Red strobe effect when panning... please help !

[Dominic Jones]

Open gate gives you a view of 2x your shooting rate - so if you´re shooting 24fps open gate shows a 48fps image.

Any way to get this in your footage? Sure - shoot and project at 48fps...

The strobing you´re talking about is perfectly normal for 24fps footage - someone else presented a link to safe panning speeds for 24fps earlier in this thread. Follow that. The reason why you don´t tend to see this on "film" is that operators and directors used to working on film are used to dealing with the framerate and avoid shots that break said rules as a matter of course - it´s got nothing to do with the camera in question, be it film, Genesis, D20/21, Red or anything else, although super-clean HD images don´t help in this regard.

Happy shooting (in whatever framerate you like!),
Dom.

 

[David Wyatt]

It's funny that a lot of people want the "film look" (progressive, 35mm DOF etc) but when it comes to another trait like strobing suddenly they don't want it !!

Seriously though, Red's strobing is pretty bad if you're foolish enough to ignore safe panning speeds (and you're dealing with high contrast details with wider lenses etc), but I think part of why it seems worse is that everything is so much sharper on Red than film or other HD cameras. It's definitely worth you viewing some strobing tests transferred to 35mm because the very act of transferring it to film may take the edge off it (we did some test screenings of Red-shot 35mm footage recently and I can't say I really noticed the strobing standing out as being unacceptable).

 

[Monteiro]

You need to look closer. The big difference between a 24th of a second film frame exposure and a 24P progressive scan exposure is that 24 means two entirely different things. In 24p 1/24th of a second is how long it takes the image sensor to scan from the top to the bottom of the frame and thus record one image much the way your flat bed scanner does. In film 1/24th of a second is how long the entire frame of the film is exposed to light. Let's say you are doing a swish pan past a white pole leaning up against a black wall. see example (www.sea-cam.com/red/b1.jpg) If the pole passes through the shot from the extreme left to right in a single Film frame, it will leave a blurr across the entire frame (assuming you are using a wide open shutter). As you increase the shutter speed the blur becomes narrower until at a very narrow angle it becomes a sharp vertical pole you would see in a still photograph. Not so with a progressive scan sensor. If you pan across that pole in one 24P frame you will get a diagonal pole starting in the upper left corner of the frame ending in the lower right corner of the frame due to the fact that the frame is scanned from top to bottom during the course of one 24th of a second. see example (www.sea-cam.com/red/b2.jpg) In other words the top of the pole is recorded in the beginning fraction of that 24th of a second and the bottom of the pole is recorded at the very end of that 24th of a second. The pole retains it's actual width during that one frame exposure but is distorted diagonally just like a Xerox copy is distorted when you slide your document off the scan surface while it is still scanning. Whereas every part of the film frame is exposed for 1/24th of a second at 24FPS no part of the Progressive scan frame is exposed for 1/24th of a second in fact it is substantially less. That is why 24P with a 360 Degree shutter angle looks like film shot with a much narrower shutter angle with the unfortunate sideffect of having your verticles go diagonal on you. I have learned to live with the diagonals since the first CCD cameras came out but since the shutter angle is effectively less due to the nature of progressive scanning. Can someone from Red tell me if there is there a way to do a 720 degree shutter effect or frame blend like what happens in the undercrank mode when you get longer frame exposures? I tried doing that in Motion with the Optical Flow feature but the results were not very pleasing. Again it would be great of the "Open Gate" feature on the monitor could be somehow recorded.

 

[Stuart English]

Strobe

Strobe

I saw Quantum of Solace this week on a VERY soft film projection.

One scene in particular still stood out: white window frames in the background were strobing away .....

 

[Kenn Michael]

Yep, I had the same experience watching 'Traitor' with Don Cheadle - shot 35mm - tons of the EXACT same strobing that bothered me with Red.

Now, the Red strobing doesn't bother me.

 

[Paris Remillard]

You need to look closer. The big difference between a 24th of a second film frame exposure and a 24P progressive scan exposure is that 24 means two entirely different things. In 24p 1/24th of a second is how long it takes the image sensor to scan from the top to the bottom of the frame and thus record one image much the way your flat bed scanner does. In film 1/24th of a second is how long the entire frame of the film is exposed to light. Let's say you are doing a swish pan past a white pole leaning up against a black wall. see example (www.sea-cam.com/red/b1.jpg) If the pole passes through the shot from the extreme left to right in a single Film frame, it will leave a blurr across the entire frame (assuming you are using a wide open shutter). As you increase the shutter speed the blur becomes narrower until at a very narrow angle it becomes a sharp vertical pole you would see in a still photograph. Not so with a progressive scan sensor. If you pan across that pole in one 24P frame you will get a diagonal pole starting in the upper left corner of the frame ending in the lower right corner of the frame due to the fact that the frame is scanned from top to bottom during the course of one 24th of a second. see example (www.sea-cam.com/red/b2.jpg) In other words the top of the pole is recorded in the beginning fraction of that 24th of a second and the bottom of the pole is recorded at the very end of that 24th of a second. The pole retains it's actual width during that one frame exposure but is distorted diagonally just like a Xerox copy is distorted when you slide your document off the scan surface while it is still scanning. Whereas every part of the film frame is exposed for 1/24th of a second at 24FPS no part of the Progressive scan frame is exposed for 1/24th of a second in fact it is substantially less. That is why 24P with a 360 Degree shutter angle looks like film shot with a much narrower shutter angle with the unfortunate sideffect of having your verticles go diagonal on you. I have learned to live with the diagonals since the first CCD cameras came out but since the shutter angle is effectively less due to the nature of progressive scanning. Can someone from Red tell me if there is there a way to do a 720 degree shutter effect or frame blend like what happens in the undercrank mode when you get longer frame exposures? I tried doing that in Motion with the Optical Flow feature but the results were not very pleasing. Again it would be great of the "Open Gate" feature on the monitor could be somehow recorded.

What you are describing is skew. It's not a progressive scanning artifact, it's a rolling shutter artifact.

 

[Patrick Tresch]

Hello Monteiro,

Here is the manual V16:

Open Gate: lets the camera preview images at 48Hz (50Hz) update rate when operating in
23.98 or 24.00 fps (25 fps) Project Frame Rates. In record, all monitor path images will be
viewed at 48Hz, but recorded at 23.98 or 24.00 fps (viewed at 50Hz, recorded at 25 fps)

Note: Use Open Gate with caution. Due to the doubling of sensor frame rate
relative to capture rate the following operational restrictions should be noted.

- Open Gate is not available in Varispeed or Ramp modes.
- Open Gate is not available for 50.00 or 59.94 Project Frame Rates.
- Video Genlock may not be available when operating in Open Gate.
- 360-degree shutter is not available when operating in Open Gate.

So yes it's a viewing mode but you could probably have the same smooth motion effect using a 48p or 50p Fps project downconverting to HD 50interlaced final master if in Pal.

?

Patrick


PS: SORRY DIDN'T SEE THE OTHER POST SPEAKING ABOUT THAT...:clown2:

 

[Keith Putnam]

Just to be horribly pedantic, this is not strictly accurate. At a 24fps film transport speed and a standard 180 degree shutter angle each frame is exposed for 1/48th of a second.

 

[David Rasberry]

Just to be horribly pedantic, this is not strictly accurate. At a 24fps film transport speed and a standard 180 degree shutter angle each frame is exposed for 1/48th of a second.

The film frame is also exposed progressively as the shutter wipes across the frame. Perhaps not as extreme as electronic shutter, but an issue nonetheless.

Has RED or anyone tried a center out circular iris algorithm for the shutter? It would be interesting to see if this would help.