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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 :)

Exposing for the RAW format

I mean "expose to the right" And that implies #4 given there is no play left in factors 1 and 2. Use more light or less ND if that's what it takes. That's what you would do with slow film in the same situation. Boosting the gain (#3) is exactly NOT what I'm talking about.

The "LinLog" type of nonlinear CMOS specifically fixes the main problems of the older style "log" CMOS (the fixed pattern noise and rolling shutter being the two worst problems) And the roll-off is programmable. You could even use it as a normal linear sensor if you wanted to.

The beauty of LinLog is that it protects the highlights without requiring that you under expose to the point that the "meat" of the image is down in the noise. And the highlights will have a nice "logy" rolloff. The images produced should be very filmic as a result.

Of course, fabricating a 12 megapixel LinLog would require a LOT of transistors. But the total is still less than a modern CPU. It should be do-able. I'm sure there are fabs that could do it.
 
Sorry LordTangent, I did not read you correctly.

I read the information on LinLog page that you mentioned. It seems interesting with the programmable option of switching between the linear and log region.
 
another interesting post by Stu on exposing to right or to left

http://prolost.blogspot.com/2008/03/exposing-to-left-vs-exposing-to-right.html

seems to come down to experience , knowing your camera, knowing what you want , adding in light/fill or whatever it takes or not adding anything and YOU deciding which exposure is best for the shot -
to the right or to the left = you decide ...
 
Stu is completely right. But (and I'm biased here so bear with me) he seems to be espousing the expose to the right philosophy without realizing it.

If the goal is to get the cleanest shot possible without over exposing it implies "exposing to the right". (Even when the histogram doesn't show a distinct bump at the right. )

If you don't care at all about noise then put the exposure anywhere you want.
 
twlim said:
While Stu summary is valid, what about this logic on exposing to the right for maximum S/N ratio - http://www.luminous-landscape.com/tutorials/expose-right.shtml
Click to expand...

Stu does not talk about the statistics of the noise!

Typically with digital sensors the S/N improves by "exposing to the right" because the statistics of temporal noise make it converge to a fixed number given sufficient time.

Hence, noise which appears random in shadows, "smoothes" out with in increase in exposure value (EV), whether, brought by an increased aperture size, or by larger integration time.
 
Red Exposed

Red Exposed

Great post by Stu. In the Autumn I came to some similar conclusions about getting the most dynamic range out of Red. By setting Red to 320 ISO and setting middle grey at 30-35% (instead of 45-50%) on the waveform and Caucasian skin tone to 40-45% (instead of 60-65%) you'll capture the best dynamic range.

I realize now though that if the scene has low contrast you should overexpose by up to 2 stops to get the least amount of noise. Essentially I agree that exposing to right is the way to go. Move your histogram as far to the right as you can without clipping and you can create the 'mood' later when the .r3d's are processed (with the cleanest image possible). The main problem I find is that the REC709 monitoring is quite poor. I've desperately tried to get a DSC ChromaDuMonde chart to line up with the Vectorscope boxes from the 720p HD SDI out and couldn't. The HD SDI out is deficient.
 
Gregorios said:
Great post by Stu. In the Autumn I came to some similar conclusions about getting the most dynamic range out of Red. By setting Red to 320 ISO and setting middle grey at 30-35% (instead of 45-50%) on the waveform and Caucasian skin tone to 40-45% (instead of 60-65%) you'll capture the best dynamic range.
Click to expand...

Isn't that the same thing as rating the camera at 640 ASA?
 
I am getting confused.... I have been shooting with Canon and Nikon DSLRs for years, exposing perfectly (most of the time ;).

What I don't understand is how you can rate the ISO from 100 to whatever, but it doesn't really change the sensitivity? So this means you are grossly underexposing and then compensating in the post software?

If this is the case, what good is the histogram at anything other than the cameras base ISO? If you set the ISO to 320 and 'expose to the right' then you are really like 1.5 stops under and your highlights are really way down in the middle, am I right?
 
That is a good question that makes me wonder: What is the histogram a histogram of? Is it the actual values form the sensor or the tone mapped values? And how is it relateded to the ISO set on the Red One? (I'm not an owner and I don't have a manual to look at)
 
I've posted in the beginning of this thread without the experience shooting with RED. Now I've done a project under real world circumstances and that's what I find:

1. The histogram one sees on the camera display is based upon the rec 709 LUT which is created in the camera - definately not from the actual values of the sensor.

2. 320 ASA at 5000K seems the way to go, after evaluating the footage in REDCine.

3. In doubt, closing the aperture about half a stop is not doing a harm, on the contrary, essentially exposing for 500 ASA.

4. On very flat lit scenes it may be apropriate to expose in a 250 ASA direction, although noise in such scenes is not an issue IMO.

5. Noise is visible and not really avoidable, at least if there are a lot of shadows and strong highlights (high contrast).

6. I don't find RED's noise distracting and surely less than found on a f900R for instance.

7. We never used the monitor for exposure, always a lightmeter as it were
film.

8. The monitor maybe usefull some day if one is used to it's shortcomings and knows how to interpretated the picture exposure wise. Otherwise a LUT that mimics the sensors values would be great.

Hans
 
Hans von Sonntag said:
I've posted in the beginning of this thread without the experience shooting with RED. Now I've done a project under real world circumstances and that's what I find:

1. The histogram one sees on the camera display is based upon the rec 709 LUT which is created in the camera - definately not from the actual values of the sensor.
Click to expand...

You may not want to see actual sensor values. They don't necessarily correspond to any standard color space and need to be adjusted to any appropriate color space for viewing. Given two different digital sensors viewing the same scene the internal signals generated may be different and LUT-type mappings map these different signals to the same output signal for display on the same chosen display.

