throbi's blog

Hyperfocal distance in action

posted by throbi, May 22, 2006 11:45 PM — 4 comments

Most of us know that hyperfocal distance is "the closest distance at which a lens can be focused while keeping objects at infinity acceptably sharp; that is, the focus distance with the maximum depth of field. 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." [en.wikipedia.org/wiki/Hyperfocal_distance]

Based on the definition one can figure out that focusing to the hyperfocal distance is mostly useful for (but not limited to) landscapes and cityscapes. While focusing to infinity or the farthest object is usually enough, one can capture extra detail by focusing to (or beyond) the hyperfocal distance. Google for “hyperfocal distance” and in the image section you can find many pictures taken with this technique. Please note that both near and far objects are sharp.

On the linked pages you can find the mathematical formula of the hyperfocal distance. But in practice it is enough to know that it depends on the focal length of your lens, the aperture size and a chosen smallest circle of confusion. See the linked material for explanation of these terms. I'll try to be as practical as possible so let's get to the chase.

Marked and unmarked lenses
Most of new lenses have auto focus but no distance scale or other markings. The following steps are based on these lenses but shortcuts for lenses with distance scale and/or aperture markings are also discussed. Yes, those numbers on old lens barrels actually mean something and they can make life easier. Especially when one tries to focus to the hyperfocal distance.

Do the homework
Some paperwork is involved and the cheat-sheets come handy on the field. I wrote the resulting tables on stickers and sticked them to the barrel of my lenses. This way it takes me no more than a couple of seconds to focus to the hyperfocal distance (or beyond).

First step: focal length
Find the focal length of your lens/lenses. For my zoom lenses I only used the two extremes. For digital SLR cameras in most cases you will need to multiply the focal length with 1.6 (or other factor based on the size of your sensor) to get the actual focal length of your lens. Fortunately more advanced DOF calculators do this for your camera by default (the one linked in this tutorial does).

Example:


Second step: aperture sizes
Now you need to find the “f/” values the lens supports. As I said before, the hyperfocal distance depends on the aperture size, too. You can find these values by switching your camera to aperture priority mode (Av for Canon SLR s). Then spin the dial and put all the displayed values into the table.

Example:



Third step: calculate the hyperfocal distances
This can be done with one of many depth of field calculators available online. For instance: www.dofmaster.com/dofjs.html. Just enter the type of your digital camera or 35mm for film cameras and the focal length of the lens. Chose the f/ number and enter an arbitrary subject distance. Subject distance has no meaning for hyperfocal distance focusing. Everything from the half of the hyperfocal distance to infinity will be in “acceptable” focus.

Example: HFD (hyperfocal distance) given in meters.



Homework done!

On the field
We see in front of us a beautiful landscape and we want to get the most out of it. We want to cut out some non-interesting parts, so we decide to use our 50mm lens. To have the largest depth of field we stop down as much as possible. But let's say its a sunset, not too much light so f/2.8 is the most we can get without a tripod. Our cheat-sheet tells us, that our hyperfocal distance is at 29.5 meters from the film/sensor. What are we doing now? It depends on the markings/scales on the barrel of the lens.

- best case: distance scale
The scale on the barrel tells us exactly the focusing distance. We spin it to 29.5. If the resolution of the scale is not too accurate it's OK to go a little bit over, let's say 30. Compose. Shoot.

- medium case: aperture marking only
These markings look something like this (hopefully more detailed):

On manual focus we spin it to infinity and slowly come back until the “|” mark next to the infinity sign meets the marking of our f/ number. For the 2.8 in our example and the scale above this could be difficult. However, we still can use plan B, the worst case scenario and get back to this step to double check the settings. This is what I usually do :-)

- worst case: no markings at all
This case applies to most starter-kit lenses. It requires a little practicing but after you get the feeling of it, it is really fast. So leave your camera at auto focus and try to guess the distance. Those 29.5 meters. Or about 90 feet. Find an object that is approximately at that distance. Auto focus on that object, recompose the picture, and shoot. That's it. Simple, isn't it? One last tip: it's safer to focus a little bit beyond the hyperfocal distance. Let's say to 36 meters instead of 29.5. That will still give us a depth of field from 18 meters to infinity.

Wrap it up
- First we need to do the homework and calculate the hyperfocal distances for our favorite lenses and aperture sizes.
- On the field:
1. decide what lens with which aperture size to use
2. set the aperture size
3. look up the hyperfocal distance for the lens and aperture
4. focus to the hyperfocal distance (or a little bit beyond) using one of the three scenarios above.
5. shoot

----------------------
Read more:
www.dofmaster.com/hyperfocal.html
www.fortunecity.com/marina/marine/569/rusrngfdrs/focusing.html

Comments are welcome!
While I'm a beginner myself and I only figured out recently these things about the hyperfocal distance the tutorial might contain some errors. If you spot one please tell me about it!



Comments | RSS

1. posted by escan, Aug 20, 2010 2:56 PM

Thanks info!!!


2. posted by trainer2, May 31, 2013 9:18 AM

Useful for me.


3. posted by contactsA, Jun 21, 2013 1:14 PM

Nice tut!!
Thanks


4. posted by carlislekm, Jul 29, 2013 4:35 AM

Very interesting

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