Hyperfocal Distance

When shooting landscape shots, you will likely want the greatest depth of field your lens can achieve.  The greatest depth of field your lens is capable of is acquired by focusing at your lenses’ hyperfocal distance. Hyperfocal distance is not a set distance of your lens, it varies with both your aperture and detail demands. The more detail you demand, the more detail you can extract by adjusting your formula.

When you focus your lens on a subject, some areas will be in focus and other areas will be out of focus.  The area in focus is covered in your depth of field, and is considered to be within the focal plane.   When you focus at the hyperfocal distance point, everything from half the distance of Hyperfocal Point and back to infinity will be in focus. Think of your depth of field as an area in front of a focal point, and behind it all of which also appear as focused and/or sharp.

Hyperfocal distance is calculated as the following:

H =  (focal length^2)/(aperture x Circle of Confusion)     
The circle of confusion on the  canon XSI is .019 a default setting provided by this site.

so the hyperfocal distance for  a 17mm  lens at  5.6 aperture on the Xsi = 
(17×17)/(5.6x.019) = H = 2716.16 mm   or  2.71 meters    

This means, at an aperture of  5.6   and a focal length of  17mm on your Canon XSi  your lens hyperfocal distance point is  2.71 meters (8.8 feet) away.  So how does this help you?   It basically indicates that if you focus at something 2.71 meters away then all subject matter from  half the distance of your focus point to you, and all the way to infinity will be in focus.   So  4.4 feet  to infinity would be in focus, if you focused at 8.8 feet.  This is a helpful understanding of depth of field, and will prevent you from suffering diffraction by using too narrow of an aperture.  Try to avoid anything over F11 if possible when using normal non macro lenses.

In this image I used 17mm and 8.0 aperture. I focused on a target 6.3 feet away (the yellow boat tie) as you can see because I focused at the hyperfocal distance of my lens at the selected aperture, I was able to get everything from approximately half way between me and the yellow subject matter and onward to infinity as sharp and in focus. I like this example because it shows you how the bench I put my camera on is not quite in focus, outside the depth of field but as we approach the end of the bench and hit the sidewalk in front of it we are now within the depth of field. Also take note that the bridge and trees in the background are of adequate sharpness to appear in focus.

So this was a very simplified explanation, and you may still have questions.  One major question might be, well how do I know how far away a target is?   Well there is really no great answer to this question…  The good news is,  wide angle lenses such as the 17-40 L are appropriate for this technique and are easier to implement the hyperfocal distance.

 

Wide angle lenses have much closer focusing distances for their hyperfocal points. As the previous calculation indicated, 8 feet away would be the appropriate focal point for the hyperfocal distance of a 17mm lens at 5.6 aperture. You can pretty easily figure out a relatively accurate estimate of 8 feet away from you. If you can’t, you can always grab a tape measure and figure out how far away it is. After a few times of using your preferred lens, you’ll get a good idea of the distance these calculations come up with.

Telephoto lenses dont really benefit from this technique, and while it will work …. there isn’t much point to using a telephoto for this type of shot. A telephoto lens can have 100′s of feet for the hyperfocal distance, a large contrast to the 8 feet required by the 17mm lens.

You will also want to use a tripod, a self timer or remote, and if you really want to get the best results you will also use the custom function for mirror lock to reduce vibrations.

What about focusing at infinity? I read online that I should focus at infinity and then drop the aperture down? That this technique was superior than the hyperfocal distance.

When shooting a landscape shot, if you want the entire scene to be in focus and sharp, you would use hyperfocal distance. If you are literally only capturing a subject at infinity or far in the background, and have nothing in the foreground what so ever… then focus at infinity would be ok.

Now, there is a publication out there which is free for download it was written by Harold Merklinger. If you read his publication, he basically attempted to discover a new method of focusing. Merklinger goes on to state he is able to extract more detail by focusing at infinity and then dropping aperture, thereby getting more detail from far subject matter then hyperfocal distance is capable of.

Many people will say, focus at infinity and link to this guys publication as PROOF!

