# Why 'more or less stopped using ISO'?

Started 10 months ago | Questions thread
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 Re: Maybe this will help. In reply to crames, 10 months ago

crames wrote:

bobn2 wrote:

How does brightness figure into this? That is, CIE brightness, or are you using another definition?

I don't see how the connection between luminance and brightness would cause there to be "no such thing as ISO."

You can calculate a brightness for an sRGB value of 118, since the viewing conditions are defined and you have enough info to plug into a CIECAM02 calculator.

What would be the brightness for an sRGB value of 118, in candela per square metre?

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Bob

CIECAM02 brightness correlate Q of the 8 bit sRGB value (118,118,118), Q=102.28.

Candelas per square meter are the units for luminance, not the unit-less brightness, so your question doesn't make sense.

You're obviously fishing around for something, without explaining how brightness, that is CIE brightness as discussed in this sub-thread, has anything to do with the existence or non-existence of "ISO."

Apparently "'brightness' is dependent on 'absolute luminance of the stimulus' ".

While you mull things over,

Sorry, you have the mulling the wrong way round. It's you that needs to be mulling. Apparently 'brightness' is dependent on 'absolute luminance of the stimulus' and yet we find that 'brightness' has nothing to do with luminance, so mull that one over.

here's a question for you, Bob:

I take a picture at f/16 1/100 ISO 100. Now I want to take another shot where the final image is twice as bright. What ISO setting should I use?

I wouldn't be using f/16, 1/100 in the first place, so it's a hypothetical. But I wouldn't be using 'ISO' or exposure to set the brightness, whatever.

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Bob

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