Fuji ISO and Light. Is Fuji Cheating?

I have often read online that people say Fuji cheats with ISO and the images from Fuji are constantly darker than with other cameras.  Additionally I’ve read that Full Frame intrinsically gathers more light (this is kinda  a fallacy, but more on that later).   So I decided to do a little test by photographing the world’s most interesting subject… my wall (I don’t own a TV currently so staring at the wall is a new hobby of mine).

I’ll be using my Xpro2 (therefore these results should apply to all the modern cameras) and my 1DsIII.

The Xpro2 has a 23mm f/1.4 lens attached.

The 1DsIII has a Sigma 35 1.4 lens attached.

I know ideally I’d adapt the same lens so differences in lens design (glass thickness etc.) don’t affect the results.  However, for this simple test I’ll forgo being super scientific (also I don’t own an adapter that’ll work).

NOTE: Apparently the camera I compared to (the 1DsIII) is the last camera in which Canon “cheated” as much as Fuji.  Still, this just would mean Fuji aren’t cheating any more than any other camera maker has/does.

Light gathering!

OK right into it.  Both cameras were set to the same ISO settings, f-stop and shutter speed.  In the case below that’s 200iso (Fuji’s Base ISO), f/1.4 and 1/100

Left is 1DsIII and right is Xpro2

Not a huge difference, hard to tell by looking at first.  Maybe the high end is a little more grey on the Fuji (right), but the darks seem a  bit darker on the 1DsIII (left).  Let’s have a look at histograms:

Obviously the 35mm is the 1DsIII and the 23mm is the Fuji.  Hard to tell by staring, let’s try an overlay, by which I mean I drew a line around perfectly lined up histograms:

Red is the Fuji Histogram, Aqua is the Canon.

Not enough difference to write a blog post about (but I’m gonna keep going anyway).

So, they’re not cheats?  Surely they’re doing some sort of manipulation to make them match! I mean this is heresy, suggesting Fuji aren’t cheating!!!!!!

Actually yeh, ISO itself is manipulation in a way.  The makers decide which standard they’re gonna follow (there’s two of them) and they follow it.  Why then do Fuji have a reputation of cheating with ISO?


I have theory:


As I mentioned above, there’s two ISO standards for photography.

ISO itself is just a measure of amplification from the base ISO.  You have the sensitivity of a sensor that’s its set for at its base, when the normal amount of power/sensitivity is set.  Anything over that is amplifying the power of the sensor (which is why noise is introduced).  I’m not going to go into a long winded explanation of how that works exactly because… I don’t know how it works exactly, but I’m sure someone out there has writen about it and here’s a handy site for you: www.google.com 😛

Anyway, two standards of ISO.  They are…

ISO SOS (Standard Output Sensitivity)

This is the standard Fuji and I believe Olympus/Panasonic and some others.  It’s based on a measurment from a base image/jpeg, which means it’s less random and more standard than REI.


ISO REI (Recommended Exposure Index)

This type of ISO setting is used by Canon and some others (I think Nikon and Sony too).  Basically the camera maker arbitrarily adjusts the ISO settings/number to best match their camera.  Of course they don’t vary too much since they don’t want people complaining and accusing them of cheating… ahem…


So is Fuji cheating? I think not.  However, why does it seem that some people have exposure mismatches?  I think maybe Fuji have slightly changed their settings (maybe switched to REI) in the newer cameras.  Perhaps this exposure mismatch is more an issue with the older sensor too (turns out this is wrong, the fact is the 1DsIII also “cheated” in the past… funny how Canon were never accused of cheating on their ISO).


Full Frame = More light?

Last point, I’ve heard it claimed by some people that Full Frame intrinsically gathers more light.  Well that’s kinda true as the opening/sensor area is a bit wider so technically more photons are entering the camera, sorta.  But the spread of the light is the same evenness over the image.  So there’s theoretically no exposure difference.

What’s all that nonsense mean?  Assuming they follow the same ISO standard, you have the same shutter speed and aperture, then your images from Full Frame or Crop will have the same exposure.


Fuji aren’t cheating… not anymore than the other camera makers at least.

Thanks for reading, and as usual, if you disagree with me or have new information for me, I’m more than happy to update the blog post if I’m wrong.