First off, I love the product, well done. I spent several hours with it today, over Christmas and New Year mind you ;-).
I would like to see some more documentation on what each filter can do. Specifically if there are such hidden features as the ability to increase or decrease the size of celestial bodies such as the Moon.
Regarding celestial bodies, I sometimes have a hard time finding the moon and orienting and adjusting it correctly. Unless it is in the scene, I cannot increases or decreases its size or move it to a new position. Perhaps the ability to place the moon (or any other object) at user defined position might help here.
When editing the images I took and cycling through the filters, I noticed not all filters support landscape, even if the picture was taken in landscape.
I noticed that the filters are not aware of each others masks. For example take a given photograph, add a night sky filter, save that image. Use that newly saved image and apply yet another filter, the first filters mask area is excluded from the effect area for the second filter. Allow for filter stacking could result in some spectacular results.
I like that the filter application is non-destructive and that the original is always saved (via an option) .
I thought I saw an option to add or propose your own filters. I don't see that anymore.
If there is a possibility to add your own filters, are there instructions on how to create them and share them?
Design or User Experience
If I have understood your question well I can tell you about the size of the effects, as you comment on the moon, you can increase, decrease its size and also perform a rotation, with two fingers on the screen.