We bet that you have heard the phrase ‘crop factor’ maybe without even knowing what it meant. However, if you look at your camera’s technical specifications, you will see that it says 1.6x, 1.5x, 1.3x, or 1x crop factor. But what do these figures mean and what do they have to do with image quality?
In this article we’ll talk about megapixels, sensor size of your camera, image quality, and depth of field in order to explain you what crop factor really is in simple words. Check it out!
We may guess that earlier, when you knew almost nothing about photography and were about to purchase your first point-and-shoot camera, you though that the more megapixels your camera has, the better photos it makes. But then you started learning more and more about your hobby and found out that the number of megapixels doesn’t matter too much if your camera has a small sensor.
And that’s true indeed. Just imagine yourself a puzzle game. It’s great when there are a lot of puzzle pieces, but would they serve you if the puzzle game is made of, say, 200 pieces and you have 1000? Of course not. And that’s exactly what happens with megapixel number and sensor size.
The standard sensor size is 35mm, which is also called full frame. To be more exact, it’s 36x24mm and only professional DSLR cameras are fitted with it. A 35mm sensor is the standard and therefore it has crop factor of 1x.
However, the majority of entry-level DSLRs have different crop factors like 1.5x for Nikon DSLRs (23.6x15.7mm) and 1.6x for Canon DSLRs (22.2x14.8mm). Fixed-lens DSLR cameras usually have a four thirds sensor and point-and-shoot cameras usually have the smallest sensors possible.
Well, now you understand what crop factor is. But what does it influence and why is it so important?
Firstly, the bigger your sensor size, the more information will be included in one shot. In other words, a camera with 1.5x crop factor will capture a picture 1.5 times smaller than a 35mm sensor camera.
Secondly, different lenses are used for crop cameras (those that have a sensor smaller than 35mm) and full-frame cameras. Together with the image size, the focal length of your lens will also change. In order to calculate the focal length of your crop lens on a 35mm sensor camera, just multiply its focal length by the crop factor of your crop camera.
For example, if you use a f/1.8 50mm prime lens on a Canon 1100D camera, which has the crop factor of 1.6x, your 35mm lens equivalent will be 81mm. However, you should mind that though you can calculate the 35mm focal length equivalent of your crop lens, you won’t be able to use it on a full-frame camera unless you want to get a photo with black edges.
Thirdly, the sensor size, and therefore the crop factor, has to do with the depth of field in lenses. Let’s take the same f/1.8mm prime lens on a Canon 1100D camera. The 35mm depth of field equivalent for this lens bearing in mind the crop factor of 1.6x will be f/2.8.
In other words, by multiplying the focal length of your crop lens by the crop factor, you will find out the aperture value that will give you the same bokeh on a 35mm camera and full-frame lens. You can also calculate the focal distance the same way, be sure to use these advanced focal length and depth of field calculators.
But please remember that irrespective of your crop factor, the amount of light getting into your lens will be the same at f/1.8, f/2.8, or f/29. We’re talking only about the depth of field equivalency here.
And now the most important question. Why do you need to know all of this? The answer is simple. You won’t use a 1.5x or 1.6x sensor camera all your life if you’re planning to go professional. In this case you will need to do all calculations of focal length and depth of field equivalents well beforehand buying new lenses.
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