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Old January 29th, 2009, 01:57 PM   #1
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new way to lock aperture on ef lens

I have been babbling in several threads about trying Mylar to block the electrical connection to the Canon EF lens. I tried it this morning and it worked great. Total cost: $3.

Background: If you block the electrical signals to the lens, then it will stay at a constant aperture. This makes the problem of controlling exposure on the 5D2 video much easier. You can then lock it on any aperture, ISO, and speed, using methods not covered here (within the limitations of 30 fps). Existing methods to do this include rotating the lens or applying tape to the contacts. Rotating has the problem that the lens may fall off and putting adhesive tape in could get gunk inside your camera.

Preparation: I went to a crafts store an purchased some thin Mylar film. I think acetate would also work. It doesn't have to be transparent. I took the cap of the back of a lens and laid the film over it. I then used an Exacto knife to cut around the inside of the lens lip and created a perfectly sized disk that fit in the mount. No lenses were harmed in the process. I put the disc in the mount hole and mounted the lens. The film was thin enough that I didn't feel any extra force when turning. At this point looking through the VF showed an ugly filmy look (duh). But the F-Stop showed 00 which was what I wanted.

Then I cut out a rectangle in the middle of the disk that matched the rectangle hole in the mount. I dropped the film back in and rotated it so the light wasn't obstructed, and mounted the lens again. This time the VF showed a clear image. I carefully checked the edges to make sure no film was intruding on the image.

Usage: Put in the lens normally without the film. Adjust the aperture to what you want. Hold down the DOF Preview button and remove the lens. Drop the film in rotated correctly, remount the lens, and you have a locked lens.

I personally consider this less of a kludge than paying for Nikon lens and using them with an adapter.
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Old January 29th, 2009, 02:44 PM   #2
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While it's certainly cheaper than buying an equivalent Nikon lens and an adapter, it's certainly not less kludgy! Just look at the steps:
1) Cut a ring of mylar film,
2) Set the aperture using the camera body's controls,
3) Hold down the DOF Preview button,
4) Remove the lens,
5) Insert the mylar film,
6) Reattach the lens,
7) Shoot the clip,
8) Remove the mylar film.

Compare this to using a Nikon lens with manual aperture control:

1) Attach the lens (with adapter),
2) Adjust the aperture ring,
3) Shoot the clip.
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Old January 29th, 2009, 03:19 PM   #3
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I wonder if you can cover just the data pin(s), and still get power to an IS motor - and have it work. Keeping the mylar from rotating when mounting could be a challenge.

The ultimate solution would allow connecting and disconnecting just the data pin without having to remove the lens. If that were the case, the steps would be...

1) Attach the lens with super-mylar device.
2) Switch the data pin ON.
3) Adjust aperture.
4) Press the DOF preview button
5) Switch the data pin OFF.
6) Shoot the clip - including IS (while using an external mic, of course!)

This would be a sweet setup with a Canon IS lens. Setting the aperture wouldn't be a bit slower than with a Nikon, but not bad - especially in the context of setting shutter and ISO. Besides, I'm likely to set aperture and shutter the same from scene to scene while varying ISO to optimize for the light level. Setting the aperture doesn't have to be done for every take.
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Old January 29th, 2009, 04:46 PM   #4
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Quote:
Originally Posted by Jon Fairhurst View Post
I wonder if you can cover just the data pin(s), and still get power to an IS motor - and have it work.
The same for AF. Is it possible to get it?
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Old January 29th, 2009, 04:47 PM   #5
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Quote:
Originally Posted by Mark Hahn View Post
I have been babbling in several threads about trying Mylar to block the electrical connection to the Canon EF lens. I tried it this morning and it worked great. Total cost: $3.

Background: If you block the electrical signals to the lens, then it will stay at a constant aperture. This makes the problem of controlling exposure on the 5D2 video much easier. You can then lock it on any aperture, ISO, and speed, using methods not covered here (within the limitations of 30 fps). Existing methods to do this include rotating the lens or applying tape to the contacts. Rotating has the problem that the lens may fall off and putting adhesive tape in could get gunk inside your camera.

Preparation: I went to a crafts store an purchased some thin Mylar film. I think acetate would also work. It doesn't have to be transparent. I took the cap of the back of a lens and laid the film over it. I then used an Exacto knife to cut around the inside of the lens lip and created a perfectly sized disk that fit in the mount. No lenses were harmed in the process. I put the disc in the mount hole and mounted the lens. The film was thin enough that I didn't feel any extra force when turning. At this point looking through the VF showed an ugly filmy look (duh). But the F-Stop showed 00 which was what I wanted.

Then I cut out a rectangle in the middle of the disk that matched the rectangle hole in the mount. I dropped the film back in and rotated it so the light wasn't obstructed, and mounted the lens again. This time the VF showed a clear image. I carefully checked the edges to make sure no film was intruding on the image.

Usage: Put in the lens normally without the film. Adjust the aperture to what you want. Hold down the DOF Preview button and remove the lens. Drop the film in rotated correctly, remount the lens, and you have a locked lens.

