Originally posted by nanhi A good WA Converter is a life saver in many situations, and it need not be expensive.
For the "poor" guy and certainly students, it is a great lens to experiment wide angle photography with. Here are some sample shots by my son, a student like Turf, with his Yashica 0.7X Converter on the 18-55 Kit lens - the Yashica WA & Tele set in 55mm filter mount cost him $ 24 on eBay + shipping.
OK, but you're talking about something totally different here - using a converter on an already-wide lens to get you to an even wider angle that would be prohibitively expensive otherwise. The OP is looking at using it on a telephoto lens to get to a "normal" field of view, and normal lenses are at least as cheap as even that $24 converter. For that matter, I'd expect the kit lens to noticeably outperform a 50 plus just about any wide angle converter.
Quote: Note: the photo has been sized for ease of comparison. Img 3570 is with Kit Lens and 3594 is Kit Lens with the Converter.
Yes, decent converters can often do a decent job of preserving IQ in the part of the image that you could have captured without the converter. More to the point, though, is how the edges of the image look - the parts that you wouldn't have captured with the converter.
Also if it's a question of using the converter to get you to a 12mm field of view, well, then, one can't really complain if the results aren't very sharp - like I said, it's not like you were going to get that FOV any other way. But given that a decent 28mm lens can be had for about the same price as the converter, and I suspect the 28mm lens would absolutely *demolish* the 50 + converter combo when it came to the edges - that's why we're recommending against the converter. As a way of getting to 12mm for cheap, sure. As a way of doing 28mm, it's not likely to compare favorably in price or quality with a 28 prime or even the kit lens.