I'm confused about something. I've never shot video with a 5d, but have been using a Letus extreme and Nikon primes with my Canon H1 and A1. With this rig, you have iris on the camera as well as on the lens.Obviously the more important setting is on the lens, but you also have some leeway on the camera itself.

On the 7d how does that work? For example, when you put a canon prime on the 7d body, do you control the iris by the lens, or only in the camera, or both?

I plan to use my Nikon lenses with an adapter when I get a 7d, and have the same question there. Do I control the iris on the lens, with the camera , or both?
Is there a difference berween canon and Nikon lenses in how this works on the 7d?
Thanks in advance.
Bruce Yarock

The current canon lenses don't have an aperture ring. You have to control that from the camera body.

There is no iris on the camera body. Only in the lens.

The camera can't control a Nikon lens. It will be 100% manual control using the rings on the lens.

Chris,
What do you mean by this?

"There is on iris on the camera body. Only in the lens."

So Canon lenses doen't have aperture rings like the Nikons do, correct? So when using a nikon lens with adapter on the 7d, how does that work?
Bruce Yarock

Thanks, Chris. So with Nikon lenses,the camera iris has no effect on anything?

There is no camera body iris on any DLSR... the only items on the body that affect the output for this discussion is... shutter/shutter speed and ISO adjustment.

The lens has the iris blades that you adjust either fully open or fully closed and any intermediated settings between open and closed. (Canon lenses are controlled with electrons, Nikon lenses are controlled mechanic levers)

when you use a letus 35mm adaptor your actually just taking footage from a scene that is
projected on a small piece of ground glass... as you know the onboard camera lens has the
iris mostly wide open so when the lens is focused on the ground glass screen you don't stop
down the onboard lens to the point that you pick up the granularity properties of the ground
glass.. so there's not much room there for you to play with... but the added lens at the
end of the 35mm adaptor has no restrictions as to how much iris you place, depending how
you want the footage to look... short DOF(more open iris) or long DOF(more closed iris)

That is correct. No aperture rings on the Canon lenses. There is a selector wheel on the body that let you change the lens setting. You rotate the wheel and it adjusts the aperture by the step amount you have chosen in the menu (1 stop vs 1/3 stop steps).

With the Nikon glass you will adjust everything with the rings on the lens.

Ray-
I meant to say "f stop".
I also shoot with a Nikon D200, and was trying to visualize how this would all work wirh 7d video.

Chris,
I now understand that the only control using the Nikons is the aperture ring on the lens itself. So the f stop wheel on the 7d has no control over anything while using the Nikons?
thanks for your patience.
Bruce Yarock

You are most welcome. Ask anytime. :)

Chris,
You didn't answer this-
"So the f stop wheel on the 7d has no control over anything while using the Nikons?"

Bruce yarock

Chris,
You didn't answer this-
"So the f stop wheel on the 7d has no control over anything while using the Nikons?"

Bruce yarock

Sorry Bruce,

That is correct. The camera won't register any aperture information from the Nikon glass nor will it control it. The wheel will not have a function with that setup.

Bruce,

Just to fully clarify your questions. Canon lenses (for the EOS series) have the iris diaphragm blades in the lens between elements but no aperture ring on the lens to control them. The iris opens and closes at the command of the camera body based on exposure mode and settings "dialed in" on the camera body. The body sends electrical commands that cause a motor in the lens to drive the iris blades to the proper aperture.

As was pointed out Nikon (and many other manual lenses) have no way of communicating with a Canon body and most do have a manual aperture ring. When mounted on a Canon EOS body with an adapter both aperture and focus are done by manually turning the appropriate ring. Even though the lens cannot communicate it's settings to the camera, the body's metering system is still "aware" of the amount of light coming in and on my T1i the body adjusts ISO and shutter to get the right exposure for that "amount" of light.

I'll find out how that works on the 7D when mine gets here in 3 days.

What do you mean by this?

"There is on iris on the camera body. Only in the lens." That was a simple typo. He meant to say "There is no iris in the camera body." I've fixed his post.