![]() ![]() When choosing camera/sensor-size and lenses, the main parameter defining the Depth of Field and the Blurriness of the for- and background is the *Diameter* of the aperture. Let me add another way of analysing depth of field - illustrated by your examples. I'm not really sure why that's surprising, since that's how it works. "Surprisingly the larger sensor size would require longer lenses" Just because a person is choosing each of those variables doesn't mean the person is necessary for how those variables interact. But when you reduce everything down to the most basic elements, the fact remains: Focal length, aperture, and distance-to-subject. You could say a person is responsible for depth of field in the sense that they're choosing a focal length, aperture, and focus distance. Saying sensor size affects depth of field is like saying a person affects depth of field. Doesn't add a variable, just changes the values of the existing variables. Equivalent field of view is just a different combination of those variables. So, again, for the cheap seats:įocal length, aperture (I guess I should more specifically say, F/#), and distance-to-subject. How's this for simple: the reason equivalent field of view appears to support your argument is because you're simply compensating by adjusting two of the variables that already affect depth of field: focal length and distance to subject. Depth of field operates independently of this concept, therefore it isn't an actual variable. You're adding criteria that doesn't need to exist to explain depth of field. This is the argument everybody tries to use to support the whole "sensor size affects DOF" nonsense. "To be able to photograph the same scene with different sized sensors you need to position the camera to the exact same location" Ironically, you've just made it more complicated. This shows the depth of field is not influenced by the sensor size when aperture, focal length, and distance to the subject are kept the same. This becomes visible when we enlarge part of the full frame photo to match that of the crop photo. Of course, the 120mm acts like a 192mm lens when used with the crop camera, but the depth of field is exactly the same with both sensor sizes. There are a few things that we see when these pictures are held next to one another. The distance to the subject was kept exactly the same. To test the depth of field, I placed my camera on a tripod and shot a scene with full frame and crop, with the same focal length of 120mm and both with the same aperture of f/2.8. I don't want to make it more difficult than necessary. ![]() But let us ignore this for the sake of simplicity. Although the minimum focal length of the EF-S lens is shorter, it acts like a 27mm lens.ĭepth of field is affected also by the way you view a picture, how much it is enlarged, what the viewing distance is, and the pixel density on the sensor. Two lenses at the left the EF 24-70mm and at right the EF-S 17-85mm for crop. This is visible in the example below, which shows what you capture with a full frame and a crop when using exactly the same focal length (120mm in this case). In other words, it looks like the picture is shot with the focal length of the lens multiplied by the crop factor. Thus, the picture with a crop sensor looks like it is magnified compared to what a full frame would show. Therefore, it captures only a part of what a full sensor would capture when using the same focal length. But before I do so, I find it important to realize a few things.įirst of all, a crop sensor is smaller than a full frame sensor (which is obvious). So I took a Canon 1.6x crop camera and a Canon full frame camera to make some shots and to figure out how much difference there is. (Canon 1D X 85mm f/1.2L II | ISO100 | f/1.2 | 1/250)Because I give workshops and masterclasses, I found it important to see the difference myself and to be able to explain it to my students when the question arises. Using a small depth of field can isolate your subject from the surroundings, like this shot where the bride is in focus and the hair dresser not.
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