Luminous Landscape have published a brief comparative test of the new professional level Canon EF 24-105mm F/4L IS lens (pictured) and the older consumer Canon EF 28-135mm IS lens.

“For the past year I have been using the 28~135 IS USM because it is relatively inexpensive, portable, has good zoom range and is an eminently decent quality lens. I knew it wasn’t top-of-the-line Canon, but it worked well for me. Along came the 24~105 offering portability (only a wee bit heavier than the 28~135), good zoom range and top quality at three times the price. Quandary: is it worth sinking about USD $1250 on top of the $400 I spent last year on the 28~135? The solution: test and see.”

Website: Luminous Landscape - How I Decided to Up-Grade From a Canon 28-135 IS to a Canon 24-105 F/4L IS