How to expose to minimize noise when shooting against black backdrop?

[PatrickFaith]

I like to back light the "black" area till it's a touch greyish ... then pull that down during color correction. This way also allows more flexibility when you go to DCP jpeg(that way you don't get those compression "blocks" in the dark background).

 

[ericyoung]

I like to back light the "black" area till it's a touch greyish ... then pull that down during color correction. This way also allows more flexibility when you go to DCP jpeg(that way you don't get those compression "blocks" in the dark background).

While that will avoid noise in the black background, that would also crush shadows on the subject. As Peter in post 18 above says, the black background needs to be less exposed than subject blacks for crushing not to adversely affect the subject.

 

[Joel Arvidsson]

I think Kim You are misunderstanding Joel. He did not say he does not want (or like) "black" - he said "crushed blacks". Basically he wants black BCKG, but he is wandering how to best light it. If You ETTR and leave some headroom in the blacks to avoid noise - you will have to crash the blacks - which will in return crash the subject too (unless you go to painful secondaries). If You expose the BCKG as black - it WILL be noisy. We have just completed high-end shoot on the Epic in this exact scenario. Our situation was even more complicated as there was a deliberate light falloff on the black floor. Joel actually answered himself - the best solution is to separate the black levels of the subject from the black levels of the BCKG by selective lighting. If there is at least one stop difference between the black levels (use a black chart in the place of the subject if you can), you can then ETTR and leave headroom in the black channel. You will be able to easily isolate the BCKG black levels from those of the the subject and therefore be able to crush them down without noise and without crushing the blacks of the subject...

Just my two yen..

Peter

Thanks Peter and all other for all thoughts. Next time I make sure to make a better separation between the foreground subject and background so I can crush the noisefloor of the blacks while keeping the subject intact.
I will also try a lower iso but maby not as low as 320 since Im still like some highlight protection until Im 100% comfortable with the camera. I do like to thank everybody once more for your time, its really appreciated as always.

 

[Noah Yuan-Vogel]

I think the native ISO of the Scarlet is 320. If you go into ISO 320 and switch between RAW and normal (not RAW) view the histogram does not change. However if you are @ 800 and you switch between RAW and normal the histogram totally changes.

Just my 2c...

Jack

"Raw" view is based on the same curve used for ISO320, but that is completely arbitrary. That may be just because it was first implemented in the R1-M in which firmware default ISO was 320. I would not overanalyze RED's use of the ISO320 curve in RAW mode to mean anything in particular.

If you want the least noise, shoot at lower ISOs and always expose to the right. You will almost definitely have to crush blacks with custom curves or contrast setting or grading if you want a solid black background since most of RED's built in looks have very milky blacks. Personally I will probably always shoot with a custom curve set in camera with proper black levels since I find such milky blacks can be misleading when monitoring. Poor contrast in shadows often give the appearance of lack of noise, and then when you set black to a proper level, increasing the shadow contrast, noise can become more visible. Noise gets worse as your photosites are less saturated, so better to overexpose your RAW as much as possible and crush than to try to under expose your shadows trying to make your milky shadows look blacker. Of course you have to be careful about your highlights then

Also plan to apply DRX in post for low ISO values since any blown highlights get very magenta without it,

 

[John Schick]

I found that this thread answers a lot of questions regarding ISO:
http://www.reduser.net/forum/showthread.php?67317-Scarlet-Native-ISO

Especially all of Graeme's posts:

Just to be clear - Dynamic Range is constant. It doesn't matter what ISO you shoot, the total DR available is the same. This would not be the case in an analogue gain situation where typically a stop of DR is lost for every stop up in ISO you go.

What does change is highlight (and because DR is constant, consequently shadow) latitude. For each stop in ISO you go up, you gain a stop of highlight latitude and loose a stop in the shadows. Another way of thinking of "loosing" the stop in the shadows is that the shadows will get more noise in them.

Similarly if you go down a stop in ISO, you loose highlight lattitude and gain it in the shadows. This is fine until the point where you loose too much in the highlights and start to get clipping. That is why we only recommend you go below ISO320 if you're very careful and watch those highlights!

Graeme

 

[conrad gaunt]

I'm personally not debating - just inquiring myself as Im really still new to RED.

Can you please explain how moving up on ISO protects the highlights? Im still trying to wrap my head around that one.

FWIW ive been reading these forums 2-3 hrs a day since nov 3 and I have yet to find an explanation I totally get.

Thanks in advance...

When people say ISO is just metadata, they mean if your dial the iso from 320 to 800 the image on the LCD looks brighter, but actually, the camera is still recording exactly the same data. If your ISO is low, your LCD will look dark, so you will throw more light at your shot, possibly clipping highlights. On the other hand, if your LCD looks brighter because you've already effectively amplified the recorded image ,digitally, you're more likely to not go over-the-top with exposure. If you get exposure right, whilst shooting at ISO800, you shouldn't have any noise issues, but you've got space for highlights. At its simplest, when you change ISO upwards, the LCD gets brighter, ISO downwards darkens the LCD .. both record EXACTLY THE SAME IMAGE, but your lighting decisions may get influenced by what you see on the LCD.. so use the histogram too, its your friend (or should be)!

 

[Joel Arvidsson]

Did a quick test today with better separation. Next time I would add more rimlight and maby a kicker.

 

[Thomas Koch]

Under daylight balanced lights ISO 800 looks fine but under tungsten lights it's too noisy.

 

[Thomas Kruesselmann]

I would be very much interested in how ALMOST black looks on the Scarlet. (Haven`t got mine yet.) For my personal work I often use a charcoal background which I don`t light at all - it just catches some of the primary light for the model. With Video-Cams and 35mbit compression
it is hard not to have awful noise in the background.

As for the ISO question: What I mostly read here is that people stick to 800 no matter what. And I read a lot of posts;-)

Cheers,

Thomas

 

[Thomas Kruesselmann]

To me, the answer you gave yourself is absolutely right: Move much further away from the black backdrop, so it catches no light at all.

 

[Joel Arvidsson]

Yes this time i installed a backdrop further back wich made it easy to keep the background pure black. I have not shot with tungsten yet with it so I dont know how much noise that would alter. Did use a arri tungsten with gel as hairlight thoe.

 

[Mark Kern]

Some really good tips here. I finally understand the ISO 800 thing now. We had the example come up in REDucation class this past week. Stuff shot at 320 definitely made the operator over compensate, leading to a lack of definition in the highlights because of slight overexposure. I wasn't able to wrap by head around it at the time I saw the examples on the 4k projector in class, but this makes total sense now.

A lot of shooting RED seems to be making sure you are filling the sensor with as much good info as possible, and shooting at 800 keeps you in the best range for "eyeballing" it. We also got a tip from our instructor that its better to tweak the ISO to get the DP to put things in the right range rather than arguing about the stop. Also, "predator mode view" can help spot the extremes of the range by coloring the pixels on the monitor that are in danger of being out of bounds. We have to "unlearn" what we know about ISO.

Redcolor3 also looked fantastic and does the "black crushing" in a subtle and natural way for great preview or daily footage. Can't wait for this update!