whats going on here?

i have a reverse adaptor, 49-50 something mm, a 50mm screw thread lens, 3 extension tubes 12, 18 and 25mm , a x2 screw thread teleconverter and a telephoto lens adaptor.

when i put the tubes together with the telephoto lens adaptor, it makes things massive, more so when i put the lenses in the camera. yet removing the front of the 50mm lens and putting the 3 extension tubes makes things large again.

also, when i have the reverse adaptor, the lens and the 3 extension tubes mounted on my k-1000 and i attach the screwthread x2 teleconvter, everything goes the right way, why is that? :

I'm trying to follow your description... can you describe it more clearly. Something like "Body + 50mm lens + reverse adaptor + 50mm lens"
Need to know the order before commenting!
Matt

body, adaptor, 50mm lens, tubes

It's a brave soul that even starts to reply to that....

When a lens is the right way round the distance to the subject is large, the distance to the film small. You get a normal sized image. Reverse the lens and you reverse that logic and end up with huge magnification. Try putting a wide angle lens in reverse on the front of a telephoto and see what happens.

By a telephoto lens adapter do you mean a teleconverter, or maybe a macro converter? These increase the focal length of a lens so bringing things closer. But the minimum focusing distance remains the same so you can get large magnifications.

Extension tubes move the lens elements away from the film plane, which is what you do when you focus a lens closer, but more so. So again you get very close up pictures.

There are some good books on photographic optics if you want to pursue the theory, otherwise, give it a whirl and see for yourself what the various effects are!

i worked it out my self a few moments ago, i think i'll go lie down, its unnatural seeing a 5p that large

Very wise!