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HDR in Video


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#1 Daniel Smith

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Posted 23 August 2007 - 09:25 AM

Hi.

Recently I've been experimenting with HDR (High Dynamic Range) and tone mapping.

I done this picture the other day: http://ashleysmithd....da-Sky-62930477

I'd love to replicate the same effects in video.

So, how could I do it? Is there any editing software you guys can recommend?

And I'm presuming formats like MiniDV wouldn't hold up at all. Because of the limited dynamic range.

And tips or advice appreciated.
Dan.
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#2 Jason Debus

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Posted 23 August 2007 - 10:18 AM

Doesn't HDR rely on bracketed exposures? Not sure how you would do this with a video camera, seems like the best that could be done is some timelapse with a stills camera.
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#3 Daniel Smith

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Posted 23 August 2007 - 10:30 AM

Doesn't HDR rely on bracketed exposures? Not sure how you would do this with a video camera, seems like the best that could be done is some timelapse with a stills camera.

It's better with bracketed exposures, but can be done with a single plate. (The darks and highlights go noisy)
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#4 Patrick Neary

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Posted 23 August 2007 - 10:32 AM

hi there-

I think Clairmont or Otto Nemenz had/has a rig kind of like a 3-D setup that allowed you to shoot the same image simultaneously with two cameras, so you could roll one with color, one with B&W or something similar, and combine them in an optical printing step. I suppose you could also use it to run one camera exposed for highlights and one exposed for shadows and then do an HDR kind of thing in post.
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#5 Daniel Smith

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Posted 26 August 2007 - 01:21 PM

hi there-

I think Clairmont or Otto Nemenz had/has a rig kind of like a 3-D setup that allowed you to shoot the same image simultaneously with two cameras, so you could roll one with color, one with B&W or something similar, and combine them in an optical printing step. I suppose you could also use it to run one camera exposed for highlights and one exposed for shadows and then do an HDR kind of thing in post.

Yeh I've seen a robotic arm around somewhere, that can mimick the exact move again and again. I think they used it for Saving Private Ryan.

Although, it's a bit out of reach.

What I need is just some software that can do it with the available dynamic range.

I'm currently trying to work out if I can batch process a whole bunch of frames in the stills software I've got, and use the same settings for each picture. (But I still can't see it working, I still think it's going to be different between each frame)
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#6 Phil Rhodes

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Posted 26 August 2007 - 08:04 PM

Possibly workable:

Build a rotating shutter assembly which puts an n-stop ND filter in front of the lens every other frame. Ideally shoot at twice the target frame rate, such as with a JVC GY-HD250. Extract every other frame and perform optical flow interpolation. Assuming the interpolation is 100% accurate, which it isn't, you now have one base frame and one frame with n-stop underexposure. Batch process with HDRshop. You could even use an LCD shutter for the filtered state, since you don't need to achieve full black. This would allow you to put the LCD shutter in one filter tray and the accompanying polariser in a rotating stage, so you could vary the amount of underexposure applied to the alternate frames at the cost of the stop loss associated with the polariser. Ideally you would use customised optical flow software such as that created for the Lightstage project, which would use positioning information from the bright frames to optimise transformation of the dark ones into an equivalent geometry. This could be tried with existing technology.

Better:

Build a camera which uses single, Bayer-filtered chips. Use two or three, in a splitter block arrangement as in a 3-chip video camera. Apply varying amounts of ND (or more to the point use mirrors of varying reflectivity in the block). Do the HDR processing in electronics. By this technique it would be possible to build a camera with extremely high dynamic range, near to three times that of a conventional CCD, with ease of handling similar to any 3-chip block camera. CCDs capable of this already exist (Red, Dalsa, etc). You'd want to record it in 32-bit float.

Phil
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#7 Daniel Smith

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Posted 05 December 2007 - 03:25 PM

Totally forgot about this thread..

