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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 :)

ASA rating and meters

ISO, ISO, it´s called ISO, not ASA anymore...

BTW, when i was working with a lightmeter with the RED i was getting confusing readings. As i once posted, my readings set the camera at 160ISO at the Salt Flats in Utah, but again we were working in RAW, so you might be better preserving highlights by rating it at 320. More tests should be performed anyway.

I threw the lightmeter at the end of the day. It was useless.
 
macgregor said:
ISO, ISO, it´s called ISO, not ASA anymore...

BTW, when i was working with a lightmeter with the RED i was getting confusing readings. As i once posted, my readings set the camera at 160ISO at the Salt Flats in Utah, but again we were working in RAW, so you might be better preserving highlights by rating it at 320. More tests should be performed anyway.

I threw the lightmeter at the end of the day. It was useless.
Click to expand...

I'll take it...send it to me.
 
Emmanuel Cambier said:
Exactly
This is precisely the question that needs answering, are false color and zebras affected by changes made to monitoring settings?
And clearly it shouldn't be so.:help:

Emmanuel
Click to expand...

I agree, it shouldn't be, but it is. False color (and the other exposure tools) are not an absolute for the camera. Being that we are working in RAW, I would prefer tools that are an absolute of what the camera can and can't handle. That's a little subjective on the shadow side (based on your personal tolerance for noise) but as far as clipping, when it's gone, it's gone!

Unless something has changed in this regard, when I shot in October, the false color settings, waveform etc. all change based on the ISO. Therefore if you were rating at 500 ISO and you were clipping (red in false color) and then turned your ISO down to 320, you wouldn't be clipping anymore.

So false color doesn't tell you when the sensor clips, just when you are hitting 100% at your working ISO. This is why it is so important to not shoot at 100 ISO because then you are just overexposing the camera and you can be reaching sensor clip (aka: full well) without even being told you are clipping at all!

The false color (and waveform, zebras etc) are all based on the viewing channel (which has a REC 709 LUT on it to begin with*) so if you load a look into THAT, than yes, your exposure controls will read based on that look.

The only way we found the true sensor clip was through testing. I want to corroborate my finding with future tests, but so far what we determined, when false color reads red with the camera set at 200 ISO, that is pretty close to actual "sensor clip." Which is not to say that I shoot at 200, and I don't consider this the means to determine the camera's native ISO. I still shoot primarily at 320 and let my brightest whites go red in false color mode. But when I am "iffy" on whether something is in the danger zone of being unrecoverable, I switch it over to 200 to check.


* Since the viewfinder output is REC 709, we found that when we put a waveform monitor on that signal, it correlated pretty well with what the camera was indicating in terms of exposure. I didn't have time on set to transcribe this, but does anyone have a legend for false color and what the different values are for each color?
 
Ninety-Nine said:
Hey Khmuse,

It sounds like you need a camera to test with. I would be happy to donate mine to your cause for a couple of days if you like. It looks like we are both in OC so it shouldn't be any hassle.

PM me and I will send you my info.
Click to expand...

Thanks for the very generous offer! I just sent you a PM with my contact details. I have been using Mark's (#41) for testing, but as he is in Studio City and I would certainly prefer to avoid the long drive.

Thanks again and I look forward to hearing back from you.

Kevin
 
From another thread:

Manny said:
Very important! You can set the Red to ASA 100 which is dangerous because the built in zebras, false color, histograms, etc will CHANGE based on your camera rating... you'll be effectively clipping but zebras, false color, etc may look fine.
Click to expand...

In that thread we started to discuss this and I think we came to the conclusion that this is not right. The indicators should always be based on the RAW data and not on the RGB preview.

Otherwise we get clipping without knowing it or we get serious underexposure because we only thought that we were clipping.

RED people, are you listening?
 
Thanks Jendra

But is it just the ISO settings that change the zebra and false color or also the changes to the monitoring like brightness and contrast and so on?
Because if it's only the ISO then we can just leave it to 320 and have the tools work as supposed.

Emmanuel
 
Emmanuel Cambier said:
But is it just the ISO settings that change the zebra and false color or also the changes to the monitoring like brightness and contrast and so on?
Because if it's only the ISO then we can just leave it to 320 and have the tools work as supposed.
Click to expand...

I don't think so. The indicators would still be based on the RGB preview instead of the RAW data. That's not the same, even at ISO 320.
 
On our Red#88 with firmware v9 the indicators do react to the changes we make to the ASA settings.
Just our two cents...
But I'm very interested in knowing how other red DPs are setting their exposure.
We're actually leaving for a short film shoot in two days and after testing our camera the DP decided to base his lighting onto a 250 ASA value using his lightmeter.
The DP also checked some of the footage of his testing onto our Scratch histogram. He is impressed but also surprised at how underexposed the images look still based on the 250 ASA value.

Arno
www.locared.com
 
Arno said:
On our Red#88 with firmware v9 the indicators do react to the changes we make to the ASA settings.
Just our two cents...

Arno
www.locared.com
Click to expand...

I haven't gotten another camera to retest yet, but this is exactly what I was concerned might be the case. As soon as I have one, I will go through and do a full test with each build and see if this is a consistent behavior across the various versions. My last testing revealed that with an 'ISO' setting of 241 (250 indicated), the false color and actual clipping points were coincident.
 
