Welcome to our community

Be a part of something great, join today!

Register Log in
  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

HDRx

roryhinds

roryhinds

Well-known member
Joined
Jan 15, 2007
Messages
2,144
Reaction score
0
Points
0
Location
Vancouver, BC, Canada
Website
www.minefilms.com
With ISO being metadata what is the benefit from shooting HDRx compared to just shooting 1 exposure and processing 2 separate exposures in post and comping them together.
 
Your method only gives you one shot at dynamic range. If you are only changing ISO (not actual exposure), you don't gain anything. HDRx will actual give you a track with a different (lower) exposure. It actually extends dynamic range.
 
Isn't there only ever 1 exposure as there is only one light source passing through the lens and hitting the sensor and the sensitivity of the sensor (ISO) is just metadata?
So the sensor is running at 2 ISO's when in HDRx?
Doesn't this go against ISO is just metadata?
Or what other smarts are going on?
 
roryhinds said:
Isn't there only ever 1 exposure as there is only one light source passing through the lens and hitting the sensor and the sensitivity of the sensor (ISO) is just metadata?
So the sensor is running at 2 ISO's when in HDRx?
Doesn't this go against ISO is just metadata?
Or what other smarts are going on?
Click to expand...

HDRx records "two streams" at the same time. Hence the halving of the recording time.

You get one track at the past exposure, presumably 180 degree shutter or faster. Then in 1 to 6 stops you have another exposure being taken with a faster shutter speed. Combined this can be up to 360 degrees of a shutter when added together.

It's not an ISO thing. It's literally two streams being recorded at the same time.

A word of caution. If filming lots of moving action, you'll see motion blur characteristic difference the higher the stop compensation you use. Most folks in practice like to stay in the realm of 1-3 stops of HDRx, but you can certainly do more and it's extremely useful for things like say timelapse.

There is also a key mappable toggle between the A track and X track so you can utilize your exposure tools to make sure you "got it".
 
...just to add to what Phil said.

When HDRx is set to 3 stops, it’s as if you closed your iris down 3 stops (BUT ONLY ON THE 2ND TRACK/STREAM). This gives you 3 extra stops of highlight protection on track 2 without having to close down the iris (which would cause you to lose 3 stops on the low end). In effect, you have gained 3 stops of range. You can’t get this by adjusting iso. You can only adjust the image within the range that was captured with a single track and the 3 extra stops you were hoping to gain will not have been captured.
 
Just to add to what phil said.

hDR x is achieved by simulataneously recording two streams at different shutter speeds. Works excellent on slow moving things, but things with heavy motioning and will introduce motion artifacts because by blending the exposures you are in effect blending the motion characteristics of two different shutter speeds.

Its highly effective when used with a power window and tracking.

Battistella
 
Combining different ISO developments of the same frame can allow you to extract out all the visible DR from that frame, but it doesn't extend the DR in the frame. What happens in cameras is that two exposures are taken - one normal, one dark by altering the shutter speed. That actually extends the DR that you capture. Of course, it's up to you to extract that DR in the grade and we offer some development modes to help you there.

Graeme
 
I really hope Weapon has enough horse power for a third exposure track. It's not that hard to get correct exposure but for monitoring purposes I would love to be looking at my middle exposure while filming.
 
Luke Neumann said:
I really hope Weapon has enough horse power for a third exposure track. It's not that hard to get correct exposure but for monitoring purposes I would love to be looking at my middle exposure while filming.
Click to expand...


The "official" (from what I recall) advice from RED on using HDRx has always been to expose somewhat normally, to get a thick negative, and use the extra track to save the highlights. They always cautioned against altering the "main" exposure too much while expecting to rely on the X track for too much of the overall exposure.

Adding a third track might be interesting but how would you use it? The X track already saves highlights. I suppose you could have a "Z track" which is a very long exposure to dig into shadows but the motion artifacts between the three exposures might get weird.
 
Terry VerHaar said:
The "official" (from what I recall) advice from RED on using HDRx has always been to expose somewhat normally, to get a thick negative, and use the extra track to save the highlights. They always cautioned against altering the "main" exposure too much while expecting to rely on the X track for too much of the overall exposure.

Adding a third track might be interesting but how would you use it? The X track already saves highlights. I suppose you could have a "Z track" which is a very long exposure to dig into shadows but the motion artifacts between the three exposures might get weird.
Click to expand...

I generally expose normally and then push it up about 3 stops just so I can get the most out of it. This is a specific HDR shoot though, not a lot of motion and trying to get the most DR possible. Normally I would just expose and add a 1-2 stop highlight track like you said.
 
i find in the real world hdrx is not used much. all it takes is one shot in a scene that cannot be qucikly / cost effectivly fixed with roto to kill all hdrx in a scene, and that's about 90% of the time

most of the dp's i work with turn it off, or if it's on, it's not to be trusted, only a hope / wish / prayer that no actor intersects with a highlight while moveing quickly, even a hand twisting hair is enough to totaly break hdrx beyond any resonable chance of recovery with roto in a gradeing session - even with Pablo or DS that have solid paint systems onboard.... at that point the producer needs to decide to send it to vfx or go with blown + soft cliped highlights

i have yet to see a producer pull the trigger on vfx to see if it is even possiable to recover a hdrx shot


i do often comp diffrent iso's together tho, this is more about ease of working with the shoulder than it is about expanding dr, still needs a comp, but at least you do not have motion artifacts to deal with - this is from 5 years ago when the MX sensor just came out;
https://digitalfilms.wordpress.com/2010/09/16/avid-ds-shines-for-metric/

just as valid a workflow now as it was then...
 
Has anyone posted an HDRx Dragon frame yet (with LLO OLPF)? I'd really like to see it... Obviously on a frame that can take advantage.
 
It's certainly a special tool that isn't used all the time, but it's nice to have it when you are doing something "weird".

On Dragon, since it hold the highlights a heck of a lot better than Mysterium-X and rolls off those highlights smoother I'm certainly seeing it used less. Myself included.


Sidney L. Plaut said:
Phil,

which user button are you referring too? - where you can switch to the xtrack.
Click to expand...

In the Keys dialog you can assign any button to toggle the HDRx Tracks.
 
HDRx works great on still or slow movement shots but I don't think it is "simulataneously recording two streams at the same time", I think they are sequential thus the motion artifacts are both temporal and shutter based. Try throwing a white ball around on a sunny day like we did with a 3d rig set to zero.
<font color="#f1f1f1">
 
I shoot a lot of time lapse at sunrise and sundown, without HDRx this would be very difficult to accomplish even with Dragon DR.
I have tried DSLR cameras for that purpose, but nothing beats the RED raw workflow and the coverage of the HDRx dynamic range.

There is ways to rack iris over time, but this comes at a price.

The only thing I wish for is the ability to keyframe exposure parameters in Cine-x and not having to do this by exporting multiple exposure clips and fade them in edit or comp.
 
You must log in or register to reply here.
Back
Top