Jump to content


Photo

Lens and Gate


  • Please log in to reply
8 replies to this topic

#1 Geovane Marquez

Geovane Marquez
  • Basic Members
  • PipPip
  • 78 posts
  • 2nd Assistant Camera
  • Los Angeles

Posted 16 October 2009 - 06:29 PM

There are these black dots, looks more like ripped film you can wipe off easily, I see when the camera is out of focus. I think its coming from the Gate and the mirriors inside.

Is it ok to use a lens cleaner and those Rosco Lens Tissue in the gate? And the mirror behind the shutter where you place the lens?

I would blow some air but someone told me not to do that
  • 0

#2 Chris Keth

Chris Keth
  • Sustaining Members
  • 4427 posts
  • 1st Assistant Camera
  • Los Angeles

Posted 16 October 2009 - 08:38 PM

There are these black dots, looks more like ripped film you can wipe off easily, I see when the camera is out of focus. I think its coming from the Gate and the mirriors inside.

Is it ok to use a lens cleaner and those Rosco Lens Tissue in the gate? And the mirror behind the shutter where you place the lens?

I would blow some air but someone told me not to do that


I wouldn't use tissues in the gate. They can leave fibers that will just plague you. Orangewood sticks are the right tool here. You can clean the mirror (GENTLY, it's a front surface mirror and really easily scratched) with some tissue on a swab and a little fluid.

Do these spots only show up when the scene is out of focus? Are the spots in or out of focus?
  • 0

#3 Satsuki Murashige

Satsuki Murashige
  • Sustaining Members
  • 3510 posts
  • Cinematographer
  • San Francisco, CA

Posted 17 October 2009 - 03:43 AM

There are these black dots, looks more like ripped film you can wipe off easily, I see when the camera is out of focus. I think its coming from the Gate and the mirriors inside.

If you're seeing these black dots through the viewfinder, then you're probably seeing dirt on the ground glass, which will not affect the image on the film at all. It is impossible to see hairs in the gate through the viewfinder because the mirror shutter is: 1) in front of the gate, and 2) blocking the gate when rotated in viewing position. For the same reasons, it is impossible for the dirt on the ground glass to appear on the film. You can remove the ground glass and blow the dirt off of it (if you know what you're doing). Every camera requires a slightly different method to remove the ground glass.

To check the gate you have to look through the lens port, rotate the mirror shutter out of the way, and inspect the gate with a magnifying glass: http://www.filmtools.../magnalite.html. If you see any hairs or emulsion sticking into the picture area, then you need to remove it with an orangewood stick: http://www.filmtools.com/wc-597-5.html. Just gently rub the sides of the gate with the stick until the hair or emulsion comes off.

You should check the gate as often as possible and clean it when necessary. But don't clean the mirror unless you really have to. It's very delicate and expensive, and since it's cleanliness doesn't affect the actual image on the film at all, it's not worth the risk unless you know what you're doing. If you must clean it, blow off any dust and then use a foam tip swab and some isopropyl alcohol: : http://www.filmtools...csprayfoam.html.

I know some ACs and rental houses are really anal about not using canned air anywhere near the gate. But if you're very careful to keep the can in an upright position so no coolant sprays out, and use only short gentle puffs then I think it's fine. Just don't let them see you do it...
  • 0

#4 Geovane Marquez

Geovane Marquez
  • Basic Members
  • PipPip
  • 78 posts
  • 2nd Assistant Camera
  • Los Angeles

Posted 17 October 2009 - 09:17 AM

Do these spots only show up when the scene is out of focus? Are the spots in or out of focus?



Ya when the Scene is out of focus the dots become in focus , and vice versa
  • 0

#5 Chris Keth

Chris Keth
  • Sustaining Members
  • 4427 posts
  • 1st Assistant Camera
  • Los Angeles

Posted 17 October 2009 - 10:22 AM

Ya when the Scene is out of focus the dots become in focus , and vice versa


That doesn't make any sense. If it's dust on the viewing system mirrors or on the rough side of the groundglass, it will always be in focus. If it's dirty glass in the viewing system, it will always be soft and won't change when you focus the lens. Are you absolutely sure that you just don't notice the spots when the scene is sharp and throwing the scene out of focus makes the spots stand out because they're sharp? Have you tried looking at a blank white wall so lens focus doesn't matter?
  • 0

#6 Geovane Marquez

Geovane Marquez
  • Basic Members
  • PipPip
  • 78 posts
  • 2nd Assistant Camera
  • Los Angeles

Posted 17 October 2009 - 12:48 PM

Are you absolutely sure that you just don't notice the spots when the scene is sharp and throwing the scene out of focus makes the spots stand out because they're sharp?



That's exactly what it is.
  • 0

#7 Tom Jensen

Tom Jensen
  • Basic Members
  • PipPipPipPip
  • 1234 posts
  • Camera Operator
  • Dallas, TX

Posted 17 October 2009 - 12:59 PM

What kind of camera is it and who does it belong to? If you have to ask these question, I would get someone with experience to show you how to do it. The mirror is not a typical mirror with the reflective material under the glass. The reflective material actually sits on top of the glass and is extremely susceptible to damage.

Edited by Tom Jensen, 17 October 2009 - 01:02 PM.

  • 0

#8 Geovane Marquez

Geovane Marquez
  • Basic Members
  • PipPip
  • 78 posts
  • 2nd Assistant Camera
  • Los Angeles

Posted 17 October 2009 - 01:02 PM

It's a 16bl
  • 0

#9 John Sprung

John Sprung
  • Sustaining Members
  • 4635 posts
  • Other

Posted 17 October 2009 - 04:59 PM

With any Arriflex viewfinder, you won't see dirt on the mirror shutter as sharp spots when the camera is running -- because the mirror is moving. With the camera stopped, dirt on the shutter would appear way out of focus, and you can diagnose it immediately just by inching a little. If it moves it's on the shutter. If not, it's somewhere else.

This being a 16 BL, with a wide lens focused close and a deep stop, you might be able to see crud on the optical flat of the lens housing. This would show up both in the finder and on the film.

If you're focusing the finder rather than the taking lens, you might be racking to where you have the back side of the ground glass sharp. IIRC, on the BL that side of the GG is exposed when you open the door, so dust there is a real possibility.




-- J.S.
  • 0


Paralinx LLC

CineTape

Opal

Ritter Battery

Gamma Ray Digital Inc

Technodolly

Willys Widgets

The Slider

Rig Wheels Passport

Visual Products

Aerial Filmworks

Glidecam

Broadcast Solutions Inc

Tai Audio

Abel Cine

rebotnix Technologies

Media Blackout - Custom Cables and AKS

CineLab

FJS International, LLC

Wooden Camera

Metropolis Post

Tai Audio

Glidecam

Technodolly

Aerial Filmworks

Abel Cine

Media Blackout - Custom Cables and AKS

Metropolis Post

Visual Products

The Slider

Ritter Battery

Willys Widgets

Rig Wheels Passport

CineTape

FJS International, LLC

Paralinx LLC

rebotnix Technologies

Gamma Ray Digital Inc

Broadcast Solutions Inc

CineLab

Opal

Wooden Camera