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-   -   Controlling the iris with MTF adapter (https://www.dvinfo.net/forum/sony-xdcam-pmw-f3-cinealta/492594-controlling-iris-mtf-adapter.html)

Andrew Stone March 3rd, 2011 09:19 AM

Controlling the iris with MTF adapter
Question about controlling the iris with the MTF adapter.

I understood that one 'rotates' the blue collar to control the iris on attached Nikon lenses but I have heard a comment recently about using the the small knurled knob to control the iris.

Can someone with the adapter please clarify it's use with both Nikon lenses that have physical iris rings and the "G" series lenses that are designed to control the iris from within the Nikon camera body.

Jim Tittle March 3rd, 2011 09:35 AM

Re: Controlling the iris with MTF adapter
Knob is a set screw. It acts as a handle for moving the collar. When you tighten it, you prevent the collar from moving.

The knob is knurled, but it's small. If you're out in the cold, if you have big fingers, or if you're wearing gloves, it can be hard to manipulate. You don't have to tighten the screw, but then you risk having your aperture setting change.

If you were to put a bigger knob on the set screw, that might help. But, it might also make it easier to strip the threads on the set screw. This screw seems like the most vulnerable part of the adapter.

Jim Tittle March 3rd, 2011 09:46 AM

Re: Controlling the iris with MTF adapter
Now that I think about it, it might not be a really good idea to use the set screw as an adjustment knob. It doesn't look like it can take a lot of abuse. When I loosen it enough to let the ring rotate freely, it gets shaky. And, since the screw diameter is about 1/16", it seems like I could snap if off pretty easily. Also, when it's loosened enough to unlock, it wobbles. If you don't loosen it enough, it grinds when you adjust the aperture.

If the adjustment collar (the blue part) had a rubber surface, or a texture, it would be easy to adjust. But it's slippery. And that means I'm constantly grabbing that little lock knob.

Andrew Stone March 3rd, 2011 11:39 AM

Re: Controlling the iris with MTF adapter
My plan is to add one of these Zacuto zip gears...


if you only want to buy one...


Ola Christoffersson March 3rd, 2011 02:53 PM

Re: Controlling the iris with MTF adapter
What - are you not supposed to use the knob for changing aperture?! There is no way I could run and gun without using the knob. Actually, I've been forced to extend it to be able to reach it properly (www.kamrat.tv). Anyway, using a scredriver you can make sure that it is not wobbling but still not locking the thing up.
Putting gears on it might make things better. Are you planning on using a follow focus to set the aperture? Maybe a tight broad rubber band around the thing could give it a better grip but it's is still hard to reach because of the width of the camera.
If you are going to put gears on it, these might work as well (Half Inch Rails DSLR Support). Much cheaper than Zacuto.

Andrew Stone March 3rd, 2011 04:01 PM

Re: Controlling the iris with MTF adapter
Hi Ola,

The gear band would serve two functions. Primary reason is to attach a motor for iris control on Steadicam with a major side benefit being added grip.

There is probably some off the shelf hardware store solution where you could have a decent looking band clamp with a short paddle attached to it that wouldn't look too "Canadian" as someone mentioned in another thread.

Andrew Stone March 3rd, 2011 04:15 PM

Re: Controlling the iris with MTF adapter
One more question... How freely does the blue collar on the MTF adapter move when you are adjusting the iris? Is it so close to frictionless that you have to tighten down the set screw after making an iris adjustment?

Thierry Humeau March 3rd, 2011 10:52 PM

Re: Controlling the iris with MTF adapter
There is a bit of friction (and you can adjust the amount of friction by titghtening the knob slightly) so no need to tighten the know. I assume they made it this way to it could actually be tighten in application where the camera may be subjected to vibrations, then, I could see the iris ring move by itself.


Alister Chapman March 4th, 2011 06:27 AM

Re: Controlling the iris with MTF adapter
I'm finding I don't need to tighten the locking screw on mine. I would say there is just the right amount of friction, not too tight, not too loose.

Jim Tittle March 4th, 2011 06:54 AM

Re: picking nits
One other tiny, little thing I don't like about the MTF adapter--the pin that actuates the iris control lever on the lens is a screw, with fine threads. Those sharp little threads make contact with the smooth surface of the lever. If you look at old Nikkors, you'll see that that control lever gets worn. Of course, on an SLR, that actuator gets a lot more use, since the camera stops down every time you push the shutter. Whether having sharp screw threads as part of the iris control linkage will really cause any damage remains to be seen.

Don't get me wrong--I really like the MTF adapter, and I'm glad I have one. Being able to use Nikon lenses on this camera is great!

Ola Christoffersson March 5th, 2011 10:14 AM

Re: Controlling the iris with MTF adapter
1 Attachment(s)
My aperture control mod is getting less and less Canadian.
Here is the latest 1 version made from a Zip tie and a piece of hard plastic (the thing you use on bolts to distance the nut. Sorry if these are not the correct terms in english).
This version is separate from the locking knob so I will not risk breaking anything when changing aperture. Now, I just have to cut it to the right lenght and find some kind of rubber thing to put at the end of it to get a nice feel to the touch.

Voila - smooth aperture control with the touch of my thumb instead of hidden behind the front of the camera.

Jim Tittle March 5th, 2011 12:22 PM

Re: Controlling the iris with MTF adapter
Ja, nu ser det ut som en svensk gjort det.

Steve Cahill March 24th, 2011 07:40 AM

Re: Controlling the iris with MTF adapter
3 Attachment(s)
Here is a modification I did to the MTF I just received. I have applied several layers of heat shrink tubing to it. Heat shrink provides enough flex, not to bend the delicate locking screw. It also provides enough force to tighten and un-tighten the screw and makes it easier to find if it unthreads in travel. Over time we shall see how this will work.

Updated with Ola Christoffersson's method of attachment, better design. Thank you Ola.

Leonard Levy March 24th, 2011 11:31 AM

Re: Controlling the iris with MTF adapter
Steve, I see the heat shrink, but what is the other thing?

It looks like a follow focus ring with a handle

Years ago I used t have a great little tool that was a ring that went around a lens with a handle that was easy to snug up on a lens for pulling focus, but I can't find them any more.


Steve Cahill March 24th, 2011 11:47 AM

Re: Controlling the iris with MTF adapter
Black handle iris control heat shrink is similar to Ola's picture-design, previous post. The red heat shrink is the MTF blue locking knob now with heat shrink on it. Right now the locking knob and the iris contol retrofit is such that both of the knobs are friction fit so the locking knob will not turn. Additionally I applied removable Locktite to keep the tiny locking screw knob from becoming loose and lost.

I await F3 to try it all out in the real world.

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