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ION led dimming

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Jeff Toussieng Posted: 04-30-2012 12:35 AM

Sorry, still not getting led dimming.  I am using Chauvet QWash 560Z led fixtures and can't for the life of me get them to fade into their color from 0.  They claim they have 0 - 100 dimming but I don't see it.  They always start at a particular intensity at GO then fade into their cue color in the cue time.  I watch led's actually either fade off or fade on during the cue time.

If a cue is on an intensity fader when I bring up the cue/fader nothing happens until 2% shows then it pops on and starts fading up from there.

In some cues they pop on at the last color value then fade in the cue time to that cue value.

They seem to do smooth color transitions when going from a lit cue to another lit cue, but from black different story.

LED's ehhhhhhhh

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Posts 1,420

That sounds like the fixture has an imperfect dimmer, nothing to do with the console.

This is fairly common at the lower end of LED, getting the very bottom end of the fade smooth is extremely difficult.

The human eye is also amazingly good at detecting very small changes, so looking directly at the diodes on the face of the fixture will make this appear much worse than it really is. (Once fully dark-adapted, it's actually possible to see 16-bit steps in LED fades - you can actually see individual photons!)

LED also reacts so fast that any tiny jitter in your hand as you move the wheel or fader will be visible unless the fixture does smoothing for you internally, so when checking this kind of thing you should use a timed fade.
- Tungsten and even mechanical dimmers fundamentally have much more smoothing than LED, simply due to the thermal or physical mass of the filament/shutter blade.

The coming on in the previous cue colour then fading to the new one sounds like you forgot to Mark the colour.
All fades are "from where we are to where we're going", so unless you tell it to change colour it will stay in that colour - even when off.

Think back to how you'd do a colour change before automated lighting - you'd send a guy to swap out the piece of coloured plastic on the front of the light. If you didn't tell him to go change it, then it would still be the old colour. It takes him a while to do it.

If you use "Automark" then the console will figure out most of these 'Marks' to change Colours, Pan/Tilt, gobos etc.
Sometimes the cue timing means that Automark doesn't have time to finish those marks, so you'll need to override the times (eg Mark Time in Setup, or setting FCB times in the cue where the lights come up) or create your own Marks futher back.

Keep on trying till you run out of cake.

ETC Field Service, London

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Posts 292

Hey Richard,

Thanks so much for your detailed and easy to understand explanation.  Non-smooth AND NOT 0% to ? dimming was what I really didn't want to hear but expected :-).  And with LED's being so intense even 1% can be seen on stage.  I did a show a few weeks ago that used a lot of 1% up to 7% looks.  As you said, in a dark room it's pretty visible.  So looks like I'm, we're all stuck with this.  Most of my fades range from 3 to 5 seconds however when I set them at 20 that initial "on" pops and that's what is the issue.  I'm guessing it's the charge of the gas in the led or whatever fires it that can't be easily smoothed to on.  I'm sure some genius will figure that out since tungsten's on its way out.

Because users wanted a tungsten filament type of true fade Chauvet does have a fixture feature that allows it to be set for fade delay at 0, 1, 2, 3, or 4, however when it's set higher than 0 a quick black out isn't possible, and again, with led's it's very visible; much more so than tungsten.  Found that out in my last event.  Needed to do a quick bright flash of lights then sudden black, but because I had the fixtures set at 4 the black was delayed and the performers were seen moving while they faded out.  That delay also doesn't work for up fades, only down, obviously because a lamp doesn't warm UP (so to speak), it cools DOWN.  Oh, you know what I mean :-)

Anyway regarding marking.  That was also a thought but I keep forgetting to check to see if auto-mark is on.  Must not be because there are no M marks showing.  However, I would like to ask if you don't mind, does marking set every new change except intensity and does it work that way on led's?  I did update one cue last night with a manual mark but when I ran it from the previous cue I still saw all 5 colors come up then those not needed fade off to the blue I wanted.  I am also using True Color rather than HS, which was highly recommended.

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Posts 170

Jeff,

I found these low end fade problems a particular issue with the Chauvets - they are very bright, so a little can go a long way, and the bump to 1% is not ideal. If the dimming mode was controllable via DMX, they would be a lot more suitable for theatrical use IMHO.  When I used them, I had to do a lot with parting color times and adding auto follows to deal with more subtle fades. 

LEDs have come a long way in the past few years, but dimming, blending, and CRI are all inherent issues with LED that manufacturers have to overcome. I think picking from one maker or another is as different as picking leko, fresnel, par, etc with incandescent. Selador, Chroma Q, and Prism, for example, all have much more appealing dimming curves than the Chauvets. 

