Started Jan 16, 2013 | Discussions thread
Mark H
Mark H Veteran Member • Posts: 3,491
Re: IS0-100~200...

Steen Bay wrote:

Mark H wrote:

Steen Bay wrote:
Yes, ISO 100 on the X10 is clearly a 'real' ISO. According to DxO the measured ISO at ISO 100/200 is ISO 124/232, so ISO 100 has almost 1 stop higher saturation capacity than ISO 200.

Not really - (although it depends exactly what/how you measure).

In normal usage, with the camera metering by the respective ISO settings, IS0-100 and ISO-200 would have just the same highlight range relative to their respective exposure levels (assuming 'DR100%').

Relative to the cameras metering, yes, but the X10 sensor can 'handle' almost twice the amount of light/photons at ISO 100 as it can at ISO 200 (assuming 'DR100%')

As I said - it 'depends on what/ how you measure'.

So in 'absolute' terms yes - in 'relative' terms no.

The one difference is, that ISO-200 only uses the lower 50% of the sensor range, and completely discards the upper 50% (that may or may not contain any signal) - but relative to each respective ISO's mean exposure level their highlight ranges will still be the same.

The exception to this though is, that at ISO-200 then 'DR200%' (non EXR) can be facilitated by re-utilising the otherwise unused/discarded sensor's upper 50%, thereby adding an 'apparent' extra 1EV of highlight range (albeit at the expense of higher ISO/noise/lower exposure).

Don't know why ISO 125/160 also are missing on the X10, but although the missing ISOs don't tell us anything in itself, then I still find it most likely that ISO 100 is an extended ISO on X20. Partly because it is on the other cameras with X-Trans sensors, and also because there isn't a single ISO 100 image in Fuji's X20 gallery.

Well for that to be true, all of Fuji's published spec's, the printed brochure and website, would all have to be incorrect/omitting to say so - not impossible, but seems unlikely at this stage.

It's not just ISO 100, it also at the other end of the ISO scale. Does it seem right that ISO 12,800 is a 'normal' ISO on the X20, while it's an extended ISO (or 'with boost') on X100S, X-E1 and X-Pro1?

That is a reasonable and valid observation (although still no different to the X10).

Note that DPReview have since updated their X20 spec's to include ISO-100 since they first published, although whether that was in response to readers like me, or whether they double checked with Fuji, who knows).

As for Fuji's gallery photos - to quote one of the photographers, they were taken with an "...early pre-production version of the X20 with basic firmware" , and it's possible, if not likely, that those cameras' firmware may well have had a lowest setting of ISO200, but this has since been changed to ISO-100.

Only time will tell.

Yes, we'll have to wait and see.

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