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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

HMIs and the Red

M

Mike McCall

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Ok, so we have started to see a problem and was hoping someone might know an answer. Shooting 4K HD in daylight lit studio on white. 23.98 timebase and 24fps, 180 degree shutter. We are seeing a roll inline going through the image, especially if you scrub through the footage in the edit system. This problem is worse when shooting at a 90 or 45 degree shutter. While shooting it is hard to see the roll at 180 degrees, on a monitor, but very evident at 90 and 45. Also it does not matter if on battery power or power supply.

We have went back and tested each light and ballast with the Red thinking it is an HMI problem, but all the lights had some sort of roll to it, even our new 1200s. The 12K was very pronounced, but at a 360 degree shutter it is not evident. This looks very similar to a hum roll, but much more even.

Ideas? Do you think it is a camera issue, light issue? We did have the fan go out on the last shoot day, but now in the edit, we are seeing in on stuff that was shot the first day, when everything was fine. Now I am being told at it is not the first time we have seen this by the editors, but it was very evident this time since it was an all white background.
 
What kind of HMI's ?

not that i think it matters

i was just really excited to get a certain brand and now this scares me:crying:

please chime in Red Gods ......

i got my fingers crossed, no whammies no whammies stop!......
 
What kind of HMI's ?

not that i think it matters
Click to expand...

Arri

Electronic or magnetic ballasts?
Click to expand...

Both. The new 1200s are electronic with Flicker Free on and off mode. They were having the same issue as the magnetic ballasts, although the 12K magnetic was worse.

Thanks for the link Frank I will check it over and confer with the DP. We have a big mixture of old and new HMIs, but all seem to do the same things I was describing, but to different degrees.
 
So I read the article Frank pointed out and here is what I got out of it. Magnetic is not so good, but electronic can have problems too. Well that is exactly what we found out today in our tests. Also a 144 degree shutter will many times take care of the problem. Which, and I didn't mention this before is also something I noticed today, at 144 it is not noticeable, but what if I want to shoot at a different degree?
Surely Red has better capabilities than that.
 
This is not a problem. It is a fact of life with shooting with discharge lighting. Has been as long as there have been moving pictures and discharge lighting. If you want to shoot at any angle and any frame rate, go get a bunch of maxi brutes.

Nick
 
We shoot with HMIs with electronic ballasts (some old, some new) all the time, and never have any issues. This is definitely not a RED problem. If you are seeing rolling artifacts with the RED, I'd be willing to bet you'd almost certainly see them on a film camera, as well.

Stephen
 
Nick Gardner said:
This is not a problem. It is a fact of life with shooting with discharge lighting. Has been as long as there have been moving pictures and discharge lighting. If you want to shoot at any angle and any frame rate, go get a bunch of maxi brutes.

Nick
Click to expand...

Agreed!

use these tables if you must use a specific shutter angle/speed
 
So you probably weren't using a generator, were you?
 
Mike McCall said:
Ok, so we have started to see a problem and was hoping someone might know an answer. Shooting 4K HD in daylight lit studio on white. 23.98 timebase and 24fps, 180 degree shutter. We are seeing a roll inline going through the image, especially if you scrub through the footage in the edit system. This problem is worse when shooting at a 90 or 45 degree shutter. While shooting it is hard to see the roll at 180 degrees, on a monitor, but very evident at 90 and 45. Also it does not matter if on battery power or power supply.
Click to expand...

At 24 fps a 180 degree shutter delivers 1/48th exposure time. For 50 Hz countries, Europe for instance, it does make a lot of sense to use 172.8 degree shutter to expose at 1/50th which matches the local powersupplies frequency.

This said, there is always a possibility that a flickerfree ballast is not working properly or, for some reason, by mistake on one light a non-flicker free ballast was used causing what you describe. Even minor frequency-offsets are visible. I've been bitten by this not only once shooting 35mm (mostly a dysfunction of the gennies automatic frequency system) and the RedOne acts the same in this regard. I'm sure it's a frequency-offset.

Hans
 
Nick Gardner said:
This is not a problem. It is a fact of life with shooting with discharge lighting. Has been as long as there have been moving pictures and discharge lighting. If you want to shoot at any angle and any frame rate, go get a bunch of maxi brutes.

Nick
Click to expand...

Time to get yourself some carbon arcs and operators :laugh:

Actually, I'd be really excited to see how RED handles carbon arcs. Has anyone tried it? The last time that I know of carbon arcs being used on film was for a feature in Hawai'i in the late 1990s... the name is escaping me, but the quality of the light was amazing; modern stocks with oldskool lighting.

I started off making a joke, but now I'm kind of serious about wondering what it would look like.
 
Thanks for all the replies everyone.

Agreed!

use these tables if you must use a specific shutter angle/speed
Click to expand...

What tables. I have several different charts and each say different things, but most are specific to film, and I have found Red is not always like film.


So you probably weren't using a generator, were you?
Click to expand...

We are using grid power, we have a 3 phase feed from the city to the building and then breaks out from there.

Did you Varispeed the 24fps or are you just reporting what the screen says?
Click to expand...

I checked for sure this morning and it was not in Varispeed, this could be an issue since we are at 23.98 time base, but I will test today.
 
RedRoll HMIs

RedRoll HMIs

Hey Guys-
I'm the DP on Mike McCall's shoot and I need to weigh in with a few facts:

First, I have never had a problem in 20 years of shooting film with a 180 degree shutter at 24fps with magnetic ballasts, including the exact ballasts we used on the shoot in question. So, a camera problem is possible here.

Second, in one test yesterday, Mike set up a Panasonic HPX-2000 next to the red with "half" or 1/48 shutter and did not see the roll issues with that camera.

Third, I have seen a "wave" effect with high frame rates and different shutter angles, but never this "roll" effect. It is the same regardless of framing. It is pretty weird.

So... I don't need theoretical ideas about what should happen in normal shooting and correct shutter angles. I want to know if you have seen this effect yourself and under what conditions. I'm not happy that we can't use our 12k with this camera in a "normal" situation.

Again: Mag. ballast, 60 hz, not a genny, 180 deg. shutter, 23.98 time base, 24 fps. 24mm on a cyc wall same as 65mm on a white plate. Not dependent on framing.

Thanks for your time and assistance!
 
So varispeed did not matter, looked the same either way. the only time it comes close to being solid is with a 144 degree shutter.

We are going to test side by side with another Red this afternoon. It is looking like a electronic issue in the camera, but this afternoon will confirm that.
 
Test results

Test results

Mike McCall has diligently tested many combinations today.
We borrowed a friend's Red One and set it up next to ours.
The results are identical.
Here's a short summary of what we saw:

1) Updating firmware from 17 to 20 seemed to help a little.

2) With a magnetic ballast, 144 degree shutter gave perfect results. 72 degree shutter displayed a subtle strobing around the edge of the beam of the 4k par tested. All other shutter angles gave consistently bad results, predictably worse as the angle got narrower. The effect looks like phase banding, as if you were adjusting the shutter to shoot a CRT monitor.

3) Electronic ballast gave perfect results at every shutter angle tested with the 4k par.

So again... if you want to use magnetic ballasts, set the shutter angle at 144 degrees at 24 fps and you should be fine... but I would test first with each light you want to use. 72 degrees is a possibility... test first.

Electronic ballasts should work in every situation.


-Guy
 
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