tmr4:
Based on my observations above I would say that the improvement in IQ at 200mm occurs gradually from MFD through 6ft with some increase still beyond this.
Nice test. I still see some contrast degradation though. In my experiments, the focusing distance of 6 feet, was definitely showing better results than at MFD but I usually needed at least 7 feet to accept the image for print. At slightly more than 8 feet, things get to be normal but I usually (like you) set the focus limiter to 3m to avoid any problems at 200 mm.
I've suspected similar behavior from my non-IS version... the annoying thing is that you get an AF confirmation and think you're good. Anywhere away from MFD my lens is stellar, but for me, this reduces the usefulness. It's most annoying when you are just kind at the edge with anotherwise nice, but not quite sharp enough image... now all of a sudden the cheap primes blow away the L.
Ok, today I had Canon Service take a look at my 70-200L 4IS.
First the tech measured focus at a distance of 2.5m. He said the lens had a backfocus from 135mm to 200mm. Then he measured focus at 3.5m. No backfocus at all. He couldn't explain the difference to me. For that he would have to investigate the lens further. He could calibrate the lens to perfect focus at MFD over the entire range. But that would probably mean a performance penalty at other focus distances. So I didn't have my lens calibrated. He also said that the lens was focusing according to Canon's specifications. Although with a very high tolerance. I asked him if he came across this MFD issue in the past. He wouldn't answer directly. He only said that people didn't use this lens at 200mm MFD very often. Unfortunately not a new insight, only a confirmation of what I had concluded myself already. So much for that.
For me it doesn't really matter. I am not going to use this lens at 165mm-200mm MFD. I know it's limitations. I also know that this lens is designed this way. I can get acceptable results at 165mm-200mm MFD for certain purposes. Furthermore, I haven't seen one pic shot at 165mm-200mm MFD that is sharper than what my copy can produce.
Thanks for the update... It's pretty much what I figured... This basically is a design flaw it would seem... that is, focus at 200mm MFD is not going to be as good as it is at other distances...
[Edit] I do not know the exact distance to this face in the memorial... Originally I was thinking it was indeed very close to about 5 feet, but the more I think about it, it must be further away then that... Perhaps sometime soon I can go back and figure out exactly how far away it is... I'm all but certain it's no more then 7 or 8 feet away]
For what it's worth... the photos taken by me with the 70-200mm f4 IS, in the following post I made at dpreview were made at very close to MFD, probbably like 5 feet away, and this was/is at 200mm f4.5 At least the ones showing the face in the memorial that are taken straight on... the ones taken from the side showing focus accuracy were more like 7 or 8 feet away from the focus point...
I would term this more of a design compromise than a design flaw. It is too bad that comprehensive performance characteristics for all lenses aren't available so one knows what to expect prior to purchase. If they were then everyone would know ahead of time what they were getting into. I suppose that would result in fewer lens sales though.
I have used the lens at around MFD and 200mm. This is a very tight head shot on a crop body. I've gotten acceptable sharpness for my purposes. Of course this might not work for everyone where critical sharpness is needed. Still for me this is one of my sharpest lenses wide open. The 135L gives a somewhat similar FOV at its MFD and it is sharper than 70-200 f/4 IS wide open and at MFD. I find I use it more close in that the 70-200.
Leon Noel wrote:
Ok Daan I ran a few simple test shots (IS off, ~ MFD, on tripod, triggered with wired remote), here's my findings (bear in mind I believe my copy backfocuses a little, a few mm for short focus distances)
- At 70mm it beeps if I half press the shutter on remote. Picture came out sharp.
- At 100mm it flashes but no beeping, shutter would not trip (no AF obtained), so I moved the tripod back away from the subject, about 1-2cm, then it beeped. So there was a tiny shift here. Picture came out sharp.
- At 135mm it beeped again, sharp result.
- At 200mm it beeped also, sharp result.
So the only MFD shift I experienced was from 70mm jumping to 100mm, and even so it was only 1-2cm. I don't know why Canon says MFD at 200mm can be about 3.9m !!!
Hope that helps , good luck and happy shooting. ...Show more →
Mine was the same. Tack sharp at MFD at all focal lengths. I would have kept it but the aperture issue bugged me. Not enough background blurriness at f/4 and slow AF in low light.
I also didn't know anything about it when I purchased the lens thinking that I would be able to use it for near-macros of flowers as well. Of course I'm happy with the 70-200 f4 IS, but I did buy a true macro lens after learning that those soft close-ups of mine were not operator errors but rather were due to a design limitation of the zoom.
, good luck and happy shooting.