How big a lens to flex a plastic body?

Someone came into a camera store the other day and traded in his D80
for a D200. He said he did it because the large zoom (heavy) he was
using was flexing the body outward slightly at the mount. I think it
was the 80-400mm. The sales person asked if he was supporting the
lens with his hand. He said he was but still felt that the body was
being flexed slightly when he moved fast to shoot sports subjects. The
D80 body appears to be about as robust as a plastic body is right
now. Which make me wonder about the dynamics of longer heavy zooms
used on lesser bodies than the D80. Obviously, given the speed and
focal length of these lenses, it wouldn't take much misalignment to
effect focus on the sensor.

 

Hmmm, but the D80 has a metal chassis as well as a metal lens mount. I would
assume (although I didn't check), that the lens mount connects directly to
the chassis.

jue

 

: Someone came into a camera store the other day and traded in his D80
: for a D200. He said he did it because the large zoom (heavy) he was
: using was flexing the body outward slightly at the mount. I think it
: was the 80-400mm. The sales person asked if he was supporting the
: lens with his hand. He said he was but still felt that the body was
: being flexed slightly when he moved fast to shoot sports subjects. The
: D80 body appears to be about as robust as a plastic body is right
: now. Which make me wonder about the dynamics of longer heavy zooms
: used on lesser bodies than the D80. Obviously, given the speed and
: focal length of these lenses, it wouldn't take much misalignment to
: effect focus on the sensor.

I'm neither a metallurgist nor an organic chemist, but my impression is that
modern polycarbonate plastics are at least as stiff as most metals. If you use
a huge, heavy lens with any camera body and don't support it correctly, you
have to expect whatever happens.

Bob

 

Never, ever, fly in a Boeing 787 if you are afraid of plastic. It has a
plastic body.

Owl

 

If it makes him feel good and he has the money, Why not. In real life
I can't see it being a problem. However I tend to look at results and if I
am happy with them, I don't see problems. Some people spend more time
looking for problems than practicing their art. Maybe they don't know
photography is more art than science?

 

Was it your son DickA? I., mean, come on.

Greg

 

Bro, the thought of a fertile Dick[A] is too horrifying to contemplate.

 

Oh, no! Oh me, oh my... Whatever shall I do?

I just ordered the 100-400mm lens for a test drive on my shoddy, inferior,
plastic Rebel XT. No doubt, the camera will be destroyed over the next two
weeks.

Damn. Wish I'd known about this before.

dwight

 

Be carefull, that Rebel XT may blow up in your face as soon as you attach
that lens. The Rebel XT is certified for only 6 oz and under plastic
lenses.

Greg

 

RichA obsesses a lot here. Just plonk him.

 

Don't complain. Now you can do swings and tilts.

KS

 

LOL
rubber-body camera-baby

 

If the salesperson was worth his salt, he definitely sold a D200 that
day.
The "Someone" in this story is, though, a dolt.

--
THIS IS A SIG LINE; NOT TO BE TAKEN SERIOUSLY!

The White House announced that President Bush
will meet with Mexican President Felipe Calderon
next month. They have to discuss the growing
problem of illegal immigration. The two presidents
agreed to meet in Mexico's capital city, Los Angeles.

 

RichA is waiting for the Zenit B Digital. Not only is it metal, but it
has EMP proof vacuum tubes.

 

He can save money and not buy a Lensbaby ®

Just flex that funky body..

 

Unreinforced polycarbonate? I don't think so. In addition, like the
tail in the Airbus monster coming online, it is heavily reinforced
with massive carbon fibre ribs, much larger in thickness than
traditional aluminum airframe designs. The tail in the new Airbus is
something like 7 stories tall. I sure hope the glue holds...

http://www.popularmechanics.com/technology/transportation/3493516.html

BODY Composite fibers--carbon graphite, held together by epoxy--
account for 50 percent of the overall fuselage, versus the 9 percent
in the 777, making the 787 lighter and stronger than aluminum-body
aircraft.

 

Remember all the error 99 problems that people attributed to "dirty
contacts?" You had people wiping off the contacts, in many instances
no dirt was present and the camera was new. It is possible some kind
of body flexture problem produced the contact problem. Canon vaguely
attributed it in some cases to lens-body "mismatches" but it doesn't
explain why it would happen with a Canon lens on a Canon body, only an
aftermarket lens.

 

There's more than a few Error 99 problems being reported with 1dIII.
It's disgusting that Canon would use cheap plastic in a $5000 camera.

 

Maybe he was just mistaken, last time I looked most plastic bodies were just
that and nothing more, stainless steel chassis with the plastic just there
to cover the chassis.

 

Similar to camera construction, nice strong inner frame, light plastic
cover.