I posted a video showing some of the apps I use for large format photography.

https://www.youtube.com/watch?v=swxX_nn4VzU

I use three of them on every shot: Holders, Reciprocity Timer, and Mark II Artist's Viewfinder. I carry no notes in the field, so the Holders app is literally all I have to keep track of film and exposure. If my iPhone ever takes a swim I'm in big trouble.

Reciprocity Timer I've found to be extremely accurate. It matches manufacturer's recommendations for all the Fuji films I've tried. It has also been spot on for Kodak Ektar 100 which is quite impressive considering Kodak doesn't produce reciprocity info for this film. Also handy to have for Ilford Delta 100 because Ilford only produces their data in graph form without specific numbers. It's also handy to have for bellows and filter compensation, but I've found its greatest benefit is helping meter using the Zone System. I struggled for a while trying to figure out how to best meter for the ZS with my Sekonic 558, and here is what I've come up with. Let's say I meter the white water of a waterfall. I'll store this number in my meter and also input the number into the app. The meter's reading is my Zone V number. I usually place the water in Zone VIII so I'll use the app's "compensation" slider to add 3 stops. Next, I'll go back over the scene with my meter making sure all areas I want data in are no greater than 5 stops away from my original reading (5 stops away would be Zone III). I know this can be done in the meter, but the app helps keep everything clearer, especially when using a filter.

Last, the Viewfinder app was a complete game-changer for me. I can examine a scene so much better when I see it on a screen. This has allowed me to make better and faster compositions when scouting.

I know most of these apps have been mentioned before, but I thought it may be useful for some people to see them in use. Hope you enjoy.