What is Windowed Sensor ?

[RED-Tank]

Hi All,

I am new to RED, new to this forum, newly make my reservation. And also a lot to learn from you all.

Just wonder what is "Windowed Sensor" ? I believe this would affect the choice of len we can use when shooting 2k or 720p, am I right ? Then in what aspect ?

And I am a bit confuse with the latest spec:

Frame Rates:
Variable
1 – 60 fps 2540p, 4K, 2K,1080p, 720p
1 – 120 fps 2K, 720p (windowed sensor)
50 / 59.94fps 1080i, 720p

Am I read this correctly that, shooting from 1 to 60 fps for 2k & 720p, the REDONE uses full sensor, but if I shoot from 61 to 120 fps, the REDONE will uses smaller size of the full sensor.

If this is the case, I wonder what is the size of that "windowed" sensor ? will it be 1 to 1 pixel (which means a very small area of the sensor will be used to record the stream, then the FOV will be so small for many big len, am I right ?).

I wonder whether RED team can make such windowed sensor as big as possible (best is depending on the frame-rate, higher fps then use smaller area of sensor while lower frame-rate such as 75 or 100 then use slightly bigger sensor area.

I wonder the use of "windowed" sensor is due to the processing power required to down-encoding vast image data from full sensor to a much smaller 720p & 2k.

I am in very tight budget and probably can only use some 35mm SLR Nikon prime len for my work, but if the windowed-sensor mean I will have smaller FOV, this would make a lot of restriction in composition.

Sorry if I read it wrong (and I hope I am wrong), please enlight.

And thanksss~ :)

[donatello b]

windowed for 720p would = it only uses 1280x720 pixels (of the 4k sensor) to record image ...
so your field of view would be a tighter shot = 18mm lens in 35mm mode would be a wide shoot..switching to 720p mode the 18mm is now much tighter ( C/U med shot)

[RED-Tank]

Thank you Donatello :-),

Do you know when does REDONE use windowed-sensor ? the spec seems to make me think that it is depending on both frame-size and frame-rate. However it is not clear:

1-60 fps 2k & 720p (full sensor ?)
1-120 fps 2k & 720p (windowed sensor) instead of 61-120fps.

Furthermore, 1280x720, so the FOV will be changed significantly if I shoot with 2k or 720p, am I right ? Or the REDONE is clever enough to change the focal length regardless what len is used (sound impossible) in order to "resize" the full FOV image onto the windowed-sensor ?

Thanks again for any info on this.

[Rob Lohman]

Windowing is like cropping. We'll have both windowing and resizing (in RGB modes), it all depends on resolution and settings you set.

Also see: http://red.com/formatoptions.htm (might not be 100% accurate)

That doesn't list if you have windowing and/or resize options though. Stuart should be able to tell you more on that.

[Steve Freebairn]

I thought that when the camera windowed the sensor it used the middle 2k of the sensor? I'd really hate to not get S16mm FOV while shooting 120fps.

[Rob Lohman]

What did you not understand in my explanation? Windowing "crops" the (middle) of the sensor. So yes, that mode is available.

Do keep in mind that you will need the optical raw port + RED-RAID for 2K at 120 fps

[Stuart English]

To clarify - when shooting 720p RGB you are not using just the center 1280x720 pixels of the 4k sensor. 720p is an available output of the 4K or 2K RAW to RGB debayer and scaling engine. So your field of view would be approximatey the same as 35mm or S16mm.

[RED-Tank]

Thank you Rob & Stuart for the information.

So the "windowed sensor" doesn't mean taking a small portion of the sensor to do the job, it is just a slightly cropped version of full sensor to match the final output size of 1280x720p. Am I understanding it correctly ?

And Rob, you've mentioned that we will need RED-RAID in order to record 120fps for 2k. Is the same constraint go for 720p as well ? if so then by no luck I can use RED-Drive or RED-Flash to record anything more then 60fps. Is this correct ? look like more money I have to put in to enjoy the full capacity of REDONE...

[Stuart English]

Yes it can be either a scale and slight crop from the 4K (Academy 35 mm) sensor area, or a slight crop from the 2K (Super 16 mm) sensor area.

REDCODE RGB recording specification supports 720p up to 60fps in the first case and 120fps in the second case - so no need for an external 2K 120fps recording to RED-RAID if high speed 720p is what you want to achieve.

[RED-Tank]

Thank you Stuart :D :D :D, this is all I need :p