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Fading through grayscale?
MUFF WIGGLER Forum Index -> Video Synthesis  
Author Fading through grayscale?
cyklopljud
As I start to dip my toes back into the video world, I have a few questions.

I want to generate a B&W(or colour) signal and fade it smoothly through grayscale from white to black over a period of around 5 to 10 minutes.

So I have envisaged the setup as Very Low speed LFO CV out > VCA CV In > B&W generator> projector.

I understand digital would be much simpler and easier.
I’m choosing analogue, as the artifacts I get with such long fades in Digital are a huge problem, there is no organic fade out, just a blocky change through grayscale.

I’m not sure of my budget yet but I’m looking at an all in one or modular.
A simple solution would be wonderful. I know about LZX and gieskes systems, are there any DIY options or older technologies I could pick up that could do this for me.

Anyway any help would be much appreciated and I hope this wasn’t to video nooby and made some sense.

O.
lizlarsen
Hey cyklo -- I got your e-mail, but I think I understand what you're wanting to do better reading it here.

You are correct that you just need a very slow envelope or LFO. Envelope or sync'able LFO may be better, because then you can trigger it to start when you want it to.

Do you want a flat color field with no camera image or do you want to fade in/out an external image? In the former case, all you need for the LZX system are the two basic modules (Color Video Encoder + Video Sync Generator) and in the later case you would also want Triple Video Fader & Key Generator in addition to those two.

Cheers,
Lars
cyklopljud
Thanks Lars,
Ok somthing like this?


Not sure how slow the Dixie can go?

I have modified my Doepfer LFO but it has no Sync.

O.
lizlarsen
No idea on Dixie's speed either.

Keep in mind that the CVE is expecting a 1V signal. You can attenuate it at the input of the CVE, with the level/inversion controls, but if you want to attenuate it beforehand to get more control at the CVE, we have the Voltage Bridge and Voltage Interface I modules.

I'm a big fan of MATHS, because it has the attenuators on the outputs which make things easier. But I'm not sure how slow that goes either.
cyklopljud
Thanks for the input Lars, very helpful.
O.
cyklopljud
Any ideas on a DIY option B&W (Greyscale) generator?
I have DIY'd LFOs, mixers etc..

Edit: just saw the Video DIY sticky.
O.
lizlarsen
While the VSG+CVE combo definitely provide features you don't need in this case, they do a lot behind the scenes to turn an LFO voltage into a viewable video signal, and a DIY project is achievable but not trivial. Things you will need to include in your DIY circuit would be a sync/blanking generator, a blanking circuit, white/black level clipping, and a sync summer/75R output driver.
cyklopljud
Yeah, after a bit of research I see what you mean. I would very much like to stretch my budget to LZX.

There seems to be a simpler way, all be it very LoFi, using Arduino and a TV out shield connected to an LFO.

Hmmm, I guess the reselution will be very small.

O.
lizlarsen
Yes, you can use Arduino/TV out shield, but unless you have a proper blanking and clipping circuit then you are probably just going to be using the LFO into the ADC input of the Arduino, at which point your output resolution will be limited to whatever DAC output you have configured from your Arduino. This defeats the point of your original wish of having a continuous analog voltage for a long seamless transition.
cyklopljud
creatorlars wrote:
Yes, you can use Arduino/TV out shield, but unless you have a proper blanking and clipping circuit then you are probably just going to be using the LFO into the ADC input of the Arduino, at which point your output resolution will be limited to whatever DAC output you have configured from your Arduino. This defeats the point of your original wish of having a continuous analog voltage for a long seamless transition.


Your right, hmm looks like I need to find some $$.
cyklopljud
Lars,
I couldn't see the output size of the video output in the specs of the CVE, is it 768×576?
Silly question...?
lizlarsen
It's analog so there's no pixel resolution. The timing formats are standard NTSC or PAL, depending on configuration. Pixel resolution only comes into play after you decide to digitize or capture the output.
lizlarsen
But yes, typically NTSC is captured at 720x480 and PAL at 720x576 I think, but it depends somewhat on settings and capture device. These formats are also called 480i and 576i.
bitSmasher
Could you take a cheapo old consumer "video processor" that typically have Colour/Enhance/Brightness/Contrast, and modify the controls for CV input?
lizlarsen
That's a good idea, bitSmasher. You'd want to have one that can generate a color field all on it's own. A lot of these devices with faders use a ~5V control voltage coming out of the relevant slider anyway.
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