Possibly workable:

Build a rotating shutter assembly which puts an n-stop ND filter in front of the lens every other frame. Ideally shoot at twice the target frame rate, such as with a JVC GY-HD250. Extract every other frame and perform optical flow interpolation. Assuming the interpolation is 100% accurate, which it isn't, you now have one base frame and one frame with n-stop underexposure. Batch process with HDRshop. You could even use an LCD shutter for the filtered state, since you don't need to achieve full black. This would allow you to put the LCD shutter in one filter tray and the accompanying polariser in a rotating stage, so you could vary the amount of underexposure applied to the alternate frames at the cost of the stop loss associated with the polariser. Ideally you would use customised optical flow software such as that created for the Lightstage project, which would use positioning information from the bright frames to optimise transformation of the dark ones into an equivalent geometry. This could be tried with existing technology.

Better:

Build a camera which uses single, Bayer-filtered chips. Use two or three, in a splitter block arrangement as in a 3-chip video camera. Apply varying amounts of ND (or more to the point use mirrors of varying reflectivity in the block). Do the HDR processing in electronics. By this technique it would be possible to build a camera with extremely high dynamic range, near to three times that of a conventional CCD, with ease of handling similar to any 3-chip block camera. CCDs capable of this already exist (Red, Dalsa, etc). You'd want to record it in 32-bit float.

Phil

Hmms I like the idea, but I'm not sure how confident I am at actually doing it. I'd be too scared of screwing up the internal workings. But worth keeping in mind.


What I was thinking however (and I might test this out soon if I get the chance) is shooting a locked off frame. With say 3 different exposures. On the 'correct' exposure, shoot it twice, one blank, one with the actor inside. (4 shots total)

Export the three blank video frames as filmstrips, convert them to bmp format with photoshop, load them into Photomatix (HDR program) blend the filmstrips together, save them as a bmp and convert back to filmstrip format in photoshop.

Load into editing software and pull a difference matte with the correctly exposed blank frame and correctly exposed frame with the actor inside and comp the actor onto the HDR footage.

The problem is I'm not sure how well a non-HDR element (actor) will look over a HDR element (set).

Of course without any form of motion control system, moving shots are completelly out of the question. But it could work.

Phils idea could definatelly work with just a single shot (with actor and no multiple takes)

Edited by Daniel Ashley-Smith, 05 December 2007 - 03:28 PM.

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#8 Daniel Sheehy

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Posted 05 December 2007 - 03:45 PM

The problem is I'm not sure how well a non-HDR element (actor) will look over a HDR element (set).

You could try it using a digital camera that shoots raw - SI or RED.

The dynamic range contained in the raw files might allow you to batch process the frames and then recombine the sequence. It'd take a load of processing power though...
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#9 Daniel Smith

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Posted 05 December 2007 - 03:47 PM

You could try it using a digital camera that shoots raw - SI or RED.

The dynamic range contained in the raw files might allow you to batch process the frames and then recombine the sequence. It'd take a load of processing power though...

Perhaps.. I could always record directly from the HD-SDI, may work..

Just got to get off my butt and test.
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#10 Michael Nash

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Posted 05 December 2007 - 03:49 PM

Try shooting film to capture the maximum dynamic range, and do three separate telecine passes of the same shot -- one to protect the highlights, one for mids, and one for shadows. Composite each pass as a separate layer, grading each as necessary.
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#11 Daniel Smith

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Posted 05 December 2007 - 03:56 PM

Try shooting film to capture the maximum dynamic range, and do three separate telecine passes of the same shot -- one to protect the highlights, one for mids, and one for shadows. Composite each pass as a separate layer, grading each as necessary.

That would be nice, but I really can't see myself being able to do that for years. Haven't got the money.
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#12 K Borowski

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Posted 05 December 2007 - 10:58 PM

That would be nice, but I really can't see myself being able to do that for years. Haven't got the money.

(Note, not trying to be snide, but)

. . . then you can't do a real HDR. Even with slide film, I've seen stuff done with HDR (it's only HDR-esque though, as you really don't have the highlight information to work with, just the same problem as with video), so it's possible to time the footage to three different densities, photomerge and then get something more out of it than your raw footage, but you're not going to get the same dynamicism possible with multiple images or a multi-scanned negative.
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