aryagoel1
Part 1 - Image 1 (f/5.0)
The lens used is a Canon EFS 18-135mm Marco Lens. The focal length of the image is 71mm with aperture of f/5.0. So N = 5.0 and f = 71. The camera shot is 600mm (60 cm) from the subject at focus, so U = 600. The only remaining variable is the size of the circle of confusion which for my camera was 0.02, C = 0.02.
Therefore, plugging the information into the formula gives me: (2CNU^2)/(f^2) = (2(0.02)(5.0)(600)^2)/(71^2)
= 14.3mm is the expected DOF when ruler is horizontal.
However, the ruler is foreshortened, because it's at an angle of 45 degrees. 14.3 mm of depth being in focus should mean a space of sqrt(2)*14.3 mm on the ruler looks sharp. Sqrt(2)*14.3 = 20.2 mm.
Looking at the image, I would say it's in focus between the 17 cm mark and the 19.5 cm mark. That's 25mm, which is pretty close to the calculated value... Success!
Part 1 - Image 1 (f/5.0)
The lens used is a Canon EFS 18-135mm Marco Lens. The focal length of the image is 71mm with aperture of f/5.0. So N = 5.0 and f = 71. The camera shot is 600mm (60 cm) from the subject at focus, so U = 600. The only remaining variable is the size of the circle of confusion which for my camera was 0.02, C = 0.02.
Therefore, plugging the information into the formula gives me: (2CNU^2)/(f^2) = (2(0.02)(5.0)(600)^2)/(71^2)
= 14.3mm is the expected DOF when ruler is horizontal.
However, the ruler is foreshortened, because it's at an angle of 45 degrees. 14.3 mm of depth being in focus should mean a space of sqrt(2)*14.3 mm on the ruler looks sharp. Sqrt(2)*14.3 = 20.2 mm.
Looking at the image, I would say it's in focus between the 17 cm mark and the 19.5 cm mark. That's 25mm, which is pretty close to the calculated value... Success!