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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 160??

taylor said:
I seem to be arriving at an ASA rating of 160 for my camera. I am at 23.97 fps with 1/48 shutter 5600K build 13. Have used all 3 of my meters (even the old trusty Spectra) What am I doing wrong as I thought the camera was rated at 320. Thoughts?
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What was your method? You only mention you have light meters... are the histograms in camera at ISO 320 too low, for instance?

I FINALLY got my lens mount today... so I'll be able to duplicate some of this.
 
Don't fixate on putting middle grey in, well, the middle. Learn the histogram!

Think of Red as a DSLR on steroids. Just like DSLRs the lowest ISO (100) is it's native sensitivity. As you increase the ISO you are amplifying the signal to increase its sensitivity or it's effective ISO. This produces a noisier or grainier picture. It's been my unscientific observation that Red's ISO is either the same or less 'grainy' then the corresponding 35 film stock.

All that being said, setting the Red camera to monitor at 320 ISO will give the best view of the sensor in order to avoid clipping.
 
Yes, i'm sorry for not explaining my method. I light a 18% gray chart evenly, then meter that with a spot meter(set to 320asa) and double check w/ my ball meter at the chart. Then with camera set as explained above, I set the stop for what the meter says. The gray scale now comes up a full stop lower than what I am used to in my waveform. To double check this I now place a white card (nice and new) in the same place as the gray chart was. I am now seeing on the waveform that I have a full stop of room before I hit 100ire. So what I lit for a 5.6 is now really a 4 before white hits 100ire. Am I wrong for thinking that my white level should be at 100ire? Are my methods screwy?
 
taylor said:
Am I wrong for thinking that my white level should be at 100ire? Are my methods screwy?
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Shoot some tests at different f-stops and bring the footage into RedCine to see where the whites are really clipping. The histograms never really see represent the raw sensor data as I understand it. And they change when the ISO changes... which really doesn't make sense.

I personally wouldn't be surprised if RED's really more like ASA 160. It is clearly slower than other cameras I've used. BUT - RED likes to be underexposed because it holds the shadows pretty well and only has a couple stops of overexposure. So you're safer underexposing (in relation to a gray card reading). The bonus question is when does that become too noisy. At 500? At 1000?

So in situations with no highlights to blow you might end up with minimal noise by setting the ISO to 160 or lower. Just not sure - that would require some real testing.
 
Build 16 will make this much easier to figure out. But basically, you are exposing at ISO 320 to protect the highlights (think of a film positive). You can always pull up info from below, but never recover blown out highlights.

Jim
 
Taylor, What waveform? remember that the video out (both sdi and evf/onboard) have a rec709 LUT applied to them. They aren't very good representations of the true raw data your recording. Thats why a lot of us have been asking for some kind of simulated raw output. Try looking at it once you get it into a computer.

it's been stated that the Red has it's best dynamic range at 320, but in some instances keeping a pristine noise free image is more important than DR, so I agree that at times you should rate it lower.
 
I'm guessing Build 16 puts in some sort of pre-compression log curve? Or something similar? Noise reduction wouldn't affect exposure logic... only available dynamic range at the low end.
 
Great...Thats very helpful to know and I will keep that in mind. That was my hunch but I wanted to be sure I was not mucking the test up. I look forward to many great shoots with my new camera. Oh and Jim, Robert H. deserves a little extra this week...he has been a champ throughout the whole purchase and follow up process. Nice work by all your team!

Taylor
 
taylor said:
Great...Thats very helpful to know and I will keep that in mind. That was my hunch but I wanted to be sure I was not mucking the test up. I look forward to many great shoots with my new camera. Oh and Jim, Robert H. deserves a little extra this week...he has been a champ throughout the whole purchase and follow up process. Nice work by all your team!

Taylor
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I'll buy him lunch tomorrow... oh, we buy everyone lunch everyday. I'll think of something.

Thanks,

Jim
 
Okay, now I'm a little confused again. I've read changing the ISO/ASA is a metadata change for viewing purposes only and not the same as changing the ISO of film.

Is it correct in thinking then that the light sensitivity of Red's sensor is set (unless it's changed by the red wizards and therefore it comes in the form of an update/upgrade)?
 
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