optical issue... any ideas?

  • Thread starter Thread starter SeanEmer
  • Start date Start date
S

SeanEmer

Guest
Hey, I posted this at cinematography.com and got some good input but while I wait for the director to run through the tests suggested I figured I'd see if anyone over here had any ideas. Here's my original post:

Got footage back from my first 35mm shoot. Exposure, focus, framing, etc. were all spot on, but we did run into an odd problem. For some shots, bright offscreen objects were mirror reflected as a mild fog in the lower right part of the frame. Has anyone seen something like this before? It was not apparent in the viewfinder while shooting, which initially led us to think something might have been wrong with the gate... but we can't shake the feeling that this must be a lens issue of some kind. Below are links to a still frame and a short clip of one of the shots.

Thanks for any help!

Still Frame

Video Clip
Click to expand...

Thanks guys, i know this isn't exactly the right forum for this kind of thing but you never know... I know some of you guys are pretty good with film ;)
 
That is certainly interesting.

I think it's a lens issue of some sort. Looks like a rogue refraction of light within the lens... my guess. The interesting thing is... if it were the lens, wouldn't you see it when shooting? Of course assuming you *would have* spotted it. That is a very small 'blur' and it could have gone unnoticed by some of the best ops.

I'd say it's not a movement issue or shutter, considering it's not uniform horizontally across the image. At first I thought slight off sync shutter which would cause the bright objects to be ghosted in the areas of lesser exposure... but then I realized that it only happens on the right side of frame. Notice how also, when the camera turns off, and the exposure time increases, there is a greater amount of light hitting the right side, although i've never really studied the tail of an exposure to see if that's normal or not.

Did you have any filters in the matte box, which might not have been parallel with the lens? That *could* cause a bias reflection of light to *mirror* in the frame.

Plus who's to know what happened in the telecine machine. That just might have something off. Do you see this on projected dailies or footage?
 
Last edited:
Hey Ryan,

I did not see this in the viewfinder while shooting, and believe me I would have noticed it. That means the problem must be somewhere behind the shutter, which is what has stumped me. I dont have ocn to look at and I'm waiting for the director to check it for me.

We never used more than one filter on the mattebox either. I think that the bad telecine idea might be more reasonable, but again I am waiting for confirmation.

We saw the issue when we brought the film to the posthouse for a davinci treatment and watched it for the first time. This was before digitizing to tape, so the film was on some optical scanner for the session... I can't remember the name of it. None of us have a 35 projector so we will have to manually check with a lupe... which is annoying because the first optical problem is more than a few shots into roll 1.
 
That is very odd. I'd be curious what you find when you examine the film. At least you have a good excuse to find, thread up, and watch your 35mm negative. Let us know your findings or verdict!
 
I've never encountered this myself, but I've seen what you describe in several movies.

Only movie I could think of right now is A Better Tomorrow haha, http://www.youtube.com/watch?v=SR7q9_8qmak.
Very often you see reflections of highlights, at 0:39 you can see a blurry reflection of a flame. Is this similar to your problem?

I've always thought it was a reflection caused by several filters in the mattebox, but then again I've never experienced this problem.
 
I think it looks fine. I dont really see a problem with it. However, it depends on the type of scene it is and how it fits with the type of story you're trying to tell. If it enhances the story, great; if it degrades it, better figure out whats wrong. Sorry I can't help much more.
 
We already screened a cut with this problem in it to neutral parties and nobody ever noticed, so we aren't very concerned with it affecting the story. At this point we are just curious as to what it is.
 
Could you tell us what kind of 35mm movie camera you were using? Some of them, especially the early Arri IIA/B/C had baffling problems. Which is why they put the baffles in there in the first place. If part of the interior of your gate assembly is missing the black paint to control baffling, that too may be your problem. Stray light is hitting a specular part of the assembly and reflecting into another part of your frame most likely. Edges of the gate, over sized image circle, can contribute to this problem.

Typical clues are that highlights get reflected in or "fog" a part of the frame.

That's just my guess anyways. Good luck tracking it down - you might want to tell the guys who lent you the camera once you find out.
 
Good guess, sir... we shot on a disturbingly old Arri IIB. However we checked the camera with the help of a much more experienced cinematographer and found that the baffles were intact, at least as far as we could tell. I agree that this sounds like a probable cause since, if memory serves, the baffles are behind the shutter (or am I going crazy?) but we didn't find any chipped or exposed/shiny areas at all.

When I head back up there I will give the camera another look, but from what I recall all was well with the baffles.
 
Right, they are behind the shutter. You might want to check them out again if you plan on using it again. It sounds suspciously like a baffle or part of the assembly lost its paint. Another example why it's scary sometimes shooting film, especially on older cameras! But exciting :).
 
I definitely will. And are you kidding!? It was a blast! I've never had so much fun! Thankfully when working at the low budgets that we tend to the more expensive your format the more professional the crew gets... nobody wants to be "that guy" who screws something up. I would love to shoot on it again but we are all out of money just in time for thesis films to roll around...

We're in the same boat as before I guess as far as this problem is concerned... still waiting for the director to get back to me. Last I heard he was seen sailing somewhere off the LI coast. This guy is mysterious...
 
You must log in or register to reply here.
Back
Top