Great news! Ninety-Nine has generously offered a loan of his camera so that we can conduct a full test on this behavior. We will be posting the results here in the next few days.
 
If that is true, I agree that the histogram and false color data should be an indication of what is being captured in RAW independent of the ASA rating selected, if the entire point of RED is to use the RAW format to its fullest.

If Jendra is correct, I guess we could switch the camera temporarily to 200 ASA to check that info, but that seems inconvenient.
 
I will do a second testing round tomorrow and confirm the behavior with as many builds as I can. I will also reconfirm the native sensitivity and map out the clipping points based upon actual illumination values at the sensor.

Kevin
 
khmuse said:
I will do a second testing round tomorrow and confirm the behavior with as many builds as I can. I will also reconfirm the native sensitivity and map out the clipping points based upon actual illumination values at the sensor.

Kevin
Click to expand...

Kevin rules!

I actually haven't been all that concerned about this issue because I'll rate (slightly) higher but never down... When I rate higher I DO want the meters to transpose because I need to know where I'm at and it's my only reference. It's the relativity of the range I'm interested in. BTW - you're gonna get the same results with the SDI outs with a waveform and/or monitor with a waveform. I don't think there should be an ISO 100 available though... That's where dangers may lie.
 
big lebowski said:
I don't think so. The indicators would still be based on the RGB preview instead of the RAW data. That's not the same, even at ISO 320.
Click to expand...

I second that!

My post from the other thread: A DSLR works in the same way: if you shoot RAW and use the histogram to check exposure, you can't fully trust on what you see, because the histogram is the translation of a JPEG-transformation, which differs from the information of the RAW-image.
 
khmuse said:
I will do a second testing round tomorrow and confirm the behavior with as many builds as I can. I will also reconfirm the native sensitivity and map out the clipping points based upon actual illumination values at the sensor.

Kevin
Click to expand...

I'm all for more tests that benefit the community, but I had a long talk with Stuart from RED yesterday, and confirmed that nothing has changed as far as the exposure indicators reading the REC 709 signal, not the RAW. The way all these work: false color, zebra, histogram, waveform etc. are all based on video signals, not RAW data. There is currently no way to meter RAW data, but they are thinking about this issue...
 
Jendra said:
exposure indicators reading the REC 709 signal, not the RAW. The way all these work: false color, zebra, histogram, waveform etc. are all based on video signals, not RAW data. There is currently no way to meter RAW data, but they are thinking about this issue...
Click to expand...

Then I guess you'd have to do what Jendra did, devise a test. For example, shoot some chip charts in RAW and figure out the real clip point, then play around with the ASA ratings until the false color & histograms give you the same indication for clipping and use that as your guide. Or learn to use a spot meter after you've figured out how many stops over your key exposure can a bright area be and not clip.
 
Jendra said:
I'm all for more tests that benefit the community, but I had a long talk with Stuart from RED yesterday, and confirmed that nothing has changed as far as the exposure indicators reading the REC 709 signal, not the RAW. The way all these work: false color, zebra, histogram, waveform etc. are all based on video signals, not RAW data. There is currently no way to meter RAW data, but they are thinking about this issue...
Click to expand...

Thanks Jendra for the info.

So the classis shooting control tethered is still not possible with RED.

Shooting tethered is something the most people here are interested in.

They said (RED) that all is in RAW and later you could do what ever you want(!?).

You MUST bring the files immediately to computer to see what you got.

Otherwise you do not know.

Don't trust to your preview monitor.

That's the most frustrating for a lot of users.

Fortunately people have laptops or desktops in studio or in field and they could immediately try out to "squeeze" the best from the cam.

Make notes and continue.

TESTS, TESTS and more TESTS before you make decision to have a real ACTION.

I see shooting with RED only like this.

You test and test, you learn and learn, then you go to shoot.

Maybe one day when you learn a lot then you could master RED.
 
Jendra said:
I'm all for more tests that benefit the community, but I had a long talk with Stuart from RED yesterday, and confirmed that nothing has changed as far as the exposure indicators reading the REC 709 signal, not the RAW. The way all these work: false color, zebra, histogram, waveform etc. are all based on video signals, not RAW data. There is currently no way to meter RAW data, but they are thinking about this issue...
Click to expand...

This concurs with my earlier testing (end of September). If, all the monitoring paths are via the same decoded signal (including zebras, histogram, etc) then what would be useful is to know an in camera setup that provides the best correlation with the actual raw recorded signal. My intention is to quantify the actual illumination level on the surface of the sensor necessary to just hit the clipping point (this will be a repeat of my earlier test). I will then work back to find in camera settings that corresponds as closely as possible to the actual raw data set.

If anyone has any suggestions for other testing that would be useful, please feel free to post it here and if time allows, I will perform and quantify the results.

Kevin
 
If we would have TETHEARED SHOOTING with REDCINE something like photographers have with Aperture, Lightroom, CapturePro etc.

What does it mean?

Answer/quote:

"...Captured images are sent directly to the computer,
and in many cases you can even control your camera's settings
and trigger the shutter directly from your desktop.
Many studio photographers love to shoot tethered.
The photographer can focus on the subject while an editor
or art director watches the images appear on screen as they are captured..."

Link>>

We all need:

What You See Is What You Get ( WYSIWYG )
 
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