Hi Rob
Here is what I found using my Tak Mewlon 180 F12, fitted with the Baader Astro Photo Film with OD=3.8.
Details:- Full aperture Baader Astro Photo Film
- Mewlon 180mm operating at F12 prime focus
- Canon 40D
- ISO 100
- 1/3200 sec
The histogram is as shown in the attached screen print, as is the FOV.
Remember, I was using the OD=3.8 Photo Film and not the denser OD=5 Visual Film.
This was around 10:42am on 31 July 2011 so the settings may be different with the Sun much lower towards the horizon.
Cheers
Dennis