70-400G lens

Started Feb 3, 2013 | Discussions thread
WaltKnapp
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Re: It's a bit of a beast to master...
In reply to JerryCurtis, Feb 5, 2013

JerryCurtis wrote:

For some reason (balance, I expect) it doesn't perform well on, even a decent tripod, like the Manfrotto 055X PROB, with a pan/tilt head. I've gotten sharper shots hand-held and braced against something with SSS on - and even freehand-held with SSS on. I find that a gimbal head with the Arca-Swiss mounting plate to be much better, because you can perfectly balance the camera/lens on this setup - even with the lens fully extended. (I guess using the Arca-Swiss plate on a pan/tilt head would also work better than the Manfrotto-type mount). I often use mine at 400mm and wide open and am usually quite pleased with the results, but it took a while to get consistently good results with this lens.

I have a 055 CF tripod and very early on with the 70-400G determined it was not stable enough for good work with that lens.  I use either the Gitzo CF 3541 XLS or the Gitzo CF 5541LS tripods with the Custom Brackets CB Gimbal.  Used to use the Wimberley gimbal but the CB is a more modern version with some advantages.

I'm not surprised that someone might to better handheld with long tele than with the 055, especially if it's not being used to it's optimum. My 055 only sees use with short focal length lenses, or when I must use the lightest tripod and not taking long lenses.

It's not really a beast to master long tele, but it does require undoing a lot of what you do with short lenses and developing specific stuff for the long work. Unfortunately many people, rather than working on learning try shortcuts like super high ISO or extreme cropping for long shots.  They are not optimum for best quality.

Tests have shown that stopping down from 5.6 at full-zoom gives very little gain in sharpness. SLR Gear in this review:

http://www.slrgear.com/reviews/showproduct.php/product/1223/cat/83

says:

"Stopping down to ƒ/5.6 provides tack-sharp results under 200mm. It isn't until ƒ/16 at focal lengths below 200mm that image quality is affected by diffraction limiting and shows a reduction in overall sharpness. Image sharpness actually degrades slightly at 400mm as the aperture is stopped down smaller than ƒ/5.6, so there's little reason to use the lens at anything but its widest aperture."

200mm is not what we are talking about, it's barely telephoto.  And I don't see a degradation in the 400mm end as I stop down.  I expect that a lot of that is poor use of support by folks finding that.

I used to blame any "misses" on the lack of MLU on my A350, but, even on the A77, I still get "misses". At 400mm and f/5.6, the DOF is very thin, so, if you miss your intended focus point by just a little, you'll notice it. You really have to pay attention to how you hold the camera and lens, how smoothly you press the shutter button, and even your breathing and stance to get consistently good results.

The main cause of "misses" is motion, not focus. DOF is not as thin as folks want to claim. Of course those folks that insist on shooting wide open regardless are at greatest risk of not getting everything necessary in focus.

It's easy to blame the lens and very difficult to prove or disprove whether the lens is AF'ing correctly or not, because it's so difficult to eliminate the other causes of unsharpness - even decent tripods and remote triggering is not 100% safe - although with the A77 and A99 (no mirror movement and electronic 1st-curtain shutter) a lot of the sources of minor movement/vibration are eliminated.

When AF fails it rarely does so by some micro amount, so is easy to see.  The extent of micro motion in the world of photography is a very poorly understood area, even though it's so important particularly in macro and long tele, both of which magnify all motion.

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