Depth of field?
- Thread starter DJMorgan
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- Ryan
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What did you not understand from it am sure there's a good few who can point you in the right direction...
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- Nigel
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Quite simple really:
Wide aperture - massive amount of light, shorter shutter speeds, really shallow depth of field.
Small aperture - small amount of light, long shutter speeds, really broad depth of field.
Think of a pinhole camera - EVERYTHING is in focus - hence no need for a lens, then compare it to a nifty-fifty - what is in the focussing dot is spot on, and then superbly rapid drop-off of focussing moving away from that distance.
Examples:
Narrow DoF: [stands are out of focus]
Large DoF: [FG still in focus, as well as BG]
Clearer?
p.s. yes the second photo does look washed out - what can I say - I took it ages ago...
Wide aperture - massive amount of light, shorter shutter speeds, really shallow depth of field.
Small aperture - small amount of light, long shutter speeds, really broad depth of field.
Think of a pinhole camera - EVERYTHING is in focus - hence no need for a lens, then compare it to a nifty-fifty - what is in the focussing dot is spot on, and then superbly rapid drop-off of focussing moving away from that distance.
Examples:
Narrow DoF: [stands are out of focus]
Large DoF: [FG still in focus, as well as BG]
Clearer?
p.s. yes the second photo does look washed out - what can I say - I took it ages ago...
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- Richard
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Depth of field - dof - is the amount of the subject that appears to be in focus. It is a product of aperture and magnification.
Look at the drawing below
Only objects within the plane of focus are truly sharp - this is the black circle - but objects in front of and behind the subject will become less and less sharp, giving a blurred outline. The distance between the points that are acceptably sharp behind and in front of the plane of focus is the dof
With a wide aperture (low f number), in the top drawing, you can see that the angle of the light is steep and forms a wide blur at the film/sensor, therefore shallow dof, whereas with the smaller aperture (high f number) in the lower drawing, the rays of light reaching the film/sensor has a much shallower angle, so the blurring is less, hence greater dof.
Generally, dof is 2/3 behind the plane of focus and 1/3 in front, but in close-up the dof is equally distributed.
You will most often see it written that dof relies on the focal length of the lens, but this is incorrect - it depends on magnification. The shutter speed has no effect.
Look at the drawing below
Only objects within the plane of focus are truly sharp - this is the black circle - but objects in front of and behind the subject will become less and less sharp, giving a blurred outline. The distance between the points that are acceptably sharp behind and in front of the plane of focus is the dof
With a wide aperture (low f number), in the top drawing, you can see that the angle of the light is steep and forms a wide blur at the film/sensor, therefore shallow dof, whereas with the smaller aperture (high f number) in the lower drawing, the rays of light reaching the film/sensor has a much shallower angle, so the blurring is less, hence greater dof.
Generally, dof is 2/3 behind the plane of focus and 1/3 in front, but in close-up the dof is equally distributed.
You will most often see it written that dof relies on the focal length of the lens, but this is incorrect - it depends on magnification. The shutter speed has no effect.
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Have a play with this - http://www.photonhead.com/simcam/shutteraperture.php 