'd get, not the same lens number.
Why the Popular Version of This Claim Survives
Photographers almost always compare cameras by the shot they'd actually take, not by mounting the identical real focal length across formats — nobody puts a 24mm lens on both a full-frame and a Micro Four Thirds body and calls that a fair comparison, since the field of view would be completely different. Framed correctly, the equivalent-framing comparison is the one that matches real shooting, which is exactly why 'smaller sensor, more forgiving depth of field' became the common wisdom — it's true for the comparison people actually mean, just not for the one the sentence literally describes.
Compare both scenarios directly for your own cameras in the DoF & Hyperfocal Calculator.
Frequently Asked Questions
So is 'smaller sensor equals more depth of field' true or false?
Both, depending on what's held constant — false at the identical real focal length (smaller sensor gives less), true at matched field of view (smaller sensor gives more, because it needs a shorter real focal length to match the shot). Most everyday photography conversations mean the second version.
Which comparison does the DoF & Hyperfocal Calculator show?
Whichever one you set up — enter the same real focal length for two sensor selections to see the same-focal-length comparison, or enter each format's own equivalent focal length (from the Crop-Factor & Equivalence Converter) to see the matched-framing comparison most photographers actually mean.