Canon 300 f/4L vs 100-400

I am looking for responses from individuals who have experience with both of these lenses. I have owned the 300mm for several years. It is extremely sharp and has beautiful bokeh. For these reasons, I hate to think of getting a different long lens. However, the inflexibility of a fixed lens has caused me to miss a number of avian/wildlife shots that I could have gotten with a zoom lens. I have a 1.4TC for the 300mm that works very well also, so I am not looking to add any length, I am just wanting more flexibility in a lens. I do not have to sell the 300mm in order to buy the 100-400, but realistically I'm never going to be carrying both of these lenses at one time so I will end up having to choose between the two of them. So for those of you with experience with both of these lenses, if I start using the 100-400 for avian/wildlife shots, will I notice a decrease in the quality of my photos?

if I start using the 100-400 for avian/wildlife shots, will I notice a decrease in the quality of my photos?

Yes, unfortunately. If you had never seen the image quality of the 300mm, you'd probably be fine with the 100-400mm. It's very good, but not stellar. After many weeks of research and asking the questions you asked, I scratched it off my list.

Having said that, there have been very fine images posted with that lens. I dunno... maybe if you get PhotoKit Sharpener or the Nik version to really throw some expert sharpening at the images, it'll be just fine. Someone may pop on here and say I'm nuts, the lens is great, so it's hard to say. Any chance you can borrow one to test? Or, if you don't mind spending $102, you can rent one for a week (that price includes shipping and insurance).

If there's any one lens that Canon sould do a version II on, it should be that one. Boost the optics and somehow do internal zoom and focus, and it'd be a winner.

I am a birder / photographer. I switched to the 300 f/4L from the 100-400 several years ago. I use the 300 with 1.4X Converter on a Canon 40D which has a 1.6 crop factor as my walk around birding camera set-up. The effective focal length is 672 mm - - very adequate for birding and other wildlife shots. But that's not why I changed. First, the act of changing the focal length on the 100/400 can pump dusty air into the camera, making specks an issue. You can google this as it is a common problem. Second, I found auto focusing with the 300 prime lens faster, which meant I had more keeper pictures of quickly moving birds. Third, I found I using the long end of the 100-400 lens most of the time for the wildlife and using another wide angel set-up for landscape. I did this because the low 100 mm end was to long for that purpose. So to me the advantages of the 300 prime in focusing speed and less dust outweighed the additional reach. I did not use a converter on the 100-400, but added it when I went to the 300. For another POV, you may want to Google Stuart Healy, an Arizona bird guide who also made the switch to the 300. His web site has pictures done with both and some commentary I think on why he switched.

I have rented the 100-400 twice. The result was 1st time the shots were decent not stellar. The Push pull is ok I was used to the format with my old film camera but the lens is long at 400mm. The second time I sent the lens back after shooting for one day. 6 months later I bought the 300mm f4 IS and have been very happy with it. Yes there have been a few times when something shorter would have been nice but the pluses far exceed the limitations. I think renting is a very good option but keep in mind that the 100-400mm has a reputation of great variability in IQ from lens to lens. When you get a good one I think they are very good maybe not quite to the level of a prime but close.

I would say the 100-400 is better for landscape than wildlife. When the light is moving fast, the time it takes to switch lenses is too long. With the 100-400 you can capture quickly both the details of a scene and semi-wide shots no problem. I wouldn't bring it anywhere dusty though. As for when it rains, a handy pair of gloves can absorb the water and keep it from entering the lens when zooming out. I have found the sharpness acceptable when coupled with my 1.6x sensor. In certain situations though, the sharpness of a lens is less important. For example using high iso's will bring down every part of image quality ESPECIALLY WHEN SHOOTING WILDLIFE at sunrise or sunset. The 300mm has no advantage in f stop when used with a 1.4tc. High iso noise would be my main concern, not the sharpness of the lens. with a 1.6x crop sensor, which i'm guessing you have, the sharpness will not be too disappointing. Hope this helped.

Thanks for the responses. They really helped in my decision making process. I'll stick with my 300mm for now and continue to dream that one day Canon will come out with a stellar 200-400mm f/4L IS. That would be ideal for me!