Is ISO a Sensor adjustment or Image Processor adjustment?

[Brennan Klensch]

Specifically in RAW capture, what does ISO affect, the way the sensor is capturing the image, or the way the image captured RAW is being processed?

 

[Stephen Williams]

Specifically in RAW capture, what does ISO affect, the way the sensor is capturing the image, or the way the image captured RAW is being processed?

Nothing at all, just metadata.

 

[Brennan Klensch]

what about f-tsops and shutter speed when capturing RAW

 

[David Battistella]

THink of it as a post tool rather that a aquisition tool.

If you shot a dark scene wide open on a t1.8 lens, you could set the camera at 320 or 4000 ISO but niether of those settings would affect how much light is hitting the sensor plane.

Do you get what I mean?

It just means pushing the r3d in post will make for a better image than previously. The m-x sensor is probably faster (more light sensitive) but it is a combination of things (including new post tools) that will allow you to extract better image quality from the r3d.

David


David

 

[Stuart English]

ISO rating

ISO rating

Nothing at all, just metadata.

..but only "true" if you ignore that the camera is operated by a human who can interact with the visual results of an ISO adjustment.

He / She may affect how the sensor sees light, by adding an ND or changing an Iris value based on the monitor output.

 

[Stephen Strangways]

The resolution, frame rate, and shutter speed you select affect the sensor, and are things you can't change later in raw processing.

ISO, white balance, and color space are just metadata, and can be changed later in raw processing. Changing them on-set, however, may change how you expose the sensor.

Anything on the lens, the aperture, where the focus is set, and of course how much light is in your scene, definitely affect the sensor, and can't be changed later in raw processing.

 

[David Nardini]

Specifically in RAW capture, what does ISO affect, the way the sensor is capturing the image, or the way the image captured RAW is being processed?

If you use 'view = RAW' you will notice that changing the ISO / ASA does not affect what you see in the monitor (and by checking the histogram you will know what the light levels are for the native sensor).

 

[Brennan Klensch]

so, hate to be naive when it comes to the technical side of things but what is metadata in relation to the images

 

[Michael Schmitt]

It's a lot to learn if you don't already have a Red to practice on.

 

[David Mullen ASC]

so, hate to be naive when it comes to the technical side of things but what is metadata in relation to the images

Metadata is just a set of instructions or settings attached to the R3D file to be applied to the RAW signal when it is time to process it in post. The metadata settings also are applied to the video-out that goes to the eyepiece and monitor.

Of course, since they manipulate the image seen on the set, the metadata settings will affect how you interpret and adjust the image. For example, if you set the camera to 1000 ASA and 3200K color balance, then a scene lit and exposed at 1000 ASA in 3200K lighting will look correctly exposed and neutral in color (though it may look noisier). The actual R3D frame would be rather dim and orangey since the camera is closer to 320 ASA and 5000K, but the metadata settings are basically telling an image processor (either in camera for the monitor out, or in post) to boost the overall underexposed signal and boost the blue channel to compensate. You can choose to ignore the metadata settings if you want to work with something closer to the way it really looks in the original recording.

However, shutter speed is not metadata, it actually affects the recording, just like the f-stop of the lens, the frame rate, and what colors you use in lighting, how you focused the shot, etc.

 

[Brennan Klensch]

thanks so much, very useful!

 

[David Battistella]

Another way of looking at it is if you are familiar with GAIN settings on video cameras.

IE:
ISO 250 -3db GAIN
ISO 320 -0db GAIN
ISO 400 +3db GAIN
ISO 500 +6db GAIN

Etc.

The higher you go with GAIN or ISO the more noise. The BIGGEST difference is that with the RED the gain is NON DESTRUCTIVE and in a video camera the gain is BAKED IN.

David

 

[Stephen Williams]

Hi Stuart,

He/She may well adjust the light hitting the sensor, however changing the ISO has ZERO effect whatsoever, my answer was correct to the specific question asked.
There is no analogue pre gain, for example if testing showed there was +/- 5 stops of DR at 320 ISO then there would be -10 stops & + 0 Stops @ ISO 10160

Best,

Stephen

 

[Brian D. Goff]

Hi Stuart,

He/She may well adjust the light hitting the sensor, however changing the ISO has ZERO effect whatsoever, my answer was correct to the specific question asked.
There is no analogue pre gain, for example if testing showed there was +/- 5 stops of DR at 320 ISO then there would be -10 stops & + 0 Stops @ ISO 10160

Best,

Stephen

So I'm wondering, does canon do the same and there iso is a "post-effect" too? Or what must be done to create "real" iso changes on the sensor level?

 

[Stuart English]

ISO

ISO

Hi Stuart,

He/She may well adjust the light hitting the sensor, however changing the ISO has ZERO effect whatsoever, my answer was correct to the specific question asked.
There is no analogue pre gain, for example if testing showed there was +/- 5 stops of DR at 320 ISO then there would be -10 stops & + 0 Stops @ ISO 10160

Best,

Stephen

I acknowledged what you said was correct Stephen, but my point is the operator may well react to the ISO change and add an ND or adjust the Iris.

In that sense it's not "just" metadata.

 

[Joel Arvidsson]

If you use the "RAW view" wich should be accurate in next "update". Do you even have to care about iso while shooting? I mean since changing iso does not effect what you se in the monitor in "RAW view" mode.

How come a higher iso will protect the highlights more and give an nicer rollof? Is it cause higher iso makes the dynamic range wider wich explains the more pronounced noise.

 

[Joel Kaye]

How come a higher iso will protect the highlights more and give an nicer rollof?

A higher ISO just "tricks" people into lower exposure therefore protecting highlights. A raw viewing mode with real overexposure indicators would be best. Knowing the ISO is helpful when matching light meters, other types of cameras etc.

 

[Stephen Williams]

Another way of looking at it is if you are familiar with GAIN settings on video cameras.

IE:
ISO 250 -3db GAIN
ISO 320 -0db GAIN
ISO 400 +3db GAIN
ISO 500 +6db GAIN

Etc.

The higher you go with GAIN or ISO the more noise. The BIGGEST difference is that with the RED the gain is NON DESTRUCTIVE and in a video camera the gain is BAKED IN.

David

Analouge gain being applied, it's not the same at all.

 

[David Battistella]

Analouge gain being applied, it's not the same at all.

It's an effing analogy for god sake. A comparative example.

Geez.

David

 

[Stephen Williams]

It's an effing analogy for god sake. A comparative example.

Geez.

David

Excuse me but the original question was "Specifically in RAW capture, what does ISO affect, the way the sensor is capturing the image, or the way the image captured RAW is being processed?"

Your analogy would appear to be inaccurate.