The Digital Picture reviewed Canon EF 24-105mm f/4 L IS USM and commented:
” The Canon EF 24-105mm f/4 L IS USM Lens’ color and contrast are excellent. The rectangular baffle (above) over the rear of the lens is purposed to increase contrast and reduce flare/ghosting. CA (Chromatic Aberration) is well controlled with some CA visible at 24mm in very harsh contrast situations – mostly at full-frame edges.
Eight circular aperture blades provide excellent quality defocused image quality (bokeh – foreground/background blur). While f/4 in this focal length range is not the best at creating diffusely blurred backgrounds, close subjects at 105mm can have pleasingly defocused backgrounds.
Canon’s latest generation Image Stabilizer (IS) provides an additional 3-stops of handholdability in the Canon EF 24-105mm f/4 L IS USM Lens. This is definitely my favorite feature of the 24-105 L. The 24-105 L’s IS is very quiet and very well behaved (does not jump when starting, …). IS does not stop subject motion blur, but it is excellent for stopping camera shake. IS allows use of narrower aperture settings to increase DOF (Depth of Field) in handheld shots with non-moving subjects (landscapes, sculptures, art …). IS allows use of longer shutter speeds to create motion blurs – such as moving water. “