REID2169 thank you very much for the beautiful video you shared. It's very significant. As for the background, you are absolutely right. With the Tube TH50 you can see very well, it's wonderful. However, with the RS75, details are more detailed at target range and the background is blurred. I'm not surprised by all this because optical physics teaches us that a large focal length lens (75 mm) has a much more limited depth of field than a 50 mm lens. In practice it means that, if with the 75 mm lens you put a target in perfect focus at a short distance... at a great distance the image will be completely out of focus. So, in summary, if you want to have a better and more "pleasing" image for the eyes in almost the entire field of view, it is better to use a 50mm lens. Infiray was forced to use a 75mm lens with the 1280x1024@12micron hd sensor... , if they had opted for a 50mm lens they would have obtained a minimum optical magnification of only 1.45X. When the new 1280x1024@8micron sensor arrives, probably next year, we will finally no longer need a large, expensive, bulky, exposed to possible shocks, 75 mm lens. Furthermore we will again have an excellent depth of field, with the image in focus over the entire field of view.