# Dynamic Range -- what it is, what it's good for, and how much you 'need'

Started Oct 17, 2011 | Discussions thread
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 Math In reply to boggis the cat, Oct 20, 2011

Lots of verbiage elided.

boggis the cat wrote:

From 24x36 to 15.8x23.6 is about 1.2 stops.
From 15.8x23.6 to 13x17.3 is about 0.73 stops.

(Using "stops" to denote "noise equalisation through ISO change" and not exposure, obviously.)

And?

That's for "1.5x" APS-C.

That's for Nikon DX, yes. The best APS-C cameras available at the moment.

Canon APS-C is 14.8 x 22.2 mm, or 1.4 and 0.55 "stops" respectively.

They aren't "stops" , they are stops .

These calculations ignore the additional aspect ratio efficiency of 4:3 over 3:2, which is roughly 4%. This changes e.g. the Canon APS-C to FT ratio from 0.55 to 0.49 "stops", and the 135 to FT ratio from 1.94 to 1.89 "stops".

You lost it there.

Do you really think that calls for an adverb like 'considerably'?

Is 1.2 litres considerably more than 0.73 litres? It's not that far from double the amount, Rikke.

Are liters an exponential measure, Boggis? Stops are:

exp₂(1.2) = 2.3
exp₂(0.73) = 1.7

2.3/1.7 = 1.35, not even close to double the amount, Boggis.

1.2 stops are 15% more than 1 stop.
0.73 stops are 15% less than 1 stop.

We are talking deviations of less than 1/6. For all practical purposes insignificant. How accurate do you think the labeling of your aperture and shutter speed settings are?

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Rikke