I have a Fujifilm Instax Mini 8 . I have three film packs and I changed packs depending on the photo I wanted to take, later I realised it was a very bad idea. I am wasting film because the camera automatically goes to the S symbol thinking that it is a new pack and the lid/tongue has to be removed but it is not there, so I am wasting film (because i get a blank film with no photo on it). How can I change the setting so it goes past the S symbol and make it realise there is no lid/tongue? Thank you.
The Instax is a camera which uses light-sensitive film to capture photos. The film packs include a cover that prevents light from reaching the film inside while it is being transferred from the package to the camera.
Once the pack has been installed and the camera has ejected the cover, the individual sheets of film are exposed, allowing light to reach the one at the front when the shutter is opened. Removing the pack from the camera exposes the sheet at the front of the pack to light and ruins it, so even if you were already able to convince the camera that it didn't need to eject the cover, the sheet of film at the front of the just-installed pack would be useless.
The only way you would be able to accomplish a swap without destroying one exposure would be to do so in a film changing bag. Packs not on the camera that don't have the factory-installed cover would have to be stored in light-tight containers. By examining the pack, you may find that it's possible to re-install the cover after it has been ejected, but even if you are able to do that, I would still recommend storing partially-used packs in light-tight containers.
After swapping the pack, you would need to take one picture to determine whether or not the camera opens the shutter when the exposure counter is in the S position. (Given the simplicity of the camera, this is a possibility.)
Once the pack is inserted, it spits out the light guard that keeps the rest of the film from being exposed, so once you open the back of the camera to swap a pack, the rest of the pack that's loaded is toast. This is the nature of a film camera, and there's no way to put the lid/tongue back on the pack.
You could also use a changing bag, and light-tight containers to hold the partially-used packs, but there's always the danger of stray light and it's awkward and not particularly fast or convenient to do--especially in the field.
Your best bet, if you have to do this, is to get multiple cameras, load them up with the different packs you want to use, and label them [or get them in different colors and be consistent about which type of film goes in each color camera]. Then switch cameras at need. Given that we're talking about $60 plastic cameras, it's probably the path of least resistance.