Merklinger, for whatever reason felt his method was worthy of promotion. Many people take it as some type of expert method. However, I disagree with Merklinger’s method and even he has addressed its short comings in his book. He does not compare and contrast hyperfocal and his method to enough degree to actually validate his method. 

The two methods compare very similarly and in fact  his method is just a form of reducing the COC of your equation to the smallest possible.  If you reduce your COC to the smallest possible, you have diminished your ability to capture your near subjects within the depth of field.

Merklinger, wants people to focus at infinity, and then drop aperture down in order to create more DOF in front of the focal point. He has a photo with a canon in the foreground and a small village in the background. Merklinger states that had he used hyperfocal distance, he could never have acquired the details of the village he was able to. He then states, the canon and grass are a bit fuzzy in the foreground, but they are “recognizable”.

If I were in the same situation, I could have estimated how far away the canon was, and calculated a hyperfocal distant point that would have allowed me to extend the DOF between the Canon and village were both resolved with excellent detail.  When I take a photo, I always shoot for the best that I can.  I like the idea of using front and rear depth of field zones. 

The fundamental flaw of Merklinger’s claim is that although he admits the circle of confusion for hyperfocal distance can be adjusted, he does not implement it in his comparisons. He stays with a fixed COC of .035 which is a rather old standard, and not used in digital photography.

To really understand why his concept is flawed, you have to think about DOF and your focal point. By now you know that there is depth of field in front of and behind your focal point. If you focus at infinity, there is depth of field behind infinity, but whats behind infinity? nothing..

So to use infinity focusing throws away the rear depth of field.  The rear depth of field is able to resolve details sharply, but not to the same degree as focusing on them would have.  The point of hyperfocal distance is to achieve sharpness in both the foreground and rear. 

When the depth of field is moved forward away from infinity and towards the hyperfocal distance, all of a sudden we have more of the front area of our image in focus and sharp! We also have the back area in focus and sharp! That is what hyperfocal is all about… but according to Merklinger (who obfuscates the ability of hyperfocal to adjust its COC to higher demands) hyperfocal distance is set at .035 COC and therefore the subject matter further away can not be enlarged and detail captured.

Learnslr believes the reason hyperfocal is superior is because it captures both front and rear depth of field of any given focal point.  Its efficient, its the equivalent of firing on all cylidners not just half.

But what about that COC of .035?  COC is a made up number, you can adjust it on the fly…. if you want to go from .019 like I suggest and then use .001 you can, just adjust the formula and all of a sudden you have a new hyperfocal point that will allow you to achieve the detail you require.

What is the tradeoff? on a wide angle lens, not much… Back to my example of the 17-40 mm wide angle lens. We are using 17mm and an aperture of 8.0 with a COC of .019 and my hyperfocal distance is 6.9 feet. That means everything from 3.45 feet through infinity will appear sharp and covered by the depth of field.  What if I want to be really demanding about the areas far away and I review my print and see that I can’t blow them up to huge resolutions and maintain highly demanding detail…. what do I do? focus at infinity? no.. I change my COC I change it to for instance .007. The smaller your COC the more demanding your are being on the lens and sensor for further distances. 

We revise our equation to resolve more detail further away.  Now with 17mm aperture of 8 and a COC of .007 my hyperfocal distance is now 17 feet. So from 8.5 feet until infinity is our depth of field… We lost approximately 5 feet of near distance, but we still use our depth of field efficiently to maximize the sharpness and focus of our scene throughout. What was the tradeoff?  well we had to focus at 17 feet which was a bit more work then focusing at 6.9 feet, we lost 5 feet of up front depth field, but gained more detail in the background.

So here we have a precise method where we make self determined tradeoffs to achieve the focus results we want. Or we can use a method which disregards the rear depth of field, and has the potential to introduce lens diffraction.  One requires more work, one requires less care.

All we ask is that if someone tries to tell you hyperfocal distance does not work, try it for yourself with your wide angel lens. Its a technique that many photographers value, and will help you achieve creative shots with excellent accuracy.