LF format sizes

**Leigh** · 10-Feb-2011, 11:41

DoF and hyperfocal distance do not change with film size.

What MAY change is the diameter of the Circle of Confusion, typically being larger for the larger formats.

But that's the only difference from 8mm through 8"x10" and larger.

- Leigh

**myoptic** · 10-Feb-2011, 12:00

Originally Posted by Leigh

DoF and hyperfocal distance do not change with film size.

What MAY change is the diameter of the Circle of Confusion, typically being larger for the larger formats.

But that's the only difference from 8mm through 8"x10" and larger.

- Leigh

Hyperfocal distance changes with lens focal length, which generally changes with format/film size, standard lenses for 4x5 are approx. 50% the length of 8x10. My apologies if I was unclear.
I'm using the formulae here .. http://www.dofmaster.com/equations.html

**Leigh** · 10-Feb-2011, 12:06

Originally Posted by myoptic

Hyperfocal distance changes with lens focal length, which generally changes with format/film size...

Of course DoF and hyperfocal distance change with lens focal length. My comment was about film size.

I certainly don't see any correlation between format and focal length. I use the same or similar focal lengths on all formats from half-frame 35mm through 4"x5".

- Leigh

**Emmanuel BIGLER** · 10-Feb-2011, 12:07

??? 13x15 ???

Hello from France !

If this size is in centimetres, it might be a typo ; after 10x15 cm, "the postcard size" an old European film size for which Voigtländer had some cameras on catalog before WW-II, comes 13x18 cm, so close to 5"x7" that both format are often considered as the same.
13x18 was widely used in Europe until the 1960's. Among Jacques Lartigue's first cameras he was offered before WW-I, there was one 13x18 cm plate camera that he used hand-held for action shots.
For DOF calculations, 13x18 cm and 5"x7" are exactly the same, but you'll have hard time to insert a "true" 13x18cm film inside a 5"x7" holder

The classical value for the circle of least confusion is equal to the diagonal of the format divided by 1720. This means an angular diameter of 2 minutes of arc for the minimum visible feature size when the print is examined at a distance equal to its diagonal. This good ol' rule is only a sound rule of thumb, a good base for computing comparative DOF charts for all formats, certainly not an absolute law of Physics like E=mc2