Hyperfocus: How a Cheap Lens Changed the Way I Shoot

For me, photography is all about having fun. I do not want it to be another job. I’m not saying I do not want to be a pro. In fact, I would like to get paid just traveling and taking photos. I may have taken this “fun” thing into a different level because I have grown a dislike for heavy (i.e. expensive) equipment. Yes, a 70-200/2.8 VR2 is nice to have but I seriously can’t shoot with it for 15 minutes straight without having to shake my arms to relieve myself of that tingling sensation behind my wrist. Yes, I’m cheap and that cheapness had me lose a fair amount of money because I am forced to discard my cheap equipment for something a bit less cheaper. And that brings us to the subject of this post: my cheap Sigma 17-70mm lens.

Like I said, I have grown a dislike for heavy equipment and that includes my stupid Nikon D700. So before I went for a holiday in the Philippines, I decided to get a lighter camera. It has to be small and light but it should not sacrifice image quality and most importantly, it should not get in the way of photography. So I bought a Pentax K5 which was not so cheap back then. And because I’m a cheapskate I was forced to buy the cheapest lens with the best possible zoom range because there is no way I’m gonna get another lens. One camera, one lens. That’s it and nothing more. The Sigma 17-70mm fit the bill. Very good zoom range for just about anything. It goes from 2.8 at the widest end and closes down to 4.5 at full zoom. At $339 AUD it was perfect. Not!!!

It wasn’t until the following day after that errant purchase that I noticed that this lens is terribly soft especially at the corners. At 17mm the corners are so blurry unless I stop down to f11 and even at that aperture it is never sharp. Worse, this lens can never get the focus right. I have updated the camera firmware because the K5 is known to have focus issues in the older firmware versions but that did not fix the problem. I have returned 3 copies of the lens but all of them had the same back-focusing issue. I have grown in love with my camera so I can’t return it but on the other hand, I have this lens that I can’t replace because I’m a cheapskate.

What does a cheapskate got to do? I taught myself how to hyperfocus!

First things first, let’s tackle depth of field, aka, how much of our photo is in sharp focus. We all know (I assume we all know) that we can control our depth of field by changing the lens aperture. The smaller the aperture (f11) the deeper the depth of field. If we want our subject to appear to pop out of the frame, we use a bigger aperture (f2.8) to make the background go out of focus in a creamy blur we call bokeh. Every amateur photographer should understand this. It doesn’t stop there. Another factor in depth of field control is the focal length. Longer focal length means shallower depth of field. Lastly, there is distance to subject. The closer the subject in focus is, the more blurry the background becomes. So again, depth of field is controlled by 3 variables: 1) lens aperture, 2) lens focal length, 3) distance to subject. We need a firm grasp of these 3 basic concepts otherwise the subsequent discussion would be tricky to comprehend. Actually there’s another factor which is the sensor size (or crop factor) but let’s not deal with that because we can cheat as I will show you later.

In landscape photography, we usually would want to capture the grand vista and make everything from the foreground to the background in sharp focus. A very common mistake made by beginners is to allow the camera autofocus mechanism to pick a focal point. Depending on how the camera is aimed, it may focus on the horizon and result on a blurry foreground or focus on the nearest rock and make the background go out of focus. Night time photography would be a lot more difficult because your lens would just hunt and fail to focus properly. Sometimes we get lucky and have everything in sharp focus but we want to control this instead of just relying on luck.

This depth of field control is called hyperfocusing. I’ll go slowly this time and try to explain without using any diagrams (coz I can’t).

If the camera is focused on the far horizon (infinity focus), everything from that horizon up to a certain distance between you and the horizon will be in sharp focus. So if you are standing on point A and the horizon is point C, there is a point B between A and C where everything between B and C is in sharp focus. Keep repeating that sentence until you undertand the concept. Move to the next paragraph when you think you’re ready for the next concept.

