Maximizing Dynamic Range

Andre De Clercq · September 21st, 2004, 09:49 AM

Jeff, was this an intra scene variable DR system?

Jeff Donald · September 23rd, 2004, 01:58 PM

I haven't forgotten your post Andre, I've been looking for the paper I read on the patent. But as I recall it was for intra scene improvement of DR. I'm still looking though.

Valeriu Campan · September 23rd, 2004, 04:19 PM

I was using recently on a shoot a technique with employed two exposures with the camera locked off. The second exposure was for highlights only with the in-camera ND filter. The images were blended later in AfterEfects and looked stunning.... Would have been nice to have a motion control rig with this as well...
Following this why not having a second chip installed on a prism with only an ND filter attached? I am not a video technician but just thinking out loud: the signal from the second "ND-ed" chip could be mixed (overlaid) with the main one after some filtering is applied to it, similar to audio LowPass or HighPass filters?

Brett Erskine · September 24th, 2004, 01:34 AM

What a great idea! ;-)

Jim Lafferty · September 24th, 2004, 11:00 AM

Quote:

I was using recently on a shoot a technique with employed two exposures with the camera locked off. The second exposure was for highlights only with the in-camera ND filter. The images were blended later in AfterEfects and looked stunning.... Would have been nice to have a motion control rig with this as well...

This is an interesting idea -- someone showed me HDR stills recently, compiled from a blend of High, Low and Balanced exposures -- each shot he took was comprised of those three settings, then the software allowed him to use the interpolations to do an array of things like dodge/burn accurately...

For video, this would take three separate CCD and lense systems, recording streams simultaneously :/ Or...perhaps a 90fps recorder that would arrange the high/mid/low exposures across every third frame. Either would take a bit of work...

- jim

Dan Stewart · September 24th, 2004, 11:26 AM

Am I missing something obvious in the idea of a bayer style ND filter pattern on all 3 chips of a 3 chip system?
Of course the beamsplitter-lens arrangement gets more complicated but the system exists in every decent camcorder.

The grid would look like:

----------
0 | +1
----------
+2 | -1
----------

Surely a decent HDRI could be interpolated? There would be less data lost than in a bayer pattern because of the exposure overlaps.

In theory this could be done in conjunction with a bayer filter on a single chip system, as long as you had the spare resolution, like a 2k chip for SD output. Or am I missing something?

Valeriu Campan · September 24th, 2004, 05:00 PM

I was thinking at only two chips with a three stops ND filter. This could push the dynamic range to ~11-12 stops. But Dan's idea is interesting too. Why not use a single Bayer chip config, similar to the one in Fuji digital cameras (a honeycomb config with chips of different sizes - the smaller ones to be activated only on higher levels of light...) Don't have a URL handy but it's worth a look

Aaron Shaw · September 24th, 2004, 05:07 PM

The honeycomb structure is really rather interesting. Quite ingenious actually! I wonder why we haven't seen this sort of thing introduced for video yet though... even high end cinema cameras don't use this (As far as I know). Perhaps it has something to do with the patent?

Quote:

The images were blended later in AfterEfects and looked stunning.... Would have been nice to have a motion control rig with this as well...

How did this work exactly? Was it simply a still shot of, say, nature or were there actors on screen? I imagine it would be incredibly difficult to match two sets of footage in post if actors were moving about. Even with the camera locked off. Hence the reason it would be so nice to have RAW video. You could pull the necessary highlight clip and shadow clip from a single shot/take.

Valeriu Campan · September 24th, 2004, 06:28 PM

<<<-- Originally posted by Aaron Shaw :
How did this work exactly? Was it simply a still shot of, say, nature or were there actors on screen? I imagine it would be incredibly difficult to match two sets of footage in post if actors were moving about. Even with the camera locked off. Hence the reason it would be so nice to have RAW video. You could pull the necessary highlight clip and shadow clip from a single shot/take. -->>>

Aaron,
There were locked off shots. The foreground action was recorded with the proper exposure (~1/3 - 1/2 stop under). The second exposure employed one of the ND filters in the camera. We did not need to repeat the foreground action because that area will fall into the mask space.
The shots were layered in AE masked and blended. The advantage is that the mask can be "painted" only in the area you wish to.
I don't think that a RAW file will support such a dynamic range. With the method described above, you could claim almost 15 stops.
Just try to shoot RAW with a digital camera and experiment. The main advantage would be for the colour correction where yo can choose in post the colour space and minor luminance variations.

