Field of View: How Your Lens and Sensor Collaborate

         

"Get a 50mm lens." That is a statement that many photographers will tell you. But do they mean a 50mm lens or the equivalent of a 50mm lens on your camera? Make no mistake, a 50mm lens is a 50mm lens, but sensors have magnification and crop factors depending on your camera model.


Sensor sizes

Click here to see this chart larger

Here's an old chart that shows off the different sensor sizes of various cameras. Now, keep in mind that full frame is approximately the size of 35mm film.

APS-C sized sensors are in most DSLR cameras, like the Canon Rebels and the lower-end Sony and Nikon series cameras as well. Because they are smaller than a full-frame sensor, full-frame lenses will have a crop/multiplication factor.

For Canon, this multiplication factor is 1.6x. That means that if you're using a 100mm lens, your multiplication and field of view will be an equivalent of 160mm.

For Nikon, Sony, and Pentax the multiplication factor is 1.5x. So your 100mm lens will have a field of view and equivalent of 150mm.

Four-thirds and Micro four-thirds sensors have a 2x crop. So the 100mm lens will be 200mm.

APS-H sensors are in the Canon 1D series, and have a multiplication factor of 1.3x.

Lenses

Different lenses are designed to be used with different sensor sizes. By that, I mean that there are lenses designed to be used with full-frame cameras, and lenses designed to be used with smaller sensors. Full-frame lenses can go onto APS-C bodies, and be subject to the crop/multiplication factor. If you put an APS-C lens on a full-frame body, it either won't work, or will only take a photo using a very small portion of the sensor. This is because of the size of the imaging circle around the part of the lens that goes into the body.

In the case that the circle is too small, only a small area of the sensor will be used to capture an image. If the imaging circle is larger than the camera sensor, the sensor will generally only capture the middle area of the lens's field of view—hence the crop factor.

What Does This Look Like?

To demonstrate the crop factor, I'm going to use my Canon 5D Mk II, 7D and 35mm F/1.4 L lens.

Above is a photo taken with the Canon 35mm F/1.4 L on a Canon 5D Mk II. The focal length is a true 35mm. When this lens gets mounted on the 5D Mk II, the full-frame sensor is utilizing the entire imaging circle of the lens.

When you put the 35mm F/1.4 L on the Canon 7D, you get a 56mm field of view equivalent, due to the crop factor magnification. When the lens is mounted on the 7D, the cropped APS-C sized sensor is utilizing only the center of the lens circle.

Each of the above photos was taken from the exact same location.

Discussion 5

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Hi, there is an adapter to use an APS-C lens (i.e. the tokina 11-16) on a full frame camera without vigneting? Doesn't matter if the 11-16 becomes 18-26mm cause the 1.6x crop factor.

Thanks

My Sony a7ii has a crop setting in the menu, if you turn it on it will fill the frame but lower the megapixel to approximate half. I use that same exact lens with great results on the a7ii. Not sure how it works on Canon though

Anonymous wrote:

My Sony a7ii has a crop setting in the menu, if you turn it on it will fill the frame but lower the megapixel to approximate half. I use that same exact lens with great results on the a7ii. Not sure how it works on Canon though

I've got exactly the same camera - and question. Can you help me by steering me to where on the A711 menu this option is located?

The a7S II does have an APS-C size sensor mode, which would enable one to use lenses designed for cameras with that format sensor.  In the camera’s menu, under (Custom Settings), you should see [APS-C Size Capture].  Here you could choose from three different settings:  on (the camera captures in APS-C mode), Auto (the default setting where the camera switches to APS-C when that format lens is detected), and Off (the cameral always captures 35mm full frame images). 

would have been a neat introduction to a real article.

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