-Josh 

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Posts 292

Absolutely Josh.

For all the readers who don't alreday know this: I compared my Chauvet QWashes with Selador Ice and Fire and there is no comparison.  They have a true 0% - 100% curve - amongst many other features of course.  Select them and start rolling the wheel very slowly and they will start dimming up slowly.  Slowly roll the wheel with Chauvets and when they get to 2% they "pop" on at 2% then dim up from there, even though they advertise 0 - 100%.  Doesn't do real well in the theatre.  Concerts a different story.

Unfortunately two things happened for me: ETC/Selador don't have any mover washes to my knowledge yet and I wanted to get going on it now AND I wouldn't be able to afford them anyway since I do all my lighting as a ministry; basically donations only.  Bummer.

Regarding some of your work-a-rounds.  I'd like to know a little more about "parting color times" and "auto follows" that help the popping on and off.

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Boy do I resonate with your budget limitations. Budgets are really tight as we are raising money to put a building on the land we purchased last year. (We're currently performing in a small 104 year old church.) I have a handful of cheap LED PARs that were loaned to me. There are a couple tricks that I've learned to make them less obnoxious coming from a blackout.

First, fade from black on both color and intensity. The cheap LED units seem to just multiply the color % by the dimmer % to get the output value for each color. So 1% of 100% red is 1% output, while 1% of 1% is 0.01% output.

Second, if the LEDs still pop too much because the tungsten fixtures are taking a moment to warm up, delay the start of the fade for the LED units until the tungsten lights have a chance to start to fade up.

I can't give specifics how to do these on an ION as I'm still working on convincing the "powers that be" to buy an ION system.

-- David

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Posts 219

I have had luck with creating a dimming curve with fading starting at 10%. This way your conventionals have time to warm up and start showing onstage when the led units start to kick in.  YOu can create a curve in the Record Targets section of Browser window.  Then add the curve to the fixture in Patch.

JP Gagnon High Output, Inc. Portland, ME

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Posts 292

David,

I thought I posted to this however I see it aparantly didn't go out.

Thanks for your input.  I'm not real clear what you mean fading from black on both color and intensity.  The way I compared the Chauvets to the Seladors is I selected both fixtures and a color and hit Enter, then rolled the wheel very slowly and the Chauvets popped on at 2%.  I'm guessing when I selected the color and hit Enter that set it, so the color wasn't "rolling up".  I'll have to figure out what to do different to fade from black on both color and intensity on my ION.

On another note, actually the really cheap led's don't have an intensity channel, so it's either just color for intensity or in some cases, as in the ION, an intensity channel is added in the library.  In the case of these Chauvet washes, they do have an intensity channel.

Regarding conventionals, I can do delays and other things but there are often times when only led's are used.  I guess that 's the price I pay for chooooooosing Chauvet.

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Posts 292

Hey there.  Thanks for the input.  Thought I sent out posts on the last couple of replies but they aparantly didn't go out.  iPhone stuff.

Anyway, as you can see in my other post, there are often instances where all I am using is the led's in a cue.  Otherwise covering it up with conventionals is a great idea and will be used.

Top 75 Contributor
Posts 170

Jeff Toussieng:

Regarding some of your work-a-rounds.  I'd like to know a little more about "parting color times" and "auto follows" that help the popping on and off.

Really just hiding the popping as much as possible.  If doing a color crossfade where new colors turn on, I might delay the colors coming up from zero.  If colors were fading out, I would delay those until other colors came up to their levels.  If coming up from black and the color used the white LED's, I would fade those up first and then autofollow into a cue that added the other colors and possibly dimmed the white.

I couldn't eliminate the lack of low end fade, but sometimes I could hide it a bit.

HTH,

Josh

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Posts 8

Sorry I was traveling this weekend. We went to see my second child get her Bachelor of Arts in Theater! Now I just have to finish paying for it.

By "fading from black on both color and intensity" I meant that the color and intensity DMX outputs should start at 0 and fade up to the final levels over the full fade time. If the ION is marking the color in the blackout, then the DMX outputs for the color are probably at their final values and only the intensity fades from 0 to the final value.

I've got an Express 250 so each device DMX output takes up a separate displayed channel. So going from full black out in cue 1 to an intense dark blue in cue 2 would have all zeros in cue 1, and the channels for blue and the intensity on the device at full in cue 2.

-- David

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