Home of Professional Cinematography since 1996

Red Camera Speed Ramps

Published : 18th December 2010

Can anybody tell me whether the Red camera can do speed ramps in-camera? A very good friend of mine who is also a Director/Producer wants to shoot our next project on the Red camera, where as I feel that the project would be better suited to film. Can the Red camera do speed ramps in camera or do they have to be done in-post?

Anna Carrington
Cinematographer
London
UK


 

Yes you can do speed ramps in camera if what you mean is a transition over Time from the Frame Rate to an End Rate.

Page 36 of the current manual details how.

Jim Jannard


Just to add you can also set it up to do RAMP via event with a remote or push of the record button.

Dane Brehm
DIT
SF & LA


How are you planning to compensate for the ramp, and what sort of speed change?

I don't know of way to synchronise a RED ramp with an iris motor. It might be doable. I assume that if you have the shutter in "normal" mode, the exposure time will stay the same, regardless of FPS.

I haven't tested that.

Nick Vernon
DIT
UK/SWE


Set the shutter to "normal." Then set the shutter speed to the same fraction of a second as your highest frame rate. IE. You want to ramp from 24fps to 96fps. Set your shutter to 1/96th of a second. Now when you ramp there is no need for exposure compensation. That being said you will have a 90˚ shutter @ 24fps for the head of the clip.

cheers

J. Eric Camp
NYC


>> I assume that if you have the shutter in "normal" mode, the exposure time will stay the same, >>regardless of FPS. I haven't tested that.

You are correct Nick. In effect leaving the camera in "normal" shutter mode is also known as Shutter Compensation for the FPS ramp but by doing that it is increasing the shutter angle thus motion blur. If you want to keep the same shutter angle use "relative" mode and an iris motor.

I may need to ask an 1st AC, but I'm sure with a Preston FIZ unit ( or Cmotion) you can set the IRIS range then trigger the camera ramp by hitting record.

To be honest, I would shoot your max ramp speed then adjust in Post. It is an efficient use of time on-set. I remember trying to sync iris and a ramp with a car moving on a 435 some years back. Way to much work.

Dane Brehm
DIT : Data Tech
SF & LA
Phantom | Red | KiPro


J. Eric Camp wrote:

>>"Set the shutter to "normal." Then set the shutter speed to the same fraction of a second as your >>highest frame rate. IE. You want to ramp from 24fps to 96fps. Set your shutter to 1/96th of a >>second. Now when you ramp there is no need for exposure compensation.

So what's actually happening inside the camera for it to compensate for the light difference when doing speed ramps - is it changing shutter speed or shutter angle? Can anybody point me to an online example of a speed ramp from a Red?

Anna Carrington
Cinematographer & Camera Operator
London
UK


It's not changing the exposure time, it's keeping it the same.

If you think of a film camera going from 25 to 50 fps, you go from 90 to 180 degree shutter to compensate. This keeps the exposure time the same. So with a RED keeping the exposure time the same, it basically does the same thing as adjusting the shutter angle.

Shutter speeds on the RED act differently to a rotating shutter in a film camera so I would test any ramp before you use it in production.

As mentioned before, if you are involved in the post work it might be an idea to shoot the whole shot at the highest frame rate and do the ramp in post.

Just as a side note, it's easy to forget that if you shoot higher speeds with the RED you can't shoot full resolution so have to use a smaller area of the sensor. If the high speed shot happens to be wide, you might need a wider lens with you.

Nick Vernon
DIT
UK/SWE


 

As Nick mentioned, the electronic shutter in the RED camera has different properties than a mechanical shutter by nature. In "normal" shutter mode the exposure time for each frame is defined regardless of frame rate. With that said the frame rate will affect available exposure times. IE shooting at 24fps will allow a maximum exposure time of 1/24th of a second. So if I set my exposure time for a fraction available to me at my highest frame rate then I can ramp from a slower frame rate to the higher with no light loss. That being said again I agree with Nick. With this method you are already exposing each frame for the shorter amount of time anyway. You might as well shoot the whole shot at the higher fps and do the speed effect in post, giving you the flexibility to choose the exact duration and timing of the ramp.

Lastly as Nick touched on as well: The RED has to window the sensor down to achieve higher frame rates.
A basic rule of thumb is:
1-30fps = 4k
30-60fps = 3k
60-120fps = 2k

4k being 35mm equivalent
2k being 16mm equivalent
3k being in the middle

I order to ramp to a frame rate you must be in the resolution setting to allow for it. So again to ramp from 24 - 96 one would need to be in 2k to start.

Please note that since the sensor is windowed your FOV will decrease for any 35mm lens on the camera. (Almost like putting the 35mm lens on a 16mm camera for a 2k setting for example.)

cheers

J. Eric Camp
NYC


Dane Brehm said :

>>“I'm sure with a Preston FIZ unit ( or Cmotion) you can set the IRIS range then trigger the camera >>ramp by hitting record.”

C-motion, yes, with the cdisplay it’s a very easy process to programme. Preston yes, but with the F/X unit. I’m not sure what the newer Mk3 Preston FIZ has on offer for added new features in this area. Not many rental houses have them in London. Mk2 main stay. Of the times I have used a Mk3, it’s for the usual simple stuff. I think the Arri units only talk to Arri cameras when it comes to ramping.

Anna Carrington said “So what's actually happening inside the camera for it to compensate for the light difference when doing speed ramps…”

Depending whether you need to go with iris or shutter - shutter uses electronic gain.

If in a controlled situation, the easiest way is to use a hard wire trigger set to one of the GPIO sockets. Make sure its set up properly in the menu as it can also be used for 12v power options. Or, as others have stated, just use the highest frame rate and do it in post. In principle, it’s very similar to how you would set up an Arricam.

J. Eric Camp said “A basic rule of thumb is: 1-30fps = 4k 30-60fps = 3k 60-120fps = 2k “

The quoted resolutions are for 2:1 aspect ratio. If recording at 16x9, the options are different. At 25fps time base – 3K/16x9 50fps and 2k/16x9 = 100fps are your caps.

There is a degradation in quality at the lower frame rates, resolution and detail, which has been much talked about in the past. If you’ve got the budget to shoot on film, it’s a no brainer. It all depends on your end deliverable / budget and all that good stuff…

Good luck,

Danny Gagatt
1st AC / DIT
London, UK


Nick and Dane,

I did some speed ramps on a non-fiction show I shot in San Francisco a few months ago where we did speed ramps for a specific shot.

As I recall (I don't have the camera in front of me), the RedOne allows you to set the shutter in absolute terms, i.e. 1/48 sec 1/30 sec, etc. in ADDITION to degrees of rotation like we are used to on film cameras. I believe the distinction was normal vs. relative. You want normal.

I set the shutter to normal on our show and ran the ramps like that, there was no need to compensate for anything in post and the ramps looked great. I will note that the ramps are essentially all about the motion and longer exposure times seem to feel smoother.

Jonathan Flack
http://www.TwoFourO.com
+1 310 359-3510


This has definitely been thoroughly explained:)

I recommend doing a test as adjusting the shutter mode defines both the sensor timing and corresponding shutter angle/motion blur. Thess are define as a "red" or "yellow" highlight shutter angle in the GUI

I would recommending testing the specific GPI trigger as some 3rd party (there all 3rd party) can short it out. Some rental houses have their own for this reason.

Preston and Cmotion both have a RS style cable which is below the lcd/evf ports to communicate to the camera.

Good luck,

Dane Brehm
IA600 DIT
SF & LA
Phantom / Red / KiPro