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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 :)

Why not ISO 100?

Jannard said:
Did you ever shoot ISO 1000 film and rate it at ISO 100? While this is an exaggerated example, it makes the point.

Jim
Click to expand...

Hi Jim,

Not sure it does, so you are saying that by exposing RED at 100 ISO the resoloution is less than exposing at 320 ISO. The fastest motion picture film currently available is 500 ISO, if I rate it at 100 ISO the resoloution is not lower than if I rate it at 500 ISO so I dont get what your trying to say.

100 ISO film has more Resoloution than 500 ISO film, but that is another matter.

Respectfully,

Stephen
 
ibloom said:
I don't think Red is going to implement white rolloff as an algorithm in their camera. That would just mean sacrificing some of the data coming off of their sensor in order to create the appearance of rolloff. The great thing is they give you all the data they have and let you create rolloff with curves in post.

IBloom
Click to expand...

Probably you're right but if not in-camera than at least off-camera meaning REDSpace will have some new tweaks and tricks to make a better roll-off happen.

Remember REDCine Rec709? How bad is the roll-off in this gamma curve compared to REDLog. As there has been different qualities regarding the roll-off I assume there is still room for improvement which RED is now plumbing.

Otherwise I don't understand how overexposed hights will be better smoothed out to get away with an overexposure of 2 Stops (ASA 100). Currently 100 ASA in build 15 is only possible in very flat lit scenes.

Hans
 
From what I can understand, if you over-rate the sensor, ie to say 1000 iso, you're using the lower end of the whole dynamic range, you'll get a lower signal-to-noise ratio, thus more noise, but less likely to clip in highlights. But if you under-rate the sensor, say to 100 iso, you're using the higher end of the dynamic range, less noise but easier to clip the highlights. So the optimum is to stick with the native iso, so you have room to move in both directions.
 
Escargot said:
From what I can understand, if you over-rate the sensor, ie to say 1000 iso, you're using the lower end of the whole dynamic range, you'll get a lower signal-to-noise ratio, thus more noise, but less likely to clip in highlights. But if you under-rate the sensor, say to 100 iso, you're using the higher end of the dynamic range, less noise but easier to clip the highlights. So the optimum is to stick with the native iso, so you have room to move in both directions.
Click to expand...

I am repeating all the time that ISO 320 is still the king.

Probably with B16 it has got a lot "fatter" then before in B15...

So in RA you can nicely "dig up or pull down" to get picture of your "dreams".

ISO 100<<< ... <<<<ISO 320>>>> ... >>>ISO 2000.
 
Stephen Williams said:
Hi Jim,

Not sure it does, so you are saying that by exposing RED at 100 ISO the resoloution is less than exposing at 320 ISO. The fastest motion picture film currently available is 500 ISO, if I rate it at 100 ISO the resoloution is not lower than if I rate it at 500 ISO so I dont get what your trying to say.

100 ISO film has more Resoloution than 500 ISO film, but that is another matter.

Respectfully,

Stephen
Click to expand...

Stephen... this was my quote:

RED is not film. But it does act in a similar way. If you take ISO 100 film and rate it at 1000, it will be noisier than if you shot it at 100. If you rate ISO 1000 film at 100, it will not have the resolution of ISO 100 film. The mistake in most people's thinking is they think shooting the RED ONE at ISO 100 should give the best image. It does not. Following the film example, if you replaced the Mysterium ISO 320-500 sensor with a native ISO 100 sensor, you would get the best image at ISO 100. But that is not what we are doing.

Jim
 
Jannard said:
If you lower the ISO to 100, you will reduce resolution and get a "more sterile" looking image. Not much, but it should be noted.

Jim
Click to expand...

Maybe Stephen meant to quote this.
 
eastco said:
Maybe Stephen meant to quote this.
Click to expand...

Why don't you ask a straight question... it will be easier to respond.

Are you questioning the analogy or the conclusion?

Jim
 
The "film ISO" is an analogy. And like all analogies, when taken too far, it fails. As Jim says, "Red isn't film".

Using the "film" term, ISO, makes people apply ALL their ISO knowledge and experience to the sensor. Me included. But it's not working. It's causing more confusion. (I don't mean to be critical to anyone, though).

This is my understanding, please correct me if I'm wrong.

Changing film "ISO" changes the film--literally. But changing Red "ISO" doesn't change the sensor.

With film, if part of the scene is clipping, there are four ways to reduce it on camera: aperture, shutter, ISO, ND. With Red, only three ways, aperture, shutter, ND.

With film, changing ISO changes the grain/noise. With Red, changing the ISO doesn't change the noise. Yes, Red's noiselessness has been improved and expanded (as if you were using ISO...), but it's still a set given.

With film, changing ISO changes resolution. With Red, resolution is also a set given (mostly).

With film, changing ISO changes color sensitivity/fidelity (not sure if that's the right word). If I wanted to capture the subtle color variations of a flower or canyon, ISO 100 will capture more then 400 or 1000. With Red, color sensitivity/fidelity is also a set given.

Edit: The one thing that I can think of that the analogy does work and is applicable is "light sensitivity". The sensor's light sensitivity is equivalent to ISO 320 (or whatever number it is).
 
