HDR video - am I deluded?

R

richblend

Active member
Hey, ive been playing with HDR photos recently, and was wondering how it could be applied to video. Obviously you could use the same method as with still cameras, but it means you have to film exactly the same thing multiple times, which is impossible unless its a repetetive motion or static scene.

So my idea is this. Im 90% sure theres a reason why it wouldnt work, but I cant see it..


How about getting say, 3 HV20's or something. You set one up to under expose, one to over expose, and one in the middle.

Arrange them in an array, and put some kind of prism in front of them, that splits the exact same image into each camera, so each camera is recording the exact same footage.

Then you'd just need the same HDR technology that photoshop uses to go through frame by frame and merge the iamges together.

Am I insane?

Rich
 
There is one problem: "put some kind of prism in front of them, that splits the exact same image into each camera"

When you find that prism, please report back.

Another option would of course be an automatic tripod head that would pan the exact same way every time or a dolly that would automaticaly move the same way every time. I think they are available. If there is an actor though...then that doesn't really work.
 
I just assumed there must be some kind of prism that could split light into 2 seperate images (which would halve the light though I guess). Guess not...
 
Richblend, I think you're onto something. I know you're speaking hypothetically and don't expect this prism to actually exist but the potential for this apparatus is there.

I wouldn't be surprised if this technology pops up sometime in the future.
It's probably being developed as we speak, er, write.
 
the other way around it (if you are rich) would be to get 3x scarlet 5ks... if you could get them perfectly in line, set your exposures.... then in post... crop out the sections you want to HDR. If you were cropping down to 2k... i'm sure you could line up the footage to make your HDR.
 
richblend said:
How about getting say, 3 HV20's or something. You set one up to under expose, one to over expose, and one in the middle.

Arrange them in an array, and put some kind of prism in front of them, that splits the exact same image into each camera, so each camera is recording the exact same footage.
Click to expand...

This is what is done to get the one 'beam' from the lens, into the 3 sensors...whether it was ancient Technicolor, color TV cameras with analog tubes, or 3 chip digitial video cameras...

The problem is that any 'glass' you put in front of the lense of a camera, degrades the image in someway, whether just lowering the amount of light at the sensor, or mangling the resolution.

So, in order to put a good enough beam splitter in front of your three cameras... you've already spent enough to by the next level up in camera...


There is another reason to put 2 cheap cameras on a fixed bracket, with views adusted to 'match'... cheap stereo imagery... aka 3-D... but then all you have to do is have some adjustment set screws, to align the cameras, and some software to amalgamate the images into a '3-d' stream... but nothing in front of the fixed lens of the cheap camera.
 
I tried this in 2005 by shooting a still subject at three different exposure settings (on a DVX), then combining the images in the NLE. The problem is that you get solarization on the bits of the picture which overlap. You can see the effects of solarization on still HDR photos, but the effect is especially noticeable (and distracting) on video.

To do it properly, I think you'd need a beam-splitter going to at least two cameras, and have the cameras in perfect sync.
 
I have looked into programming sensors to shoot in HDR in the past. Here is the process:

What I was trying to do is get 3 exposures every frame using a single sensor. Say you have a 1080p sensor and divide 1920 by 3. That gives you three 640 pixel images. Every image would have a different exposure time. So you would collect shadow details with the long exposure, mids with the medium exposure, and highlights with the short exposure. Combine the 3 videos in post to get HDR.

Unfortunately SDK wont let you do this. Its just not the way sensors are meant to work.
 
The other way to do this is to take 3 rapid exposures.

Long - med - short.

But you would have to shoot at 3x the framerate. The downside to that is any kind of movement would not work since it would be out of sync.
 
Yeah, it's definitely about two camera heads and a beam splitter. Not really so daunting. Think about how bullet time is done. Many camera heads, side by side. HDR motion picture capture would be a less cumbersome rig than bullet time.

