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Old Mar 24, 2006, 11:49 AM   #1
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On film camera lenses, I could pick an f stop and rotate the focus ring until the infinity mark lined up with that aperture mark on the fixed ring. I was then focussedat the hyperfocal distance. To be conservative, I couldmove to the nextlarger f stop mark (5.6 when the lens is let to f8 and be sure everythingis in focus.A lens like my Canon 50mm1.4,has a distance scale butno corresponding f stop marks on the barrel to align the infinity mark. I know there are DOF calculators that will determine the hyperfocal distance. I was curious if anyone had an easy trick for AF lenses like the 50 1.4. Also, how does the 1.6sensor factor affect the DOF? Would I calculate the hyperfocal distance as if the lens were 80mm?
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Old Mar 24, 2006, 12:06 PM   #2
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Here is a handy DOF calculator. Plug in a camera model, aperture, actual focal length and focus distance for calculations. Make sure to use the actual focal length of the lens (50mm in your example).

Depth of Field will be greater when a lens is used on a camera with a smaller sensor compared to 35mm film (since the subject will fill a greater percentage of the frame for any actual focal length because of a narrower angle of view).

http://www.dofmaster.com/dofjs.html

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Old Mar 26, 2006, 1:57 AM   #3
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JimC wrote:
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Here is a handy DOF calculator. Plug in a camera model, aperture, actual focal length and focus distance for calculations. Make sure to use the actual focal length of the lens (50mm in your example).

Depth of Field will be greater when a lens is used on a camera with a smaller sensor compared to 35mm film (since the subject will fill a greater percentage of the frame for any actual focal length because of a narrower angle of view).

http://www.dofmaster.com/dofjs.html
Hyperfocal distance concerns the lens only. It matters not what body you have the lens on. Be it Canon 10D or 5D.The subject on the film or ccd will be the same size, but the ccd will be severely cropped as the focal plane is the same on both body`s. the lens does not know what body it is on.When you buy a new lens, the info supplied is for 35mm only.So the ccd sensor will only get a portion of the image from the lens. The two shots that I supplied of the scots doll showing the 50mm shot on a cropped sensor is larger due to the greater enlargment of the smaller sensor.Also shows the whole shot is cropped. Giving the impression of a telephoto lens.With its enlarged subject and smaller angle of view.
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Old Mar 26, 2006, 2:15 AM   #4
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On a cropped shot the C of C will be larger due too the enlargment. So at a given viewing distance the DOF will look less due to bigger circles.
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Old Mar 26, 2006, 2:45 AM   #5
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Why cannot I remember what too type. If you check on Calculations for D O F you will see that the c of C for a compact camera is much smaller to compensate for the amount of enlargment, Example Canon 5D = .015. Canon G2 compact .006.

Take this example. When calculating enlargment, always work with diagnols.The preview on my monitor is 150mm*100mm, diagnol = 180.27mm. The diagnol for 35mm (5D) = 43.26. The diagnol for the 10D sensor is 27.26. Divide these two sensors into the peview, the enlargment is 35mm = 4,16. The enlargment for the 10D is 6.61. So the enlargment to fill the preview frame with the 10D is greater. Result , an enlarged picture.


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