Shooting LCD Screens / Computer Monitors Heavy Moire Issue

[Peter McCoubrey]

Hi,

We did a test shoot yesterday for a project that will involve shooting lots of people using computers. We shot a RED and Sony F35. We really want to use the RED for this project, but every time a computer screen is in frame we get a heavy moire pattern on the screens with the RED. The F35 gets it as well, but it isn't nearly as severe. We tried to use various lens filtration to no avail, we were partly hoping when we projected the footage we wouldn't see it, and although projecting the footage on a large screen did help, it was still very severe. The only fixes we were able to come up with is not to shoot the screens in critical focus, or to skew the camera on a tango head and shoot the screen a little dutch. Obviously neither of these solutions are ideal.

We also tried many blur filters and post tricks, once in FCP also to no avail.

We shot at the RED at 4k and converted the files to uncompressed 4:2:2, 10 bit 1920x1080 and are using them at that resolution in FCP.

Has anyone else encountered this and is there any know work around, either something we can do on set or a special post filter to fix this problem? Any help would be greatly appreciated.

Thanks,

Pete

 

[David Mullen ASC]

Hi,

We did a test shoot yesterday for a project that will involve shooting lots of people using computers. We shot a RED and Sony F35. We really want to use the RED for this project, but every time a computer screen is in frame we get a heavy moire pattern on the screens with the RED. The F35 gets it as well, but it isn't nearly as severe. We tried to use various lens filtration to no avail, we were partly hoping when we projected the footage we wouldn't see it, and although projecting the footage on a large screen did help, it was still very severe. The only fixes we were able to come up with is not to shoot the screens in critical focus, or to skew the camera on a tango head and shoot the screen a little dutch. Obviously neither of these solutions are ideal.

I've had similar problems shooting on the Genesis, or any digital camera for that matter. Just the other day, I shot a wide shot of an old 5-story hospital building and the slate roof had moire problems.

When shooting inserts of monitors, I slightly defocus the image -- it sucks but there is no other way I've found of quickly solving the problem.

Once you record the moire, there's no real way to get rid of it in post.

Now I'm surprised that you'd have moire problems in wide shots of computers -- the lines are too fine for moire to kick in until you get closer to full-frame on most computer monitors.

On my first day of a TV pilot shooting the Genesis, I got screwed by moire problems -- I shot three set-ups of the main character running around an office on her first big day of work, and then when I went into her close-up, I discovered that the pattern in her suit jacket created a horrible moire pattern, so we actually had to reshoot everything we had shot that day with an entirely new jacket because we had several other scenes in the same wardrobe over the next couple of days and I didn't want that jacket to become established. After that, the wardrobe department had to bring every piece of clothing over to the camera in between set-ups and we looked at all of them for moire problems.

I should have thought to test this in prep, but on my last TV show on the Genesis, we solved all of these wardrobe problems on the first day as well and then didn't have an issue for the next three months, so I stopped worrying about it.

If for some reason you have moire problems on wider shots of computers, you could try putting a thin layer of diffusion gel like 1/4 Hampshire Frost, if they make such a thing, over the screens to blur the lines. Won't work for close-ups -- you'll have to stick to the trick of defocusing the lens slightly until the moire disappears.

 

[Vincent Visser]

Also discovered the 'moire pattern' problem during a camera-test today. The problem was seen on tft and lcd monitors shot in focus. It isn't there when you slightly shoot off focus. How to solve this problem when production is planning to shoot in a tv-store? Just thinking about the fact that the cameraman wants to use some 'classic soft' or the ARRI 'Varicon' infront off the lens. Will it help? We are planning to do some extra testing tomorrow.

 

[David Mullen ASC]

Diffusion filters would barely help unless they are so heavy as to wipe out all fine detail, which is really, really heavy.

No, it's just going to be a problem with fine grid patterns in real life interacting with the grid pattern of photosites on the sensor, though some moire is less in the recording and more an aspect of the display device screen interacting with the subject -- but either way, you'd want to avoid it since you'll never know what type of display your footage will be seen on, plus you have to assume it's in the original just to be safe.

Once you are tight enough to get the moire pattern on the screen, you're also tight enough to want to read the detail on the screen, so diffusing the screen itself with something like Half Hampshire Frost gel, for example, probably won't cut it. In the end, you're just going to have to ride the focus and make sure that the pattern doesn't snap into sharp-enough focus to cause a moire.

Generally in wide shots of a store, the grid pattern in the TV sets are too small to cause moire. It starts to be a problem more when you are closer to full-frame on a monitor, in that ballpark.