Clip-a-Dee-Doo-Dah : April 10, 2008
Image Data
File Name: 20D_19609
Model: Canon EOS 20D
Lens: Canon 100mm F/2.8 USM Macro
Date: 04.09.08 10:31pm
Focal Length: 100mm (160mm)
Shutter: 1/15 s
F-Stop: F2.8
ISO: 200
Program: Aperture priority
Metering Mode: Evaluative
Flash: Off
Focus Mode: Manual focus
File Name: 20D_19609
Model: Canon EOS 20D
Lens: Canon 100mm F/2.8 USM Macro
Date: 04.09.08 10:31pm
Focal Length: 100mm (160mm)
Shutter: 1/15 s
F-Stop: F2.8
ISO: 200
Program: Aperture priority
Metering Mode: Evaluative
Flash: Off
Focus Mode: Manual focus
Just a hair clip here. Not much interesting to talk about...
So I'll talk about what causes most of this photo to be blurry with just a small portion in focus. It has what we photographers would refer to a shallow depth of field (DOF).
DOF is the distance in front of and beyond the subject that appears to be in focus. Although a lens can precisely focus at only one distance, the decrease in sharpness is gradual on either side of the focused distance, so that within the DOF, the unsharpness is imperceptible under normal viewing conditions.
The DOF is determined by the subject distance, the lens focal length, and the lens f-number (aperture). For a given f-number, increasing the magnification, either by moving closer to the subject or using a lens of greater focal length, decreases the DOF; decreasing magnification increases DOF. For a given subject magnification, increasing the f-number (decreasing the aperture diameter) increases the DOF; decreasing f-number decreases DOF.
All this goes into a lot more detail, but I don't have the time or space for that...
For this photo with my 100mm lens set wide open to F/2.8, sitting 8.5" from the subject, only .3mm is actually in focus!
So I'll talk about what causes most of this photo to be blurry with just a small portion in focus. It has what we photographers would refer to a shallow depth of field (DOF).
DOF is the distance in front of and beyond the subject that appears to be in focus. Although a lens can precisely focus at only one distance, the decrease in sharpness is gradual on either side of the focused distance, so that within the DOF, the unsharpness is imperceptible under normal viewing conditions.
The DOF is determined by the subject distance, the lens focal length, and the lens f-number (aperture). For a given f-number, increasing the magnification, either by moving closer to the subject or using a lens of greater focal length, decreases the DOF; decreasing magnification increases DOF. For a given subject magnification, increasing the f-number (decreasing the aperture diameter) increases the DOF; decreasing f-number decreases DOF.
All this goes into a lot more detail, but I don't have the time or space for that...
For this photo with my 100mm lens set wide open to F/2.8, sitting 8.5" from the subject, only .3mm is actually in focus!
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