Fuji ISO Cheat?

Started Mar 27, 2014 | Discussions thread
Ray Sachs
Ray Sachs Forum Pro • Posts: 10,580
Re: Fuji ISO Cheat?

ebjerke wrote:

MikeNannie wrote:

I found this comment on the Sony Rumors website, but it's been insinuated various other places as well.

"At same marked ISO, and same aperture, fujifilm needs double the shutter time to achieve same brightness as nikon, that I call a cheat."

Not trying to start a war here, but I'm curious, as someone considering purchasing an X-T1 in the next couple of months, has anyone tested this claim?

Seems like a ridiculous statement to me, but I have no way to test it.



No need to test it, Mike. Dpreview has done it for you, well, at least with three other cameras which I THINK (someone will correct me) use the same sensors. Here is what they have to say:

"The actual sensitivity of each indicated ISO is measured using the same shots as are used to measure ISO noise levels, we simply compare the exposure for each shot to the metered light level (using a calibrated Sekonic L-358), middle gray matched. We estimate the accuracy of these results to be +/- 1/6 EV (the margin of error given in the ISO specifications). Note that these tests are based on the sRGB JPEG output of the cameras, in accordance with ISO 12232:2006, the standard used by camera manufacturers.

By our tests, the X100S's measured sensitivities are within 1/6EV of indicated, which is within the tolerance allowed by the ISO specification. In other words, ISO 100 indicated = ISO 100. Interestingly, when we looked at the X-Pro 1 and X-E1, we found that their measured ISO sensitivities are about 1/3 to 1/2 stop lower than marked. This discrepancy (which has little importance for real-world photography) explains why the X100S's measured noise in Raw mode appears higher than these cameras overall (see graphs below). In JPEG mode, the X100S's measured noise is a little higher than the X-Pro 1 and X-E1 at lower ISO sensitivities, and a fraction lower at the very highest ISO sensitivities. This is due to changes that Fujifilm has made to its noise-reduction algorithms - changes which again, make a negligible difference in everyday photography."

And yet in the XE2 review, again with the same sensor, they conclude:

"By our tests, the X-E2's measured sensitivities are around 1/2 - 2/3EV lower than marked, which is unusual for a modern camera. This means that for any given light level, the X-E2 has to use a significantly slower shutter speed, brighter aperture or higher ISO to get an image of the same brightness as an accurately-rated camera.

It's unusual to see this sort of discrepancy and we're disappointed that Fujifilm persists with a system that, while technically compliant with the ISO standard, ends up appearing rather disingenuous.

The X-E2, in common with previous X-Trans cameras, does a great job of keeping noise to a minimum while retaining detail. Up until ISO 6400, it comfortably out-performs most of its peers, both in terms of noise level and detail retention. Above that, where the lack of ability to shoot Raw files suggests a simple doubling or quadrupling of data to provide the extra two stops of ISO range, the quality drops off a little, but it's still performing well.

However, a significant part of this advantage stems from the camera's need for longer exposures to achieve the same JPEG brightness level as its rivals. This is the way the ISO standard is measured, and the basis on which we conduct this test. However the X-E2's need for unusually long exposures explains much of the difference we see between it and the Sony NEX-6; in fact it's probably better compared to the performance of its peers set 1EV lower (i.e. ISO 400 on the Fujifilm compared to ISO 200 on its rivals)." (emphasis added)

In my experience, their conclusions in the XE2 review are closer to the reality I find in my shooting. I'm fine with the Fuji gear the way it is, but prospective buyers who are looking into Fuji because of it's seeming low light prowess should certainly understand what's going on here and what they're actually buying.

We judge photographers by the photographs we see. We judge cameras by the photographs we miss - Haim Zamir

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