Recently been having a problem with halftone banding, waves are appearing within the halftone patterns when exposed, onto the screen.
Image is 40lpi onto a 71t mesh (Something i've NEVER had a problem exposing before) EDIT: Halftone angle is 45 degrees, i know this is commonly known as a moire pattern, but it has never happened before.
Exposure time is 9mins 20secs through 8 actinic backlight bulbs in my Lumitron Odyssey vacuum lightbox.
The ONLY thing i have changed recently is my film brand, i have upgraded to an A2 roll from a different brand as sticking 2 pieces of A3 just wasn't cutting it anymore.
Could it possibly be the film brand? it's fantastic usually, 0 issues with it, ink dries faster, and is more opaque etc. The only reason i think its the film brand is that is the only recently changed variable and every halftone screen i have made with this film has these 'waves' within the halftones.
Another thing i thought it might be was my mesh tension? but again, never been a problem with halftones before.
Or possibly one of the 8 bulbs is under-performing therefore the light is undercutting the film, but they all turn on and operate fine as far as i can see.
This is the film over a white piece of paper:
This the film over my light box:
Both have no banding within the halftones, flush photo.
This is the test print:
As you can see, there are waves of halftone variation that shouldn't be there.
Any help is greatly appreciated.