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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 :)

Red's ISO and light meters

JustinGD

JustinGD

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So I thought I had this all figured out, but now I'm not so sure.

The Red One's ISO is rated at 320. I thought this was official and final. However, now I have read that light meters should be set to 160ISO to give an accurate reading. I usually just exposed with false colour, but after reading that I tried it with my light meter and sure enough, you have to open it up 1.3 stops from what a light meter set at 320 tells you.

Can somebody explain this to me? and what to say when a DP asks me if the camera is natively 160ISO?
 
First, is your light meter calibrated to the RED?

Sounds like it is not - therefore you have to compensate which is where you're getting 160ISO. I believe and could be mistaken, but I don't think so.
 
I wouldn't mind getting a clear answer on this. My DP recently rated a shoot a f/4 @ 320 ISO but we had to shoot f/2.8 to make it look right.

We blamed the lenses, but it would be nice to know if there is a consistent way to read the light meter.

Cheers,

Jim
 
This is the quote that got me thinking, it's from Macgregor's Profile: SC 4.1 250ISO post

"Now another problem for the old school DPs that want to use lightmeters when shooting digital, is that the readings from their lightmeter set at 320ISO do not match the false colour and readings when exposing with the RED ONE at 320ISO setting. Usually the difference is about 1 stop and 1/3 in 709 mode and 1 stop in RedSpace. This sets the real world sensitivity of the default RED ONE about 160ISO. Not good."

He follows this by explaining how to compensate, but the question I keep getting asked by DP's is: Why is the Red One rated at 320ISO if light meters tell us the proper exposer only when set to 160ISO?
 
Every time when you shooting film you always making test of lighmater with this film and laboratory .
And after this test shoot you can manage my ISO . Film can be old or labaratory can be wrond in process .
Same for me is working with red. Laboratory is Calibrated Monitor .
And you need to make some tests and understand difference in your
lighmater and red.
For me when i am shooting outdoor with Highlight iso 320 , to be more
protected with Highlights .
With indoor shoots with low light yes 160 is perfect . Also 160 is perfect with Tungsten lights .
 
Vigen's remark is very true: the iso will change depending on the light quality: daylight or tungsten.
That is in principle the same as with film: you would rate your daylight film on a slower speed when shooting on Tungsten AND using a filter!
With the Red , your filter is electronic, but in fact it pushes the blue channel out of balance with the other colors. The effective iSO is lower than 320, but you increase the gain on Blue, making it appear as if you keep the 320 ASA/ISO, but if you look closer at the shadows you will see the increased noise....

Anyway, the 320 is in most cases a bit optimistic, in my opinion. I would say 250 on daylight, 160 on Tungsten, if you want the best (noiseless) quality.
 
You have to adjust your meter to the RED.... Then you get 320 -

But yes, like film, every situation can be different...
 
On other posts I was reading that the latitude of the the red sensor is best when set to 320, would the 160 setting negate this? Or do you just set your lightmeter to this and keep the red set at 320.
 
anabatic said:
On other posts I was reading that the latitude of the the red sensor is best when set to 320, would the 160 setting negate this? Or do you just set your lightmeter to this and keep the red set at 320.
Click to expand...

No, don't do that. Set up the camera, a grey card - light the card and calibrate your meter. You can find instructions in your meter manual as well as through the link I have posted in this thread.

Once you adjust your meter, your meter will have to be changed again to work in film....
 
I have been shooting for 4 days out in the mountains, a little worried about this ISO stuff I've been reading all around... but the truth, in my case (with a Sekonic L-558 Cine) is that it got the match in 320 ISO... don't know why, but in RAW mode it just got it right. I used it to know how much NDs would I need to get to a T/4, and it always gave me the right mesure to get a good reading in the RAW histogram....
Hope this can help!
 
Shawn Booth said:
You have to adjust your meter to the RED.... Then you get 320 -
Click to expand...

Shawn, I get your point... one must calibrate their meter for their acquisition format.

But if you try to tell somebody that their light meter is wrong - after they've used it for dozens of films on dozens of film stocks - and that they just have to recalibrate it for the RED... it won't go over well. If the 320 ASA setting is accurate for 320 ASA film stock but is a stop under for the "320 ASA" RED, the RED's effective sensitivity is 160 ASA. Recalibrating the meter is just changing a label to represent the same amount of light with a more appealing number.

If I'm forced to explain the RED in terms of ASA, I find it most effective to describe it as 160-200 effective ASA in most situations and 320-500 effective ASA in high-contrast day exteriors. That sentence, however, would come with a long discussion about why using a light meter for exposure is a bad decision... and how we're throwing fixed values at something for which they simply do not apply.

Use the meter to give your rigging crew a desired stop and use it to work out ratios... but lose it when it comes time to shoot. The camera is a big, complex spot meter. Incident readings just don't apply in an effective, repeatable manner.

At least that's this man's opinion.
 
If you take a grey card out into direct sunlight and meter it with a spot meter and then set your exposure using False Color in Red Space you will find the camera dead on 320 ISO. Where it gets more complicated is in understanding where the 18% grey reading falls on an incident meter Vs. a reflective one. To calibrate your incident meter take it outside on a sunny day (after 10AM and before 4PM) an calibrate it using sunny 16. That's f16 at 1/ISO. I recommend 1/250th at 250 ISO, you should read exactly f16.
If that's the case your meter is calibrated to a known source. The Red generally has 4-5 stops under and 2-3 stops over middle gray of latitude. If you try to "expose to the right" which is a good idea whenever possible, the you may find yourself at anywhere between 160-640 ISO according to an incident light meter.
 
Your light meter is not wrong. (probably)

For me shooting red for 1.5 years, 99% of the time, I set the camera to 320 and my meter to 200 and they seem to agree. I base my reds exposure using the Raw Histo.
 
Vigen Vartanov said:
Every time when you shooting film you always making test of lighmater with this film and laboratory .
Click to expand...


What??

I've never in 30 years done this ..... the beauty of the lattitude of film I guess.

The meter is meant as a guide, a measuring stick. Dont treat it as some instrument to determine finite exposure....it merely tells you how much light falls onto or is reflected from an object...... its ball park.

Use your gut and your brain for the rest.... digital OR film.....
 
Rich Schaefer said:
Your light meter is not wrong. (probably)

For me shooting red for 1.5 years, 99% of the time, I set the camera to 320 and my meter to 200 and they seem to agree. I base my reds exposure using the Raw Histo.
Click to expand...

Very well Rich. Red's metadata ASA is misleading. Many expect the next generation of Red cameras to be real world 500 ASA. One big step in Red's effort to come close to film. 200 ASA is pretty slow.

BTW: The lightmeter is the benchmark never the stock, sensor, what ever. Calibrating a light meter to Red's metadata ASA is not making the RedOne faster.

Hans
 
I totally agree with Tony, once your eye is "set in" with the meter,normally about 2 hrs into a shoot, I never really look at my meter again, squint or a pan glass does it for me.
Never trust any monitors ever. I agree it was easier when you look down a viewfinder of a film camera, but put a lens on a Directors viewfinder, you will have the same feel or just squint. With experience and practice you will feel the stop.
 
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