HDRX and Global Shutter

[Christian Jadot]

Will it be possible to shoot in HDRX with the Global Shutter? I have a general layman's idea how HDRX works, and I am not sure if it is possible to do the same trick with a global shutter. Will the Komodo be capable of shooting in HDRX at all? With a global shutter can samples be taken from the same exposure?

 

[Rakesh Malik]

AFAIK the only thing that might hold the Komodo back from being able to use HDRx is the maximum frame rate. Well, that plus the data rate. I'm hardly an expert on this, but I don't believe that global vs rolling shutter has any bearing on the camera's ability to support HDRx.

 

[Robert Hofmeyr]

AFAIK the only thing that might hold the Komodo back from being able to use HDRx is the maximum frame rate. Well, that plus the data rate. I'm hardly an expert on this, but I don't believe that global vs rolling shutter has any bearing on the camera's ability to support HDRx.

Agreed. It definitely wont be possible at 6K, unless you shoot at 20fps, since HDRX halves your max frame rate. And I doubt Red would enable it for lower resolutions only.

 

[Gregory Karydis]

Agreed. It definitely wont be possible at 6K, unless you shoot at 20fps, since HDRX halves your max frame rate. And I doubt Red would enable it for lower resolutions only.

Would be nice if we have the HDRX option.
But, as you have all mentioned already, frame rate is identified as the limiting factor.
You never know, If we crop down to either 6K WS or even at some flavour of 5K, HDRX might just be viable...?
I shoot most of my work at 24fps and on a rare occasion I might overcrank to 40.

 

[Robert Hofmeyr]

Would be nice if we have the HDRX option.
But, as you have all mentioned already, frame rate is identified as the limiting factor.
You never know, If we crop down to either 6K WS or even at some flavour of 5K, HDRX might just be viable...?
I shoot most of my work at 24fps and on a rare occasion I might overcrank to 40.

Hey Gregory. Yeah, I agree it's probably viable, but not sure Red would implement it. I do really wish 6k went up to 50fps, but looks like we will have to wait for Komodo v2 for that.

 

[Rakesh Malik]

Agreed. It definitely wont be possible at 6K, unless you shoot at 20fps, since HDRX halves your max frame rate. And I doubt Red would enable it for lower resolutions only.

On my Epic-W, I can use HDRx in 6K but not 8K... so Red has been fine to enable HDRx in cropped rather than open gate on cameras that aren't able to handle the required data rate. So I'm guessing that it's going to keep doing that for Komodo, but I have a feeling that even if HDRx got pushed so that Red could bring the new sensor to market with its first global shutter and PDAF implementations, then that's life. I have a feeling that although a few users might complain about it a bit, given how nice this little beast will be, the complaining won't last long.

 

[Robert Hofmeyr]

On my Epic-W, I can use HDRx in 6K but not 8K... so Red has been fine to enable HDRx in cropped rather than open gate on cameras that aren't able to handle the required data rate.

Thanks Rakesh, I did not know that.

 

[David Rasberry]

With the exceptional DR of the current gen Reds, HDRX is perhaps not as needed as it used to be.

 

[Gregory Karydis]

I agree David, the current crop of RED sensors don't need it as much.
But HDRX has a secondary use which is not as widespread.
When dealing with VFX, the HDRX stream can help a lot, even if it doesn't end up in the finished footage.

 

[Christian Jadot]

With the exceptional DR of the current gen Reds, HDRX is perhaps not as needed as it used to be.

I still need it, I do a fair amount of shooting inside military aircraft while they are operating. I know it is not common and I know most people use RED cameras in controlled environments, but there are always exceptions to the rule. One day I want to capture both the faces of the pilots in a dark cockpit, and be able to make out the cloud detail in the sky from above. Or shoot cargo being loaded up where it is not silhouetting from the inside of the aircraft. I know these extremes that most won't come across, but sometimes you just need every bit of dynamic range you can squeeze out of a camera.

 

[Rakesh Malik]

I agree David, the current crop of RED sensors don't need it as much.
But HDRX has a secondary use which is not as widespread.
When dealing with VFX, the HDRX stream can help a lot, even if it doesn't end up in the finished footage.

I actually have been surprised to not have needed it yet myself, though I probably ought to try it in the near future just to get used to working with it.

Out of curiosity though, what's the benefit that you get for VFX from HDRx?

I can see it in extreme situations where you have to push the camera to plaid to handle ridiculous contrast ratios like Christian mentioned, but I don't have that much experience on the VFX side of things yet.

 

[Gregory Karydis]

...Out of curiosity though, what's the benefit that you get for VFX from HDRx?

I can see it in extreme situations where you have to push the camera to plaid to handle ridiculous contrast ratios like Christian mentioned, but I don't have that much experience on the VFX side of things yet.

Doesn't matter whether its a low or high budget production, the over (or under) exposed plate has proven vital especially when it comes to rotoscoping.
HDRx saved my ass a bunch of times when an inexperienced director or DoP insisted they "knew better" and they were convinced I'd "fix it in post"... little did they know that I snuck in and activated it before we rolled

First time that happened, I found out the steadi operator accidentally turned it on while fiddling with the menu and when it came time for post, the footage from the DoP was over exposed (for dramatic effect) and after a few calls I found out that the DIT had a single backup of the X frame.

I've got more horror stories and I can imagine other VFX artists have similar experiences.

Another instance is when you'd like to stabilise shaky footage and the A frames are too blurry to automate the detection. Set the X track at 2-3 stops lower and presto! Stabilised blurry footage where the X track is used only in Post.

HDRx is also helpful for object replacement as you can imagine.
The list is endless!

