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Old September 20th, 2003, 12:07 AM   #1
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Car shot. . .for next time

I shot through a windshield from a flatbed truck that was towing a car the other day, with not the greatest results. I had my cicular polarizer on, but I could only adjust it for either when there were no trees overhead, or trees overhead, as the reflections looked different. During the drive, we would pass under trees, and the actors would become nearly invisible. If I ever do this again, what easy cheap tips does anyone have about lighting in a situation like this? It was an overcast day, if that matters. I have a 20 watt or so flourscent that's daylight balanced and can be battery powered. . .thought of hanging from the car's interior and using it, but forgot.
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Old September 20th, 2003, 09:24 AM   #2
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Have the Ninjews bust out the front window.

Ok seriously, if you want that kind of shot then you need to plan your shot/route/time of day. Not only are the overhead trees an issue, but if you make any turns then your polarizer will also need to be adjusted to follow the angle of incidence... sorry, er, I mean you need to twist the polarizer to keep the glass clear.

Find out what angle gets the best image while your on the truck and somebody is in the car... while nothing's moving... then get "locked down" there and make sure your chosen route is straight enough to not change your polarizer setting. (From the angle of light.) Popping that 20w light up on the visor(s) will help too.

Of course this has been a "Mr. Obvious" reply so I'm sorry if I sound like a dope.

I've done a couple projects with other people and even though they'll have a full script they usually don't account for technical issues like these... then when something comes up they simply accept whatever's happening... When we get back to the computer I say, "see that's what I was talking about"... Sometimes it's best to accept compromises in your original vision in order to overcome a technical obstacle.

I guess what I'm trying to say is that the fluorescent you have would have helped but I doubt it would have fixed the problem on it's own.

P.S. If you really want to get nuts with tweaking a shot like this you can experiment with some K-Line Dulling Spray and fully control what's clearly reflected in the edges of the windshield and what isn't... but now my OCD is showing. Sorry.
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Old September 20th, 2003, 08:49 PM   #3
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You can also cover over the windshield with something similar to the visors that used to be put on cars up until the early 60's, just longer. Kind of like a bill on a cap.
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Old September 20th, 2003, 11:32 PM   #4
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Cover the windshield how? I'm sorry. . .not getting it from your description.

Polarizer question: what's the difference between the circular one and the 4x4 that I have?
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Old September 21st, 2003, 04:14 AM   #5
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What Mike is suggesting, I think, is to fly a solid over the windshield. Think of extending the roof of the car out over the windshield, so that it reflects the solid rather than the sky and trees. This will take some serious rigging, however, to keep it from flying off in the wind.

More to the point, I'm not getting why your pola didn't work. Given that the angle to the windshield remains constant, the proper rotation of the polarizer should have full effect regardless of the angle of the sun, direction of the car etc. Polarization is optimized for reflections at a 45 degree angle, same as most car windshields. Dialing out the trees should have been pretty effective, and at any driving direction.

The circular vs linear polarizer debate has raged on this board at length. I'm personally unconvinced that you need a circular pola for video, and I believe that a lot of folks have spent unnecessary $$ buying same. A good quality pola (B&W/Schneider True Pol is the industry standard) will do everything you need with a video camera.
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Old September 22nd, 2003, 02:52 AM   #6
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Perhaps, but what is the difference? The circular causes changes as it rotates, but what am I changing? Does the 4x4 do the same?

With the polarizar. . .I don't know what the deal was. All I know is that before the vehicles started moving, I rotated it until I was happy, and able to clearly see the actors despite the reflections that my eye could see, and once we were alternating between open sky and canopied, problems ensued.
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Old September 22nd, 2003, 08:13 AM   #7
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The 4x4 should have the same effect as the circular pola. Different manufacturers have varying degrees of polarization, but both should effect changes in the image as you rotate through 90 degrees

Josh, please describe the exact scenario you were experiencing. Is it that you were able to knock down the sky reflection, but the trees were visible? or was the amount of sky reflection changing as the car changed directions?
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Old September 23rd, 2003, 08:26 PM   #8
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Were their hills involved? if the car was going at a slight incline and then a slight decline that might change the reflection off the windshield (I think)
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Old September 23rd, 2003, 09:19 PM   #9
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I'm starting to second-guess myself, but as I have always thought of it, the polarization of the light is a function of the 45 degree angle of the windshield. Imagine an arrow being shot straight down at the windshield and bouncing off, right at the lens. That's what's happening to all of the light rays that are being reflected off the windshield. The polarizer at the camera is removing all or most of the light rays that come straight at the lens, while the rest of the light in the scene is coming from every possible angle.

As long as the camera stays pointing straight at the windshield and the windshield remains at the same angle to the camera (if there was a hill, presumably both camera car and picture car are still relatively at the same angle to each other), all should remain constant.

Here's what I'm trying to get. Josh, if you found that you were able to knock out all of the sky reflection in the windshield, making the windshield appear to be transparent, what did the trees look like when they reflected? Usually a tree will only be visible by a reverse reflection, i.e. the dark tree creates a transparent area on the window that you can see through, while the bright sky is the opaque stuff that obscures the view. If you have dialed out the sky, the trees should not have been a problem.

Don't suppose you can post some stills...?
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Old September 24th, 2003, 04:05 AM   #10
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I will post stills. Yes, you are right. . .when the trees were overhead it looked GREAT, and when bare, overcast sky was overhead it looked not so great. Part of it was an exposure issue, i.e., if I exposed for sky/trees overhead, then the other would not look right, and would be too dark/light, respectively.

Stills are up.


Go to www.freewebs.com/joshbass

Scroll down the page 'til you get to the paragraph that says "car shots". That's them.
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Old September 24th, 2003, 03:04 PM   #11
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Thanks Josh, it was helpful to see the stills.

Yes, part of it is an exposure problem. You would need to ride the iris between the shaded areas and the open areas. A better solution is to pick an area that doesn't alternate from open to shaded.

However, I don't feel like your polarizer was doing all it should in those stills. You should have been able to knock out more reflection overall. What kind of pola are you using (brand, size etc).

The best way to determine the maximized position of a polarizer is to hold it up to the eye and rotate it until the desired effect is achieved, then mount it to the camera. With a circular pola, you can make a grease-pencil mark at the 12:00 position when holding it to the eye which is easy to find once it's on the camera. With a 4x4, you have to remember the angle as best you can and then do a "touch up" in the viewfinder. If this is the case, it's best to make sure you are on manual iris while adjusting the angle of the pola, because the auto iris might adjust itself which makes it harder to determine what you are doing with the pola orientation.
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Old September 24th, 2003, 04:14 PM   #12
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The pola I was using was part of a three filter kit my girlfriend bought me a long time ago. . .came with an ND filter and a UV filter. 72mm, Tiffen. I rotated it all the way through its cycle to find what knocked out the most reflections. . .the results you saw were the best I could do. Should I use my 4x4 next time I have one of these situations?


Explain about the 12:00 position and all that? Still confused.
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Old September 24th, 2003, 05:03 PM   #13
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I believe what Charles is saying is:
-hold up the filter to your eye and rotate it until you have the best result
-place a mark on the top of the filter(12 o'clock posistion)
-screw it on the camera and make sure the mark is facing up.

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Old September 24th, 2003, 05:34 PM   #14
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Ah. . .got it.
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