It seems that in recent years, people have forgotten about hyperfocal focusing.

In fact, hands up if you've never heard of it? Now, if you have heard of it, hands up those that use it? That's not many of you I guess. 

To explain, for those of you scratching your collective heads. The hyperfocal distance is the distance at which, with the current lens and aperture settings, you will achieve the maximal depth of field possible. With all the thoughts about wide-aperture lenses and the effect on depth of field from a smaller sensor, it's no wonder we're not seemingly so concerned about getting as much as possible - for many situations we already have more than we might want! 

Hyperfocal focusing has long been the preserve of those of us who enjoy shooting landscapes. Those who more often than not want as much depth of field as we can attain to ensure sharpness from the front to the back of the scene. But, that takes the narrow view, the view where rules for one type of photography don't cross into other types. 

Just the other week I was photographing Artic Terns in flight on Inner Farne, and being the sort of photographer I am, I was trying to think of different techniques I could use (not for me the idea of being creative with the subject, more the idea of being creative with techniques!). An idea popped into my head - slow sync flash. The sky was dark, but to really get some mood into the image, I'd need some flash on the underside to provide some detail. It was a good start, but then I began to think about wider angle lenses. Why should you photograph a bird in flight with a longer lens? I'd had success in the past with wide-angle shots of birds flying close over-head, so why not give it a go again?

Now you may be wondering where on earth hyperfocal focusing fits in to all this. Well, I'll tell you. Artic Terns get close. Very close. So close in fact that you'd best wear a hat or risk them drawing blood on your scalp as they protect their nests.  They're also quick. there is no way you're going to track focus them as they dive-bomb you from such close range, so you need to find a different solution. You could always pre-focus on the sort of distance you think they might be at when you shoot, by why not better make use of hyperfocal focusing? 

I was shooting with an EF24-105mm f/4L IS USM lens at 24mm. I wanted depth of field to get as much in as posible and I wanted a slowish shutter speed to give some blur in the wings. Assuming the birds would be around 50cm away, I could set that as my focal distance, but then my depth of field (on the EOS 5D Mark II I was using) would have been about 85cm in total stretching from 0.32cm to 1.17m. Not bad, and probably enough to get the result I wanted, but that depth of field is not that wide. With such fast moving birds, there is no guarantee they'll be in focus. The hyperfocal distance however was 0.87cm. Set the lens to that and I'd ended up with depth of field that stretches from 44cm to infinity - more than enough to ensure I got the whole bird in focus provided it didn't get closer than 44cm. 

Is that the end of it? Well, yes and no. Assuming I actually wanted that depth of field to strech a little closer just in case the birds got really close, I could have shortened the total depth of field by focusing a little closer than the hyperfocal distance. By way of example, had I focused at 65cm, my total depth of field would have stretched from 37cm to 2.55m - far enough that I would have had no problems because I was waiting for the birds to get closer than that, and also giving me an extra 7cm close distance for the really near ones. 

So how do you calculate the hyperfocal focus distance? Sadly, it's not possible to do in your head (well, at least I can't do it in my head!). You can find many calculators online to do it for you, I like www.dofmaster.com and there are also many apps for the iPhone (try PhotoCalc for example) and other smart phones. You can even get an excel sheet to do the calculations for you. 

So, do you ever use hyperfocal focusing? If so, what for?

Which is more sensitive, One Shot or AI Servo focusing? This is a question I was asked the other day by someone who thought they were seeing differences in the ability of the camera to lock onto a subject in low light situations depending on which AF mode they use.

Well, there is a simple answer, but it's not the answer you'll most likely be wanting!

One Shot is more likely to achieve focus in low light situations. And there is a simple reason why as well... In AI Servo, the camera does not have as long to perform the AF operation becasue it is constantly re-calculating. As such, the AF sensors don't get chance to gather as much light in AI Servo and therefore focus is less likely to lock, or be as accurate. In One Shot AF, the focus sensors can have a bit longer to collect light and therefore they can perform a more accurate AF operation. 

While this won't help if you're trying to focus on a moving subject in low light, at least you know that it's not an issue with your camera and that that is exactly how it's meant to be.