Lens camouflage?

[Frank Kolwicz]

If you've ever spent much time photographing birds, you've probably noticed how they often shy away when the lens is turned directly on them. A bird will be feeding or preening or loafing until you put it in your viewfinder and then it more or less slowly turns it's back and moves away. I've seen it happen scores of times in the last few months and many more times over the years with many species, but especially with those ever-wary waterfowl.

I suppose it's that big round lens that looks so much like a giant eye that spooks them, so, is there any way to disguise the lens itself without deteriorating the image?

How about a filter that has a reflective pattern, but no transmission pattern? There are some radical materials that optical physicists use that might do that. Or just something to break up the circle that could clamp onto the hood? Anyone tried anything like that?

[Bob Atkins]

I suspect that a sheet of camo material draped over the lens and hood is about the best you will do. I don't think there's any practical way to disguise the actual front element and I doubt that they can even really see it if it's shaded by a hood and camo netting. Breaking up the general shape of the lens (and you and the tripod) might help.

I doubt they see it as an eye, but perhaps they've learned that having anything pointed at them isn't a good idea!

[Frank Kolwicz]

I suspect that a sheet of camo material draped over the lens and hood is about the best you will do. I don't think there's any practical way to disguise the actual front element and I doubt that they can even really see it if it's shaded by a hood and camo netting. Breaking up the general shape of the lens (and you and the tripod) might help.

I doubt they see it as an eye, but perhaps they've learned that having anything pointed at them isn't a good idea!

Well, Bob, in that you might be wrong. I went out to the yard with my 500L on a tripod, facing north and looked directly into the lens from about 50' away (I and the background behind me was in full sun). Guess what, the reflection in the objective lens is *really* visible, not at all blacked-out by the fully extended hood. It looks like a big eye to my notably deficient human eyesight (20/20 or better), compared to birds. Not only that. but as my view of the lens came close to the optical axis, it got much brighter rather quickly, a few degrees off-center is rather darker than near-on-axis. That sudden increase in visibility of the round lens may be quite troubling to prey birds, like an eye opening directly at them. The only thing I can think of that would be worse is a pair of such "eyes".

[Bob Atkins]

That's interesting. I guess the front element of the lens is a flat glass filter, so it will act like a plane mirror to some extent (even though it is anti-reflection coated). I can't see anything you could do about that. You could in theory use a tilted front filter, but the filter would have to be large and there's no easy way to fit one. You might also get multiple ghosts under some conditions.

I suspect that it's something you may just have to live with.

[Frank Kolwicz]

The front element is not flat, I can see some distortion, but I guess it's a large enough radius that it's not reflecting at wide angles and the hood is deep, so that limits the ability to see the reflection until you're pretty close to dead-on.

[Bob Atkins]

The front element of the 500/4.5L should be flat since the first element is fluorite and so has to be protected. However I'm sure it's very effectively AR coated. Perhaps the first element isn't so well AR coated because of the difficulties involved with fluorite elements. In that case it may have a more visible reflection than the front filter and so the reflection you see will show some distortion.

[Frank Kolwicz]

Yep, the flat glass can be practically invisible depending on having a bright on-axis object to reflect (I had to use a flashlight to see the reflection), but the curved fluorite element easily catches bright objects well off-axis to make it visible. The effect is as if the front flat piece is invisible under many circumstances.

I note that the diagram shows another flat element at the rear, where the drop-in filter is located and that reminds me that I have a vague memory from decades ago that that flat filter was supposed to be present, either a clear element or colored filter, but not removed. Is that true?

[Bob Atkins]

Yes, the optical design calls for a filter in the rear position. However I remember doing some tests many years ago and I found it made little or no difference to the image sharpness. It does affect focus position, but AF (and MF) work fine without it there. It's just that if you focused first, then added the filter, the focus would shift slightly. I think Canon supply a clear (UV?) filter with the lens. It's a standard 48mm thread, but a thin filter is needed. There's also a drop in gell holder which has a clear filter built into it but which also allows you to add gel filters.

[Flash]

What would happen if you changed the shape of your "eye"?
Build a rectangular housing out of black or camo cardboard for the front of your lens, and maybe even include a piece of oblique window glass to obscure reflections off the front element?

cardboard box
   _____________  
          \               ]________
            \             [             |-----------------------  
              \           [             |
                \         [             |    Lens
                  \       [ _______|----------------------
    _________\ __ ]

                     ^^ glass panel

[Frank Kolwicz]

Reply to Flash:

I don't see that the box itself would do anything as the lens would still be pointed straight at the subject.

The down-angled flat glass element would probably be as invisible as the factory flat glass is. The large curved front element, just behind the flat one, easily catches reflections from the sky and other bright objects, even with the hood on and shows up readily while the flat glass is more likely to reflect something darker and becomes invisible. At least, that's what I've seen when I've viewed the front of the lens from a distance to try to get the subject's-eye view at near ground level.

An added flat element that was angled UP, however, might catch the sky reflection and that might blot out the reflection from the curved element, but then there are potential problems with flare and rain (I'm in Oregon), at least some of the time. This has possibilities.

[klindup]

Would a polarising filter kill any reflections of the front surface?  I guess it would if it is glass but assuming that coatings are metallic, this may not be the case. Just a thought.
Ken

[Bob Atkins]

Even if you could do it (which you can't with the long, fast telephotos) it wouldn't help. The front element of the lens is anti-reflection coated glass. Many polarizers aren't AR coated, and even the ones that are would reflect no less light from their front surface than the front element does.

[klindup]

I seem to recall that some bird photographers in bygone days would leave a lens out for days or even a few weeks so that the birds got used to it and it just became part of the environment.  I even remember reading of one who used a hide and had someone go in it with him.  the idea being that the birds could not count and when the friend left they thought the hide was empty. The idea of letting the lens become part of the environment seems to have some merit. 

[Frank Kolwicz]

I remember that advice, too, but have never had a reason to test it.

For my purposes, most of the time I can't stay in one place long enough or I'm not allowed to set up any kind of dummy camera/lens, so that's no help. Also, I suspect that it won't often work since the birds I've been photographing are very alert to movements and get really disturbed when the lens points right at them and often flee. I think it's the "big eye" that sets them off, which is why I'm trying to figure out how to kill that impression with some kind of camouflage.

For the times I'm working in my own yard, where I could set up a dummy camera, I haven't found it to be necessary as the birds are more or less familiar with my comings and goings and, if they flush, then they settle down after I move away or when I get into my portable blind, but some just don't like the lens pointed at them.

[klindup]

Eric Hosking was a British bird photographer (he died in 1991, before the digital age) of great renown.  If you can get a copy of his book An Eye for Bird you will find a lot of great information on the techniques that he employed to get his photographs.  It is worth trying to obtain a copy. It is available from used book stores.
Ken Lindup