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  • 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 :)

exposure

L

lib

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Sorry I know it has been mentioned loads before but I still can quite figure out how red is rated at 320. When using a gretagmacbeth grey card and setting iris to 45 ire using false color, external waveform monitors and zebras on red and comparing this to my light meter at either incident or spot I always seem to rate the camera at 125iso. Has anyone else found this or do I need to check my light meter.
 
I can monitor in raw, redspace or rec709 but it still baffles me. I understand there is more info than what I am monitoring in rec709 but what I can't work out is when I set up a grey card to 45 ire on red monitoring or external scope and set iris for this, (image looks correctly exposed) then when I take a reading from my spot or incident meter on the same grey card setting my light meter at 320iso it gives me a completely different exposure, where it looks like I need to set my light meter at 125 iso to match the exposure I had when using the waveform monitor. Now I know my light meter is correct because I have exposed film correctly with it and it seems that when I expose using the waveform the camera's exposure looks correct so I can only conclude that the camera is not 320 but around 125iso. Does anyone have any idea how this figures out. Every dop who has used this camera has said the same thing that it doesn't match their meter at 320.
 
i recall there was another thread with same findings as you - i believe they were told to go into the menu and click on RESET and then they got matching readings ...

i use light meters and i come up with 320 and i prefer 250 under tungsten .. i don't think we can just use a spot meter on a grey card and determine exposure like we do in film nor can we just try to match it up to a wave form ( video way ) ...

i use a combination of light meters ( incident & spot) , luma hist,the red stop light, looking at what is in the frame and experinece from past shots/scenes/CC ( knowing the what IF's -if i want to keep X highlight , my blacks will be under Y stops and i can pull them up to E but i might get Z noise ..

there have been some excellent test by macgrevor about a week ago and a few months ago on exposure & latitude ....
 
Thanks for your advice I will try that
 
Hi,

At 320 asa you get 1.5 stops for highlights, A Macbeth chart is only about 4.5 stops from black to white. FWIW I'ts the same story with the Viper.

Stephen
 
lib said:
...when I set up a grey card to 45 ire on red monitoring or external scope and set iris for this...
Click to expand...

I see your problem. The Red One is not a video camera. Using a waveform monitor to judge exposure on a Red is about as useful as hooking a waveform up to an Arri's video tap.

Learn to use and trust the tools the camera provides by shooting stuff and looking at it in your post chain. Scopes are for video, not for digital cinema cameras shooting Raw.
 
I understand you have a lot of flexibility of where to put mid grey depending on how much noise or overexposure you can tolerate. I suppose what confuses me is that I always thought mid grey was about 45ire, but when working with red this seems to go out the window. When using red exposure tools 45ire seems to be 125iso on my light meter I would have thought they would have matched. I will reset my camera and try again tomorrow but I somehow doubt I am going to gain some stops by doing this.
 
How are you processing your R3D files to see true dynamic range and where your mid grey sits? Redcine? RedAlert as 16bit TIFFs into Photoshop?
 
Sorry by calling this thread exposure was probably wrong , i should have called it why my light meter rates red at 125asa.
I understand that where I put my mid grey on red effects this test but I always thought that is was a known that a 18% grey chart was 45ire, therefore using red's false color measuring tool I set my chart for green or my external waveform to 45ire, I have another known constant my light meter which in incident mode is supposed to give me a read out for 18% grey, so why are the two so different when camera and meter are set to 320. Am I missing something really important here or just being stupid.
If I wanted to match my scope and incident meter I would have to set the scope at something like 20ire which just seems way too underexposed to me.
 
lib said:
Sorry by calling this thread exposure was probably wrong , i should have called it why my light meter rates red at 125asa.
Click to expand...

I'm not sure you can rate RED off a midtone because there's more usable detail in the shadows than the highlights. You just have to test shoot different exposures and take the shots all the way through color correction to see what works best for your shooting situation(s). If you can't do those tests then rate it 320 and you'll probably be fine IMHO.
 
I found the same thing on the last show I shot on the HDX900 - with the grey card at 50 IRE, the camera was rated at about 100-200 (I forget).

Since I know the camera is faster than that, I decided to screw the meter, and light off of the waveform on my monitor.

I believe this is typical of digital imagers. ASA just doesn't mean much in digital - maybe its time for a new standard...

BTW, I know the waveform doesn't work for RED, but RED has its own tools.
 
CrewPix.com said:
Please re-read my post #7 in this thread. Scopes are useless and irrelevant. Red is not a video camera.
Click to expand...

Would you say the same about the scopes in color when grading?
 
so would you say that the RAW image isn't digital. The scope on my Panasonic 17" monitor is useless when exposing my RED image? Not that i use the scope , but is this true?

cheers
 
please explain.
 
Bob.H said:
please explain.
Click to expand...

The scopes aren't useless. You'd just have to test all the way through post and change RED's metadata (iso, look, viewing space) so that the scope works as you anticipate.

The problem is that RED's output via HD-SDI is not the actual raw signal it's capturing. Instead it outputs a low rez interpreted/corrrected image based on your metadata and colorspace. So if you set the ISO to 1000 you'll get scopes that are way different than what you are really capturing as raw data to the drive/CF card.
 
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