I'll try and ask the question as straight as possible. I think that the issue people are having is with clipping and the new ISO more than the loss of resolution. I think everybody understands that with less and better looking noise, they can rate the camera faster with great results.

The problem we're having is with rating the camera slower. From what I understand it is all still metadata and there is no reduction in pre AD gain or other type of sensitivity governor. I think we also find that the 100 to 1000 analogy only creates more questions. If I rated ISO 1000 film at 100 I wouldn't loose resolution exactly, I would have grossly overexposed my neg. I understand that you made that analogy as an exaggerated example, but I don't know if it cleared anything up.

The question I have is if I set my light meter to 100 ASA and shot the same scene with the camera set to 100 and then set to 320 and then in Redcine set my ASA for both clips to 100, would there be a difference between the two?


Edit: what Jason said is also along the same lines. He's just faster at typing.
 
Jannard said:
Stephen... this was my quote:

RED is not film. But it does act in a similar way. If you take ISO 100 film and rate it at 1000, it will be noisier than if you shot it at 100. If you rate ISO 1000 film at 100, it will not have the resolution of ISO 100 film. The mistake in most people's thinking is they think shooting the RED ONE at ISO 100 should give the best image. It does not. Following the film example, if you replaced the Mysterium ISO 320-500 sensor with a native ISO 100 sensor, you would get the best image at ISO 100. But that is not what we are doing.

Jim
Click to expand...

Hi Jim,

I still don't see the connection with rating the Red one at 100 ISO & loosing resolution over rating the Red One at 320 ISO.

Stephen
 
SF Geek said:
I think everybody understands that with less and better looking noise, they can rate the camera faster with great results.
Click to expand...
From what I understand, the camera isn't faster or slower. The "less and better looking noise" is the same at all "ISO"s.

So I sort of think of it like... I can shoot in dimmer light then previously, raise the shadows in post, and get less to no noise at a greater range of darker values (deeper shadows) then previous builds.

But i guess that's what you said, sf greek.
 
The camera itself is no faster but if there is no color shift and less noise, you can rate it faster with the same results, compared to build 15.
 
But why?

But why?

David J Bernstein said:
By redefining the sensor as ISO 100, we are now saying that 100 photons is 18% grey. This pegs 100% white at 556eV (remember the sensor still has approx 1244 steps available above this value).
Click to expand...

Redefining the sensor at ISO 100 is overexposing your sensor so there would be higher eV levels not lower.

This 100 ISO question arose when Jim stated :

"If you lower the ISO to 100, you will reduce resolution and get a "more sterile" looking image"
Click to expand...

I can understand that pushing your "virtual" 18% gray closer to the clipping point by 1 1/3 stop (this is exposing @100 ISO) it would give you more latitude in the darks (because we are 1 1/3 stop further of the noise floor) and decrease latitude to the high light because we are closer to the clipping point.

BUT why should it decrease color rendition and reduce resolution if we have a linear treatment of the light without any slope or rolloff in the highlights?

This is usually what happen when we map a curve on standard video cameras Cinealta (not raw)... to get a nice roll off in the high lights.

Joofa spoke :
In other words those (higher) frequencies that are (more) visible in higher contrast are now difficult to see and hence a perception of decrease in resolution.
Click to expand...

Is this resolution loss related to the color mapping to the 12bit values ?

????:detective2:

Thanks.

Patrick
 
film analogy

film analogy

SF Geek said:
If I rated ISO 1000 film at 100 I wouldn't loose resolution exactly, I would have grossly overexposed my neg.
Click to expand...

In that hypothetical example, I assume he meant you would also do "pull processing" after overexposing the film. Basically, use a weaker developer chemistry and/or shorter developing time. Naturally, the "nominal" film rating gives best results and the farther you push or pull the negative during processing, the more damage is done to the image quality overall. Of course shooting ISO 1000 stock for 100 is a bit of an exaggeration in that most films can be effectively pulled only 1 or 2 stops. Though maybe there are some films you can pull more (?)

Ultimately I think these questions are going to be fully answered only when the build is released and we can each do our own tests.

Pull Processing
from http://www.ilfordphoto.com/applications/page.asp?n=89

Pull processing is a technique that compensates for overexposed film by under- developing it at the processing stage; thus it is the opposite of push processing.

Pull processing is most commonly used to compensate for accidental overexposure of a film; for example if a roll of ISO 125 film has been exposed with the camera set to ISO 50, pull processing can be used in an attempt to minimise the damage. It is only of use if the complete roll of film has been overexposed in this manner. In general, the technique is not to be recommended as there are rarely advantages in exposing a film at a slower speed rating than normal and the resultant negatives are difficult to print well. A minor exception is that it is sometimes possible to make negatives exposed in brilliant sunlight easier to print by overexposing the film half a stop or so, and cutting development by about 20%.
 
Downscaling a 4K image to 2K or HD or SD reduces our perception of noise, does the same happen with exposing at ISO 100 on 4K, then downscaling, that will reduce the penalty you were talking about?
 
Jannard said:
This is a really good point. The above info is for Daylight... which is native to our sensor.

We will probably have another set of ISO ranges for tungsten that recommend slightly lower ISOs. We'll do some more tests and post.

Jim
Click to expand...

Has anybody done an ISO testing for tungsten yet?
Would be really interesting to know.

Thanks
totti
 
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