I personally consider this less of a kludge than paying for Nikon lens and using them with an adapter.
Merci for your effort. Might you provide a few pictures or video?
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Old January 29th, 2009, 05:48 PM   #6
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Quote:
Originally Posted by Julian Frost View Post
While it's certainly cheaper than buying an equivalent Nikon lens and an adapter, it's certainly not less kludgy! Just look at the steps:
1) Cut a ring of mylar film,
2) Set the aperture using the camera body's controls,
3) Hold down the DOF Preview button,
4) Remove the lens,
5) Insert the mylar film,
6) Reattach the lens,
7) Shoot the clip,
8) Remove the mylar film.

Compare this to using a Nikon lens with manual aperture control:

1) Attach the lens (with adapter),
2) Adjust the aperture ring,
3) Shoot the clip.
You left a step off your method (removing the lens), but I won't quibble. :-)

Steps 2 through 8 are fast and easy. You may find something un-aesthetical about it, but it is functional, easy, reliable, and safe. And I can't repeat this often enough, it lets me use my existing Canon lens.
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Old January 29th, 2009, 05:54 PM   #7
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Quote:
Originally Posted by Jon Fairhurst View Post
I wonder if you can cover just the data pin(s), and still get power to an IS motor - and have it work. Keeping the mylar from rotating when mounting could be a challenge.

The ultimate solution would allow connecting and disconnecting just the data pin without having to remove the lens. If that were the case, the steps would be...

1) Attach the lens with super-mylar device.
2) Switch the data pin ON.
3) Adjust aperture.
4) Press the DOF preview button
5) Switch the data pin OFF.
6) Shoot the clip - including IS (while using an external mic, of course!)

This would be a sweet setup with a Canon IS lens. Setting the aperture wouldn't be a bit slower than with a Nikon, but not bad - especially in the context of setting shutter and ISO. Besides, I'm likely to set aperture and shutter the same from scene to scene while varying ISO to optimize for the light level. Setting the aperture doesn't have to be done for every take.
That would be great, but the idea needs a lot of work. They print copper conductors on this kind of film to make flexible circuits, so I'm sure something electronic could be done. I'm just not up to the task. I don't think you could breadboard that kind of thing. Also getting the signals out of the mount area while the lens is mounted would be a bitch.
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Old January 29th, 2009, 05:55 PM   #8
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Originally Posted by Mathieu Kassovitz View Post
Merci for your effort. Might you provide a few pictures or video?
I did this over at dp review: photos of the process
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Old January 29th, 2009, 06:02 PM   #9
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Not un-aesthetical, but kludgy, time-consuming and potentially error prone. It's certainly cheaper (if you already have lenses you want to use), I'll give you that! The time spent without a lens on the camera, and therefore the camera open to dust, is significantly greater with the mylar-method than the simple, no-fuss lens switch. It also doesn't allow for a simple aperture change, unlike that the manual aperture ring on a manual Nikon lens affords.

But to each his own. Personally, I'd hate to have the mylar fall into the camera, or move as I'm screwing on the lens, or wrinkle and require replacement at an in-opportune time, or blow away in a strong gust of wind, or need a rapid aperture change during a fast setup, or forget to hold the DOF preview button as I'm removing the lens, or... :-) But it's your camera, and they're your lenses, you do what you want, however you you want it! It's certainly another way of doing it which may appeal to some, or even many. More power to you for looking into this method. It would still be better if Canon just gave us manual control in a firmware update.

Julian
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Old January 29th, 2009, 06:51 PM   #10
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Quote:
Originally Posted by Julian Frost View Post
Personally, I'd hate to have the mylar fall into the camera, or move as I'm screwing on the lens, or wrinkle and require replacement at an in-opportune time, or blow away in a strong gust of wind, or need a rapid aperture change during a fast setup, or forget to hold the DOF preview button as I'm removing the lens, or... :-)
I can't disagree with your needs/opinion. I just place more value on being able to use my good L lenses. And yes, good lenses do matter even in 2 MPixel HD.

Also, the setup time for each shot in a production is much longer than the time it takes to use the Mylar. We have to pull focus, set the actors and lighting, make multiple takes, etc. Dealing with the aperture is insignificant.

For the record, so far in my testing today, there is no chance the the Mylar can fall into the camera. It doesn't fit through the hole. It does rotate a small amount when mounting the lens, but it isn't a problem so far. Mylar doesn't wrinkle, keeping replacements is no problem, and it fits too snug to blow away, unless I dropped it or something.
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Old May 4th, 2009, 04:57 PM   #11
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Hey, Mark. I'm planning on buying some mylar here soon. Do you think, if you found some time, you could post some pictures up how the mylar looks when attached? I wanna shoot with my 1.4 lens wide open! Thanks, Mark!
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Old May 4th, 2009, 11:33 PM   #12
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Originally Posted by Douglas Joseph View Post
Hey, Mark. I'm planning on buying some mylar here soon. Do you think, if you found some time, you could post some pictures up how the mylar looks when attached? I wanna shoot with my 1.4 lens wide open! Thanks, Mark!
Here is my first effort. It kind of sucked:

http://forums.dpreview.com/forums/re...ssage=30834264

I've been experimenting with using less and less mylar. It makes it easier to insert, remove, and less area for reflection. My current version looks like a C with the ends stopping at the point where the interior rectangle meets the circle. When I get a chance I'll shoot a pic.

It would be great if I only had something covering the contacts, but that wouldn't stay in place.
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