Perhaps you have heard the term “crop factor” before, but you’re not sure what it really means. If that’s the case, you’re probably also unaware of what an important part it plays in making the most of your digital camera. The camera settings we still use–ISO, aperture, and f-stop–were designed for film and do not take into account the wide variety of sensor sizes used by digital cameras; we use crop factor to account for these shortcomings in camera design. If you use a camera with a smaller sensor, the following video could completely change the way you shoot:
What is Crop Factor?
So, what is crop factor, anyway? As Tony Northrup tells us, it is the size ratio of smaller sensors to a 35mm film frame. For example, a Micro Four Thirds sensor is half the size of a 35mm frame, so it has a crop factor of 2. It might seem logical that full-frame cameras, whose sensors are the same size as 35mm frames, would naturally make better pictures, since they have a larger sensor and can take in more photographic information. However, Northrup shows us that this is actually a myth. And he tells us how to take photographs with smaller-sensor cameras that are just as good.
There are a number of camera settings that must be adjusted by the crop factor:
- Focal Length – A camera with a smaller sensor will make an image appear closer, even with the exact same lens and focal length. Focal length must be reduced according to the crop factor to achieve the same angle of view.
- ISO – The ISO standards were created decades ago and were meant for film; they measure the amount of light captured per square inch, not total light captured by the sensor. To account for this, divide a given ISO by the square of your camera’s crop factor.
- Depth of Field – Smaller sensors give your camera more depth of field, even on the same f-stop as a full-frame camera. If you want a shallower depth of field, be sure to increase BOTH the aperture (by the crop factor) and the ISO (by the crop factor, squared), so that your camera receives the right amount of light.
To better understand these concepts, let’s take a look at some examples:
The above image shows three photographs of a white wall (which appears gray), taken with three cameras of different sensor sizes. The ISO, aperture, and shutter speed were exactly the same for all three. But as you can see, the smaller the sensor size, the noisier the image looks, because smaller sensors receive less total light.
These photos were taken with three different cameras as above, but the crop factor has been applied. The appropriate ISO makes it possible to take a relatively noise-free photograph, even with a small sensor.
Above is a great example of everything the crop factor can do, in one image. The photograph on the left was taken with a full-frame camera; on the right, with a Micro Four Thirds camera (with a crop factor of 2). The focal length on the left is 100mm; on the right, 200mm. As you can see, though the settings are different, the two photos have a similar viewing angle, depth of field, and brightness. They are not exactly the same, but they’re very close!
Are You Being Scammed By Your Lens Manufacturer?
Dishonest marketing by several camera companies fails to account for all aspects of crop factor. This leaves many photographers disappointed with their purchases and unable to get the results they’re looking for. Northrup suggests you stick with gear from Nikon, Canon, and Fuji, as these companies are more truthful in their advertising. But, by understanding crop factor, you can make smarter purchasing decisions next time you’re in the market for a lens from any manufacturer.
Applying crop factor also helps you get better photos using the gear you already own. Though full-frame digital cameras are more expensive and are often thought to be objectively “better” than those with smaller sensors, Northrup has debunked this myth by showing us that image quality doesn’t have to suffer if you do the right math.
“All you have to do is apply the crop factor appropriately, and you can get exactly the same image with small sensors.” – Tony Northrup
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