That point B, is your hyperfocal point. What that means is, if you focus at point B, there is a point X approximately half-way between point A and B where everything between X and C are in sharp focus. Still with me? So we have something that looks like this:

A—-X—-B—————-C

Point B is the hyperfocal point and everything between X and C are in sharp focus. Take your time to digest those concepts before continuing to the next few paragraphs.

The question is, how do you find point B? Others would tell you to focus one-third of the way to your subject. It’s probably a good approximation but that does not work for me. What I do is memorize a few combinations of numbers. What numbers? You probably guessed it already: the numbers that pertain to the 3 factors that control depth of field.

Here’s an example: My lens goes from 17-70mm. I’m shooting landscape so I want to go as wide as possible so I choose 17mm as my focal length. I know that my camera is soft in the corners unless I stop down to f11 so I use that as my aperture. What’s left is the distance to subject and this is where I cheat 😀 Open another tab in you web browser and point to this URL: http://www.dofmaster.com/dofjs.html. Remember that other factor that controls depth of field? Yep, the sensor size. From there choose your camera model. Yours might not be in there just like my K5 so I chose the Pentax K7 instead. And that’s cheat number one. Now enter the values of your chosen aperture and focal length in the remaining fields. In my case that would be 17 for focal length and f11 for aperture. Never mind the distance to subject field. Just click calculate and the frame on the right would automatically give you the hyperfocal distance and that is cheat number two. In my case this number is 4.25 feet. It means that if I focus on something that is 4.25 feet away from me then everything from 2.13 feet (that’s half-way) up to infinity will be in sharp focus. Don’t worry if the subject seems to be out of focus when viewed through the viewfinder. This is normal because your camera does open aperture metering (as opposed to stop down metering of old film cameras) so you are viewing the scene at full aperture, f2.8 which isn’t your real aperture when you click the shutter. Trust that math will save the day.

What I do is memorize the hyperfocal distance that correspond to the my most used focal lengths, say, from 17mm to 24mm. If I’m not quite sure of my numbers, I would compensate by closing down a stop further. For example, my lens has distance markings on the barrel. There’s one for 3 feet and the next one is 7 feet and then 10 feet and then infinity (that drunk number 8 lying on the floor). Supposing that my chosen composition requires me to zoom in to around 24mm to avoid clutter. I’m not quite sure what my hyperfocal distance is for that focal length. What I do is I set my lens focus distance to that 7 feet marker and stop down to f16. Had I remained at f11, subjects near the horizon will not be in sharp focus. By stopping down to f16, my hyperfocal distance changes such that I could get everything between 3.5 feet and infinity in focus. Neat!

So what’s the moral of the story? Do not let crappy equipment hinder your photography. Instead, try to find ways to work around the minor issues. In my case, I learned how to hyperfocus (and I hope you learned as well from reading this post). Everytime I shoot landscape, I never use autofocus. Hyperfocusing is way superior.

Until then, have fun shooting!

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6 thoughts on “Hyperfocus: How a Cheap Lens Changed the Way I Shoot”

  1. nice entry.

    Though when it comes to landscape, I just focus to infinity.
    I seldom stop down beyond f11, as I’ve read somewhere that there is some lens diffraction.
    Newbie here.

  2. Great write up. Thanks for sharing, you have explained things it better than most matter I have read on the subject . One thing that is still not clear to me is why not just focus on something 4ft away from you every time so that everything from there to infinity is in focus? Perhaps I have still not understood.

    1. Thanks for the kind words.

      The reason 4ft won’t work all the time is because depth of field is also affected by focal length and aperture. Different focal length and aperture combinations will have different hyperfocal distance. You could, in practice, make 4ft work for you all the time but that means you will have to shoot really wide, say 10mm, and stop down to say, f22. With that focal length and aperture combination though, you could focus less than 2ft and have everything from the tip of your lens to infinity in sharp focus 🙂

      It’s not wise to shoot at f22 all the time though because your images will start to get soft due of diffraction. So I would advise that you find out the sweet spot of your lens (usually 3 stops down from maximum aperture) and work from there.

      Have a play with that web DoF cheat tool 🙂 Most of all have fun shooting.

      Cheers.

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