35mm on 16mm

orestis lambrou · November 16, 2004

I have a question regarding focus pulling. What is the deapth of field of a lens designed for 35mm cameras when used on a 16mm camera? Should one use a 16mm kelly scale for example and just double the focal length of the lens, or simply use a kelly for 35mm? I'm confused. Any thoughts are usefull.

Cheers,

Orestis.

David Mullen ASC · November 16, 2004

Depth of field is determined by the focal length, distance focused, f-stop, and circle of confusion chosen, so if you are using a 50mm lens, use the depth of field chart for a 50mm lens, whether it is on a 16mm camera or a 35mm camera.

What putting a 50mm lens on a 16mm does is make it look more telephoto than it does on a 35mm camera, so you may find yourself chosing shorter focal lengths.

orestis lambrou · November 17, 2004

Thanks but I'm still a bit confused. For example I thought that a 50mm lens designed for 35 use, will give a result on a 16mm neg, that will be roughly the same as when a 100mm (for 16) lens is used. so if I used a chart for 16mm I would calculate the deapth of field for a 100mm lens. is that wrong? Does a 50mm lens(for 35) have the same deapth of field regardless the look it gives on the neg wether thats a 35mm or a 16mm neg?

David Mullen ASC · November 17, 2004

I'll repeat: a 50mm lens is a 50mm lens and if you use a 50mm lens, whether on a 16mm or a 35mm camera, you use the 50mm lens depth of field chart.

The field of view will look narrower when that lens is on the 16mm camera though. Hence why one might change it to a 25mm lens if one wants the same field of view, and a 25mm lens will have more depth of field than a 50mm lens, hence why shooting in 16mm tends to give you more depth of field -- because you will chose shorter focal lengths on average to get the same field of view as in 35mm. And if you switch from a 50mm lens to a 25mm lens in order to match the field of view in 35mm shooting, you'd then use the 25mm depth of field chart, get it?

Repeat to yourself: a 50mm lens is a 50mm lens whether on a 16mm or a 35mm camera... the depth of field does not change, only the field of view. So you get a more telephoto effect when the lens is on a 16mm camera, but retain the depth of field as when it is on a 35mm camera.