How to do a Focus Test
So how do you know whether your Canon 7D is really having an OOF issue? Test it of course!
A basic test is to set your camera up on a tripod and make sure that what you are going to photograph is set a minimum of 50 times further away than the focal length of your lens. The formula for this is:
•In Meters: 50 * [camera focal length]/1000
35mm Lens: (50 * 35)/1000 = 1.75 Meters
•In Feet: (50 * [camera focal length]/1000 )*3.28
35mm Lens: (50 * 35)/1000 = 1.75 * 3.28 = 5.74 feet
This ensure that depth of field doesn’t produce any softness. And when taking your shots, make sure to either use a remote trigger or the timer, this ensures no added vibrations to your shot (when depressing the shutter button).
Next, set your ISO to the lowest setting you can (to reduce noise) and set your camera to aperture-priority mode. Choose the highest f/stop of the lens (e.g. f/22).
Set your lens to manual focus and manually focus the subject you are shooting to be crystal clear. Take the shot and it is recommended to take at least 3.
Finally, set your lens to auto-focus and be sure the camera is set to Single-Shot AF. Now allow the camera to choose the focus point and again take 3 more shots.
Load the shots into whatever software you use to manager your library and compare results. 100% magnification will most likely see some slight variation for Auto-Focus, but anything ‘out of the ordinary’ would need further attention.
So how do you know whether your Canon 7D is really having an OOF issue? Test it of course!
A basic test is to set your camera up on a tripod and make sure that what you are going to photograph is set a minimum of 50 times further away than the focal length of your lens. The formula for this is:
•In Meters: 50 * [camera focal length]/1000
35mm Lens: (50 * 35)/1000 = 1.75 Meters
•In Feet: (50 * [camera focal length]/1000 )*3.28
35mm Lens: (50 * 35)/1000 = 1.75 * 3.28 = 5.74 feet
This ensure that depth of field doesn’t produce any softness. And when taking your shots, make sure to either use a remote trigger or the timer, this ensures no added vibrations to your shot (when depressing the shutter button).
Next, set your ISO to the lowest setting you can (to reduce noise) and set your camera to aperture-priority mode. Choose the highest f/stop of the lens (e.g. f/22).
Set your lens to manual focus and manually focus the subject you are shooting to be crystal clear. Take the shot and it is recommended to take at least 3.
Finally, set your lens to auto-focus and be sure the camera is set to Single-Shot AF. Now allow the camera to choose the focus point and again take 3 more shots.
Load the shots into whatever software you use to manager your library and compare results. 100% magnification will most likely see some slight variation for Auto-Focus, but anything ‘out of the ordinary’ would need further attention.
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