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class="style16"> RED 64asa Against 18% Grey Card

Published : 13th September 2009


We are currently completing some camera tests with the RED ONE camera running build 17 with the new hardware upgrade (S4i/Audio upgrade). What we have discovered is that camera is giving us a 64asa rating.

The camera is set up to 4k 16x9 @ 25 timebase, 1/50 shutter. The camera has been reset to factory default (look, user, system). An 18% gray card was placed in front of the camera, the RAW 'look' HDSDI was monitored on various waveform monitors and exposure was adjusted to 50%. Reflected readings were taken from multiple Sekonic and Minolta light meters - which indicated the same conclusion.


This was compared against the REC709 LUT, which was measuring at 250.....A slight change from build 16, which read at 160.


I am very confused why this is happening. Is this a build 17 or hardware thing, or is there some sort of issue with what we are doing.


Would be really interested to hear any similar experiences.


Cheers,


Rob Morton



There is little difference between Build 16, 17 and 18 in terms of Image. Most of the improvements are menu, protocol, and port configs.


I personally wouldn't judge a 18% Card off a HD-SDI monitor because what your truly looking at is a RAW image at Rec709. The Tap compresses the signal in addition to the live debayer can color shift from camera to camera.

Are you using RedAlert at all?


Based off my tests I've gotten 160 asa off a 18% Grey card, which hasn't changed since B16. There is an inherent issue with metering RAW de-bayer camera's like HD/Video cameras the results aren't the same.


Good luck,


Dane Brehm
310.710.2658
Cinema Data Tech / IA600 DIT
Phantom | Red | D21



There've been a number of people who say that you can't judge the ASA of the camera by placing the histogram at 50% on a waveform because effective speed has more to do with acceptable noise level than where middle gray falls on a waveform. Still, when working outside, I've found that my meter matches up with the exposure I set using the camera's tools most closely at 160--so that's what I light to, and I set the exposure separately using the histograms.


If you go by RedSpace or Rec709 and use the same method you'll end up at 160. Raw mode is darker than the other modes, as there's less gamma being applied, so I wouldn't go by that. I usually shoot in RedSpace, with one of the user buttons set to toggle into raw mode just to see what's really clipping.


I won't say the camera is ASA 320, but it's also not ASA 64. I vote for 160-250.


Art Adams | dp
San Jose, CA USA - "Silicon Valley"
showreel -> www.artadams.net
trade writing -> art.provideocoalition.com
mobile phone -> 415.760.5167



Would you set a film camera's exposure based on the video tap's output? Equally inaccurate to what you are doing.


Mitch Gross
Applications Specialist
Abel Cine Tech



What output mode did you use exactly? "View Raw" ?


Because question is : what's exactly the "view raw" output on the red camera?


Antoine Baumann
vfx artist
Zurich/Switzerland
mobile: +41 77 403 48 78



View Raw is a user menu designation for your user keys to toggle between Look Up Tables the choices are Rec709, Redpspace or RAW. This also brings up the histogram or rgb parade on the GUI.


The best "view raw" output on the Red is the EVF. The problem is they tend to wig out and solarise after a while.


I had 6 Asa settings I would toggle between with the DP and Gaffer. All according to DP Dan Stoloffs and I discussions about acceptable noise and color. I did most of these via RedAlert with a LUT. 2600kelvin @ 500 asa is not the best image I've seen but worked for the story and the character of lighting.
Here are a few setting I like to recommend …These are primarily for Dailies or the Offline Edit.
Daylight Cloudy - 160asa@6500k
Daylight Exterior - 160asa@5600k
Daylight Interior - 250asa@4500k
Nighttime Interior - 320asa@3200k
Nighttime Exterior 400asa@3200k


Good luck,


Dane Brehm
310.710.2658
Cinema Data Tech/ IA600 DIT
Phantom | Red | D21



Dane Brehm wrote:


>>“Daylight Cloudy - 160asa@6500k
>>Daylight Exterior - 160asa@5600k
>>Daylight Interior - 250asa@4500k
>>Nighttime Interior - 320asa@3200k
>>Nighttime Exterior 400asa@3200k”


From my experience until now with three DI for film out with RED, I would suggest exactly the opposite… due to RED lack of the same DR range in tungsten and daylight.


So to fill the shadows with enough light in order to reduce noise at night with tungsten lighting, the 160ASA is recommended to avoid the colourless gray shadows. In cases that there is no highlight even a 100ASA would help greatly.


On the other hand in daylight RED is less noisy additionally you need to keep the highlights, so a normal setting would be 320ASA… a more aggressive setting to keep the highlights would be 400ASA or even 500ASA…


Evangelos Achillopoulos
Elec. Eng.
DIT, DI supervisor,
Motion FX, Athens, Greece



These are primarily for Dailies or the Offline Edit. Those are the light meter settings for the DP and Gaffer.
We all understand its 320@5000k anyways. I do understand that your thinking of a on-set practice, where you set your meter at 500asa to protect your highlights.


I recommend using your RGB Histogram or the RAW histogram to monitor your highlights and fill the "bit" bucket when possible.


Sorry for the confusion.


Good luck,


Dane Brehm
310.710.2658
Cinema Data Tech
Phantom | Red | D21



It's tricky, because when I expose in full sun according to zebras, the stop on the lens matches my meter at 160. In backlight, though, it's a different ball game, because when using film I could let highlights blow, whereas I can't let that slide on the RED quite as easily. That's why I only rely on my meter for lighting for the RED, not exposing.


The higher ASA under tungsten light makes sense in that you want to keep red from clipping prematurely, but I'm not happy about the noise levels at higher ASA's. Filters like the Schneider CTB's or 80C or 80D can reign in red but at the expense of exposure, as you're passing all the blue light but blocking a lot of the red and green.


Mike Fecik at Tiffen had an interesting idea: why not use a CC20C or CC30C filter instead? Cyan would pass both blue and green, meaning less light loss, while reigning in red. I don't know that anyone locally has any CC filters, but if someone elsewhere does and wants to try them I'd be curious if they extended the RED's latitude under tungsten light without as much of an exposure compensation requirement.


Art Adams | dp
San Jose, CA USA - "Silicon Valley"



Mike Fecik at Tiffen had an interesting idea: why not use a CC20C or CC30C filter instead?
Never really? thought of those, I have a Red job next week that I can try it on. I'll post any tests I do.


Good luck,


Dane Brehm
310.710.2658
Cinema Data Tech / IA600 DIT
Phantom | Red | D21


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