Long time lurker, first time poster.
The title of this thread says it all really. I've been using the Canon 17-55mm and Sigma 50-150mm lenses a lot on my 550D assuming that the old trick of zooming into a subject, focussing, and then crashing out wide would give me a nice sharp image to shoot with. But it's only recently that I've noticed particularly with the Canon that the image seems soft when I do this. I've never had any of my glass in for service so perhaps that would solve my issue, but really I'd like to invite anyone on the forum to post their findings with regards to zoom lenses that maintain focus throughout their range.
With the new Speedbooster adapter soon available in the UK, I'm looking at the Canon 24-105 being a potentially wonderful partnership in the making with my recently adopted FS700, but I worry that it's not parfocal.
Also, if anyone has any recommends in London for lens servicing, I'm all ears. Or eyes I guess, as this is a forum isn't it?