Does shooting on HDRX have any disadvantages other than file size and compression?

[Lee M]

If I shoot on HDRX does it come with any disadvantages other than doubling the file size and compression? I don't need need it but it would be nice to have just in case I over expose or something. Also is 10:1 compression good enough or should I be filming on 5:1 and eliminate the HDRX? It is for a short film, want it to be very high quality but not sure if the compression makes a difference in that range.

 

[Bob Gundu]

Motion blur is usualy a problem because the higher shutter track has less motion blur than the other track.

 

[Nick Morrison]

Motion blur is usualy a problem because the higher shutter track has less motion blur than the other track.

What Bob said.

 

[Lee M]

So even if I only used track A in the end will there still be motion blur or a quality difference? Also should I be filming at the lowest compression possible?

 

[paulherrin]

you can try using something like reelsmart motion blur to match the tracks before doing some compositing tricks to get a final shot

you don't necessarily need to shoot with the lowest possible compression for every shot. for narrative work most folks (i think) pick a compression ratio they can use throughout... maybe 8:1

 

[Lee M]

So if I film in HDRX but only use the track A will there be any noticeable difference by only using the single track?

 

[Lee M]

I see this on Red's page, kinda answers my question.

IN PRACTICE

Most use the A frame as a normal exposure and the X frame as the under-exposed highlight protection frame. This is generally recommended since it makes HDRx easily reversible if the X frames are later deemed unnecessary. However, one could instead shoot “over-under,” where the A frame is overexposed and the X frame is underexposed (but less so than otherwise). One might do this if they wanted to apply some of the dynamic range extension to the shadows in addition to just the highlights.

http://www.red.com/learn/red-101/hdrx-high-dynamic-range-video

 

[Owen Rennie]

Just use HDRX when it's needed and suitable... (when you need the DR and there's very minimal movement in the scene). Otherwise use the lowest compression you can and light and shoot your scene

 

[Christoffer Glans]

You can easily apply post motion blur to most types of shots. I wouldn't do high motion action with HDRx, but normal scenes work great even at 6 stops difference. I've tested shooting handheld at 6 stops, doing a over and under exposure for each track combining them into a 25 stops HDR image with really nice roll off into both shadows and highlights. Just remember that when shooting like this, keep both tracks shutter speed as fast as possible.

If you want some really good roll off capabilities you could also shoot at only 2 stops, which will keep the different shutter speeds closer to each other on each track and therefor won't make the differences very noticeable.

 

[Björn Benckert]

So even if I only used track A in the end will there still be motion blur or a quality difference? Also should I be filming at the lowest compression possible?

No the A track is intact, no motion blur differences only compression can not go as low as if you shoot single track.

The B track is simply an earlier readout while the photosites are filling up. So all you loose for recording it is disc space and compression, simply you need to compress twice as hard to get the same file size if you shoot HDRx.

Then in post yes there can be motion blur issues when using both tracks. if you shoot 180 deg 2 stop HDRX you get A track at 180deg shutter and B track is simply 45 deg. So sure it couldbe difficult to combind the two but three is rather good motion blur plugins that that can sort it anda lot of times the issue is not visable. Depends on what you shoot ofcourse.