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“My Impression? Fujifilm X-H2S High ISO Performance is 1.5 Stops Better than X-T4 thanks to Four Analog to Digital Converters” – REPORT


ISO Boost?

So far we know (and it has been well documented) that the Fujifilm X-H2S has a vastly improved dynamic range performance in video over the the previous generation sensor, with 14+ stops compared to the previous 12 stops).

But so far we don’t have any word about the dynamic range or ISO performance for stills. And that makes sense, as it is pre-production and we better wait for the final thing before we make any judgments.

With this disclaimer printed clearly on top of the article, I’d like to share a video overview of the X-H2s plus new lenses shared by Ringfoto.

It’s in German, so let me translate the part I’d like you to hear.

Martin at Ringfoto shows samples he took with the Fujinon XF150-600mmF5.6-8 of his cute dogs running around. He talks very positively about the autofocus.

Then he addresses the concern that f/8 at 600mm (900 equiv.) might be perceived as too slow by some, as you will have to shoot at higher ISO. But here is what he says:

Opposite to other X-Trans cameras, the X-H2S has four analogue-to-digital converters [admin note: X-T4 & Co have two A-D-C]

Thanks to the new sensor and new technology inside the camera and the four analogue-to-digital converters, my feeling with this pre-production X-H2S at this point is that ISO performance on X-H2S is 1.5 stops better than on the X-T4, which would be sensational.

I want to be careful for now, but it looks very promising.

So what is Ringfoto talking about when they mention the analog-to-digital converter (ADC)?

We know the Fujifilm X-T3 and X-T4 (and all other ISOless or ISO invariant Fuji cameras) have two analogue-to-digital converters. On the X-T3 it works like this: every image recorded under ISO 640 “travels” through one ADC, and every image above ISO 640 goes through another ADC. This helps to improve noise performance.

This can have the paradoxical effect that an image taken in camera at ISO500 can be more noisy than an image taken in camera at ISO800 or even ISO1200, because after ISO640 the other ADC kicks in to improve performance, as you can see at the photonstophotos technical chart here.

What the real life implications of this are has been explained by Rico in several articles, such as the GFX 50 Series is an ISO-less Classic

What’s important for us to know in this article, is that those analog-to-digital converters are a good thing when it comes to noise performance.

And now that we know thanks to Martin that the Fujifilm X-H2S has four AD-converters as opposed to two ADC in the previous X-Trans cameras, then this could indeed explain what Martin observed: a sensational improvement in ISO performance.

Now, to my knowledge Fujifilm has not made any public statement about the increased number of ADC or about the improved ISO performance in stills.

All we could observe until now is that in video the noise performance is shockingly good, as documented also by Gerald Undone and we reported here.

My final word?

Well, there is no final world.

I will wait for final production samples to be tested side by side with other Fujifilm cameras. And this is what also Martin at Ringfoto said, that he wants to validate (or not) his impression with a final production camera.

And once he did that, I will do my job, report and translate his findings for you.