Following a recent discussion regarding DOF (depth of field), extension tubes, and a 50mm lens,
I decided to shoot an example to illustrate the differences that can be obtained by using the extension tubes
I decided to shoot an example to illustrate the differences that can be obtained by using the extension tubes
I shot four series of shots, all of them using the Canon 7D and the Canon 50mm f/1.8 lens. Because the 7D uses an APS-C sensor, the 50mm is equivalent to 80mm on a full-frame sensor. I used my tripod, cable release, and the mirror lock-up function in the camera. Each series contains 8 shots, taken at 1 stop increments from f/2.0 - f/22. The images have been converted to B&W in Lightroom and have been adjusted for contrast and exposure. They have not been cropped. In all of the images, the number 10 is the center of focus. In each of the images, pay attention to how much of the ruler is in focus on either side of the 10" mark.
This first series was shot with just the 50mm lens. The focal distance was about 23".
Notice that at f/22, the DOF is several inches, at f/2.0, the DOF has shrunk to less than one inch.
Notice that at f/22, the DOF is several inches, at f/2.0, the DOF has shrunk to less than one inch.
f/22 - 2.0 Sec - ISO 400
f/16 - 1.0 Sec - ISO 400
f/11 - 0.5 Sec - ISO 400
f/8 - 1/4 Sec - ISO 400
f/5.6 - 1/8 Sec - ISO 400
f/4.0 - 1/15 Sec - ISO 400
f/2.8 - 1/30 Sec - ISO 400
f/2.0 - 1/60 Sec - ISO 400
In the second series, I added a 12mm Extension Tube. With the addition of the 12mm extension tube, the focal distance is now about 10".
Notice that in addition to the subject filling more of the frame, the size of the DOF has gotten smaller at every stop.
f/22 - 2 Sec - ISO 400
f/16 - 1 Sec - ISO 400
f/11 - 0.5 Sec - ISO 400
f/8 - 1/4 Sec - ISO 400
f/5.6 - 1/8 Sec - ISO 400
f/4.0 - 1/15 Sec - ISO 400
f/2.8 - 1/30 Sec - ISO 400
f/2.0 - 1/60 Sec - ISO 400
In the third series, I switched the Extension Tube out for a 20mm. The focal distance in this series is about 9".
While it isn't a big jump from the 12mm tube, you can still see a difference in the amount of the frame that has been filled as well as the DOF.
f/22 - 2.5 Sec - ISO 400
f/16 - 1.3 Sec - ISO 400
f/11 - 0.6 Sec - ISO 400
f/8.0 - 0.3 Sec - ISO 400
f/5.6 - 1/8 Sec - ISO 400
f/4.0 - 1/15 Sec - ISO 400
f/2.8 - 1/30 Sec - ISO 400
f/2.0 - 1/50 Sec - ISO 400
In the final series, I used the 36mm Extension Tube. The focal distance dropped to 7".
You can see that there is a significant difference in the amount of the frame that is filled by the ruler.
In addition you can see that the DOF is significantly smaller in all of the images, especially when compared to the first series.
At f/2.0, the DOF is no more than about 1/16 of an inch.
f/22 - 6 Sec - ISO 400
f/16 - 3.2 Sec - ISO 400
f/11 - 1.6 Sec - ISO 400
f/8.0 - 0.8 Sec - ISO 400
f/5.6 - 0.4 Sec - ISO 400
f/4.0 - 1/5 Sec - ISO 400
f/2.8 - 1/10 Sec - ISO 400
f/2.0 - 1/20 Sec - ISO 400
In the second series, I added a 12mm Extension Tube. With the addition of the 12mm extension tube, the focal distance is now about 10".
Notice that in addition to the subject filling more of the frame, the size of the DOF has gotten smaller at every stop.
In the third series, I switched the Extension Tube out for a 20mm. The focal distance in this series is about 9".
While it isn't a big jump from the 12mm tube, you can still see a difference in the amount of the frame that has been filled as well as the DOF.
In the final series, I used the 36mm Extension Tube. The focal distance dropped to 7".
You can see that there is a significant difference in the amount of the frame that is filled by the ruler.
In addition you can see that the DOF is significantly smaller in all of the images, especially when compared to the first series.
At f/2.0, the DOF is no more than about 1/16 of an inch.
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