There are times when it would be challenging in post to make things work, but truely, who knows what software/hardware possibilities there might be in the future when HDR motion appears.

Yep, DPs make it happen now and sometimes the images are astonishing. But you can't impede progress just to save jobs. And anyway, in this case, DPs would be just as important as ever.
 
Postmaster said:
Now you know what that super wide Red sensor is for.

Frank
Click to expand...

No. Not really. Why?

Anyway, it is all about a prism to split the light. But this is not possible with the HVX as is. The best way to do this was to have one taking lens at the front, which has it's light split into two directions falling onto two CCD planes of focus. This would require back focus and prism adjustments and removing the lenses from the cameras.

It is possible but hardly in a DIY setting.
 
Hi,

the are no teoretic, technical or practical problems to do HDR in video.
There are several triks to do this.

Mechanicaly.
Mount a mecanical opturator on a 50/60hz multi-format camera like hvx.
Record in 50fps mode.
Sincronize the opturator to 1/50sec
The opturator it realy a circular frame where you munt 2 ND filters or any combination, clear/ND, CTB/ND, CTB/clear e.t.c.
Sincronize 1 filter with the frame 01 and the 2 ND filter with 02frame and so on.
Digitalize the material as 50fps stream, in editor you se a strobo efect because of the exposure diferences betwed frame 01-02.
Separate in 2 layers the ND -2 frame from ND+2 frames.
Export the material in TIFF for phoshotop where with HDR you generate the master F stop. Go back to editor and do a conform 50fps/25fps, this the master with the master T stop.
In the editor or a composit software you must have 3 layers at 25fps.
The dificult task it to make a program to make a sort of pul-down action like in varicam wich generate the active frames.
In our case the active frames in a 50hz stream it all the frame exposed with ND-2 or ND+2 Ex. ND-2/01f ND+2/02f ND-2/03f

Now, the futures it that a camera, must work as a capture device, capturing information at +100fps. The camera must decide that 1 grup of frame are for HDR, another grup for selective color reproducion....
There are working at such technology, camera capturing at +1000fps syncronizes with diferent light scenaryous, internal filters e.t.c.

Another technique it to separate the light. Some speed cameras to this with a large circular tambor prism sincronzed.
Or simply mount a optical block and replace the CMOS senzor from a 1:1 digital camera and mount 3 senzors from the actual photo camera with multishoots exposure. In the end it posible to generate 4-8 min. But the cost for a decent optic block it wery hi so i prefer the in-camera pul-down HDR function with mecanical filter Weel sincronization.

I made a HDR video test with huge rezults but fails because i manualy manage/extract the active frames and work only on specific frames with multi shoots exposure for the hi-lights/sky, mid-tones and shaddows and later in photoshop i make masks but only for the static zones where it posibile a 1/1 pixel mach. This technique it used in rotoscopie and matte paiting.

All the best
Gabriel Bordas
 
Gabriel Bordas said:
Hi,

the are no teoretic, technical or practical problems to do HDR in video.
There are several triks to do this.

Mechanicaly.
Mount a mecanical opturator on a 50/60hz multi-format camera like hvx.
Record in 50fps mode.
Sincronize the opturator to 1/50sec
The opturator it realy a circular frame where you munt 2 ND filters or any combination, clear/ND, CTB/ND, CTB/clear e.t.c.
Sincronize 1 filter with the frame 01 and the 2 ND filter with 02frame and so on.
Digitalize the material as 50fps stream, in editor you se a strobo efect because of the exposure diferences betwed frame 01-02.
Separate in 2 layers the ND -2 frame from ND+2 frames.
Export the material in TIFF for phoshotop where with HDR you generate the master F stop. Go back to editor and do a conform 50fps/25fps, this the master with the master T stop.
Click to expand...

I would think combining alternating frames into one HDR frame would have slight differences with each other causing slight motion blur like effects. Meaning if something was moving fast, the two frames (although side by side) would be slightly different. This ghosting effect would happen throughout the footage.

No?
 
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