Thank You TimberClipse for reply! Every advice is very important for me
Sooo... Now It's focusing only on things between 0-50cm MAX. I've got REALLY BIG macro lens To make photo by this lens I had to get max value of zoom in my Canon - 20x, after set this zoom view from the lens fills all of the photo-display. There's my questions: 1. how many lenses should I add to tube? One more could be enough? 2. are these lenses should be fixed or mobile? (I would have set one value of zoom, but can it effect on focusing?) 3. how to calculate the distance between lenses? method of trials and faults?