How to utilise this scale?

[Octarine]

But I think manufacturers should include this info on the LCD screen though, as it is not hard to do so since the focal length and aperture value are available on the camera.

And soon our viewfinder looks like the weapon display in Apache helicopter Distance, movements, DOF and many more all arranged in dancing scales and numbers around the viewfinder. Not sure if I'd like this or search for the "off" button

 

[two200]

Its the Infrared focus point I believe..

Thanks J-Chan

From the pic, the lens is focusing at 2 ft. If you set aperture to f/16, the DOF range will be from 0.5 to 5 ft, and anything within this range will be considered sharp.

This is actually how we derive at the hyperfocal distance. Let's think back in reverse: if we want the DOF to be from some distance x to infinity, e.g. at aperture f/16, then we'll need x to be on one side of f/16 and infinity on the other side of f/16 (remember that's how we define DOF). So, we just set infinity to f/16, and we can find out what x, and the focusing point is. Interesting isn't it?

Thanks ziploc, this makes it easier for understanding and to work in the field. I have no manual cos I bought it 2nd hand

wow... which lens is that? I've not seen that on the EF lenses I've been working on lol,
guess we entry grade DSLR users have it easy =)

Mine is Sigma 20mm f1.8

A lot of Nikon zoom lenses don't have the scale either. That's because the scale is different at different focal length. If it is not available on your lens then the other ways are to either print a DOF wheel, or download a DOF calculation software to your PDA/phone (see DOFMaster website mentioned above). But I think manufacturers should include this info on the LCD screen though, as it is not hard to do so since the focal length and aperture value are available on the camera.

I find modern lens does not have such scale. I remember my old film camera manual lens have them, just that I was too lazy to learn! :bsmilie: