rmorrison1116 Loc: Near Valley Forge, Pennsylvania

I have a Canon EF 100-400 f/4.5-5.6L IS II zoom lens that I primarily use on a 7D II body to photograph birds. I've noticed that a substantial percentage of the time, when I press the AF button and lock in on a potential subject, they appear to know and fly off.

I'm usually well camouflaged, as is the lens, and far enough away from the birds that they shouldn't even realize I'm there. Yet more often than not, as soon as I get focus, poof, the bird is gone.

Could it be possible the hood is acting like a megaphone and projecting the sound from the image stabilizer and ultra sonic motor in the direction of the birds, letting them know something they're not accustom to is going on?

I know it sounds a little far fetched, but what are the odds of this happening as often as it does and it happens often and only when I'm using the 100-400 lens!

Kmgw9v Loc: Miami, Florida

Canons always make noise.

Rongnongno Loc: FL

Good observation and yes a hood not only amplify the noise but also directs it...

It acts like a speaker casing.

BHC Loc: Strawberry Valley, JF, USA

Serious question...... Would flocking the inside of the hood help dampen the noise?

N4646W

That's an interesting question. Flocking might help, but most likely the frequency range is high enough that it is directional instead of radial as in low frequency noise. Baffling would be a better alternative so as to disperse and cancel. Why not try manual focus as an experiment?

Ron

joer Loc: Colorado/Illinois

Some of it may be coincidence but most likely your explanation is correct.

Bird senses are extremely acute. What really amazes me is how sometimes they flinch when my flash fires and ruin the shot.

wetnwld

Is the auto-focus an infra-red function? The critters can probably or possibly se the flash of light. Watch your camera through a video camera to see the infra red light flash. This is also a good way to test your tv remotes.

Wenonah Loc: Winona, MN

This article says that birds can't see infrared light and it gives other possible explanations for what might be scaring the birds.

http://www.reddit.com/r/whatsthisbird/comments/35d1fh/can_birds_see_infrared_light/

Big Bill Loc: Phoenix, AZ

No, on a 7D II the autofocus is done the same way it is on pretty much any DSLR.
The only time the camera uses a light to aid autofocus is in low light, then it uses the on-board flash.

amfoto1 Loc: San Jose, Calif. USA

One of my favorite places to photograph birds is a wooded area along a stream, with a busy road nearby. The road noise covers the noise of my camera nicely. So much so that a heron intent on hunting almost stepped on me one time, while I was shooting there. He came so close that my 300mm lens could no longer focus and I had to stop shooting. He looked rather shocked when he realized that he was face-to-face with a photographer hiding behind a camera.

There are noise dampening devices you might try.... "blimps" for the cameras. A "LensCoat" neoprene cover might reduce the noise of the lens a bit, too.

Failing that, try manual focus and/or pre-focusing the lens. Also try IS off, to see if that makes a difference. Both AF and IS make some noise.

Another thing might be to work to acclimate the critters to accept your presence and learn that you pose no threat, so they ignore you. Most animals' senses are so much more acute than human beings', that they probably know you're there long before you spot them.

It took me a month or more working with her (almost daily) before this young coyote would relax with me close enough to photographer her with a 135mm lens...

LFingar Loc: Claverack, NY

Leaving the lens cap on might help dampen the noise projecting forward. :-D
Seriously though, I have a 7DII and 100-400 L II and have never noticed this happening. Perhaps I am shooting at a different distance or there is some other factor. I'll have to pay closer attention. One factor may be how accustomed to human activity the birds are. Most of my bird shots are in areas of considerable activity and the birds are no doubt used to various noises.

rbfanman

Many animals can hear sounds from a distance...even sounds that we can't hear. Manual focus instead.

rmalarz Loc: Tempe, Arizona

It might improve the image quality, too. It is a Canon.
--Bob
8-)

SharpShooter Loc: NorCal

Many big hoods are focked inside but I think it's more to do with isolating bouncing light than with sound but could be for both! ;-)
SS

BHC Loc: Strawberry Valley, JF, USA

Matte black paint would suppress reflecting light; I would think the texture of flocking would be akin to hanging drapes in an auditorium to surprises echoes. But I also understand the idea of the hood acting as a sound tunnel, isolating external sound waves straight ahead.

For the musicians among us, particularly those who plays brass instruments, what would be the effect of flocking the inside of the bell of a trumpet or other horn?