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What is Hyperfocal Distance and Why Should I Care? 

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The Detailed Among You May Read On

Below you'll find an explanation of the math behind calculating the hyperfocal distance for you lens/camera combination. If you use a system other than 35mm, Medium Format (4x5 or 6x6), or a digital SLR you can use this information to create a hyperfocal chart for your own system. We'd recommend downloading the Excel spreadsheet first as it will make the process a bit easier.

Understanding The Math 
Most of us can skip this part and just refer to the chart for the point on which to focus our lens. But for those wanting to calculate other formats or recalculate using a different value for the circle of confusion we've provided the formulas.

         (L x L) 
H = ------------ 
         (F x D)

H = Hyperfocal distance (in millimeters)
L = Lens focal length (i.e., 35mm, 100mm)
F = Lens aperture f-stop
D = Diameter of circle of least confusion (in millimeters)
Digital SLRs D = 0.02
35mm format D = 0.03
6x6cm format D = 0.06
4x5in format D = 0.15

Why use a different value for the circle of confusion? The constant used here is based on what is considered to be acceptable sharpness in an 8x10 print at a normal viewing distance. The problem is that "normal" and "acceptable" open the door for interpretation.

The constant we used has been around for a while and is widely accepted. But it's been argued that this constant doesn't take into account the tremendous improvements in lens design and film sharpness that we've seen over the last few years. Search around the Web for a while and you'll find numerous values to substitute for the circle of confusion constant, along with very technical sounding arguments for each that can even make it sound like the author knows what they're talking about.

In reality the markings on your lens barrel aren't all that accurate and if you're shooting with a newer lens you don't even have the lens markings going for you. That means you're estimating where the hyperfocal point is. So unless you're using and electronic rangefinder the slight differences in hyperfocal distance you'll get by recalculating with a different constant for the circle of confusion just won't make any difference for real photographers in the real world.

Also useful is being able to determine your near focus distance:

                H x D
NF =   ----------------
             H + (D - L)

NF = Near focus limit (millimeters)
H = Hyperfocal distance (in millimeters from equation above)
D = Lens focus distance (in millimeters)
L = Lens focal length (ex. 35mm, 50mm, etc.)


For the Technically Obsessed 
Let's say you're the photographer who not only has every gadget in the world but you're obsessive about details. You can get the ultimate in accuracy by purchasing an Electronic rangefinder.

The one shown here is a Disto Lite5 hand held laser meter from Leica Geosystems. It sells for around $375 and will give you accurate distance readings from 0.2 to 200 meters (8 inches to 650 feet). How accurate? How about 3mm!

A number of companies make laser rangefinder systems ranging from handheld units to tripod mounted monsters that cover big distances and cost big dollars. Will they make a difference in your photography? 

Heck no! 

But you'll have a cool toy that none of your buddies have in their camera bag. 

"Look Chuck that tree is exactly 142.69 meters away!"


Calculating Circle of Confusion for Other Formats: 

CoC = -------------- 
             1300 / d

D = diagonal of chip in mm

To find the hypotenuse (diagonal) of a film or digital format:


          a & b are the length of each side of the format. 

This constant in this formula is based on 4 lines per mm viewing resolution. 

I have seen some charts whose results are based on 5 lines per mm viewing resolution and seen it argued that 6 or even 8 lines per mm should be used in this equation. 

The fact of the matter is that substituting those constants makes no appreciable difference in the real world.

References for the mathematically inclined

Applied Depth of Field, by Alfred A. Blaker, Focal Press 
ISBN 024051730X

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