Rechecked - you are right ! Before I focused my tube lens to the distant tree. I had to focus to the "very very" distant tree This difference gave me wrong understanding, that I can make "micro" magnification adjustments by changing distance between tube lens and objective.makes me think that your setup has the rear lens focused somewhere other than infinity
Thanks for the link. Few years ago in the the printed Edmund catalog version I saw very similar information (not available in the later editions)
How too short distance can cause vignetting ? In the combination with the normal 200mm (70-200 other members or 70-300 in my case) lens we are trying to keep objective as close as possible . With Sigma Life size attachment - same story ( with bigger distance results were not good). When I tested Mitutoyo 5x/Reichert tube lens, gap was around 1cm and results were pretty goodIt is important to note that 76.5mm is the recommended distance since these objectives are infinity corrected. However, if the distance is too short, the system may experience vignetting
http://www.photomacrography.net/forum/v ... hp?t=30766
Am I missing something ?