I tested on my older iPhone the other day and had some issues with preview quality, I asked Cascable about this and got the following which may be useful information to some:
"it sounds like you have an older iOS device with not much RAM. Working with the enormous IIQ files on devices with a small amount of RAM is a challenge, and Cascable scales back accordingly — and on some older/lower-end models, there's no enough RAM to make a decent preview at all.
Our own documentation on this will go live tomorrow, but I'll paste in what we wrote about it here:
> At present, whenever you display an IIQ RAW image in Cascable, you’re seeing a JPEG preview at a lower resolution than the full 150MP that the IQ4 can provide. The more RAM your iOS device has, the higher resolution this preview will be. For the very best results, a 2021 iPad Pro with the Apple M1 chip is recommended.
> If your iOS device doesn’t have enough available RAM to render IIQ previews at all, you may see a “no entry” symbol instead. Don’t worry! While you won’t be able to preview these images, you’ll still be able to manage them as described below. For reliable IIQ preview rendering on iPhone, an iPhone XS or newer is recommended. On iPad, a 4th Generation iPad Air (introduced in late 2020) or 2nd Generation iPad Pro (introduced in mid 2017) is recommended.
> When managing your IIQ RAW images (i.e., copying them to external storage, copying them to other locations on your iOS device, accessing them via the Files app, sharing them to other devices via AirDrop, and so on), Cascable always works with the original image file without modification or quality loss."