Gain vs ISO on FS700?

P

pifemaster

Well-known member
Sorry if this seems like a very basic question. Is there any difference between setting up the FS700 to display gain as opposed to ISO. Is it just a matter of preference, or is there some real difference when choosing one over the other.

If there is no difference, I can wrap my brain around ISO a little better and would prefer to use it.

Thank you,
Robert Pfeifer
www.pifemaster.com
 
I believe it's the same thing, just different terminology.

Gain is from the video camera world while ISO is from the film camera world.
 
gene_can_sing said:
I believe it's the same thing, just different terminology.

Gain is from the video camera world while ISO is from the film camera world.
Click to expand...

yep, both that and other interchangeable terms are offered as a part of the inerface just encase the owner or op is more familiar to one set of say, dslr terms over video terms. just like shutter speed vs shutter angle, they are one and the same
 
pifemaster said:
Sorry if this seems like a very basic question. Is there any difference between setting up the FS700 to display gain as opposed to ISO. Is it just a matter of preference, or is there some real difference when choosing one over the other.

If there is no difference, I can wrap my brain around ISO a little better and would prefer to use it.

Thank you,
Robert Pfeifer
www.pifemaster.com
Click to expand...

Gain represents an analogue or digital boost applied to the signal. If you add +3db gain, you double the signal strength. After about +9db (8x the signal strength) you start getting a noticeable increase in noise.

ISO represents exactly the same thing, however, it is interpreted through the prism of the gamma curve applied to the linear Raw output by the picture profile/gamma selected. In this instance the ISO is a reference point that allows you place important tones (e.g. mid-grey, skin tones) in the right place on this curve.

Which is a round about way of saying that the base ISO/no gain added position moves about depending upon which gamma curve you have selected in the picture profile.

So, depending upon which gamma you use +0dB gain may be ISO 360, 400, 500, or 2000 and each doubling of the ISO represent a increased gain of +3dB

For example, if you select the Cine 1 gamma then the 'base' ISO of that curve is ISO 500 (as I recall). So ISO 500 = +0dB gain. ISO 1000 = +3dB gain, 2000 = +6dB gain and ISO 4000 = +9dB gain (you can generally push it this far without a noticeable increase in noise).

If you're more comfortable using ISOs, you can stick with them.
 
The nice thing about using ISO is that if you are using multiple cams it is easy to set up the same exposure.

As ISO is an actual sensitivity to light number. Gain varies with cameras and PPs.

So if you use a 700 and a Canon C100 for example in a 2 cam shoot, then if both are set to ISO 500 then your shutter speed and f stop will be the same on both cameras.

It also is easy to use a light meter to set exposure using ISO, something I often do in a audio situation.
 
Doubling of ISO is a change of one f/stop in exposure index, so represents a 6dB change in electrical power output vs light input.
 
Razz16mm said:
Doubling of ISO is a change of one f/stop in exposure index, so represents a 6dB change in electrical power output vs light input.
Click to expand...

You're right. I realised that last night when playing about with the settings! For some reason I always had it in my head that +3dB was 1 stop!
 
Here's the equation: linear = 10^(dB/20)
So +6dB = 2x amplitude
+12 = 4x
+18 = 8x
+24 = 16x
(rounded)

A way to remember is every +6dB doubles the linear output, every -6dB halves it (approx, up to +/- 30dB)
 
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