Mame allows you to sort of cheat, which makes the illusion that control is Ok with a low resolution spinner on a high resolution game... with analog adjustments that the user can tweak.
How does it work? Instead of each optical signal counting as one pixel movement on screen... mame can allow you to make each signal worth 10 pixels movement on screen.
While this gives the needed resolution to use a low resolution spinner... it does not give the player precise accurate control. The players movements can also be a bit jumpy visually. It can also make the game easier, by limiting the range of possible responses.
On the other hand, a spinner too sensitive may not work well with a low res game... unless you can adjust the sensitivity by a huge factor. Many high resolution laser mice have a button or setting which enables you to do just that. Ive not checked Randys method, and Im sure he will chime in, but it probably works the same way. (as I dont think mame has enough range to reduce the resolution enough on its own)
Is there a way to increase the resolution of an old optical spinner (like a Tempest spinner)?
Would creating a new encoder disc with more holes make any difference?
Tempest has an encoder which has a ton of holes on it as is.. and putting more on it would create structural problems with the disc itself. Dust would also be a big problem at that level of density. As far as it appears from looking at the outside assembly, the high res encoders are near microscopic, and are fully enclosed to prevent any damage and dust issues.
There might be a way to modify an older spinner with a lasermouse on a encoder wheel what has no holes on it. Only problem is that lasermice are probably still fairly pricey, and theres still modification needed. Anything less than a decent lasermouse is probably going to be too erratic and laggy.