Crop factor describes how a smaller camera sensor narrows the field of view compared with full frame – effectively making lenses appear more zoomed in. The key is knowing how it changes your effective focal length. Here’s crop factor explained.
Welcome to this quick-fire guide to understanding your camera’s crop factor and how it affects your photos. If you don’t have a lot of time right now, simply download the PDF version of this guide to read offline.
What is a Crop Factor?
All digital cameras that don’t have a full-frame sensor are referred to as cropped sensors. It means they are smaller than a full-sized one. This difference in size will reflect a difference in your photographs.
The size of your camera’s sensor will change the focal length of any lens you use. For example, a 50mm lens will never be truly 50mm on a cropped sensor.
Common Crop Factors
1.29x crop factor for APS-H Sensors (Canon)
1.52x crop factor for APS-C Sensors (Other Brands)
1.61x crop factor for APS-C Sensors (Canon)
2.0x crop factor for Micro 4/3rd Cameras
2.72x crop factor for Compact Cameras
How to Work Out Crop Factor
To work out your crop factor and how it changes your focal length simply multiply
FOCAL LENGTH X FORM FACTOR
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Examples of Crop Factor in Practise
50mm (focal length) x 1.29 (crop factor) = 64.5mm (equivalent focal length to 35mm/full frame)
85mm (focal length) x 1.52 (crop factor) = 129.2mm (equivalent focal length to 35mm/full frame)
100mm (focal length) x 2.0 (crop factor) = 200mm (equivalent focal length to 35mm/full frame)
Crop Factor Applies to Zoom Lenses Too
The same goes for zoom lenses. If you have a standard kit lens (18-55mm) on an entry level DSLR camera (APS-C sized sensor) the once crop factor is applied that lens will actually be giving you equivalent focal lengths of between 27.36-83.6mm lens
For more, read our guide to full-frame vs crop sensors.
Frequently Asked Questions
What is crop factor?
A multiplier (around 1.5x for APS-C, 2x for Micro Four Thirds) describing how much a smaller sensor narrows the field of view compared with full frame. It makes lenses behave as if more zoomed in.
How do I calculate effective focal length with crop factor?
Multiply the lens’s focal length by the crop factor. A 50mm lens on a 1.5x crop body frames like a 75mm on full frame; on a 2x Micro Four Thirds body, like a 100mm.
Is crop factor good or bad?
Neither, just different. It gives extra reach (great for wildlife and sport) but a narrower view (so wide-angle shots need wider lenses). It is a trade-off, not a fault.
Does crop factor change my aperture?
The f-number stays the same for exposure, but the smaller sensor gives more depth of field at a given aperture and framing, so backgrounds blur a little less than on full frame.
How does crop factor affect wide-angle shots?
It narrows the view, so you need a wider lens to get the same broad framing. A 24mm lens on a 1.5x crop body frames like a 36mm, less wide, which matters for landscapes and interiors.