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View Full Version : Exposure Time - Speed v's Angles


Stuart English
07-01-2007, 08:58 AM
Following up on the question about exposure time when in ramps, here is a quick comparison of exposure times when expressed in 1 / xx seconds v's xx degrees. Calculations are at 24 fps.

If you want to convert shutter speed to shutter angles at 24 fps the math is (24 x 360) / Time Fraction i.e 8640 / xx where xx is 1/ xx sec

So the equivalent shutter angle for 1/50 sec shutter speed is 8640 / 50 = 172.8 i.e 172.8 degrees

Sec Equivalent Degrees

1/32 270

1/48 180

1/50 172.8

1/60 144

1/96 90

1/120 72



The camera's Sync Scan function permits any shutter speed in the range 1/32 - 1/2000 (or equivalent angles) - i.e these are not preset speeds but fully variable.



To find a shutter speed that relates to a known shutter angle, do the math in reverse

At 24 fps it is (24 x 360) / Shutter Angle i.e 8640 / xx where xx is xx degrees

So the shutter speed for 144 degrees 8640 / 144 = 60 i.e 1/60 th sec


Degrees Sec

270 1/32

180 1/48

178.8 1/50

144 1/60

90 1/96

72 1/120

45 1/198

22.5 1/348

11 1/696

8.6 1/1000
David Mullen ASC
07-01-2007, 10:19 AM
Even though I come from a film background, I prefer digital cameras list shutter speed options in time, not angle, since they don't use a spinning mechanical shutter anyway. I don't want to have to mentally convert 270 degrees over to 1/32nd at 24 fps.
Evin Grant
07-01-2007, 02:02 PM
The camera's Sync Scan function permits any shutter speed in the range 1/32 - 1/2000 (or equivalent angles) - i.e these are not preset speeds but fully variable.


Stuart, does this mean there is no 360º or 1/24th shutter option on the camera?
Stuart English
07-01-2007, 05:31 PM
It just means that as of the time of writing this, the cameras' tested shutter speed range is 1/32 - 1/2000th sec
SF Geek
07-01-2007, 10:52 PM
Also would this mean that the camera has not been tested at anything less than 24 fps? I figured that there should be no problem getting a 1/24 or 1/12 shutter speed at under-cranked frame rates. I guess that's what I get for assuming.
Stephen Williams
07-02-2007, 01:34 PM
Even though I come from a film background, I prefer digital cameras list shutter speed options in time, not angle, since they don't use a spinning mechanical shutter anyway. I don't want to have to mentally convert 270 degrees over to 1/32nd at 24 fps.

Hi David,

I agree, sounds very complicated to work out at 2.00 am. Can't we just have shutter angle and camera speed?

Stephen
Steve Freebairn
07-02-2007, 02:03 PM
Why not do both side by side?
Stephen Williams
07-02-2007, 02:18 PM
Why not do both side by side?

Hi,

Adding milliseconds as well/instead of FPS if you really want to confuse people.

Stephen
Brook Willard
07-02-2007, 02:20 PM
And arc-minutes. ;)
chuck colburn
07-02-2007, 02:34 PM
And arc-minutes. ;)

HAHAHAHA!!

Use that for calculating in camera fades and dissolves.
Stuart English
07-02-2007, 03:36 PM
Can't we just have shutter angle and camera speed?


Yes.

Point is you can have something else if you want, and the preset speeds do match up to famiiar angles if you are coming to RED from a film world.
Stuart English
07-02-2007, 03:42 PM
I figured that there should be no problem getting a 1/24 or 1/12 shutter speed at under-cranked frame rates. I guess that's what I get for assuming.

Its a very reasonable assumption.
Stephen Williams
07-03-2007, 06:42 AM
Yes.

Point is you can have something else if you want, and the preset speeds do match up to famiiar angles if you are coming to RED from a film world.

Thanks Stuart

Stephen
Mark B.
07-03-2007, 12:42 PM
Will the still-photo capabilities allow for shutter speeds closer to 1/8000?