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Focal Length Analysis

March 28, 2013  |  Cameras Technique Workflow


So, I’ve been contemplating a buying a new lens, but I couldn’t decide on what focal length I needed.  Did I want 11-16? 24-70? 24-105? 100-400?  600?

I could make arguments for any of these, but I was still indecisive.  So, I decided to see what focal lengths I have been shooting at to guide me.  And the best way to do that would be to get some statistical analysis going.  Luckily, this isn’t terribly difficult to do with the right tools.

I use Adobe Lightroom as my image catalog/workflow manager and I knew that Lightroom’s catalog files are simply SQLite databases, storing everything from file system locations of images to EXIF metadata to develop settings. And buried in that EXIF data is the focal length of every image in the catalog.  To get to my analysis, here are the steps I followed:

  1. Select a Lightroom catalog to do analysis on.  I chose my main 2011-2012 catalog, which would provide roughly 60,000 images to glean information from.
  2. Open the catalog using SQLite Database Browser and find the table that contains EXIF data.  This table is AgHarvestedExifMetadata.
  3. Export to csv.
  4. Open in Excel.  Round each focal length to its nearest whole number (some cameras write extremely precise decimal representations of focal length, but we’re only interested in the whole number.
  5. Group by focal length and sum the number of images in each focal length.
  6. Create a line graph.

And voila!:

imageanalysis

As you can see, most of my images fall into the 20-100 range of focal lengths.  Therefore, I would probably get the most use out of something like Canon’s 24-105 L series glass.

Of course, this lens is only f4, so it’s not the fastest.  I could do more analysis on the apertures I’ve used over the last few years as well, but I know from experience that I mostly shoot landscapes and urban photography at f8 or higher, so I should be covered.  Also, today’s cameras’ high-ISO performance and that this particular lens has image stabilization that adds roughly three stops of light should cover me.



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