Long exposure reciprocity failure on fujifilm instax

[hiroko]

Anyone care to share how to calculate the reciprocity failure for fujifilm instax film? Cant seems to find it in fujifilm datasheet. What i have noticed is that it will turn blue cast for anything more than 1s exposure. Its more for experimental and fun project use.

 

[Donald Qualls]

I've done limited pinhole in Instax Wide; I used 3 for 2 exposure time (i.e. every stop got 3x the time instead of twice) starting at 0.1 seconds -- my prints still came out on the dark side, so I might be tempted to give another stop on top of that (likely by metering at lower EI).

 

[xya]

I have taken an ordinary film factor which has worked fine for me:

1s x 1.25
5s x 1.5
15s x 2
45s x 2.5
2m x 3
5m x 4
10m x 5
20m x 6

But there is another factor for Instax film to take into account. The 800 ISO are only valid for medium light. It's 400 for dimly lit situations and 1600 for brightest sunshine, pinhole or normal lens.

 

[hsandler]

Some more info in this earlier thread: https://www.photrio.com/forum/threads/reciprocity-and-long-exposure-on-instax-film.143619/