Exposing from a white balance card

K

KevinP

Well-known member
The Waveform on the HPX is a great tool.

For exposure, what I started doing is using a white balance card in front of the talent - then using the Waveform to expose that area to 75-80%. I thought this would be a quick reliable way to ensure proper exposure.

However other threads on here are suggesting the HPX would benefit from being exposed at a higher level than 75-80. Some suggest 95-100% - and I must admit that while it always looks good I do sometimes think the footage needs a bit of a kick.

What is your feeling about getting the right exposure level for nice looking footage and what level of exposure to aim for?

I know all scenes are different but a white card as a standard reference must be a good start? - so what level to expose that to?
 
I would look up the "zone system." If you understand that then you should know how to expose properly, and why.

If your going to use a card, use a 18% grey card and expose it to %55 on your waveform. However, as you said you might not want every scene to have 18% grey pegged at 55%. Plus the HPX gammas do certain things to the "zones" in your scene so they are not necessarily all spread out evenly across your dynamic range. For example, depending ON the gamma, you might have 6 zones below the 55% mark and the other 3 or 4 above instead of 5 below and 5 above. So your zones might look like this:

I - II - III - VI - V (45%) --- VI --- VII --- VIII ---

Generally I expose white skin tones at 60%- 80%, 70% being the norm with the highlights, 80% max, unless I'm going for an overexposed look. Remember, exposure is relative to what you want you scene to look like. However, with HD video its generally better to use as much as your dynamic range as possible to avoid noise. Get your look though your lighting ratios. 2:1, 4:1 ect.

Using a white card at 100% isn't really correct because 100% technically would be pure white with no detail (broadcast safe that is) and I defy anyone to find something white in real life that has no detail at all. You really want to see where the middle part of the scene is going to fall (that being 18% grey) or even more importantly, your skin tones, and let the rest of the scene fall where it may (being careful of blow outs of course). Preserving your highlights might cause you to underexpose the rest of your scene if you can't fix it with lighting but you have to decide whether or not what you see in the highlights is worth preserving. For example, fixing a window blow out (100% pure white) with exposure might cause the rest of your scene to be dark while exposing for 18% grey in this situation would let the window blow out but would give you detail in the rest of your scene (indoors).

That was longer than I expected, make sense?

http://en.wikipedia.org/wiki/Zone_System

http://dpanswers.com/content/tech_zonesystem.php

http://www.normankoren.com/zonesystem.html
 
Many thanks Jimmy - some good pointers for me there - I will go and check out the Zone system now.
 
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