Crop Factor Explained

One term that you’re certain to come across when researching your next DSLR purchase is ‘Crop Factor’.

This is a slightly complex topic and many long article have been written explaining it – but to keep it simple let me attempt a short explanation.

While normal film cameras take 35mm film (it is a standard for the industry) there is much variety between manufacturers on image sensor sizes. The main reference point that people therefore use is the 35mm one which is considered ‘full frame’ size.

If you compare the size of the film in a normal SLR (film is 35mm) to the image sensor in most DSLRs you’ll find that the size of the DSLRs sensor is generally smaller (unless you get what’s called a ‘full frame’ DSLR).

Until recently ‘full frame’ cameras were largely in the realm of professional DSLRs and all lower end cameras had smaller sensors.

If you take a photo with a smaller sensor and the same lens it will only show a smaller area of the scene.

To illustrate this I’ve show how different cameras with different image sizes will see an image.

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Black – Full Frame

Red – 1.3x Crop Factor

Yellow – 1.5x Crop Factor

Green – 1.6x Crop Factor

When you enlarge images to the same size from different sensors the ones with the smaller sensors will be enlarged more – making it seem bigger.

As a result – when you fit a lens to a camera with a smaller sensor the lens is often said to have a larger equivalent lens size.

I’ve included a table below that shows the equivalent lens sizes for different crop factors. The column on th left is the lens focal length on a full frame camera.

So what crop factor does your DSLR have? Here’s some of the most popular ones.

1.3x – Canon EOS 1D/1D MkIIN

1.5x – Nikon D40/D50/D70/D70s/D80/D200/D2XD2Hs Minolta 7D/Fuji S3 Pro Pentax *istDS/K100D/K110D/K10D

1.6x – Canon EOS 300D/400D/20D/30D

2.0x – Olympus E-400/E-500/E-300/E-1