Knowledge refresh: ISO

cuthbert

cuthbert

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A long time ago, I read that it was always better to use the full stop increments (eg, ISO 100, 200, 400, 800 etc) than the in between values because the in between values were effectively software interpolations - in other words its better to use ISO3200 and apply slightly more noise reduction than to use ISO2000 even if the later gives me a decent enough shutter speed because there will be more detail recorded - especially if you need to increase the exposure in raw.

So, firstly... was this even true in the first place? And if it is, does it apply today with modern sensors?
 
I've read this too, but have never found evidence in my own images to back it up.
 
I can't remember for sure but don't the intermediate values work by the camera applying exposure compentation ?
 
the reason i started to doubt it is because it really doesn't make any sense, logically.

the entire concept of the "ISO" is a purely human construct, a hang over from the film days, somebody just calibrated the sensor's internal gain to 100, 200, 400 etc ASA film (or as close as possible), but given that the sensor's gain isn't really much different from a volume control to say that the quarter/half top increments would be software interpolated would suggest a huge amount of unnecessary over engineering.

i could perhaps understand the theory that software interpolation would be needed if the camera lets you select completely arbitrary ISO values (say 103ISO, 231ISO etc) but the number of selectable ISO values on my camera is 32 it would surely be easier to pre-determine these in the same way you determine the full stop values and write a shed load of code to do it?

maybe it's an urban legend?
 
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I'm sure that I've read in more than one camera review that performance is best at some intermediate setting (for that camera)... so these days I don't think you can automatically assume that you're going to get the best out of your camera at ISO 100, even assuming you have ISO 100.

One thing with digital though is it's easy to take a few shots and see if you can decide what your camera is best at.
 
I always thought.....

Taking a shot at "between native" iso involved the camera pushing the exposure from the previous native iso. This can introduce more noise, so you're better off moving to the next native or potentially pushing it yourself in PP, which could produce a less noisy result due to pp software doing a sophiticated job.

I also don't know if any of this is still considered relevant.
 
Glad I am not the only one!! I am sure I also read similar, 2000 ISO for example is worse than 3200. Never tried, always kept to 'proper values' like 200, 400 etc...
 
Somewhere on the internet (but I can't find it now), there is a scientific paper on this. They compared two Canon DSLRs, something like a 30D and a 5Dc. The finding was the 30D was better at the "full stop" ISOs, but the 5Dc was equally good at the intermedates.
 
I'm sure it's all interpolation but not sure any of it matters like we read.

I did a thread a while ago some may remember...

The theory was that anything under ISO800 could be adjusted in post to give the same results with higher ISO's and the results were pretty close to being identical.

Interestingly enough, if you wanted too, you could leave your camera in manual at it's detail peak ISO whatever that is for the particular camera and adjust in post to get the same results as you would by adjusting the ISO for that particular shot.

Its not something I've really practiced since doing the test but very interesting.

Back to the original question: I know my D7000 is better at 5000 than 6400.
 
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