400mm Prime or 100-400 IS L

Here are some tests done by a forum member.http://www.pbase.com/f​stopjojo/teletest

1) https://photography-on-the.net/forum/showthre​ad.php?t=43436

2) In another thread comparing the sharpness of these two lenses I realized that everyone commenting on the sharpness owned either one or *neither* of these lenses. The 3 guys who owned *both* said that there was no difference. Read here: https://photography-on-the.net/forum/showthre​ad.php?t=117354

If you have not owned BOTH lenses then you do not know what you're talking about and you're just repeating what someone else said. And then I'd say that they don't know what they're talking about.

I own both lenses, and have for a while. I have racked up many thousands of frames with both lenses. The in-field differences in sharpness between these two lenses will ALWAYS be explainable by user error. ALWAYS.

I own a 100-400 and love it,I dont use a tripod or monopod I have never owned a 400f5.6 so with these long lenses whitch am I going to get the sharpest shots out of?I will tell you now it will be my 100-400 as it has IS.

I debated the same thing back in the spring.......as many have said already...I think it will mainly come down to how much versatility you need. While the 400 is unquestionably sharper (of course it is, its a prime).....if you are going to need 400mm one minute and then 100mm or close to it a few minutes later, then it'll be hard to do that kind of zooming with your feet, or you'll be changes lenses like a madman all day long. I chose the 100-400 because thats the situation I was in, and I haven't regreted it a bit.

I have allways described the images from my own 100-400mm has "primelike"

No,. it is not up to the standards I expect from my big primes,. but the image quality is absolutely competitive with primes.. if not identical. If I am shooting with multiple lenses on an extended shoot,.. when I review the files in my viewer fro conversion,. I need to look at exif to see which lens I used. The naked eye does not suffice.

The Primes big advantage in this case is Focus speed... this difference you will likely notice without having to break out the micrometer and pink noise generator.

If you aren't getting hung up on 100% crop comparisons of image sharpness.. then you are comparing focus speed vs. zoom flexibility and IS, closer focus distance etc..

One other thing to consider - I can't speak for the 400/5.6L prime, but I have the 300/4 which is very similar in construction - it is great for manual focusing. It has a smooth-acting focus ring. I suspect that the 400/5.6 prime is similar.

Yes, manual focus is easier & better on the 400mm compared to the 100-400.

I owned both lenses for a week and compared them under controlled conditions. My findings were that at 400mm wide open (both at f5.6) the prime was a tiny bit sharper. Then, just a third stop down at f6.3 they were essentially equal. Here's some proof: http://www.pbase.com/t​ough_dog/more400mm. Michael R's review led me to get the prime since he showed that HIS zoom was very soft in comparison. Maybe I was lucky, but my zoom is quite sharp wide open over the whole 100-400mm range. There seems to be a wide range of performance attained from different samples of this and other expensive Canon lenses.

tough_dog wrote:
I owned both lenses for a week and compared them under controlled conditions. My findings were that at 400mm wide open (both at f5.6) the prime was a tiny bit sharper. Then, just a third stop down at f6.3 they were essentially equal. Here's some proof: http://www.pbase.com/t​ough_dog/more400mm. Michael R's review led me to get the prime since he showed that HIS zoom was very soft in comparison. Maybe I was lucky, but my zoom is quite sharp wide open over the whole 100-400mm range. There seems to be a wide range of performance attained from different samples of this and other expensive Canon lenses.

Reichmann undoubtedly has a poor copy of the 100400 if only for the fact that his comparison bw it and the 70200+2xTC was close in IQ, when really there is no comparison. At 400mm, my zoom is at its sharpest wide open.

Jman13 wrote:
The 400 f/5.6 is extremely sharp, the 100-400 not so much. (it's not bad, but not prime territory). If I buy a 400mm lens, I'm probably going to pick up the 400 f/5.6. I can't see myself dropping the several thousand dollars to get a 400 f/2.8.

ditto, concur, likewise, what he said

i really agree that the photographer also has a whole lot to do with the quality of the photograph. I am a novice learning to use my lenses as far as I am concerned. I also believe that handholding with IS sometimes gives a false confidence. I know it is great and really does help because I had a lens with it but I think it also made me depend on it to much. In other words I was not using it correctly so did not get the sharpest pictures. i have seen many times that no shot is better than a shot on a tripod. i know tests are done on tripods and the best pics I have seen are done on tripods... When I get my long lens a tripod with be the regular and the hand held shots will be about the other 50% of the time or less. We will see.