variable shutter speed?

[mattmiller]

i understand that the standard RED shutter speed is 1/48... my question is, is 1/48 the 'standard' because shooting at 24p is the standard? can you shoot at 24p with a shutter speed higher or lower than 1/48?

i've searched for the answer on google, but basically only found that 1/48 is the 'standard' for RED.

thank you,
matt

[Deanan]

1/48th = 180 degree shutter at 24fps.

[Adrian T.]

can you shoot at 24p with a shutter speed higher or lower than 1/48?

Of course you can.

[mattmiller]

would this be true:

1/24th = 90 degree shutter at 24fps ?

[Barry Green]

No, 1/24th = 360 degree shutter at 24fps.

[Barry Green]

Of course you can.

You can, but you better not do it on a Red (or other CMOS camera) if you're lighting with a magnetic-ballast HMI. Bad things happen as the shutter speed gets shorter, and there is no "HMI safe" speed where all shutter speeds work. Electronic-ballast HMIs appear to be much more compatible.

I'll try to post results soon, but basically you get huge rolling bands throughout the video if you take the shutter speed up to 1/192 or faster @ 24fps, and you get nasty flickering when doing VariSpeed mode at anything other than 24/30/60fps.

[Policar]

Barry, can you use a magnetic ballast with a Red at 1/60 or 1/48? I know a camera with a CCD (or film) could do both, but with a CMOS...I don't know?

[Stuart English]

is 1/48 the 'standard' because shooting at 24p is the standard? can you shoot at 24p with a shutter speed higher or lower than 1/48?

Yes, full details are in the RED-ONE Operations Guide, available as a downloadable .pdf from the www.red.com/support web site.

[Barry Green]

Barry, can you use a magnetic ballast with a Red at 1/60 or 1/48? I know a camera with a CCD (or film) could do both, but with a CMOS...I don't know?

Magnetic ballast worked at 24 fps @ 1/48 and 30fps @ 1/60, and 24fps @ 1/60. It pretty much didn't work on any frame rate or shutter speed when the shutter speed climbed above about 1/192, or the frame rate varied from 24/30/60.

[Policar]

Well, that's not ideal but it's not a big problem, either. No one's going to be doing too much high speed photography with discharge lights...but 36fps or 22fps didn't work, even with 1/60th and 1/48th shutters?

Anyhow, thanks for the info.

[Barry Green]

I didn't test every possible combination, but I ran through every shutter speed on 23.976 and every shutter speed on 24.000, and then I put it in "relative" mode in 23.976 and 24.000 timebases and ran through most every frame rate. In relative mode, only 24/30/60 worked.

So I don't know if 36 @ 1/60th worked or not, and I didn't try slower than 24.

[Policar]

Ah, makes sense. That's not too prohibitive; those are the "most important" frame rates anyway. Thanks again for the info.

[Barry Green]

Also, I tested using an electronic ballast'ed metal-halide "HMI" from www.coollights.biz. IIRC it was solid at all frame rates and shutter speeds up until I got up into the 1/1000 to 1/2000 range.

[Nick Gardner]

Are you guys saying that the Red exhibits flicker at HMI safe speeds, or are you just saying it flickers at non HMI safe speeds like every other camera ever made ?

Nick

[Barry Green]

Are you guys saying that the Red exhibits flicker at HMI safe speeds, or are you just saying it flickers at non HMI safe speeds like every other camera ever made ?
No, I'm saying it makes big thick scrolling bands of dark orange, unlike any other camera ever made. (well, unlike any CCD or film camera ever made, but all rolling shutter cameras behave this way).

It's a new phenomenon, one that shooters may want to familiarize themselves with. It ain't flicker. (although, depending on the speed, you can get what looks like flicker, just not the same familiar type of flicker, this is instead a fast-scrolling band). It's different.

Fortunately with Red, unlike with film, you can see it happening on the monitor as it's happening so it doesn't come as a big surprise in the transfer.

[Dj Joofa]

No, I'm saying it makes big thick scrolling bands of dark orange, unlike any other camera ever made. (well, unlike any CCD or film camera ever made, but all rolling shutter cameras behave this way).

It's a new phenomenon, one that shooters may want to familiarize themselves with.

The amplitude of these bands depend upon exposure time, frequency should remain constant, and the scrolling between frames (i.e., phase difference) is due to frame rate (beat frequency between frame rate and flicker frequency). Hence, if frame rate is matched correctly, then the scrolling should stop, but the static banding should stay there.

However, in theory, if exposure time is properly matched, then there is no need to match frame rate, as the amplitude of flicker has been made to vanish.

If exposure time is not matched, then the amplitude of the flicker is reduced by selecting a larger exposure time, though, at the expense of more motion blur.

[jtcoleman]

The amplitude of these bands depend upon exposure time, frequency should remain constant, and the scrolling between frames (i.e., phase difference) is due to frame rate (beat frequency between frame rate and flicker frequency). Hence, if frame rate is matched correctly, then the scrolling should stop, but the static banding should stay there.

However, in theory, if exposure time is properly matched, then there is no need to match frame rate, as the amplitude of flicker has been made to vanish.

