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- chromatic aberrations, if the primary system is not APO corrected (which most fast lenses are not) this is going to be amplified by the condensor effect of the speed booster. Even if the primary lens is not suffering from chromatic aberrations the speedbooster will probably introduce some colour fringing.
Can you elaborat a bit on this? How will the condenser amplify chromatic aberrations at the same time as it compresses the resolved detail?
Dispersion characteristics of different types of glass, as well as the effects of the glass shape; convex, concave, some kind of aspheric curvature, etc. do have different effects on part of the light spectrum. One of the most difficult challenges in lens design is to keep focus for different visible segments of the spectrum together. The complex systems that todays lenses have become are for a great part a result of calculations to compensate side effects of aberrations in lens elements in front of each other. If the lens system attached to the speed booster is not without chromatic aberrations to start with, it would be a coincidence if a lens system that has been designed for general purpose applications on many lenses for it's speed enhancing effect also corrected the chromatic aberration of the original system. In most cases the CA will stay to exist and the extra CA errors of the speedbooster will be added. It's like noise in a copy, it never disappears, you only add extra noise in every other step of processing. This is true for sound noise, this is true for photographic images, this is true for every process that emulates reality in another copy. The speed booster is another extra step in light processing and since it's a general purpose design it will most probably introduce new aberrations in the lens system that is mounted. Just do a mind experiment to imagine what it is. Mount this speed booster to a great lens and one of those super 1.4x teleconverters you mentioned. Would you expect to get the very same image as with the native lens system without the speedbooster and the teleconverter with no quality loss? I guess everyone understands that there is some loss in this setup. The question is just, how much. Tests and reviews will prove, but I bet it's more than a few of us will like. With the exception hopefully for a few of those lenses that combine very well with the speed booster. I guess, by the nature of the optical design that some symmetrical designs (Gauss type) standard lenses and a few short and medium tele lenses will work best together with a speed booster. However retrofocus designed lenses and most standard zooms will probably exhibit more from the aberrations I mentioned above.
There aren't a lot enthusiasts about the optical results of teleconverters among the high standards photographers. I guess they won't be over enthusiast about a speedbooster either. It's definitely an interesting creative tool that will be able to get you shots that you couldn't without the speedbooster and your current lens setup, but by the nature of optial design it won't come without compromises.
The latest generation of teleconverters from Canon leave little to be desired regarding image quality. But I haven't seen satisfactory results from teleconverters of any other brand.
The reason is that these converters have been designed specifically for Canon's long whites which share their basis optical design. Just compare the 300, 400, 500 and 600 diagrams and you will notice a great similarity. The converter system has always been designed to work best with these lenses. It's also the reason why the converters don't work very well with some other lenses. And even on the long whites they are not flawless. Most reviews just analyze the "sharpness / resolving power" combination of lens characteristics combined with the teleconverters. But these converters still have their negative effects on distortion and bokeh quality.
Anyway, I can afford to be an early adopter on this, and I don't expect FF quality
That's good and a realistic expectation. We look forward to your results, please share it with us. Tusentakk og ha det!