How do you use a Waveform?

A

aurantaurant

Well-known member
Here's a question from a dum dum.
I've never used a waveform before because with DV you could essentially just eyeball the footage and be okay. But since I have it now on the AF100, what's the proper way to use this tool? I'd like to know.

Is it for exposure or color or something else?

Anybody have a quick reference? I tried looking for something online, but it didn't seem to explain it very well.
 
(if you're in the USA) did you send in the coupon for the AF100 book? I have an introductory tutorial in there for using the AF100's waveform monitor.
 
What about those of us who do not have an af-100 book on the way?

I have noticed that sometimes when people ask a question that is covered in one of the many books that Barry has put out, the answer is to check the book. I remember one of my first posts on here was about the settings in the DVX and what they did. The response was to buy the book, which I did and it was extremely helpful. However, would it would have been helpful for someone to link me to a thread where it had been discussed or share some basic information on the subject and direct me to the book for a more detailed description.

So to answer your question.
http://www.ehow.com/how_2224289_use-waveform-monitor.html
There is a basic overview of waveforms in general.

And yes, without having touched an af-100 or read the book, I would suggest looking at Barry's book for a much better description.
 
Last edited:
I share pretty much everything I know for free. In response to the OP's original request, him being an AF100 owner, I answered him (not the world in general) as to where he could get info for free (since he's already entitled to it for free). That's all.
 
I'm not sure how simple or technical of an answer you want, but basically its a graph where the the x axis is the location of a pixel from left to right and the y-axis represents the pixel's luminance value measured in 0-110 ire (basically how bright it is, where 100 is white and 7.5 is black for video, its a little more complicated than this depending on whether you want to use superwhite or superblack, but I'm not getting into that at the moment). It graphs every pixel in the video signal in real time. It is good for seeing in general how bright parts of your scene are. For example, if you have a person standing against a green screen with most of the screen to either side of them, you should see a cluster of points making a line on either side of the waveform, and the level of the line is the luminance value of your greenscreen, and if the line has a lot of stray points above and below it, your greenscreen may not be that evenly lit. If youre against a white cyc that you want to blow out, you probably want those lines on either side of the person in the center to be up at or above 100 ire, and you probably want most or all of the area in the middle where the person is to fall below 100 ire.

Let me know if that makes some sense.
 
Last edited:
Hey Barry I have edited my post because I feel it may have come off the wrong way. I just think it would be helpful for people to share what they can and maybe recommend the book as well. As it would help people who just stumble upon the thread wondering what a waveform monitor is and does.
 
Adam J McKay said:
Hey Barry I have edited my post because I feel it may have come off the wrong way. I just think it would be helpful for people to share what they can and maybe recommend the book as well. As it would help people who just stumble upon the thread wondering what a waveform monitor is and does.
Click to expand...

Hey, no problem, the site here is all about free information, it's just that it's like 12 pages in the book so it's not really something I'd copy-and-paste into a response... :)

But yes, external links are certainly welcome and would assist any future readers.
 
Just throwing in my two cents, but knowledge has fiscal value (the basis of all educational systems) and as someone who makes a living off of producing documentaries and training courses; my career is based on that principal.
 
Yes to audio being clipped, particularly in the analog world. If you are over 110 in broadcast, it can pop or clip the audio coming out of the tower.
 
jaypass said:
Just skimmed that article...

"That upper end is not absolute, but too much brightness can leak into your audio, causing noise there when your video is broadcast."

Is that true? I've never heard of or experienced anything like that before!
Click to expand...

This is not a camera issue per se, it has to do with the picture signal over modulating a broadcast radio frequency transmission beyond its bandwidth limit and cross modulating the audio band. When a video goes to broadcast it should fall within legal bandwidth constraints defined by the IRE range from 0-100. Analog NTSC used a 7.5 IRE setup for reference black, but digital does not.
 
jaypass said:
Just skimmed that article...

"That upper end is not absolute, but too much brightness can leak into your audio, causing noise there when your video is broadcast."

Is that true? I've never heard of or experienced anything like that before!
Click to expand...

Latest gen video cameras are moving beyond the dynamic range that broadcast formats can render. This is great for us as shooters, but how one maps the wider dynamic range to fit the narrower range of the broadcast medium it will be viewed on needs to be addressed in post. Much like still photographers tone map HDR images to fit the limited DR range of prints, we will have to make creative choices in how we grade for highlights and shadows.
 
jaypass said:
Just skimmed that article...

"That upper end is not absolute, but too much brightness can leak into your audio, causing noise there when your video is broadcast."

Is that true? I've never heard of or experienced anything like that before!
Click to expand...

I'm sure you've heard/seen it, but weren't thinking of what it was... it happens most often when a graphic is inserted that is too bright (the logo at the end of a commercial)... it is accompanied by an unpleasant "buzz" in the sound.
 
jaypass said:
Just skimmed that article...

"That upper end is not absolute, but too much brightness can leak into your audio, causing noise there when your video is broadcast."

Is that true? I've never heard of or experienced anything like that before!
Click to expand...

In the good old days of NTSC Broadcasting, the image was broadcast as a negative, that is black used more power than white. To high a white level could send the carrier to zero and blank out the signal; you would hear it as audio noise.

Today in the digital world with 8 bits, the numbers go from 0 to 255. It's impossible to go higher than 255, so the impact with the audio is impossible.


Bob Diaz
 
You must log in or register to reply here.
Back
Top