When I do camera training workshops, one of the things that constantly seems to confuse people is the Waveform Monitor (WFM). I just had an email from someone I did a one on one Canon C300 workshop with saying that he had gone back to using zebras as he just couldn’t get his head around the WFM. So I sent him a rather long explanation in the hope that I’d clear it up once and for all. I thought it might be useful to others:
Problem with using Zebras is they are only telling you one thing. If you set them to 70%, then they will appear when exposure hits 70% luminance. If you use zebras often, you’ll probably be pretty good at seeing where they appear, then knocking exposure up or down a bit. But it’s still a guess. The WFM takes away any guess work with your exposure, so I highly recommend getting your head around it.
The waveform monitor is looking at luminance values. Blacks to whites, or 0% to 100% luminance.
To easily get your head around what you’re seeing on a WFM, lets separate left to right and top to bottom.
FROM LEFT TO RIGHT:
Looking just from left to right, this is a luminance representation of your image. So if something is on the right of frame, it will show up on the right of your WFM. Simple!
FROM TOP TO BOTTOM:
You have lines going from to to bottom. Those lines go from absolute black 0% at the bottom, where the image is so black, there is no real information being captured except black (It would be hard to pull any detail from the grade), to absolute white 100% at the top. This is when you over expose and blow out any detail in the highlights. This is definitely something to be avoided. The middle line represents middle grey *(on a regular profile – keep reading!)
All the highlights, all the blacks and all the ranges of grey in between. This is what you are looking at on the WFM. That’s why it beats using zebras hands down!
Sometimes you’ll have stuff sitting right on the bottom line – absolute black. That’s ok. There are shadows, people with black coats, night shoots etc. Just remember that you won’t be able to ‘see into’ these shadows if you want to later in the grade. Likewise, sometimes bits of your image will go past 100% white. It ain’t pretty to have blown highlights, but again, it’s unavoidable sometimes, especially shooting in uncontrolled environments such run and gun doc work!
With the C300 WFM, the 0% black and 100% white lines are actually the lines 1 step away from the top and bottom edge of the WFM box. Very helpfully, the last C300 firmware update has stuck in a little 100 and 0 to be clear 🙂
So what you’re looking for is an overall balance in your WFM, a range of luminance keeping an eye on any rouge peaks. In a controlled environment such as a completely lit interview, you shouldn’t have any blown highlights! Using the WFM is a sure fire way to check you haven’t!
Slightly trickier shooting a flat profile (Cinema on C300). This pulls all your peaks in and down. *(so your middle grey is no longer going to be on that middle line). You may feel as though your underexposing at times. The flatter the profile, the less contrast, the more compressed the wave on your WFM will get. That’s why you need to grade flat profiles!
Here’s some example images of a WFM in action (in my living room pointing at the telly). Note how highlights can blow out and go over 100% white, yet you can’t go below 0% black.
C300 with no profile: (arrows are approximate – and please overlook the fact I didn’t bother focusing!)
So in the above example, I’ve completely blown out the window and books, but the rest of the shot is exposed ok. It’s an awful shot! Maybe cinema profile will help!
C300 with Cinema Profile:
Window is still blown. I could probably stop this down a bit, get a little more out the highlights. But overall it’s a terrible shot designed to show range on the WFM!
Just to be really really clear. If that window happened to be at the bottom right of the screen with a blind pulled over the top – it would STILL show up at the TOP right of the WFM. Just as the black shadows inside the cabinet are about half way up the frame, but are represented at the BOTTOM of the WFM. Remember, we’re looking from left to right at the luminance levels!
With a flat profile, you’re blacks will no longer sit on 100% black line, as they are actually grey. Even if you stick the cap on the lens.
I hope that’s helpful! If you’re still on Zebras and thinking about getting that WFM up, do it! It will all become clear with a bit of use, and you’ll never look back!
Here’s a few more examples from Premiere, I actually shot this on a Sony F5, which has an incredibly flat image. You’ll notice that even with the F5’s amazing dynamic range, we still blew out a few highlights. This is what happens when you shoot in a dark market with only natural light. If you want to watch this little doc, you can see it here.
On the Premiere WFM, 1 is 100% white and 0.3 is 0% black. Just to confuse you!
Flat profile (S-LOG 2) straight out camera, and then graded image: