Saturday, 21 January 2012

The joy of EXIF. Part 1: EXIF for learning

Metadata -- data about data *
Digital photographs contain a lot of information embedded within them that you can’t normally see. The data remains invisible unless revealed by the use of tools available in specialist programmes (including Photoshop) or via plug-ins available for web browsers. My impression is that most normal photographers don't care much about this, even though they may vaguely be aware that items like exposure data are embedded in their digital files. But any photographer can find good uses for the masses of data that is available both in their own files and those that other photographers post on the Internet.

What is Metadata? Digital photos use file formats described as exchangeable image file formats -- otherwise known as EXIF. Within the EXIF is a pile of data which records information about the camera, lens, ISO, aperture, shutter speed and much, much more. These "data about the image data" are the metadata. It is possible for a photographer to add their own details to the metadata, to provide contact details and copyright ownership etc.

This all sounds fairly technical and geeky, so why should any normal photographer care? One simple answer is that it is a great learning tool.

Tools for Web browsers: learning from others
The current web browsers have plug-ins or add-ins that allow you to reveal data in the EXIF for images posted on the Internet. Perhaps the most widely used is Opanda IExif, a plug-in available for both Internet Explorer and Firefox under Windows (unfortunately, at the time of writing, Opanda IExif is incompatible with Firefox 9). Firefox also has other add-ons that are available on the Mac as well as Windows, including EXIF viewer and Fxif.

It is often very informative to look at the metadata that other photographers leave embedded in images posted on web forums and the like. For example, when I was trying to learn a bit about aviation photography, I was curious to know things like shutter speeds for getting propellers to look like they are rotating, or focal lengths to get a distant aircraft nicely framed. By looking at the EXIF data in really good examples of aviation photographs, I could see what tended to work well. Correspondingly, it's often useful to look at crummy examples to learn where things can go wrong. As always, it is vital to use your own judgement about what is successful or hopeless when trying to learn good and bad points of technique in this way. Just because any photographer has used a particular method, does not mean it is good!
Piper Supercub at Headcorn

Here is an example of one of my own. This picture of a Piper Supercub was taken at Headcorn, a small but busy airfield just up the way. When possible, I always like to try to get a sense of motion when I'm photographing an aircraft, by using a lowish shutter speed to give nice motion blur to the background. What I learned early on from looking at other peoples’ images is that you have to go down to quite low shutter speeds, particularly with older aircraft, to get decent background blurring. The EXIF data embedded in this one says I used 1/80 second: this gets the effect I was after. Having said that, I should point out that it was taken with a focal length of 160 mm on a crop-sensor camera: the "keeper rate" goes down exponentially with increasing focal length, especially when getting up to around 400mm.

In any case, you can apply this idea to any area of photography. Perhaps next time you see an interesting photo, it might be worth looking at the EXIF data – there might be something there to learn.


*I was talking to the final year Biochemistry students a while ago about writing up their research projects. I can't remember why, but something I said provoked one of them to say "You are such a geek!" To be called a geek by a scientist is quite something -- I think this post will simply confirm it.

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