I have a cheap camera that is supposed to take videos underwater. It is a camera in a case that is set to a single focus. I checked the specs and it is a manual set focus camera. When I asked the supplier, they told me that I can't change the setting anymore since it's already in its waterproof case.
I'd like to know if there is a certain quantitative test that would help me find the range underwater where its focus is set to capture images for. So far, all of the tests I've found online are for DSLR cameras and I don't know if they would be applicable for my camera. I know that I could just take pictures until one shows up clear but I would still like to do a proper test on it.
Thanks in advance.