Master Pedestal Setting?
 

I'm trying to understand the possible gamma-settings on my XL2.

The effect of "Setup Level", "Knee" (high, medium, low) and "Black" (stretch/normal/press) are obvious to me.

But I have no exact idea what exactly the "Master Pedestal" does...

The Canon Website says: "The Master Pedal controls the starting point of the gamma curve." That can't be true, at least it's ambiguous. Changing the starting point of the gamma curve would be rather like the "black" or "setup level" setting?

Am I missing something?

(looking at the resulting video image, the pedestal setting seems more like a general gamma value)

Take a look at the XL2 Video Tour.

Go to http://www.dvcreators.net/ and click on "Watch the XL2 Feature Tour Video" to see about Master Pedestal.

Jay

The master pedestal is used to lighten or darken areas shadowy or dark areas. It is most helpful when you have a stark contrast between your background and foreground...



ash =o)

...isn't that what the black stretch/press does?

(I assume you know that, of course... but I'm just trying to figure out what exactly the master pedestal and black-stretch functions do. Obviously they both manipulate some part of the low end of the gamma curve, and they do that in a different way...)

I'd also like to see more info about the difference between using black stretch/press and the pedestal/setup parameters.

Master Pedestal is the adjustment of where the curve bends back to the left if viewed on a graph. Black stretch/press determines how fast the curve slopes towards zero after the pedestal starts. Setup is the absolute bottom limit. It's the opposite of white clip, the absolute top limit.

Master Pedestal can be thought of as the opposite of knee point. On some cameras, the knee point can be specified as well as the knee slope.

-gb-

Pedestal effect the ENTIRE image, not just the blacks. Though it is not technically correct, I have gotten to where I describe the Setup Level and Master Pedestal as Brightness and Contrast =o)



ash =o)

With all due respect Ash, Canon and I disagree with you about pedestal. Pedestal gets its name from the more or less flat area that occurs in dark areas before the gamma curve kicks in. IOW, it looks like a pedestal.

From Canon's website regarding the XL2 features...

Are you sure you weren't referring to Master Gamma? That will shift the entire gamma curve up or down but is not adjustable on the XL2.

My understanding is that the NTSC DV pedestal is 7.5. If the XL2 is set to a Master Pedestal value of 0, is that the same as 7.5 or is it 0? If it is zero, what is the setting to get it to 7.5?

You are referring to Setup, and the default value of 0 equates to a setup level of 3.0 IRE according to Canon's website.

Setup is the absolute minimum black level the camera will output. NTSC requires no less than 7.5 IRE because beyond black is where the horizontal and vertical sync pulses occur.

This is all going to go away as we transition away from NTSC analog to ATSC digital.

-gb-

Gents

Thought I would throw in my experience with these settings.....

BLACKS: Adjusts the 'dynamic range' in the shadows.... does not adjust the lightness or darkness in the range.
[stretch] - emhasises the contrast, and gives you a 'range' of blacks.
[press] - does the opposite, it deepens the darkness and gives you less contrast in the shadows.
EG. Man in black suit next to a black curtain..... [stretch] - separates the man from the curtains. [press] - makes him 'blend' into the curtains, and 'detail' is lost.

MASTER PEDESTAL: Affects contrast AND also adjusts the overall shadow areas.
[-] - Makes dark areas darker AND increases the contrast.
[+] - Makes dark areas lighter AND reduces the contrast.

As you can see there is a subtle difference between these two settings.

Just to complete the picture....

SETUP level is used to adjust the 'black level' of the actual video signal.
[-] - gives you an overall darker picture
[+] - gives you an overall lighter picture and brightens the shadows.

Best thing to do here is to set up the XL2 in a dimly lit room. Connect a monitor to the output ( dont use the viewfinder ) and play with these settings, with the XL2 pointing into a dim corner of the room. Focus on a dark object against a dark background.

Hope this post helps a little with the discussion.

Regards

Steve

That video's description of these features is really nice. Thanks for pointing it out.

I must be needing glass....cant seem to find the video on this link page?

I remember it was on DVcreators some time ago........

Here's an alternative.....

http://syndicate.tentoe.com/canon/De..._demo_tour.mov

Hope this helps.

Cheers

Steve

I am not talking technical, I am talking practical. I try to explain these things in terms of what makes sense to people. I fully understand the pedestal settings as I am a frequent Vari shooter which has a pedestal for each color. Truth is, with the DV compression and the DV color space, certain terms become murky.

When I say the MP effects the entire image, I mean it effects more than just the BLACK areas. Anything DARK will appear less dark when you turn up the pedestal.

It is all semantics really, the important thing is to understand how these settings PRACTICALLY effect the image and adjust them according to your needs. Out of the box I feel that Canon starts the MP and setup level too high.



ash =o)