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The LED wall is interactive and the challenge is to make pictures that show both the wall and people interacting with it, without having the banding or moire effect, that often happens when taking pictures of LED wall.

See the moire here

I am shooting with either Nikon D4 or D7200. Looking for advice on what aperture works best.

My main concern is that the LED diodes are so bright or contrasting too much to the rest of the scene, that I be getting a lot of under-exposed people/scences. or highly over exposed LED screen. If I remember well, this was the problem in the past.

I will try and find some samples. The wall I photographed last, also showed some banding I seem to remember. Or it may have been lines of black, due to the re-fresh rate of the screen, and the combination of shutter speed. I guess longer shutter speed is better.

Any other views or thought on shutter speed/ISO/flash use?

I don't need to necessarily freeze all the action, but can't be too blurry either. I think min need about 1/50sec for use with 11-35mm lens (f1.8)

MikeW
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Timesnaps
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3 Answers3

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You have diferent issues here. Lets separate them.

1) You have a bright wall and dark people... It is the same case as if you have a bright window with people on an interior. Your options are limited.

  • Use aditional ilumination, like firing a flash as fill light. If you are shooting from far away this could not work. But if you have permissions you can use some asistants closer to the scene and remote triggers to light up the scene.

  • Correct in post production leveling up the dark zones or some Hdri technique. Shooting in Raw is required.

2) The "flickering" Lets get technical. A video has an intrinsec "strobe" component, a frame, then another frame. A monitor can have (or not) a refresh rate. The lcd fluorescent panels have it, and some led panels have it to dim the intensity of the light.

If you photograph that at a shutter speed lower or too close than thoose refresh rates you can have a flicker. So you need to use a shutter speed 2 or 3 times below that refresh rate. Lets think a panel has a refresh rate of 60 Hz. Then you need to shoot at lets say 1/30 or 1/15. Make some tests on your home computer, television, and the kitchen lights.

3) The moire.

You have a problem here. You can try for example focus at the closer objects so the panel is a little blurry. Use a wide aperture.

Try a "fog" filter, or a star filter in your lens. You can try a DIY aproach for example using some vaseline in an UV filter.

Rafael
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Your ways are:

  • using any film to record images instead of digital technology

  • using the camera with strong enough AA filter

  • using the camera with surplus of resolution (medium format cameras, may be very expensive)

  • using very tight aperture (big F number) so that image is blurred enough with diffraction for moire to disappear. 1,5x crop camera with F13 will show very few moire.

Here is a test scene for judging if camera has good AA filter: http://www.dpreview.com/reviews/sony-a6300/9 - there are several details in the studio test scene which have high frequency details which reveal moire. The moire is visible in centers of circles with radial lines and in coloured concentric circles in this example.

From cameras which I have looked at Canon G3x, G15, Fujifilm X30, Panasonic G6 expose very few moire. 99% of cameras expose moire which will be visible unless tight aperture is used and will be even worse with LED screen.

Older cameras were tested with another scene (looks worse in regards to detecting moire, has fewer sharp details), one of them: http://www.dpreview.com/reviews/nikond7000/21

Euri Pinhollow
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@Rafael hit the money on the head with his answer, but there is one thing that might be added:

Fill flash to help bring in faces. It can be at angles so the faces are more side lit, rather than frontally, which would spill and reflect from the LED array.

A key technique is to focus on, or slightly in front of the faces, so they are tack sharp or at least acceptably sharp. Using a shallow DoF setting, like with a 1.2 or 1 1.4 lens, the LED array will be slightly out of focus, which acts as an analog anti-aliasing filter. It won't help with refresh rate artifacts, but it will help break down the usually orthogonal LED placements. To address the refresh rate artifacts, a longer shutter speed is appropriate. In the US, 1/30 might work OK, assuming 60Hz or 30Hz scan rates (which is no longer as good of an assumption as it used to be).

In summary, fill for the subjects in front of the screen/array, and a DoF and focus to slightly defocus the panel/array.

mongo
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