# Setting Exposure with Standard Gammas – Use your judgement!

First take a long look at the image to the left. look at the 3 small grey boxes. What do you see?
Is the middle of the three grey boxes brighter than the others? Does the bottom small grey box look about the same brightness as the top one?

This post comes as the result of a discussion going on elsewhere about how to correctly expose when using standard gammas. Basically discussing how to expose when your not going to do anything to your footage in post,  for what I would call “direct to air”.
There are many ways of setting exposure. You could use a light meter, you could use zebras,  you could use a waveform monitor or histogram.

Lets imagine that grey box is a face. If you were using zebras you would normally set them to between 65% and 70% and then expose the shot so the face exhibited the zebra pattern over any parts of the face not overly highlighted or in shadow. This is the textbook way to expose using zebras. Another way to expose might be to use a mid grey card (also known as an 18% grey card). With standard and cinegammas you would normally expose this at 50% using the cameras histogram, waveform monitor or spot meter. Again this is a textbook, technically correct exposure. But this is the real world and the real world is very different to the theoretical world because light plays tricks with our eyes and the overall brightness of a scene can change the mood of the shot.

Lets say you have a room with dark coloured walls.  At one end is a window and you have an actor standing at each end of the room, one against the dark wall, one against the window. We have two shots in our scene, one looking at the actor against the dark wall, one looking at the actor against the window. What happens if we expose both faces using zebras to exactly the same textbook 65% level? Well the face against the window will look darker than the face against the black wall. Look back at the grey boxes on the left. The top and middle grey boxes are exactly the same brightness but because the middle box is against black, to our eye’s it appears brighter than the top one. Now if we were to use a histogram or waveform monitor to expose these two shots, all the extra white in the window shot might tempt you to reduce the exposure, this would make the problem even worse. In fact to expose these two shots so that the faces match as you cut between them you need to reduce the exposure on the darker shot. Looking at the grey boxes again the lowest box is actually at 45% while the other two are at 65%, yet the lower box appears to be about as bright as the top box.
So what am I trying to say? Well exposure isn’t all about setting object “X” at exposure “Y”. You must use your judgement and a known monitor or viewfinder to asses your pictures. Learn to interpret what your monitor is telling you, learn to recognise scenes that may need to be exposed away from the text book values and methods. Above all else don’t be afraid to expose for what looks right, as opposed to object “X” at value “Y”.
I suppose to follow up on this I should tell you how to calibrate your viewfinder or monitor… I’ll do that soon in a later article. Did you find this useful? let me know, I’m planning on writing more about dealing with light and lighting.

# Low Light Picture Profile for EX1/EX3

I get asked a lot about settings for shooting in low light with the EX1 and EX3. To be honest there is not much that will make a big difference that can be done, beyond adding in camera gain. There are a few tweaks you can make to the picture profiles that will help minimise noise levels and give a slightly brighter picture without resorting to overall gain and I’ll go through those here.

Gamma: By using a brighter or higher gain gamma curve you can get a slightly brighter image without an across the board gain increase. Do however consider though that gamma does add gain so a brighter gamma curve has more gain and thus more noise than a darker gamma curve. Where you light range is limited or controlled then I recommend using Standard Gamma 2 with the black gamma set to +40. Raising the black gamma helps lift shadow and dark areas of the image. For scenes with bright highlights then it’s useful to have some extra dynamic range and in this case I would choose cinegamma 4, again with the black gamma raised, this time to +50.

If you are happy with turning detail off altogether then this may be a wise choice as it will prevent any noise from being enhanced. If not in order to keep the appearance of noise to a minimum I would decrease the detail level to -10. As we are shooting in low light then I will assume there are a lot of dark areas in the image. To keep noise less visible in low contrast areas I would set the crisping to +50.  This will slightly soften the image but help control noise.

There are two principle forms of noise, chroma noise and luma noise. There’s not much we can do about luma noise other than controlling detail enhancement as above, but if we reduce the image colour saturation we can reduce the chroma noise. Better still using the low key sat function we can just reduce the chroma (colour) level in low key parts of the shot. So for my low light profile I would set Low Key Sat to somewhere around -50.

So by changing the gamma we can increase the sensitivity a little, turning off the detail correction or using crispening we can ensure that the visibility of any noise is as minimised and the Low Key Sat function will keep the noise to a manageable level.

These setting won’t turn your EX1 or EX3 into a mega low light monster, but they will give a small boost to the low light performance before you have to resort to adding gain. Talking of gain, do make sure you read this to understand what gain is doing.

EX1/EX3 Picture Profile suggestions for low light:

Gamma Standard 2, Black Gamma +40  OR Cinegamma 4, Black Gamma +50

Detail OFF or Detail Level -10, Crispening +50

Low Key Sat -50

Black level -3 (restores black to zero)