An Analog DOF Computer
Many modern zoom lenses - because of their compact size - lack the DOF scale that some older models have.
Here is a simple device serving as a kind of dummy zoom lens for DOF indication
Components / Construction
1) Get a can of approximately 5cm dia. x 8cm height
2) A piece of thin white cardboard that carries the colored f-stop lines is glued around the can.
3) In addition you need a rectangular piece of transparent film that has the distance scales (black in this example) for the focal lengths of
35 mm, 50 mm and 70 mm. The film must be slightly longer than the circumference of the can thus one of its overlapping ends can be glued on top of the other one. The cylinder made in this manner, is free to slide around the can and works just like the distance ring of a camera lens.
The example shows the gadget set to 2 m subsject distance
for a focal length of 50 mm
Read :
Far Focal Limit Near Focal Limit
Far Focal Limit Near Focal Limit f-stop= 8 : 2.5 m 1.7 m
2.5 m 1.7 mf-stop=5.6: 2.3 m1.78 m
2.3 m1.78 mA lens with DOF indication
No DOF scale here
Password: rainer
