What is crop factor?

When I first start taking photos with a DSLR, one of the most confusing term is "Crop factor". Take a bit of time to Google will provide you with a lot of technical explanation and samples comparing the images of different sensor, but how does it really affect a casual hobbyist like myself?

The main purpose initially is for user that shifted from film(35mm) to understand the change in focal length or to make people that start with a entry DSLR that stumble upon the term "crop factor" miserable :-(

Took me quite a while to understand how the sensor size will affect the photos. IMHO I concluded that it cause more confusion than helping people understand them since most hobbyist NEVER USED a 35mm before or had more than 1 camera that have different sensor size...

To summarize, I just put up some points that I think will affect our daily usage

1. The sensor size is different, so the photo capture by the lens of the same focal length will be different (refer to image below). If you used a 80mm lens for a Full frame camera, the photo taken will be identical to a smaller size sensor photo if the lens used is divided by the crop factor. eg. A photo taken with a Canon full frame camera using a 80mm lens will have a same result as a photo taken wtih a Canon smaller size sensor using a 50mm(80mm/1.6)

Example of image capture by different sensor with same focal lenght lens

2. Since crop factor affect the field of view of the photo taken. You can shoot a photo with a Full frame camera and a smaller sensor camera at the same subject, from the same distance with the same lens. The image capture by the Full frame sensor angle of view will be wider than the smaller sensor (multiply by crop factor). If you crop the image from the Full Frame sensor to have the same Field of View as the smaller sensor photos, they will be IDENTICAL (refer to the same Image).

3. Depth of View is affected by Crop factor because it is affected by the "focal" lenght and distance it is view from, but it is still the SAME IMAGE with around 30%(for canon DSLR) been crop off. Don't worried about it too much, DOF is just a guideline of the relative distance from the subject that is in focus.

4. You do not mulitple the crop factor in when calculating the minium shutter speed to stablize your camera. (1/focal length)sec

5. A smaller sensor do not actually INCREASE the focal length of your lenses. It just look bigger.

6. NO, you don't get more "bokeh" by multipling the crop factor to your lenses compare to a Full Frame camera. In fact you normally got less because you have to move further away from your subject...


Hope it helped :D