The second battery in the Flash Meter IV is only for infrared triggering of Minolta camera or flash with dedicated attachments for these purposes. I have one for triggering off camera flash to assist in flash metering.
I bought one off eBay last year and it is very easy to use. There are manuals available from Butkus. Both an owners manual and a demo manual with lots of instructions. If it needs calibration Quality Light Metric in LA can cal or repair reasonably. Check out Don Giannati for a free video on Udemy. He uses one exclusively
That's a big "Osprey " in pic #4
Follows the old adage: Your best camera is always the one you have with you.
Nice shot
Sorry about above address. Should be
rjrcooltools.com
Since it occurs only intermittently it is not likely a sensor mark. It does have the sense of motion with varied intensity. Could it be an issue with the shutter?
The pressure relief valve is just a semi permeable membrane with no moving parts or electrical requirements. The red plastic seems to only be a Pelican Case label and probably should not be removed
Norman Camera
Grand Rapids,Michigan and Kalamazoo,MI
Full service camera store. Will match B&H pricing, rental equipment, a pretty complete inventory especially Canon and Nikon
Try the Tamrac professional series Anvil 15 at B7H now for $179. Great backpack /bag