Here is a link for more info about the Fuji sensors http://www.dpreview.com/news/0301/03...superccdsr.asp and their photosites structue.

Aaron Shaw · September 24th, 2004, 06:43 PM

Ah yes of course! How simple! Thanks for the clarification. I never would have thought about doing it that way. Interesting... I'll have to try that sometime. Masking can be a real pain I assume though.

15 stops being the dynamic range of the combined footage not RAW file I presume? I know that some still photographers shoot one raw file when doing this sort of thing and others shoot two consecutive shots. The two separate shots looks somewhat better but the RAW file isn't half bad either, though significantly less useful.

Thanks for the resonse!

Valeriu Campan · September 24th, 2004, 06:50 PM

I shoot almost all the time RAW stills using two exposures and layer them in Photoshop. I will post a link to see some samples.
It is very easy. The mask can be painted with broad soft brushes or any size and shape you want. You can also make an "action" and automate the process.
I will post a link to see some samples.

Aaron Shaw · September 24th, 2004, 07:32 PM

Great! I'd love to see some examples. Do you have some video clips from the shoot you could post? I can host files if you would like.

Valeriu Campan · September 24th, 2004, 09:45 PM

I have rushes/dailies on DVD. I'll try to convert them to a QT file. I will post some examples with Photoshop files as well.

Wayne Morellini · September 25th, 2004, 06:41 AM

<<<-- Originally posted by Jeff Donald : Canon already has a patent on a CCD/CMOS variable DR imaging chip from the early '90's. If I remember correctly, it uses variable CMY dichroic filters to adjust the exposure. -->>>

Interesting, thanks.

Jeff, I have also been looking at doing a range compression trick commercialy. This Canon technique, can you tell me more about it, just in case it is the same?

September 23rd, 2004, 01:58 PM	#17
Jeff Donald Warden Join Date: Mar 2002 Location: Clearwater, FL Posts: 8,287	I haven't forgotten your post Andre, I've been looking for the paper I read on the patent. But as I recall it was for intra scene improvement of DR. I'm still looking though. __________________ Jeff Donald Carpe Diem Search DVinfo.net for quick answers \| Where to Buy? From the best in the business: DVinfo.net sponsors

September 21st, 2004, 09:49 AM	#16
Andre De Clercq Major Player Join Date: Sep 2002 Location: Belgium Posts: 804	Jeff, was this an intra scene variable DR system?

September 23rd, 2004, 04:19 PM	#18
Valeriu Campan Major Player Join Date: Mar 2004 Location: Melbourne, Australia Posts: 223	I was using recently on a shoot a technique with employed two exposures with the camera locked off. The second exposure was for highlights only with the in-camera ND filter. The images were blended later in AfterEfects and looked stunning.... Would have been nice to have a motion control rig with this as well... Following this why not having a second chip installed on a prism with only an ND filter attached? I am not a video technician but just thinking out loud: the signal from the second "ND-ed" chip could be mixed (overlaid) with the main one after some filtering is applied to it, similar to audio LowPass or HighPass filters?

September 24th, 2004, 01:34 AM	#19
Brett Erskine Major Player Join Date: Dec 2003 Location: Anaheim, CA Posts: 445	What a great idea! ;-)

September 24th, 2004, 11:26 AM	#21
Dan Stewart New Boot Join Date: Aug 2004 Location: New York Posts: 5	Am I missing something obvious in the idea of a bayer style ND filter pattern on all 3 chips of a 3 chip system? Of course the beamsplitter-lens arrangement gets more complicated but the system exists in every decent camcorder. The grid would look like: ---------- 0 \| +1 ---------- +2 \| -1 ---------- Surely a decent HDRI could be interpolated? There would be less data lost than in a bayer pattern because of the exposure overlaps. In theory this could be done in conjunction with a bayer filter on a single chip system, as long as you had the spare resolution, like a 2k chip for SD output. Or am I missing something?

