
EXIF Tooling - Approach
Fortunately, there is already an excellent tool for the extraction of the EXIF data from files, available for free at http://exiftool.org. Many thanks to Phil Harvey for implementing this for free over many years.
The diagram below shows an overview of my approach.
Use the EXIFTool program to extract the field information I was interested in , into CSV (comma separated variable) files
Write a Python program to load these files and provide the ability to mix the data into a number of different report formats (such as Heatmaps, Bar Charts, Histograms etc)
As such, there are two stages to generating the data , in that the CSV files can be created using a simple command without needing to use the python program. These CSV files can also be loaded directly into Excel to check the data and likely output to ratify the graphs generated by my program.


Additionally: -
I wanted to be able to make this functionality available without having to know what was happening under the hood, and so I had to learn how to write a very simple interface to the program
The EXIF Tool provides a huge number of fields on my files (269 at the last count) - I wanted to implement a means to restrict the fields to only the ones that I thought were useful to graph.
Also, many of the fields that are exported are not always in a format that can be used by python (or my implementation ) - and so I added a means to change the extract format from the default to one that the program supported
The Python part of this project was very useful for me to be able to implement some other non-photographic projects that I had in mind.