Here is a series of pictures taken with a 100 mm macro lens, each picture was taken at ISO 200, 1/125th sec, with a flash behind the subject, fired by PocketWizards.
This shows depth of field increasing as the aperture is reduced in size but everything else is held constant.
Here are two more series of pictures taken with the same 100 mm macro lens. The ones on the left were taken with a body having an APS-C sensor and the ones on the right were taken with a full frame body, from about the same position. The flash for the APS-C set was on-camera, bounced off of the ceiling, which did not reach the tennis ball very well so all pictures were brightened using Canon's Digital Photo Professional, which also converted the files from raw to JPG. Two flashes were repositioned to provide direct illumination for the full frame set which gives a much different tone. Each picture was taken at ISO 400, 1/125th, aperture is shown under the images.
The first ball is about 6 feet from the camera, each successive ball is two tiles, or just over 3 feet from the previous ball. The floor tiles are 13 inch tiles, laid with quarter inch spacers, so you can work out all the measurements if you want.
Notice that since the balls are further from the camera, the depth of field is much greater than in the pictures of the matches where the camera was only a few inches from the subject. For the picture of matches, it took f/32 to get all the matches in focus, but for the picture of the balls, f/2.8 has allowed about 2 feet to be in focus. The focus point was where the second ball met the tile. The focus point is about a quarter of the way into the picture. The tennis ball and first dryer ball seem sharpest in the f/32 image, slightly sharper than at f/22. The distance from first dryer ball to tennis ball is about 12.5 feet.
Two sizes of the pictures are presented, click an image to see the full file. Files for the APS-C sensor are about 9 MB and for the full frame are about 15 MB.
|APS-C sensor||Full Frame|
This Depth of Field Calculator suggests depth of field (DOF) will be deeper if a lens is on a full frame camera than if it is on a camera with an APS-C sensor. According to the calculator, a 150 mm lens wide open at f/2.8 on an APS-C body will have a DOF of 1.32 inches when focused at 9 feet. The calculator indicates the same lens, aperture and focus will result in a DOF of 2.16 inches. The camera data says the focus was at 3.2 m. Using 3.2 m in the calculator gives DOF values of 7 cm for the full frame sensor and 5 cm for the APS-C sensor. Some photographers have stated the opposite, that the full frame camera will provide a shallower depth of field.
Sensor size/film size within limits, certainly within the limits of a four thirds body to a full frame or even medium format body probably has no effect on depth of field. This is reasonable if the only difference between a full frame sensor and an APS-C sensor is the area of the image circle that is sampled. Pixel density is not expected to influence DOF. If you mount a 150 mm lens on the full frame body, and place it some distance from an object, the focused image will have some depth of field. If you leave the lens in place and mount an APS-C sensor body, the image should still be focused, the depth of field should still be the same. The sensor does not fill the image circle, but that is the only difference.
The way to find out what is correct seems to be to mount a lens on a body or two and try some test shots. Since 1.32 inches is just over 60% of 2.16 inches, there should be an obvious difference if the calculator is correct that sensor size makes a difference. The balls were placed at the same points as above and the camera was focused on the second ball. The tape measure is marked in feet and inches on one side and inches on the other. The end of the tape is under the centre of the tripod. The tripod's mounting plate is about 20 inches above the floor.
|Full Frame Canon 1 Ds Mk III|
|APS-C Canon 30D|
|APS-C Canon 550D/Rebel T2i|
Full frame or crop sensor, high density sensor or lower density, the depth of field looks the same to me.