I just received my Wista 4X loupe from B&H, and I'm not impressed. Without bashing Wista, I thought I was buying a loupe that would allow me to pre-set the focus down to the ground glass plane as opposed to focusing on what my eyes think is in focus. This loupe seems to only have the ability to adjust focus for near and far sightedness. So, maybe the concept escapes me. I've used my rectangular 8X Nikon loupe for both 35mm slide critique and groundglass focusing, but I have read several different posts both here and abroad that discuss the virtues of a so-called 'focusing' loupe, or one that has the ability to adjust the focus to different depths, where the argument seems to be that the focus should be on the grains of the groundglass side of the image, and not focus on the image the eye sees. Apparently, this concept is chiefly supported by the idea that if it is focused as such, it is therefore registering where the film will soon be, and is therefore the most critical location of focus. The usual method is where the loupe is resting on the photographer side of the ground glass, and therefore the focus being adjusted to that point is in fact wrong, in that the smooth side of the glass is 1.5-2mm farther away from the film sheet, and so out of focus. But that confuses me a little, because the image seen from the smooth side of the glass is simply the image that is being projected onto the groundglass side, where the image formation stops....right??? Unless of course, I am totally confused about what people are trying to convey. Another curiosity I notice is that some people are using the term 'focusing loupe' loosely, in that some call it by that name to indicate it's name and use: A loupe meant for focusing, while others seem to take a different tack; calling it a focusing luope because it is a loupe that has the ability to shift and lock focus for the idea mentioned about the ground glass. Could I get some clarification on this? I also note that I have been sucessful thus far by using the Nikon 8x loupe on the groundglass, with what appears to me to be satisfactory results. I must also confess that I am quite new to 4x5 and have only processesed a handful of negatives and enlargements. But for me, the whole idea of large format is twofold: The sharpest enlargement possible for my budget, and the best perspective control. So focusing is truly a critical consideration.