If exposure time is not matched, then the amplitude of the flicker is reduced by selecting a larger exposure time, though, at the expense of more motion blur.

i'm glad I happened upon this thread, because my sekonic only does (evidently) 1/30 and 1/60, there doesnt seem to be a setting for 1/48 (unless I am missing it? its possible, i'm new to this.)

I was hoping that I would be able to set my RED to either 1/30 or 1/60 so that I wouldn't have to always add or subtract half a stop on my reading... but I wasn't sure if the blur would be noticeable... or even if that would even work. i was also nervous that the amount of light between stops is logarithmic, so I was guessing that 1/48 would be (roughly) half a stop in between 1/30 and 1/60 in terms of exposure...?

obviously this is all a bit new to me, so any help would be appreciated.

thanks,

JT
Austin, Texas

[Chris Nuzzaco]

Well, that's not ideal but it's not a big problem, either. No one's going to be doing too much high speed photography with discharge lights...but 36fps or 22fps didn't work, even with 1/60th and 1/48th shutters?

Anyhow, thanks for the info.

I would beg to differ on this one. HMI is used because its so much more effective. For one, the Red likes daylight balanced light. I would hate to light high speed with gelled tungsten.... yikes, you'll catch the set on fire. You might need to look at using Phantom for those really high speed shots.

[Dj Joofa]

i'm glad I happened upon this thread, because my sekonic only does (evidently) 1/30 and 1/60, there doesnt seem to be a setting for 1/48 (unless I am missing it? its possible, i'm new to this.)

I was hoping that I would be able to set my RED to either 1/30 or 1/60 so that I wouldn't have to always add or subtract half a stop on my reading... but I wasn't sure if the blur would be noticeable... or even if that would even work. i was also nervous that the amount of light between stops is logarithmic, so I was guessing that 1/48 would be (roughly) half a stop in between 1/30 and 1/60 in terms of exposure...?

obviously this is all a bit new to me, so any help would be appreciated.

thanks,

JT
Austin, Texas

JT,

Please refer to the following graph, in which I have drawn integration time (exposure time) increasing on the x-axis and on y-axis is its effect on the amplitude of the corresponding "banding" because of flicker.

http://www.reduser.net/forum/uploaded/7051_1207022599.gif

As seen, "flicker free" are those exposure times where the red line meets the blue line. In between values are where one sees the flicker and its magnitude varies. As seen, the magnitude of flicker decreases (even when not zero) as integration times increases (to the right).

BTW, since you are in Austin, you are most welcome to drop by any time and we can discuss such topics of interests.

[Policar]

I would beg to differ on this one. HMI is used because its so much more effective. For one, the Red likes daylight balanced light. I would hate to light high speed with gelled tungsten.... yikes, you'll catch the set on fire. You might need to look at using Phantom for those really high speed shots.

I guess so...but this is a camera that "only" shoots 60fps in 3k (personally, I wouldn't use 2k for much) and that's 1/120 for the shutter, which should work fine. And if you are doing 120fps...just rent an electronic ballast for the day. I was speaking for myself, but I still think, universally, the rolling shutter should not be that big an issue even with discharge lights.

Also, I don't really see the point of lighting night interiors with 5600K. But if you need a super clean image, that's a fair point.

[jtcoleman]

JT,

Please refer to the following graph, in which I have drawn integration time (exposure time) increasing on the x-axis and on y-axis is its effect on the amplitude of the corresponding "banding" because of flicker.

http://www.reduser.net/forum/uploaded/7051_1207022599.gif

As seen, "flicker free" are those exposure times where the red line meets the blue line. In between values are where one sees the flicker and its magnitude varies. As seen, the magnitude of flicker decreases (even when not zero) as integration times increases (to the right).

BTW, since you are in Austin, you are most welcome to drop by any time and we can discuss such topics of interests.

very cool, so it's really a question of sync -- you can choose longer or shorter intervals, so long as you pick a good point on the x-axis? also, what is the unit of measure you are using there? (the chart doesnt specify it)

JT
Austin, Texas

[Dj Joofa]

very cool, so it's really a question of sync -- you can choose longer or shorter intervals, so long as you pick a good point on the x-axis? also, what is the unit of measure you are using there? (the chart doesnt specify it)

JT
Austin, Texas

The points where blue and red lines meet are at: n / (2 * f). For US it will be:
n/120, with n = 1, 2, 3, ..., i.e., 1/120, 2/120 (=1/60), 3/120 (=1/40), ...

The interesting thing is as seen in the graph the amplitude decreasing with increasing exposure time, so even if you are off from n/120, but your exposure time is large enough, the amplitude may be small enough and not affect.

[Alex Carr]

Ok, I can't get a 180 degree shutter at 36fps, Tungsten even Flickers, The only fix is shooting 1/60th, but then you need another 1/2 stop, and if it is a ramping Shot, a Iris Pull needs to be made to match the exposure change. Since Relative mode flickers under about any light at 36fps it cannot be used, the banding is much more prominent and changes speeds and sizes and directions over each shutter angle.

Unfortunately is this the disadvantage of a cmos sensor? only having 24, 30, and 60 seems limited.