 

[Mike P.]

I always kinda thought they'd use the motion mount to get a dual "HDRX" type exposure, without the motion blur problems (as the MM would be controlling the exposure/motion blur and the second fire/frame could be done while the MM's soft-shutter was part-way through the exact same frame). Alas it never happened.

The problem with global shutter at the sensor level is that it'd actually make it more difficult to double-fire the frames without having to wait for the first frame to be captured at the correct shutter angle (e.g. 180deg), and by that point the on screen motion would have moved too far and it'd re-introduce motion artifacts.

 

[Christian Jadot]

I always kinda thought they'd use the motion mount to get a dual "HDRX" type exposure, without the motion blur problems (as the MM would be controlling the exposure/motion blur and the second fire/frame could be done while the MM's soft-shutter was part-way through the exact same frame). Alas it never happened.

The problem with global shutter at the sensor level is that it'd actually make it more difficult to double-fire the frames without having to wait for the first frame to be captured at the correct shutter angle (e.g. 180deg), and by that point the on screen motion would have moved too far and it'd re-introduce motion artifacts.

This is what concerns me. The shutter works different. I don't know enough to know if it would, and how it would, affect everything.

On the other hand, can the capture frame be split in half temporally? So capture the global shutter on the "fade in" then capture on the "fade out". I don't know how to word it better.

 

[Björn Benckert]

Dont know why but when monstro is set to HDRx then shutter speed gets limited a bit "randomly" about down to 225deg depending on resolution. So no, you can not do something like 25p 360deg HDRx level 1 and get a 360 and a 180p.

I think you need to look at it as normal shutter angles ie 225 or less. Like you can shoot 180 deg and then fractions of that in the X track.


Important though, big mistake most people do with HDRx. Make sure you look at the Xtrack and place it right under clip, if you dont you just waist bandwidth.

So the only reason to go HDRx is if you histogram got red goal posts on both sides, a.e you got both under and over exposure. Then your A track needs to clip highlights and your X track should be right under clip.

 

[Björn Benckert]

This is what concerns me. The shutter works different. I don't know enough to know if it would, and how it would, affect everything.

On the other hand, can the capture frame be split in half temporally? So capture the global shutter on the "fade in" then capture on the "fade out". I don't know how to word it better.

The way HDRx works is as follows. If you look at the photosites / pixels in the sensor as buckets then total under exposure is a bucket with no photons / light in it and over exposure is a flooded bucket. Exposure time is the time the buckets are open, then between every frame they are cleaned out.


Now HDRx do a readout of each bucket without flushing them, So for example HDRx level 1 used at 25p 180 deg. Checks the buckets and do a readout for the X track at half the exposure time / 1/100 of a second then the buckets contiues to fill up and at 50/1 of a second A track is written and the buckets are flushed and then onto the next frame.

 

[Rakesh Malik]

Doesn't matter whether its a low or high budget production, the over (or under) exposed plate has proven vital especially when it comes to rotoscoping.
HDRx saved my ass a bunch of times when an inexperienced director or DoP insisted they "knew better" and they were convinced I'd "fix it in post"... little did they know that I snuck in and activated it before we rolled

Has it been helpful with footage that was well exposed as well?

First time that happened, I found out the steadi operator accidentally turned it on while fiddling with the menu and when it came time for post, the footage from the DoP was over exposed (for dramatic effect) and after a few calls I found out that the DIT had a single backup of the X frame.

So you were able to use the X frame to bring the exposure back into a range that allowed you to do the rotoscoping you needed to do? Just trying to understand how you're using it here.

Another instance is when you'd like to stabilise shaky footage and the A frames are too blurry to automate the detection. Set the X track at 2-3 stops lower and presto! Stabilised blurry footage where the X track is used only in Post.

I'll keep that one in mind next time I'm doing handheld stuff. I don't shoot hand held often, but sometimes need stabilizing with semi-stable jib footage (some parts of the jib were jury rigged).

HDRx is also helpful for object replacement as you can imagine.
The list is endless!

That makes sense also.

Sounds like there's another benefit in eventually migrating up to a Ranger from DSMC2.

 

[Björn Benckert]

Has it been helpful with footage that was well exposed as well?

Does not need to only be about exposure The X track get the same fraction of less motion blur as exposure. So if doing roto it might render much better result to use the Xtrack for the person or object you want to roto and if it lest say 2 stops under it only got 45 deg shutter.. instead of A tracks 180. but that part of the image might very well render good quality image even if you up the iso of it 2 stops.

So in other words you can get a much better roto on the drummers drumsticks from the X track exposed with a quarter of the time and lifted 2 stop in iso and then when the roto is done apply motion estimate motion blur on that layer in the comp.

Simply a way to roto sharp objects instead of things that are more smeared out while keeping the exposure high enough on the A track for other parts of the frame.

For example drum sticks on a drummer in 25p 180 deg, they are usually just streaks... and yes I been there in the pit quite a few times, I would estimate I done like at least 50 Chroma key music videos in the past... The drummer always looks shit, chromed out drums and fast rhythm, those are the worst

 

[Gregory Karydis]

You got that right Björn!
The linear velocity at the end of rotating objects like drum sticks, aircraft rotors or even the throwing arm of an athlete can blur even when perfectly exposed.
Personally I had to erase and replace aircraft rotors a bunch of times when shooting VFX rockets or other stuff past the target.
Fun times, spending many hours on a single frame... The X track always saves the day!

On the subject of drummers, taking the performance from the X track and placing it on the A track when keying is done easily this way
Overexpose the drummer cutout by however much you need to match the A track (always a known number thanks to the specific X track setting) and you are done in a fraction of the time!