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Crop Factor Calculator for Wildlife Photography

On a crop-sensor body a telephoto frames an animal the way a longer lens would on full frame — a 200-600mm on a 1.5× APS-C body frames like 300-900mm. What that buys in practice is more pixels on a distant subject. Exposure stays exactly the same, while depth of field and noise follow the smaller sensor.

Crop Factor Calculator for Wildlife Photography

Open the Crop Factor Calculator

Recommended settings

  • Sony, Nikon and Fujifilm APS-C (1.5×): a 200-600mm frames like 300-900mm, a 100-400mm like 150-600mm.
  • Canon APS-C (1.6×): an RF 100-500mm frames like 160-800mm.
  • Micro Four Thirds (2×): a 100-400mm frames like 200-800mm.
  • Exposure doesn't convert: f/6.3 is still f/6.3 for shutter speed and ISO on every format. Only for depth of field and total light gathered (and so noise at the same output size) does f/6.3 on APS-C behave like roughly f/9.5 on full frame.
  • Shutter speed: apply the reciprocal rule to the equivalent focal length, not the printed one — 600mm on a 1.5× body means about 1/1000s or faster without stabilisation. Birds in flight commonly need 1/2000s or faster whatever the format.

Tips for this niche

  • Compare pixels on the animal, not equivalent focal lengths. A 24MP full-frame file cropped to APS-C framing keeps about 10.7MP; a 26MP APS-C body with the same lens fills that framing with all 26MP.
  • A full-frame body in APS-C crop mode gives the same framing as a 1.5× body, but only its share of the pixels: a 45.7MP sensor drops to about 19-20MP, a 61MP sensor to about 26MP.
  • Teleconverters stack with the crop factor: a 1.4× costs one stop and a 2× two stops, and autofocus can slow down. A 200-600mm f/5.6-6.3 with a 1.4× on a 1.5× body frames like 420-1260mm at about f/8-f/9.
  • Distance still beats focal length. Over long distances, especially across warm ground or water, heat shimmer and haze soften the image however much equivalent reach the format gives — fieldcraft and hides that get you closer improve sharpness more.

Got your Wildlife settings dialed in?

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Want the full lesson?

This topic is covered in depth in Lesson 5: Advanced Focus & Motion Techniques.

Example scenario

A robin, about 14cm long, on a branch 8 m away, shot with a 600mm lens. On a 1.5× APS-C body (sensor 23.5mm wide) the frame covers about 31cm at that distance, so the bird fills about 45% of the width — roughly 2,800 pixels across it on a 26MP sensor. The same lens on a 24MP full-frame body covers about 48cm; the robin fills about 29% of the width, roughly 1,750 pixels. The calculator gives the 900mm-equivalent framing; the extra detail comes from the denser pixels, which is why the comparison only holds when the megapixel counts are similar.

Common mistakes

  • Converting the aperture for exposure. f/5.6 on APS-C needs no more light than f/5.6 on full frame. The converted aperture only matters when comparing depth of field and noise between formats.
  • Assuming a crop body always out-resolves full frame. a 45.7MP full-frame file cropped to APS-C framing has fewer pixels on the bird than a 26MP APS-C body, but a 61MP file cropped the same way has about as many. Compare the pixels inside the frame, not the crop factor.
  • Setting shutter speed from the printed focal length. a 400mm lens on a 1.6× body frames like 640mm, and camera shake is magnified to match. 1/400s that works on full frame can blur on the crop body.

FAQ

Does a crop sensor give more reach for wildlife?
It gives a narrower field of view from the same lens — 600mm frames like 900mm on a 1.5× body — and, at similar megapixel counts, more pixels on a distant animal. It does not change the exposure.
Is f/6.3 on APS-C the same as f/6.3 on full frame?
For exposure, yes: same shutter speed and ISO. For depth of field and overall noise at the same output size, it behaves like about f/9.5 on full frame.