Camera Focal Length - question about automatic determination from photo - DISREGARD - RESOLVED


I had to “go back to school” on digital camera sensors. Mission Planner is doing it right.

The term “35mm equivalent” stems from the fact that since digital cameras have different size sensors than 35mm film, they have to have different focal length lenses to have the same field of view. So using the “35mm equivalent” gives a photographer an easy way to have an idea of the field of view for that lens.

But for photogrammetry - it’s all about pixels. So Mission Planner has it right.

I’m using a Sony RX0ii.

There are two focal lengths mentioned in the specs - and in the EXIF meta data.

There is an 7.9mm listed as focal length - and 24mm listed as “35mm equivalent”. Both of these are in the EXIF metadata - and frequently both are mentioned on websites publishing the specs. However 24mm is usually mentioned where only one is mentioned - and it’s usually labeled as “35mm equivalent.”

In some places the 7.9mm focal length is listed as just 8mm.

My suspicion is that for the purposes of Mission Planner’s grid survey missions, the value that’s needed is 24mm - the 35mm equivalent.

However when using the option to let Mission Planner figure out camera specs by uploading a sample photo - it selects 7.9mm.

My guess is that Mission Planner is just looking at the wrong field in the EXIF - but I need someone to confirm this.

I’ve attached screen prints from Mission Planner, Sony published specs, and EXIF display for the sample photo file I used.

Can someone please offer me some guidance?

If Mission Planner is in fact using the wrong EXIF field - then that needs to be registered as a bug.

Thank you!

Addendum - I heard back from a fellow who uses the Sony RX0ii - and he reports using 7.9 with no issues. I’d still like to know more about this issue if anyone is knowledgeable about it.