Every display has a notion of primaries and the white point and the sensor signal has to be mapped to it.

Hans von Sonntag said:
7. We never used the monitor for exposure, always a lightmeter as it were
film.
Click to expand...

That may work for certain (perhaps the default ISO the camera is rated at). However, I do not know if there is always a 1-1 correspondence between metering in the film world and digital world, especially considering that if you are not operating at the camera default ISO, then its the software that is "simulating" the behavior of an intended ISO.
 
Entropy

Entropy

David Mullen ASC said:
Isn't that the same thing as rating the camera at 640 ASA?
Click to expand...

Seems like it to me. But then you wouldn't be able to confuse people like they are with the focal length of S35 and full frame SLR.

In other words you have done the logical thing which is rate the camera at an ISO that allows you set the middle grey like you have traditionally done.

Whereas if you leave it at 320 and change the standard way of doing things we can add one more level of confusion.

1) Measure distance to subject with metric tape measure then convert meters to feet. Set your feet marked lens. (Do the opposite if you are European.)

2) Set ISO to 320 and then expose to a non standard grey level.

3) Take a still photo of the scene with a full frame DSLR then divide by 1.6 to get the proper focal length to use on S35/RED.

This is called entropy: the tendency of the universe toward chaos and disorder.

Hopefully you all appreciate my wry sense of humor.:wink: :sarcasm::biggrin:
 
I had an established DP shoot with the RED last week. They really pushed the camera to see how many stops they could get out of it. The scene in question has a single light source and about the room has about 20 stops. Now they know that they can't capture the entire 20 stops, but they want to see what they can get.

Unfortunately the DP was not very familiar with the camera and put a lot of faith in the hand of the DIT that came from the camera rental house. As the DP tells it, the DIT just kept insisting that they use the FALSE COLOR mode. As long as things stayed the right shade of blue, the shot was fine.

Well the shot was not fine (thank god it was a test). The blacks were all super lifted, and the whites were totally clipped.

After transferring the shots to both REC709 and REDlog as DPX and then taking those into a Color Correct bay - it was obvious the whites were long gone. Just a huge white hole.

So the DP asked me "What do I look at on the camera to make sure this does not happen?" From the discussion on this thread, it seems like the LCD image is a very rough guide, and that the histogram is what should be trusted..the most? The DP and VFX super were both uncomfortable with not having a good sense of WYSIWYG. What else can I tell them or recommend?
 
Hans von Sonntag said:
7. We never used the monitor for exposure, always a lightmeter as it were
film.

Hans
Click to expand...

I have never used a lightmeter from the day I started shooting digital on my still shoots. The most accurate way to set exposure is with a histogram that works, and experience. A meter will get you close, but a correctly calibrated histogram should let you put the highlights and shadows exactly where you want them. The midtones are set in post.

I agree a monitor will not give you critical exposure info - but a histogram will, and an RGB histogram is even better. Not sure if RED has that yet.

At least that's how I've done it for many years with Nikon and Canon raw files.
 
At least one has to start with something. Since the picture on the monitor does not show what the sensor "feels" I can only rely on what I've learned and used before and this is a light meter. I found it working nicely.

Using other ASA ratings need probably (I said probably because I don't know it yet) quite a bit of experience with this particular sensor. One has to count in: Contrast of the scene, colour temperature (the sensor is unfortunately balanced on 5000K), oversampling rate (a given nosie is very different visible in 4K or PAL) and many more. Quite complex I find.

Hans
 
Steve Sanacore said:
I have never used a lightmeter from the day I started shooting digital on my still shoots. The most accurate way to set exposure is with a histogram that works, and experience. A meter will get you close, but a correctly calibrated histogram should let you put the highlights and shadows exactly where you want them. The midtones are set in post.

At least that's how I've done it for many years with Nikon and Canon raw files.
Click to expand...

If you get WYSWYG a histogram is the way to go probably. Since the RED's histgram is off a LUT, just an exposure friendly interpretation (with some in-build headroom for the whites) of the sensor, I find a light meter more accurate, at least now.

Hans
 
Well, I doubt there would be a situation where a highlight would be clipped on the RAW recording but visible (not clipped) on the monitor, so if they see an important area clipping on the monitor, they should worry. I would think that lighting for the dynamic range visible on the Rec 709 monitor would mean that you have a little more range beyond that on the RAW recording.

In other words, if it looks like crap on the monitor, you should stop and think... rather than just trusting that it's all there on the RAW recording. But if it's all there on the monitor, it's definitely all there on the RAW recording...

I don't see a problem with using extreme lighting as long as you are aware of how it will turn out.

Common sense should have also told the people doing the test that an object that is more than three-stops overexposed is likely to show clipping problems.

As for using a light meter and not a monitor, that's probably fine if you've done tests and are taking spot meter readings of bright areas when you aren't sure they will be clipped, and know the clip point from previous testing.
 
Hans von Sonntag said:
If you get WYSWYG a histogram is the way to go probably. Since the RED's histgram is off a LUT, just an exposure friendly interpretation (with some in-build headroom for the whites) of the sensor, I find a light meter more accurate, at least now.

Hans
Click to expand...

Seems like a lot of testing is prudent when I get my camera. I guess i'll have to send off my meters for calibration soon.....

Thanks for the info Hans. It is well appreciated.
 
I enjoyed Stu's articles very much. They are very informative and remind me that I still have a LOT of testing to do with my camera to really wrap my skills around it.
I think what's important to remember is that in order to decide where to place your exposure you need to know what your display medium will likely be. Digital projection? Filmout? Downconvert to HD or SD? (ugh) traditional video projection at a show?
There seemed to be a big difference in results according to what the end product will be.
Cheers,
Harry
 
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