EDIT :
'Netengineer' asked whether a specified E4 could be upgrade to E8 spec and in 'fancy speak' basically stated he wanted the latest technology at the lowest possible cost to him (who doesn't !)
He further stated that he intends to use the thermal camera, an FLIR E4 or other, to search for caves and for precious metals in creeks.
For some reason this perfectly reasonable proposal has been removed from his post which makes make response seem pretty abstract in its content.
My response to the original question is below.
Original response......
That E4 can be upgraded.
Whether it will do what you are expecting of it is a different matter
Are you confident that thermal imaging will reveal caves and precious metals in your scenario ? It is not a technology that I have used for such so cannot offer comment on its effectiveness.
I can state that a thermal camera cannot produce useful thermal data through great depths of rock or even shallow water. Remember, the camera can only show you temperature differential. If different materials are present but at the same surface temperature, only the different surface emissivities will allow you to discriminate between them. Place such items under water and you will only see the waters surface temperature and not what lies beneath.
If a large slab of rock contains a hollow area that is relatively near to the surface, the suns heat may well reveal a difference in the rocks thermal density at that point and the void may be discernible if the weather conditions and time if day are favourable. If the rock is covered with soil or plants, these will reduce the effect to a point that it likely cannot be seen.
The Ex range are budget cameras with a fixed focus relatively wide angle lens. It is not the best series of cameras for looking at distant objects, especially if they are small.
A more professional camera range would be the Exx series as these are equipped with a manual focus lens that may be changed to enable the use of wide angle and telephoto lenses. Neither the camera, nor the lenses are cheap though. You need to be very confident in your theory for detecting caves and metals via thermography before buying such a camera, even at used prices.
I suggest you test your theory by seeding an area with metal in a manner similar to that which you expect to find when searching for real, and rent a FLIR camera to see how it performs. You could even try it against known cave systems.
I suspect you will be disappointed with the results.
I would be approaching your challenge using different technology, namely, Geophysical sub surface Radar and an advanced spectrum analysis type metal detector. I have used both and they work well provided you are trained in both use and interpreting the results correctly.
Fraser