X20

Started Jan 16, 2013 | Discussions thread
Mark H
Senior MemberPosts: 2,813
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Re: IS0-4000~12800...
In reply to Steen Bay, Jan 21, 2013

Steen Bay wrote:

Mark H wrote:

Steen Bay wrote:

Mark H wrote:

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).

According to the X10 specs ISO 4000, 5000, 6400 and 12800 are with boost.

Where? I've not seen that stated anywhere.

In DPR's X10 specs, and also the specs in DPR's X10 review.

I wouldn't rely on that information - Fujifilm themselves certainly don't say that anywhere.

It looks to me like DPReview may have misread the Fujifilm X10 specification's foot notes which only refer to the smaller JPEG image sizes at those ISOs.

As I describe below, there is no reason to use 'extended' ISO, right up to ISO-6400 at least.

It might be argued that 'EXR-SN' is a form of 'extended ISO' - but I'd argue not, because it still produces full 12 bit signal/data off the A/D.

Those X10 ISO's produce smaller JPEG image sizes (4000~6400 it forces 6MP 'M' size and to use 'EXR-SN') and no RAW output - but I haven't seen any statement regarding 'boost'.

Because X10 ISO-4000~6400 uses 'EXR-SN', the 'internal ISO amplification' is actually the same as that of up to 3200, but the signal is doubled up by the analogue summing of pixel pairs.

The ISO-12800 value is more likely to be an 'extended/boosted' setting - but is almost certainly still based on 6MP 'EXR-SN' raw signal/data.

Of course, the X20 doesn't have 'EXR-SN' capability, so is different in at least one respect.

Incidentally - at the high ISO end, there really is not detriment to using 'extension/boost', because the high noise levels render the high bit depth completely redundant. Visually, an 8 bit/channel derived high ISO image is very often indistinguishable from a 12 bit/channel derived one, particularly so in a smaller (thereby noisier) sensor.

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