Lens stacking

Sometimes I read about strange sounding ways of photography and lens stacking is one of them. The idea is to connect two lenses together in order to get higher magnification for close up shots. This can be done with a cheap stacking ring but it requires lenses to have the same filter thread size.



I tried out combining my Canon EF-S 18-55mm IS f3.5-5.6 and Canon EF 70-210mm f4.0. I attached the 70-200mm to the camera body. The problem with this kind of setup is to find suitable settings for each lens. I left focus to manual on both and did not try to adjust that at all. The zoom settings define the magnification and it should follow this simple formula: magnification = focal length of the primary lens / focal length of the reversed lens. So in case of my lenses I have range of 1.27 - 11.7 magnification - in theory.



There are some practical issues with this combination. Setting the focal length of the primary lens to 70mm vignetting occurs and cuts a good amount of corners off. At 210mm vignetting is gone but the lack of light makes focusing difficult. A good live view helps a bit but I ended up using bright led lamp to lit up the target during focusing. The actual photo is then lit by a flash.

Focusing is done in practice by moving the camera until the right part of the target is sharp. The depth of field is extremely shallow and high magnification shows up any camera shake. Shooting handheld with this long stacked lens is pretty tricky.

I uploaded some of my experimental shots to flickr under stacked tag

More information about the theory
http://www.peterforsell.com/macro.html#Magnification_of_stacked_lenses