Wave Form Monitor - understanding

[Ian Chapman]

Wave Form Monitor - understanding
Hi All...your help, experience and advice would be most welcome on the following:

In different light, particularly outdoors, we all know how tricky it can be to see the LCD screens (I have both XF300 and XF100) in order to make an accurate exposure. The XF100 is particularly tricky to see compared to XF300.

My judgement is usually accurate after 18 months with the cameras, but not always. So I have recently tried to master the Wave Form Monitor.

Excluding the top and bottom of the bounding frame of the WFM area, there are six thick white lines and five intermediate fainter lines.

It seems to me, after much experimentation, that if the green 'blob' which represents the 'whites' is allowed to just touch the faint line next to the top thick white line (that's the one next to the top of the whole frame) then the exposure is pretty much spot-on and allows the highlights to be retained (i.e. not burn out) and the main exposure to be as accurate as I could hope for.

Would this observation be consistent with your own findings?

If not, then can anyone reveal a more accurate way to interpret the WFM and it's mushy green output?

many thanks...look forward to your replies

Ian

[Rodolfo Pena]

Hi, I also wanted to learn more about the understanding of waveform monitors and Vector Scopes and I found a very useful PDF that may help you too.

http://blog.ieba.com/wp-content/uplo...formVector.pdf

[Graham Bernard]

Rodolfo, thank you! - Very simple to grasp and I learnt more of those about those tiny Pluge bars too.

Cheers

Grazie

[Bruce Watson]

Originally Posted by Ian Chapman

...if the green 'blob' which represents the 'whites' is allowed to just touch the faint line next to the top thick white line (that's the one next to the top of the whole frame) then the exposure is pretty much spot-on and allows the highlights to be retained (i.e. not burn out) and the main exposure to be as accurate as I could hope for.

Not what I would do. But it might work for you.

First a WFM is a great and useful tool that you'll want to learn to read. The "green blob" is the luminance values for the scene in question. It's not "the whites", it's all the luminance values from shadows to highlights. The horizontal "white lines" are indicators for various IRE values, usually from 0 (shadows) at the bottom to 100 (highlights) at the top (like the ruled lines on graph paper). Some WFM go higher than 100 and lower than 0. Some have a line for 7.5 IRE which is "black" for older NTSC broadcast systems.

If all you want is to keep from clipping highlights, then your assumption is close enough -- keep all luminance values below 100 IRE. But if this is all you are looking at, you may still get a less than optimum exposure. You may end up crushing your shadows, for example, or getting less than optimal exposures for human skintones (which can also lead to color issues).

Typically what many people do is to try to keep skin tones in the range of 30-75 IRE, then alter lighting to control shadows and highlights to keep them withing the 0-100 IRE range. The reason for this is that viewers are sensitive to skin tones, and need to have them in this range to be able to easily see skin detail. If you take a darkly complected face down below 30, it becomes difficult to separate that face from the shadows, or see skin texture. If you take a lightly complected face above 75, it becomes difficult to separate that face from the highlights and see skin texture. There are, of course, plenty of exceptions to any rule of thumb. Suffice it to say, YMMV.