Which ISO Gives The Best Image Quality For The Olympus E-M1 Mark II And The Fujifilm X-T3??

Olympus E-M1 Mark II (press image)

The other day I was over at William Claff's site, Photons to Photos, looking to compare dynamic range against noise profile for a couple of cameras and, in the process, realized that the best ISO for image quality when using the Olympus E-M1 Mark II seems to be right at ISO 250.  I had never before compared dynamic range and noise profile charts for the same camera.  I had always compared two or more cameras to each other for noise or dynamic range.  

Although I no longer own a Fujifilm X-T3 (still near and dear to my heart, however), I looked up the numbers for that camera as well.  The X-T3 has, in fact, two ISOs that give the best image quality, i.e., maximum dynamic range with the minimum amount of noise.  They are ISO 80 and ISO 160.  That is most likely due to the X-T3 having a dual gain sensor.

If you are not familiar with Claff's website, you can find it here.  He extensively tests cameras for digital noise, dynamic range and other sensor based parameters.  He is certainly well respected when it comes to this kind of testing.  Others refer to his site for statistical information quite regularly.  But I digress...

I'm always trying to eek out maximum quality from my cameras and lenses so best image quality at ISO 250 surprised me.  We normally think of maximum dynamic range and lowest noise levels at the base ISO for digital cameras, which is ISO 200 for the E-M1 Mark II.  But manufacturers are doing some interesting things, it seems, with their image processors and the associated algorithms.  That, evidently, changes the game for our traditional assumptions.

Here are the two graphs from Photons to Photos for the E-M1 Mark II and you can see the best noise profile in combination with the widest dynamic range is right at ISO 250 (actually 251 but who is picking nits?). So if you want to maximize your image quality from this camera, you might want to try it at that ISO and see what you think.

From Photonstophotos.com by William Claff (click to enlarge)
The top chart is dynamic range.  The bottom is for noise.  It appears that the "sweet spot" is
right at ISO 250.  Also, most photographers don't realize how fast their cameras lose dynamic
range when the ISO is increased.  That extra dynamic range you paid for and brag about is
gone with just a flip of your ISO dial!

Here are the two charts for the Fujifilm X-T3.  The top chart is dynamic range and the bottom is the noise profile.

Dynamic Range Chart for Fujifilm X-T3.  Maximum dynamic range is achieved at ISOs 80 and 160.

Noise profile chart for the Fujifilm X-T3.  Minimum noise is achieved at ISOs 80 and 160.

Also, for those of you E-M1 Mark II landscape photographers who are hesitant to use the slowest available ISO, there seems to be little or no penalty for using ISO 64 instead of the base ISO of 200.  I wouldn't hesitate to use ISO 64 if I needed it for longer shutter speeds.

As an E-M1 Mark II user I found this very interesting and thought I would pass it along.  If you use cameras other than these two, you might want to check their ISOs versus dynamic range versus noise profiles.

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Thanks for looking. Enjoy! 

Dennis A. Mook 

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