Gear Talk > Lenses

300 f/2.8L and 400 f/2.8 at f/2.8

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I have a technical question to ask the forum.  I already have some ideas on what is going on, but I don't really know for sure and wanted to ask, since many of you are so knowledgeable.  In advance, thanks.

I tested my 300 f/2.8L I IS vs. my 400 f/2.8L I IS yesterday at a track meet.  I felt that I had more OOF shots with my 400 and wanted to see if that was really true or not.  So I set up at the end of the back straightaway, and shot runners running towards me (from curve up to about 20-30 yards away from me).  I set the lenses both to f/2.8.

I shot with the 300 and the hit rate was unbelieveable.  The faces were razor sharp almost everytime.  My settings were 1/5000, f/2.8, auto ISO.  I was in Servo mode on a 1DX.

I then shot the same settings and the hit rate was much less with the 400.  A lot of the focus was missed (can see another area in focus just slightly to the right or left on another runner) or the faces were just soft and there was no real apparent focal point anywhere in the photo.  However, it did hit a lot of photos, and again, those were incredibly sharp.

I did realize of course that with the 300 the runners are closer to me when I fire the shutter, vs. the 400, which could matter. 

Is DOF (f/2.8 is pretty thin) more difficult to manage at longer focal lengths?  Remember up until this year I had only used a 300 for sports and didn't buy the 400 until last July.  Is IS more of an issue, even at 1/5000?  Does the lens focus slower or not as accurately as the 300?  I was thinking it's not AFMA since when I shoot golf with it I never have any OOF shots, ever.  Of course they are not moving much in golf, so I'm afraid the track problem could be my bad technique with the 400. 

Just thought I'd ask since of course as you can imagine, it's sort of frustrating.  Thanks a lot!

Jack Douglas:
Hi bdunbar79,

Sorry I can't help answer your question but I thought you might be able to help with mine.  And since we're talking the same lens I'm pretty confident you'll have a comment. 

Less than two months ago I bought the 6D 300 F2.8 II and both extenders III.  I only had my Nikon D5100, AF-S 70-300 to compare with (450 eq field of view and not up to Canon L quality) and that lens was not very expensive (maybe $600 compared with $7K) so I was expecting to be impressed and I wasn't.  That's not to say that there is nothing better about the 300 2.8 II such as DOF at 2.8 etc. but I was so disappointed with detail sharpness, I interacted with Canon and two weeks ago sent those items back with my 6D body.  It's driving me nuts worrying that things won't improve because I don't have any previous experience dealing with Canon, although I hear good things.  The issue is not AFMA, it's the resolution in the focused region, sharpness.

So I'm wondering if, with your experience, you'd be able to offer what you think of what I'm getting, or alternately share something that illustrates the detail that you get.  The 6D is 20 MP compare to 18MP crop so I guess the D5100 may actually match the resolution of the 6D relative to pixel density - I would have never thought so but .....

I'm not sure if the 6D vs 1Dx would make comparison difficult.  Here is one moon shot with the 300 X1.4 from tripod that I took that didn't seem to cut it.  I used live view WiFi remote to get focus as close as humanly possible at the highest magnification.  Hope this interjection into your post isn't out of place.


Could the AFMA be off on the 400?


--- Quote from: raptor3x on April 14, 2013, 12:32:42 PM ---Could the AFMA be off on the 400?

--- End quote ---

No, I tested it.  That was my first thought, and so I shot a golf tournament and hit just about 900 out of 900 razor sharp with the lens.  Usually with AFMA you get a random distribution of OOF and in-focus shots regardless of what you are shooting.  Thanks.


I will get to your points shortly.  I wanted to demonstrate when the 400 does get it right, as in Photo 1, triple jump and when it doesn't as in Photo 2, the Women's 1500m run.


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