hyperfocal distances

[GooniesNeverSayDie11]

This may be a sort of stupid question...

Lets say a hyperfocal distance is 1.5ft. Does that mean 1.5ft in front of the camera lens, or does it mean a perceived 1.5 feet in the actual frame. Like should I hold a piece of paper up to focus on it or just choose my lower most focusing point and maybe tilt the camera just slightly to focus on something that APPEARS to be about foot within the frame? Thats the only part I can't seem to find a clear answer on. The reason I ask is because with a superwide lens at say f/16 or f/22 and 10mm, Hyperfocal distance almost seems irrelevant because if you focus on something low in the frame, the minimum Focus should be well out of frame and almost at your tripod feet or whatever. So why would you even need to try to calculate, just shoot low in the frame and you would be safe almost every time if you were using really wide angles.

 

[pgriz]

Focusing at the hyperfocal distance puts the far side of the depth of field at infinity, and the near side at a value where a point souce will yield an “out-of-focus” blur less than (or equal to) the circle of confusion (for your camera/sensor).

The hyperfocal distance varies according to the focal length, the sensor, and the f/stop that is used. According to the tables that I found at www.dofmaster.com, a 10mm lens on a sensor that has a circle of confusion of 0.019mm, will achieve hyperfocal distance when focused at 1 ft. at f/22. In this scenario, the near focus point will be at 5.3 inches. The exact same lens and camera/sensor, focused at 1 ft. with an aperture of f/8 will have a depth of field ranging from 8.3 inches at the near point, and 1’9.7” at the far edge of the range.

In practical terms, knowing the hyperfocal distance allows you to know if you focus at an object at that distance, everything beyond that point will be in focus, and that the focus will extend from the focus point to somewhere closer. Usually, once you’ve determined the range over which you need to achieve acceptable sharpness, you set the focus by using the distance scale on the lens, rather than focusing on an object (you may not actually have an object at the right point).

On a prime lens, the f-stops are marked on either side of the focusing center point on the lens barrel. To achieve hyperfocal focusing with this type of lens, you just align the f/stop you are using against the infinity mark. You can also read off the near distance off the distance scale, against the same f/stop on the near side.

Zoom lenses don’t have the f/stops engraved on the barrels, so to get the same information, you need to use tables.

 

[davebmck]

This may be a sort of stupid question...

Lets say a hyperfocal distance is 1.5ft. Does that mean 1.5ft in front of the camera lens, or does it mean a perceived 1.5 feet in the actual frame. Like should I hold a piece of paper up to focus on it or just choose my lower most focusing point and maybe tilt the camera just slightly to focus on something that APPEARS to be about foot within the frame? Thats the only part I can't seem to find a clear answer on. The reason I ask is because with a superwide lens at say f/16 or f/22 and 10mm, Hyperfocal distance almost seems irrelevant because if you focus on something low in the frame, the minimum Focus should be well out of frame and almost at your tripod feet or whatever. So why would you even need to try to calculate, just shoot low in the frame and you would be safe almost every time if you were using really wide angles.

To answer your question, if the hyper focal distance is 1.5 feet, that means you should focus on a point 1.5 feet in front of the camera (in front of the focal plane actually). When you do that, everything will be in focus from infinity to half the focal distance, in this case 3/4 of a foot.

 

[KmH]

Hyperfocus is illustrated and explained here: Online Depth of Field Calculator and here http://www.cambridgeincolour.com/tutorials/hyperfocal-distance.htm

Circle of Confusion - http://en.wikipedia.org/wiki/Circle_of_confusion (also relevent to the quality of bokeh)

Airy Disk - http://en.wikipedia.org/wiki/Airy_disk

 

[Mike_E]

Here you go... Digital Photography Tutorials

 

[GooniesNeverSayDie11]

I understand hyperfocus, and have looked at the charts. Its not an issue of knowing the correct number, its the issue of knowing how to apply that number correctly which it seems none of the articles specify. ( I had read both of the articles mentioned here, I have a DOF calculator on my phone, and I have a chart downloaded to my comp. ) For instance, lets say that the hyperfocal point is 10FT. Well if I am using a lens and the closest piece of foreground in the frame is already 8 feet away from me, do you go 10 feet from that, or do you focus 2 feet in front of that which would be 10 ft from the focus plane. ( in which case, 1/2 the hyperfocal distance would be 5 feet from the focus plane, which wouldn't even be in the frame, so technically you could have focused further into the shot. Thats what was leading to the confusion in my thought process ) Davebmck answered it. Thanks for the help guys.

 

[Garbz]

its the issue of knowing how to apply that number correctly which it seems none of the articles specify.

You look at the focus gauge on top of the lens and line up the line at the hyperfocus distance. The depth of field will extend from half of the hyperfocus distance to infinity.

Say I have an object 2m in front of me and I want it AND the background to be in focus. Then I would calculate the aperture I need for a hyperfocus distance of 4m. Set the lens to 4m and everything from 2m to infinity should be in focus.


The problem is that focus and sharpness is a term that is used as absolutes these days whereas for application of hyperfocus distance you need to consider the word "acceptable sharpness". The reality is the object 4m away will still be sharper than the object 2m away or at infinity, but hopefully if the math is right you won't notice the difference when displaying the picture on a given medium. I.e. Hyperfocus distance is much closer for a given aperture when taking a picture which will ultimately be printed 6x4 than a picture that will be plastered on the wall.