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Maximising stock latitude?


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#1 Karel Bata

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Posted 04 February 2009 - 08:15 AM

What should I do to get the max possible latitude out of color neg film? Would overexposing by a stop and then push processing by minus 1 help?

I want to shoot some tests to see if I can extract enough image information in the shadows and highlights to do HDR processing.

HDR is this kind of stuff

Cheers! Posted Image
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#2 wolfgang haak

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Posted 04 February 2009 - 11:44 AM

What should I do to get the max possible latitude out of color neg film? Would overexposing by a stop and then push processing by minus 1 help?

I want to shoot some tests to see if I can extract enough image information in the shadows and highlights to do HDR processing.

HDR is this kind of stuff

Cheers! Posted Image


Karel,
I know as much about film stocks as I do about open heart surgery, so I leave it to the pros to answer that one. But Is I know about HDR(I):
The footage you link is done by overcooking a process called tone-mapping. It tends to oversaturate colours. I don't like the stuff most of the time myself, but that is down to personal taste. Check http://www.hdrsoft.com/ for examples.

- from neg: scan the same neg using multiple exposures. (i.e. adjusting scanner back light) Process the passes in HDRI package.
Works with still images, LaserSoft do a package called SilverFast Ai that will allow you to operate most scanners this way.

- DI: adjust back light/laser/etc. Make multiple passes, process in you favourite package.

-from one DNG/RAW file: process multiple tifs (or similar) from your DNGs, in 16bit mode, pushing and pulling the exposure for each shot by 1-2 stops. Process in fav package.

- time lapse: you could shoot with off the shelf DSLR, yousing exposure bracket program. In quick succession no-one will notice motion artefacts.
Good fun for doing that are hacked canon cameras http://chdk.wikia.com/wiki/CHDK

regards,
Wolfgang
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#3 Karel Bata

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Posted 05 February 2009 - 07:22 AM

Thanks Wolfgang!

I've seen some nice examples of HDR videography (and would disagree about oversaturated colors - Horses for courses, I say). Unfortunately they're limited to time-lapse created by auto-bracketing with a stills camera because no video camera can yet do that at 24fps, which for +1 and -1 bracketing that would be 72 fps plus all the time needed to switch shutter speeds 72 times a second! It will one day be possible, but it'll cost, and I don't want to wait.

On the other hand film has much more latitude and I've seen DI do some incredible things by pullling details out of deep shadows or fixing what at first looked like burnt out areas. So I'd like to do some tests with film (it'll have to be stop frame using an SLR since I don't have a 35mm camera) scan it into my PC at different light settings and see if I can get a moving HDR image from a single sequence of film exposures.

Though someone somewhere must have tried this already methinks...? :huh:

I'll be using Photomatix software. For the uninitiated, here's how it's done:

Posted Image Posted Image

This pushes it a bit further and I very much doubt I'd be able to get this from out of one exposure

Posted Image

http://commons.wikim...uplands-HDR.jpg

http://farm1.static....537107963_b.jpg

These are more extreme:

http://www.pinktenta...mages/hdr_6.jpg

http://fc84.devianta..._by_alex12m.jpg

Now imagine actors moving around in this... http://www.flickr.co...57594155375875/

http://www.pellphoto...p?showimage=315

http://farm4.static....62f31b8d3_b.jpg

http://fc53.devianta...562d7960adf.jpg

http://www.multimedi...ormal/zaid2.jpg

This one's gorgeous http://farm1.static....ab41730c2_b.jpg Nice bokeh too.

Yup, I've spent the morning surfing the net. :rolleyes:


So, back to my question... Are there any techniques for increasing color neg latitude? :D
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#4 wolfgang haak

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Posted 05 February 2009 - 08:12 PM

Karel,

For Long distance shots with no foreground, mount three cameras in parallel on a rig and sync your footage. Bracket your exposure across the three cameras. With not too much parallax you might get away with it.
Crystal sync for film or some computerised affair for digital cams.


Have fun!
Wolfgang
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#5 Karel Bata

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Posted 15 November 2009 - 06:57 PM

Well it seems that Arri may have beaten me to it!

Arri's new cameras Everything is about to change... according to an article in High Definition magazine have a 'magic' trick up their sleeve:
"The key to the increased performance is what we call ‘Dual Read Out’ – we have on the sensor 32 output channels and we read every pixel twice through a normal gain and through a high gain. Each of these read outs happens in 14 bit depth. We then combine them and get 16 bit pixel depth for every pixel element. So that results in a very quiet image with very low noise. This is a philosophy which is similar to our scanner with its double flashing, however these read outs are happening at the same time.”

"Arri promise more ‘magic’ to do with this heavy processing which may be to do with HDR or High Dynamic Range as its known in stills photography. This is where you combine several different exposures into one, taking the best exposure elements from each to make a extraordinary image. Could this be what Arri have in mind?"
Well, if Arri aren't thinking that, other folk clearly are, and tonemapping software is now well established and it wouldn't be too difficult for a programmer to adapt it. Mark my words - it'll be the next Big Thing.
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#6 Paul Bruening

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Posted 15 November 2009 - 08:53 PM

We've talked about this a couple times in the past. Did we not decide that when shooting cine for HDRI it was better to overexpose the negative (shoot it thick) anywhere from one to three stops and burn back through on a second and maybe third scan to get the other end of the range? Then, process them back together. Is this still a popular notion?
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