Author Topic: Non-Video uses for Raw Video  (Read 7722 times)

dmilligan

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Non-Video uses for Raw Video
« on: June 22, 2014, 09:43:05 PM »
Long exposures in the daytime without an ND filter:




I can't use my ND filter with my fisheye lens due to the curvature, so I decided to use raw video instead to approximate a long exposure. One added advantage is that stacking all those individual exposures greatly reduces shadow noise, thus increasing the effective amount of DR I can capture, and there's a large amount in this particular scene (the right wall is brightly lit by the sun and the left wall is in deep shadow). The ACR settings used were +2ev, +100 shadows, +50 blacks. Even with these settings the shadows are very clean with the exception of some banding due to sensor FPN. With proper black frame correction that could be taken care of as well. The main issue is the low resolution and the aliasing in non-crop mode, so I decided to do another in crop mode where I could get a little higher resolution and less aliasing (second photo). Obviously this means I had to sacrifice some FOV, which kind of defeated the point of using the fisheye, but this technique could perhaps be useful for others, esp. on some of the higher end FF cameras, or for those who have no ND filter at all.

Both of these were taken with a 60D and MLV raw video. The first is 1728x972 (60D max res, non-crop), and the second is 2240x1080 (max res, crop). FPS override to slightly under-crank (I don't recall the exact amount but I think I used something like 18fps), and "low-light" mode to get as large a shutter angle as possible. The first is 212 frames and the second is 54 (doing the math that's an effective exposure time of ~11 seconds for the first shot and ~3 for the second). Post-processing: converted to DNG with MLRawViewer. Then I stacked the frames using PixInsight (software I typically use for astrophotography) to a 32-bit floating point TIF and then toned in ACR/Lr.

(of course there are other non-video uses of raw video, escho is doing some amazing stuff with astrophotography)

a1ex

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Re: Non-Video uses for Raw Video
« Reply #1 on: June 22, 2014, 09:53:59 PM »
Nice! Can you share the stacked DNG?

(I actually have a patch that attempts to do the stacking in the camera, but it's kinda slow - http://www.magiclantern.fm/forum/index.php?topic=10176.msg98049#msg98049 )

dmilligan

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Audionut

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Re: Non-Video uses for Raw Video
« Reply #3 on: June 23, 2014, 02:02:10 AM »
The aliasing is a little ugly (obviously), but the aliased CA!!  Did you try and process the CA, or does the line skipping prevent correction?

BTW, per your last photos in the dual ISO thread, looks like congratulations will be in order very soon.

dmilligan

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Re: Non-Video uses for Raw Video
« Reply #4 on: June 23, 2014, 01:28:00 PM »
The aliasing is a little ugly (obviously), but the aliased CA!!  Did you try and process the CA, or does the line skipping prevent correction?
I didn't even think to try to process the CA, I guess I just kind of assumed that the color distortions were just a direct result of aliasing and not a result of aliasing of optical aberrations. I'll try some things and post them after the break. I might fire up photoshop and try to work on the aliasing too.

BTW, per your last photos in the dual ISO thread, looks like congratulations will be in order very soon.
It won't be much longer now ;)