September 24th, 2004, 05:00 PM	#22
Valeriu Campan Major Player Join Date: Mar 2004 Location: Melbourne, Australia Posts: 223	I was thinking at only two chips with a three stops ND filter. This could push the dynamic range to ~11-12 stops. But Dan's idea is interesting too. Why not use a single Bayer chip config, similar to the one in Fuji digital cameras (a honeycomb config with chips of different sizes - the smaller ones to be activated only on higher levels of light...) Don't have a URL handy but it's worth a look

September 24th, 2004, 06:28 PM	#24
Valeriu Campan Major Player Join Date: Mar 2004 Location: Melbourne, Australia Posts: 223	<<<-- Originally posted by Aaron Shaw : How did this work exactly? Was it simply a still shot of, say, nature or were there actors on screen? I imagine it would be incredibly difficult to match two sets of footage in post if actors were moving about. Even with the camera locked off. Hence the reason it would be so nice to have RAW video. You could pull the necessary highlight clip and shadow clip from a single shot/take. -->>> Aaron, There were locked off shots. The foreground action was recorded with the proper exposure (~1/3 - 1/2 stop under). The second exposure employed one of the ND filters in the camera. We did not need to repeat the foreground action because that area will fall into the mask space. The shots were layered in AE masked and blended. The advantage is that the mask can be "painted" only in the area you wish to. I don't think that a RAW file will support such a dynamic range. With the method described above, you could claim almost 15 stops. Just try to shoot RAW with a digital camera and experiment. The main advantage would be for the colour correction where yo can choose in post the colour space and minor luminance variations. Here is a link for more info about the Fuji sensors http://www.dpreview.com/news/0301/03...superccdsr.asp and their photosites structue.

September 24th, 2004, 06:43 PM	#25
Aaron Shaw Major Player Join Date: Jul 2004 Posts: 587	Ah yes of course! How simple! Thanks for the clarification. I never would have thought about doing it that way. Interesting... I'll have to try that sometime. Masking can be a real pain I assume though. 15 stops being the dynamic range of the combined footage not RAW file I presume? I know that some still photographers shoot one raw file when doing this sort of thing and others shoot two consecutive shots. The two separate shots looks somewhat better but the RAW file isn't half bad either, though significantly less useful. Thanks for the resonse!

September 24th, 2004, 06:50 PM	#26
Valeriu Campan Major Player Join Date: Mar 2004 Location: Melbourne, Australia Posts: 223	I shoot almost all the time RAW stills using two exposures and layer them in Photoshop. I will post a link to see some samples. It is very easy. The mask can be painted with broad soft brushes or any size and shape you want. You can also make an "action" and automate the process. I will post a link to see some samples.

September 24th, 2004, 07:32 PM	#27
Aaron Shaw Major Player Join Date: Jul 2004 Posts: 587	Great! I'd love to see some examples. Do you have some video clips from the shoot you could post? I can host files if you would like.

September 24th, 2004, 09:45 PM	#28
Valeriu Campan Major Player Join Date: Mar 2004 Location: Melbourne, Australia Posts: 223	I have rushes/dailies on DVD. I'll try to convert them to a QT file. I will post some examples with Photoshop files as well.

September 25th, 2004, 06:41 AM	#29
Wayne Morellini Inner Circle Join Date: May 2003 Location: Australia Posts: 2,762	<<<-- Originally posted by Jeff Donald : Canon already has a patent on a CCD/CMOS variable DR imaging chip from the early '90's. If I remember correctly, it uses variable CMY dichroic filters to adjust the exposure. -->>> Interesting, thanks. Jeff, I have also been looking at doing a range compression trick commercialy. This Canon technique, can you tell me more about it, just in case it is the same?