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10-08-2009, 09:19 AM
Ooops, sorry for the wait.
Well, I've no Red to shoot with, but there's one clip in this TL reel that has a 25fps 1sec exposure stream on the waves at about 1:05. Just shot with an FX1 to try stuff out.
http://www.vimeo.com/6685310
That's about the easiest thing to do, then you can mix it up a bit with variations on the theme.
10-08-2009, 11:29 AM
Exactly -Originally Posted by ColinSmith
I've tried that too - what's also cool, is that blending 25 frames together gives you a noise-free image even if you use gain...I've shot video sections to drop into timelapse comps posted to give a 25fps stream with each post-post frame having a 1s exposure, just by shooting 25fps, 360 shutter and doing a rolling blend for 25 frames.
Exactly, again. And the higher frame rate you shoot with, the more options you have...Lots of possibilites, just by thinking a little bit outside the usual film camera setups to see some of them.
10-08-2009, 01:33 PM
Oh, BTW, i'd still be interested in some test material to have a go with my "EDR" concept - we've had some red projects since i posted the request, but i've always had too many other things on my mind and thus forgotten to shoot / ask to shoot the test footage... and, nope, i don't have a R1 of my own...
So here's the specs again, in case someone has a few minutes of extra time:
Set up a scene where there's a high contrast ratio and some motion.
Clip 1: Set camera to 2K, 24 fps, 1/48 (180 degree) shutter. Adjust the aperture so that some parts of the image are overexposed to white (by about one stop). Let it roll for a second or two (not much more to keep file size down).
Clip 2: Change frame rate to 96 fps, shutter speed to 1/96 sec. (360 degrees). Do not change anything else. Shoot a second or so.
...if my theory is correct, i should be able to extract one stop better dynamic range from the latter clip, without motion- or other artifacts.
10-08-2009, 06:48 PM
Yes, that makes sense, although the workflow would be entirely convoluted and it might be hard getting good results.
When it boils down to it, a camera catches light, not an image. The resulting frame is an estimate of the real-life "image" from averaged-together photon samples across a limited sample of space and time. With more light, you can capture with more accuracy with respect to spatial resolution (as much light per photosite, but more photosites). Or you can also capture with more accuracy with respect to time; you can use a faster shutter.
But for cinema, time's not a variable; it's (generally) a constant. 90% of theatrical footage is shot at 24fps 1/48sec shutter and distributed as such.
But a camera could capture a very high level of temporal resolution instead of ever-increasing megapixels at 24fps 1/48sec shutter. Let's say I record (standard, not over-cranking) at 240fps at 12 bits per sample. I could combine five samples linearly to get 1/48th second frames, or I could blend them in ways ensuring they don't clip--so really I'd get an underexposed image at 240fps (360º shutter), which could turn into a correctly exposed image at normal 24fps (with a "normal" s/n ratio), but I could combine data in other ways to get way more highlight detail, too. I could also choose common denominator frame-rates in post, do accurate speed ramping with mathematically perfect exposure-compensating software (with noise being the only variable), or use the extra motion for super-accurate motion vectors for post-processing and 3d tracking--even if you just use 1/48th shutter in the final image, you'd have an extra 100% more information hidden away in the odd frames, and you could use all your frames for temporal noise reduction, motion vectors, etc. even if you only end up showing half of them.
Right now, cinema cameras (though they allow speed ramping, open shutters, etc.) basically operate with temporal resolution as the constant and spatial resolution is an ever-increasing variable. But, guess what? The difference between 2k and 4k in 3D (if 3D catches on, which it may soon) is quite minor, but 24fps and 48fps in 3D are appreciably different... I think we may find a standard resolution that's good enough for normal screens; I honestly think 2k is that resolution, but others will disagree. But beyond 2k is diminishing returns for normal-sized screens. True, 6k bayer is good for true 4k, as 4k bayer is good for true 2k, but would 12k bayer help theater-goers at all? Not those watching on normal-sized screens, no. Most film prints are about 720p equivalent after all that MTF-type stuff.
So, as silicon gets faster and recording capacities increase, I think cameras will record more in the "time" dimension and time will be recorded as a coherent whole--Xfps (a multiple of 120 most likely) with a full open shutter, that a computer can then downsample, take motion vectors from, blend light from multiple samples in different ways to increase exposure latitude/reduce noise with, etc. at whim. Particularly as 3D catches on, this type of camera will be useful since we'll need 24fps 1/48sec for normal theaters and 48fps 1/96sec for 3D, and then that usefulness will only increase as computers increase in power and the digital image becomes more malleable with increasingly complex algorithms. Just as sound is temporally oversampled, I think images will be soon, too.
Last edited by Matt W.; 10-08-2009 at 07:02 PM.
10-09-2009, 06:09 AM
Yep - but the procedure could be made trasparent to the user - as easy as setting the checkbox for "EDR", or Extended Dynamic Range mode when shooting in the camera's menu (or a "24p EDR" frame rate), and choosing from a list of appropriate blending options when debayering the image in post.
I wrote a description how this could be implemented as a firmware / software update a few pages back...
http://www.reduser.net/forum/showthr...1683&page=3#25
Exactly - and the idea of using the "discardable" extra frames for noise reduction / 3D tracking is an excellent one - kudos for that... that would also work @3K resolution in R1, shooting 48 or 50 fps and 360 degree shutter...I could combine five samples linearly to get 1/48th second frames, or I could blend them...
10-09-2009, 11:31 AM
Yes, it will be interesting when cameras record with enough frames per second that we start to view frames like pixels...a kind of mesh of data that can be manipulated at whim and delivered scaled down at any resolution (60fps, 50fps, 48fps, 24fps, etc.) like we can scale film down to 2k, 1080p, DVD, iPod video, etc... This will also begin to open up whole new approaches to time remapping, over-cranking, exposure, etc.
However, it looks most likely that increased light sensitivity will first go toward scaling chips down from s35 to 2/3'' to give the extra depth of focus needed for 3d imaging. The next major camera revolution will be delivered by the first company to convert something along the lines of Cameron's PACE camera but easily and cheaply operated/monitored.
10-09-2009, 11:56 AM
Now that 4.5K wide screen mode is working, you can use a special kind of beam splitter as was used in the early Technicolor "two strip" (not the later 3-strip type, 2-strip like side-by-side stereo format) cameras to make two exposures side by side, each 2.25K images.
You then put an ND on one of the two images, and presto you get HDR in your REDONE camera, and you can adjust the HDR range with the ND filter.
The prism used makes two images from one taking lens, so both images are in sync and there is zero parallax problem.
10-09-2009, 03:21 PM
That sounds pretty kewl too...
10-09-2009, 04:02 PM
Sounds OK for the RED One... Resolution wouldn't be so high, perhaps acceptable for 1080p and a little beter with M-X.
However it would be a very good technique for the upcoming bigger sensors with more resolution (645 Monstro).
10-10-2009, 12:09 PM
You can use a 1.33:1 anamorphic as the "prime" lens for the image splitter, so you get enough resolution for 2K filmout.
Che it seems was a 2K filmout and most of the time the projector was too far out of focus to see even that.
Tests show that 35mm projection is about 600 to 800 video lines resolution, so 2.25K is enough resolution since you mix 2 images, with adjustment of the prism you can offset one of the images from the other by 1/2 pixel, then interpolate in software later to "re-gain" 4.5K "resolution".
The more important thing for filmout is to loose the "video look" by using HDR to get 2 to 4 stops more dynamic range, resolution does not mean much for 35mm filmout, but dynamic range shows at ALL RESOLUTIONS even on a DVD.
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