Hyperfocal sharpness

[Linda Barzini]

Hyperfocal has 2 definitions.

Definition 1: The hyperfocal distance is the closest distance at which a lens can be focused while keeping objects at infinity acceptably sharp. When the lens is focused at this distance, all objects at distances from half of the hyperfocal distance out to infinity will be acceptably sharp.

Definition 2: The hyperfocal distance is the distance beyond which all objects are acceptably sharp, for a lens focused at infinity.
The distinction between the two meanings is rarely made, since they have almost identical values. The value computed according to the first definition exceeds that from the second by just one focal length.

Are both equally sharp, whether you focus on the nearest point or infinity? My dof calculator tells me they are about the same, but it seems significant if the lens is focused at 20' or infinity. Has anyone noticed any difference in sharpness, either to foreground or distant background, at these 2 different focus points?

 

[Satsuki Murashige]

There are a few variables to consider when calculating focus splits. One is the sharpness and optical characteristics of the particular lens being used. A softer vintage lens being used at the same stop as a Zeiss Master Prime will be less critical. Two is the degree of magnification of the final image - a shot that will be compressed and only viewed in 1080p on the web will be less critical than one that will be projected in 4K on a 30' screen. In the latter case, it would be a good idea to choose a smaller circle of confusion for your DoF calculator and shoot a test to make sure you're good.

Just in general though, in this age of 4K+ digital cameras and 4K+ delivery I would err on the conservative side and take DoF calculator results with a big grain of salt. A lot of 1st ACs these days more or less live by the approach that the focus is either dead-on or soft. So I think definition #1 more or less is dead for high resolution digital production. Just my opinion though.

 

[Ilya O.]

What Satsuki says.

Dof calcs are based on the circle of confusion diameter of the film era.
Today the only right way is to monitor picture at its native resolution, or at least at 1:1 pixel display or magnification.

If we believe DOF calc with the circle of conf of 0,03mm (film standard) it occurs that lets say Tokina 11-16 f2,8 does not need focus ring at all since everything will be inside hyperfocus. But that is not true nowadays and this 11-16mm needs very precise focusing to be spot on! You either there, or not, and is very cleanly seen at native resolution.

 

[Björn Benckert]

The difference is due to the fact that its not a constant curve. From the focus point the focus falls of faster towards camera then infinity. So its better to have a slighly short focus set than long. In other words if your actor is in focus and takes a step towards camera is much worse than the opposite.


Hyperfocus is not an exact science. The charts where used a lot when cameras only had small dark viewfinders and shitty video feed at best. Then it was allways a bit sketchy to know what could actually be considered sharp and what would be out of focus. Today it can still be difficult, looking at small HD touchscreens, things might look splendid, then projecting it on a huge theater or 4k screen it makes the out of focus stuff look unacceptable. So viewing format is a parameter thats important, so is the type of lens and capturing format.

We use the charts at times when preprograming milo moves to know what will actually be sharp and what not. Something which is difficult to judge when looking at a 3D animatic that is often rendered without dof. But I find the charts we use to be a bit over optimisic. They might worked well when there was a lot of grain and sharpness was a bit soggy all over as its been trough the lab / printing positve process.

Same thing if you use a soft filter then that kind of improves the range of what you think is the acceptabe focus range as the soft / diffusion filter kind of takes down the focus spikes and makes the image more even. Roy Andersen shoots alot of with a 18mm ultra prime, soft filter and fixed focus that is set to a focus point that gives best coverage to the whole scene and vari Fstop toget enough range.