Originally posted by ripit @
stanislav, do you know what effect using a 1.5x converter would have as opposed to a 2x? Assuming the focal distances were the same (same distance to the camera from the teleconverter and same distance to the lens). Would I gain or loose long range focus?
anyway, here are a couple of pics. I may start a new thread for opinions when I get further and or et some better pictures but would appreciate any feedback on image quality any one would like to give..
Imageshack - imgp9093.jpg Imageshack - imgp9106d.jpg That is a hard question!
Well first I have to say that I never did such adaptation nor did I try. My experience is based on a Soligor 400mm f6.3 in Canon FD mount which I have adapted to the Pentax K and some experimentation with macro tubes as well as macro focusing teleconverter.
Now I'll try to answer your question: With 2x teleconverter you have effectively double the focal range which means that the combination (lens with attached teleconverter) is half as sensitive to thikness on the mount side. What happens with 1.5x teleconverter compared with 2x teleconverter is basically that you compare effectively lenses with two different focal lengths. So lets assume that you start with 100mm f2.8, with 2x tleconverter you'll gett effectivly 200mm f5.6 whereas with 1.5x you'll get about 150mm f4.5 (or something like that). So this is the combination that gives you both the longest focusing distance and even the DOF.
Provided that you TC's are good on the mount they are designed for (Canon FD) - meaning that you can gain the infinite focus and that lenses are alligned (no tilit/shift effect) than you should try not to fiddle with the position of the lenses in your TC. It should be however possible to slightly move the lens groups towards the lens to gain infinity focus, but then you risk to missalighn it so that the result beign something as fixed tilt/shift converter spoiling all your images.
So finally to your original question: assuming that you have removed exactly the same ammount of material from the "camera" side of your TC you would get "further" focus with your 2X TC compared to your 1.5X TC. My suggestion is that you check whether you can remove about 5mm on the mount in which case it may be worht doing the conversion (you'll still need about 1-1.5mm for the mount). Now in that assesment you have to take into account both the "thickness" of the mount and the position of the rear element. In other words if the rear element is protruding behind the mount, there is a risk that the mirror could hit it.
Well I really hope that you'll sort these things out.
PS feel free to contact me privatly as well (then I'll be able to answe faster)
cheers, and good luck!