Saturday, 31 August 2013

Circles of confusion on the increase.

The more you read online, the more you realise that hyperfocal photography is a very contensious subject indeed. Some authors insist that it's a myth which should be assigned to the dust bin. To some extent I agree with them. Choose your subject and try your best to ensure critical focus on that. There are times however when I like to achieve a massive DOF, and hyperfocal estimation seems a good solution to me. Not to say there aren't other solutions. Focus stacking will get you there assuming you are willing to invest in the software. Tilt shift is another solution, again assuming that you are willing to purchase expensive lenses.


Back in the day when out out shooting with my D300, I used to enjoy the thrill of capturing images with a very large depth of field using my favourite ultra wide angle lens (Tokina 11-16mm). The images seemed other worldly - no matter where you looked, most things were acceptably sharp. An app on my phone works out the hyperfocal distance for me at any given aperture and focal length. To setup TrueDoF you just tell it the size of your sensor and you're good to go.


Having just migrated across to a D800, things are not as they should be in the hyperfocal world. I configured the app so that distances were worked out for a full frame sensor. It reckoned that to achieve hyperfocal DOF at an aperture of f/8 I needed to focus on something just under 4 feet away. If I could manage this, the app was telling me everything from a distance just under 2 feet right up to infinity should be acceptably sharp. I estimated the distance as accurately as I was able. The results were anything but sharp and the resulting DOF was no where near where I wanted it to be. I had noticed this on previous shoots and had just put it down to me being sloppy and not estimating distance accurately enough. On a whim, I took a few shots focused further into the scene - they had a massive DOF.


Clearly something else was occuring that I was not aware of as a factor. I had considered tweaking the app, in effect telling it that the sensor in my camera was smaller than it was (in order to make it give me larger focal distances). I began to search on the web to see if others had come across the same problem. And there it was, an article by George Douvos, the designer of the app I was using. He talked of receiving lots of correspondence from other D800 users who were experiencing similar DOF problems. You can read his article about the cause, and a solution here.


Whilst talking about this subject, how can you estimate how far something is from yourself when modern lenses dont have a complete distance scale on them? Tape measure - not an option when you are shooting coastal scenes. You'd notice footprints in your shots quite quickly! Carry a big stick? What a pain that would be. Well, you may want to check out an app called EasyMeasure. It is not 100% accurate but its close enough. It shows the distance to objects seen through the camera lens of your iPhone or iPad. Simply point your phone camera at a nearby object and EasyMeasure uses the tilt angle of the phone along with the height to estimate distance. Simple and elegant.



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