Shutter speeds in 25p mode - Page 2 at

Go Back   DV Info Net > Sony XAVC / XDCAM / NXCAM / AVCHD / HDV / DV Camera Systems > Sony XDCAM EX Pro Handhelds

Sony XDCAM EX Pro Handhelds
Sony PXW-Z280, Z190, X180 etc. (going back to EX3 & EX1) recording to SxS flash memory.

Thread Tools Search this Thread
Old January 4th, 2008, 09:51 AM   #16
Join Date: Sep 2005
Location: Gilbert, AZ
Posts: 1,896
I have not see not seen this. I had a real concern since I shoot concert lighting. Most of my lights have MSD lamps. I have not checked out my LED panels with the EX1. These are the type of panels they use as backdrops on stages.
My other video cameras (HD100, global shutter) flicker when shooting these panels.
It mainly has to due the dimmer function with LEDs using PWM (Pulse Width Modulation). It's essentially a duty cycle for controlling light output.

The flicker can be reduced quite a bit by timing adjustments in the DMX control circuit for these LEDs, nonetheless, as we know, all video cameras can suffer from issues causing flicker.

It will be interesting to see how the EX1 works with these LED panels.
Steven Thomas is offline   Reply With Quote
Old January 4th, 2008, 12:08 PM   #17
Regular Crew
Join Date: Sep 2004
Location: Austin Texas
Posts: 162
Images: 3
Hey Paul, thanks for the clarification, glad there was a reason to the assumptions I've been working under even though I don't remember the source!

Okay, in my thirst for knowledge, how does angle fit into this equation? As you said "which does the same thing but also changes with framerate", does that mean that in your example of "If however you increased your frame rate to 48p ... you would also need to increase shutter to 96." If I were using angle instead of 1/48 that it would do this automatically? If so, then in 24p, what would be my desired angle?

So much to learn!

- Ray
Raymond Schlogel is offline   Reply With Quote
Old January 4th, 2008, 12:52 PM   #18
Major Player
Join Date: Nov 2007
Location: Los Angeles, CA
Posts: 498

The angle setting sets up a relative rather than absolute shutter duration.

It's based on the film tradition of the shutter being a essentally a spinning pie chart, spun by a motor at a constant speed (the frame rate). Here's a good schematic on Wikipedia:

(thanks to Anthony at IEBA Tech Thoughts for the link)

Film cameras can only open their shutters to expose film around half of the 1/24 seconds alloted to each frame (1/48 second) because the other 1/48 second is needed to move the film though the gate and register it for the next exposure.

Because a circle is 360 around, this half-pie opening is considered to be a 180 opening.

Since this is a mechanical constant in a film camera, speeding up a film camera to, say 48fps, (by spinning the motor twice as fast) will allow 1/2 of the time (1/96 second) for exposure and the other 1/96 second to "pull down" the film.

Likewise 60fps (achieved by spinning the motor faster still) creates a 1/120 second exposure and 1/120 second pulldown.

Most film cameras have variable shutters. To create a shutter opening that is 1/4 of the time alloted to each frame, one would need to close the pie opening down to 90. At 24fps this would create an exposure of 1/96 second. At 48fps it would be 1/192 second and at 60 it would be 1/240 second.

The EX1 allows one the option to use this film paradigm to set the shutter duration. When set to 180, the shutter will always be one half of the duration alloted to each frame. When set to 90 it will always be 1/4 of the duration. When you change the frame rate in the EX1 when in the shutter angle mode, the shutter duration will change proportionally.

Although not a perfect representation of motion, we have gotten used to the 180 shutter and its half-exposure, half-non-exposure ratio and associate it with a film look.

One thing that video cameras allow that film does not is the ability to open the shutter beyond 180. Turning the shutter off on the EX1 creates the look of a 360 shutter, an impossibility in film. I think as we use this 360 shutter more and grow accustomed to the larger amount of motion blur, this will become a more desirable shutter setting.
Eric Pascarelli is offline   Reply

DV Info Net refers all where-to-buy and where-to-rent questions exclusively to these trusted full line dealers and rental houses...

(800) 223-2500
New York, NY

B&H Photo Video
(866) 521-7381
New York, NY

Texas Media Systems
(512) 440-1400
Austin, TX

Precision Camera
(800) 677-1023
Austin, TX

(800) 323-2325
Mineola, NY

DV Info Net also encourages you to support local businesses and buy from an authorized dealer in your neighborhood.
  You are here: DV Info Net > Sony XAVC / XDCAM / NXCAM / AVCHD / HDV / DV Camera Systems > Sony XDCAM EX Pro Handhelds

Thread Tools Search this Thread
Search this Thread:

Advanced Search



All times are GMT -6. The time now is 02:44 PM.

DV Info Net -- Real Names, Real People, Real Info!
1998-2018 The Digital Video Information Network