Earlier this week a friend of mine asked me to take some test shots with her 100-400mm IS L lens. She said she has never been happy with the sharpness of the lens. I didn't have a tripod, so I set a beanbag on the hood of my truck and rested the lens on that. I also placed a bag of rice on top of the lens for extra stability. I didn't have a lot of time, so I only took some shots at 400mm because that's where I figured she would use this lens the most. I'm sure I would too.

When I got home a looked at the pics starting from wide open, and working my way through the apertures, I was a bit surprised. Wide open, I didn't think it was too bad, and it continued to get better as I stopped down, until I got to f/8. This was by far the WORST image of the bunch! I was expecting f/8 to be one of the sharpest images of the bunch. f/9, f/10, and f/16 all looked very good. I just couldn't believe how bad f/8 was.

Granted this wasn't the best testing environment (no tripod, cable release, outside on a windy day) but I was expecting much better performance out of an L lens.

I don't own this lens, nor to I plan on buying one, but I do have a rental reserved for a trip coming up in about a month. After seeing these images, I'm starting to wonder if I made a mistake. I will have a few days with the lens before I leave so I can test it out and figure out where the sweet spot is, but the test images make me a bit nervous.

Has anyone else who uses this lens had any problems with soft images? I wonder if she just got a bad copy of the lens, or if it needs to be sent in for adjusting. I scanned through a bunch of the reviews on this site, but didn't see anyone say anything about this lens being soft, except for wide open.

Mike, I shoot with nothing but this lens. I've always shot at F6.7 to 7.1, and have been totally happy with the results. The last time out, when I shot the yellow headed blackbirds, I found I had shot these at F8. I was pleased. These were all shot handheld, from my car.I shoot everything handheld. I've heard that stopping down to F8 will give the best results, with this lens. I've also heard that there are soft copies out there, though less than in the past. I would have to guess that the problem is that individual lens. There is a pro phographer from Ely, MN that has shot awesome wildlife photos with this lens, and he is the one that recommended F8 and smaller.

Mike, I have this lens and use it for mainly wildlife shots. I have never had any problem with the IQ. HTH.

Cheers,

WesternGuy

Just a question,

When you had the camera "planted", was the IS turned on or off? I would be curious to see if there is any different with the IS on/off. I've read that expecially when shooting from a tripod, ensure the IS is off as it can almost cause shake (don't know if there is any truth to that or not) but thought I might bring it up.

Just a question,

When you had the camera "planted", was the IS turned on or off? I would be curious to see if there is any different with the IS on/off. I've read that expecially when shooting from a tripod, ensure the IS is off as it can almost cause shake (don't know if there is any truth to that or not) but thought I might bring it up.

That's a good point, but why just affecting f8?

The Canon IS is different from Sigma, it senses when the lens is static.
Sigma 80-400 you have to turn it off, otherwise it "drifts" and the image moves despite the lens being still

...Wide open, I didn't think it was too bad, and it continued to get better as I stopped down, until I got to f/8. This was by far the WORST image of the bunch! I was expecting f/8 to be one of the sharpest images of the bunch. f/9, f/10, and f/16 all looked very good. I just couldn't believe how bad f/8 was...


Sounds strange. It should get progressively better without there being a "bad spot" along the way. I would perform some more tests with that lens under more controlled conditions.

The big advantage of the "L" lenses is that it shouldn't take much stopping down at all to reach optimal IQ for any particular lens. With primes, it may be 1/2 to 1 stop, with zooms perhaps 1 to 1 1/2 stops.

...I've heard that stopping down to F8 will give the best results, with this lens...

Sounds about right to me for this particular zoom.

It is the reason why some people have bad experience using teleconverters. If the optimum IQ comes at f/8, then using a 1.4x TC means one must shoot at no faster than f/11. For those using a 2x TC, no faster than f/16.

Far too slow for most people/situations. Tough balancing act between enough reach and enough IQ.

Thanks for all the input everyone. I did give here some suggestions about testing it herself, in more controlled environment.

I did have the IS on, and I did notice it working as soon as I pressed the shutter button half way down. As much as I had it stabilized, I still had my hand on the camera and some shake was noticeable without the IS on. It wasn't as stable as a tripod would have been so I don't think it was a result of the IS. And like Mike said, why would that only affect the shot at f/8? Unless I had everything perfectly still for that one image.

I do have another set of photos from this "test", that I haven't looked at yet. I will look at them today and see if the results are the same. Perhaps the f/8 image was just a fluke.

That's a good point, but why just affecting f8?
Phase of the moon? Alignment of the planets? Hard to say. <lol> How can you tell I've worked with computers for a long time <lol>

Only think I could imagine could possibly the aperture isn't sizing right (or only a portion of it is closing) at that level. Pure 100% speculation on that one and a very long shot I will admit.

Does the camera have a DOF preview button? May want to try viewing that when it's auto-focused and see how things look, then try it on manual focus, and see if that makes any difference. Again, just throwing ideas out there to try to eliminate possibilities, which probably creates more questions. <chuckle>

Cheers,
Greg

It is the reason why some people have bad experience using teleconverters. If the optimum IQ comes at f/8, then using a 1.4x TC means one must shoot at no faster than f/11. For those using a 2x TC, no faster than f/16.



Another reason, (off the subject), for possibly having better than optimum results using a TC with this lens is, you lose autofocus capabilities, and not everyone can manual focus like Loupey. :D

I use this lens a lot and never had focusing problems or sharpness problems.

Roger