The photos below are taken with the Canon EF 70-200 F/4 L IS USM Lens, the second photo was taken using the lens combined with a Tamron SP AF 1.4X Teleconverter.
The 70-200mm F/4 L IS USM is my first Canon "L" series lens, the coveted breed of Canon lenses that are the best technology can produce at this day and age. Although I did not see an order of magnitude difference in my photographs with this lens and my non "L" series lenses, I could definitely make out where all the hype is coming from. Perhaps the lack of major differentiation could be coming from my abilities as a photographer too, a more experienced photographer might put the lens to better use.
That said, the lens was a pleasure to handle and use. A bit on the heavier side, but with excellent build quality, the lens feels solid in the hand and balances well. It would no doubt handle better on the 40D or one of the more professional Canon SLRs than my 400D. With up to 4 stop image stabilization, one can hand hold the "heavy" lens and get sharp photographs under most circumstances with sufficient light.
Photograph taken with Canon EOS 400D and Canon EF 70-200mm F/4 L IS USM combined with Tamron SP AF 1.4X TC. One can make out the details captured and the sharpness of the lens even at 1.4X magnification from 200 mm, especially in the ants on the stem. The equivalent focal length in 35 mm is 200mm * 1.6X (FOVC) * 1.4X = 448 mm. Having a 448 mm with F/5.6 (the 1.4X TC reduces max aperture by one stop) max aperture and Image Stabilization is quite good. The reach is not sufficient for wildlife/bird photography, but is a handy zoom with 112 - 320mm without the TC and 157 - 448mm with the 1.4X TC.
There are 4 variations of the 70-200 focal range zoom in Canon's line up, in the increasing order of price, they are:
- Canon EF 70-200 F/4 L USM
- Canon EF 70-200 F/4 L IS USM
- Canon EF 70-200 F/2.8 L USM
- Canon EF 70-200 F/2.8 L IS USM
- At this focal range (or any other for that matter), IS is quite mandatory & extremely useful
- The F/2.8 lenses are quite bigger and heavier
- The 70-200mm F/4 L IS USM was the best compromise - it had IS and was much cheaper and lighter than the 70-200 F/2.8 L IS USM
- The 70-200mm F/4 L IS USM and 70-200mm F/2.8 L USM are available for almost the same price, but I prefer IS to having a one stop max aperture advantage. For those who want to stop motion and need shorter depth of field, the F/2.8 is a good choice. Note that IS will help with camera shake, but not with subject motion
- Review of Canon EF 70-200 F/4 L IS USM at The-Digital-Picture
- Review of Canon EF 70-200 F/2.8 L IS USM at DPReview