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.



Friday, 23 August 2013

Image review using Apple iPad

The Eye-Fi card is a special SD card that contains a wireless transmitter. Using such a card enables image review using for example an Apple iPad. The vastly bigger screen aids in image evaluation.

For the Apple iPod, all you need in addition to the card is an App to receive the images as they are sent from your camera. The App is free, and although its a little quirky, it works well enough. I should explain that I shoot primarily using RAW camera format. My Nikon is set to produce a low res small jpeg along with a Raw NEF file. Having set the App to direct mode I grabbed whatever I could from the camera. Everything was tranferred. This was BAD. Raw images are 12 megs each on my camera. The protracted transfer using such a setup will try your patience.

Digging a little deeper, I discovered that it was possible to transfer the small jpeg file across to the iPad without the additional NEF. This was much better. Images zipped across from the Eye-Fi card and on to my iPad in the blink of an eye. I was getting somewhere. The almost realtime review of images using the iPad transformed my image evaluation process. Great.

There was however one further fly in the ointment. Powering the Eye-Fi transmitter in the card really hammered the camera battery. Taking a spare became a must, especially on a full day shoot, miles from anywhere. I clearly needed to dig a litle deeper to see if the power requirement could be minimized.

Eye-Fi cards have been around for some time. So much so that my Nikon contains a configuration choice that will either enable or disable wireless transfer. What I generally do is take a few images with Eye-Fi transfer disabled. I then switch it on to transfer a batch of images and review from there. This will not be suitable for you if you are capturing a broad range of subjects. Its your choice - but at least you have a choice. I would recommend powering the camera off when not in use. You will drain both you iPad and camera batteries if you dont since the card and iPad are constantly communicating with each other.