Camera Comparisons: Are The Nikon Z7, Olympus E-M1 Mark II, Fujifilm X-T3 And X-H1 Comparable In Terms Of ISO And Exposure?

Each of the above images received the exact same exposure with the exact same camera settings under the exact same conditions.  As you can see the results are quite different! The difference in brightness is up to 1 1/3 stops. (click to enlarge)

This comparison experiment started with me wanting to create a Lightroom preset so I could replicate the blue skies of the Fujifilm Astia film simulation rather than have the overly magenta/blue skies I find objectionable in the Nikon Z7 (see above the differences in sky hue).  Letting my curiosity run a bit, from there I thought I would test if the ISOs of each camera were or were not equivalent as well as a) how close the ISOs came to the old Sunny 16 Rule that was used worldwide to standardize film speeds, b) how each cameras ISO ratings compared to one another and c) how the Direct Sun white balance differed among my cameras.  You can read more about this in my last post which can be found here.  This post will cover comparing the camera's ISOs and luminance or brightness.  The white balance comparison will come Friday.

Disclaimer:  As far as the look of the images is concerned, what you see on your monitor may not be what I am seeing as your a) monitor may or may not be calibrated for color, luminance, dynamic range, etc. and b) I really have no idea what Google does to image files when it processes them and posts them in Blogger. On my calibrated monitor, I can easily see differences in white balance, density, color hues, etc.  My narrative may be more relevant than how the files are displayed to you.

I set out to make identical exposures with all processing done in-camera with little or no influence from an editing program.  That means JPEG exposures and not RAW.  I attempted to create a condition where everything about the comparison was equalized in all cameras—hopefully.  Here is my setup:

Sunny day, no clouds in the sky and with sun behind me
Images made at about 11:00 a.m. which provides pretty much maximum illumination
All cameras were tripod mounted
All cameras set to manual exposure
All cameras had the Direct Sun white balance set
JPEG file format; all image processing is done in-camera with no LR interpretation
Standard/Neutral/normal camera profiles (No Velvia, Portrait, Landscape, Vivid, etc.) set
ISO 200 as that is the base ISO of two of the three brands
Sunny 16 Rule would dictate exposure as 1/200th sec. @ f/16 or equivalent (I used 1/1600th sec. @ f/5.6)
1/3 stop incremental brackets; 1 1/3 stop up to 1 1/3 stop down from Sunny 16 exposure to cover potential differences in each camera's ISO claim
24mm full frame field of view for each camera/lens combination (24mm, 12mm, 16mm respectively as shown in these posted images)
All internal camera controls for contrast/saturation, color, etc. zeroed out—null position
All cameras set for AF-S focusing
IBIS turned off in Nikon, Fujifilm X-H1 and Olympus E-M1.2; no IS in X-T3
All cameras set for Single shot

Two sets of exposures were made with each camera/lens combination, the first with an X-Rite Colorchecker Passport in the frame so I could later measure gray scale luminance to set a common standard, measure RGB color patch values as well as set white balance on one of the gray patches.  The other set are identical images but without the Colorchecker Passport included.

Based upon each camera having the same settings and all file processing done in-camera and photographing the same scene within minutes on a cloudless day, this was about as equal as I could possibly make things so the comparison could be as valid as possible.  I don't think so but I may have left something out.  You may have questions, which is fine.  This is not a scientific experiment but an attempt to conduct a carefully constructed set of circumstances to obtain valid, repeatable results.

The image at the top of this post represents a composite of the JPEG images directly out of each camera using the Sunny 16 Rule.  For illustration purposes, I did correct for white balance.  However, no other changes to luminance (brightness) was made.  On my monitor I can easily see that when all things are equal, the NIkon Z7 is significantly brighter than the Olympus and either Fujifilm camera.  I'll get to how much in a minute.

The image below is based upon measurement of the third gray patch from the bottom in the left hand column of the X-Rite Colorchecker Passport.  According to X-Rite, the nominal value of that patch should be .70.  For each camera I found the exposure, among the bracketed ones, that came closest to .70 and placed it in this composite.  Again, no adjustments made to the files except to white balance each using the gray patch on the Colorchecker.

Same scene but with the X-Rite Colorchecker Passport included.  These exposures were equalized according to the published value for the third gray square from the bottom on the left-hand row of the Colorchecker.  In other words, the third gray patch should have a nominal value of .70.  Out of the bracketed exposures from each camera I picked up the exposure that came closest to that .70 value.  These exposures are within 1/3 stop of ,70.  The differences show that the ISOs for the cameras, producing the same results, varied by 1 1/3 stops.  (click to enlarge)

Here are my findings:

As far as the Sunny 16 Rule is concerned, the Nikon actually showed 1/3 stop brighter than what would be considered the "proper" exposure.  That is the equivalent of effectively having ISO 250 instead of the camera's set ISO of 200.  You've gained 1/3 stop.  Instead of 1/1600th sec. @ f/5.6 which would be expected for the Sunny 16 Rule, this camera shows 1/2000th sec. @ f/5.6 as producing the measured nominal value on the Colorchecker.  Nikon seemingly has understated their ISOs and the sensor's light gathering ability or the Sunny 16 Rule isn't followed for this digital camera.

The Olympus showed the correct exposure for Sunny 16 is 2/3 stop more than one would expect.  This is the equivalent of effectively having ISO 125 instead of the camera's set ISO of 200.  You've lost 2/3 stop.  Instead of 1/1600th sec. @ f/5.6 for the Sunny 16 Rule, this camera shows 1/1000th sec. @ f/5.6 as producing the measured nominal value on the Colorchecker.  Olympus has seemingly overstated the ISO and the sensor's light gathering ability by 2/3 stop or, again, the Sunny 16 Rule is not followed by this manufacturer.

The Fujifilm X-T3 and X-H1 images were measured to be identical, even though the cameras are of different generations, have different sensors and different internal image processors.  Interesting.  At least Fujifilm is consistent.  Also, I decided to try two different film simulations, both natural looking to me (Astia, Pro Neg S) for my blue sky correction effort, hence why there are more than one Fujifilm image for each camera.  The Fujifilm cameras showed the correct exposure is 1 1/3 stop more than the Sunny 16 Rule.  That is the equivalent of effectively having ISO 80 instead of the camera's set ISO of 200.  You've lost 1 1/3 stop.  Instead of 1/1600th sec. @ f/5.6 for the Sunny 16 Rule, this camera shows 1/640th sec. @ f/5.6 as producing the measured nominal value on the Colorchecker.  Fujifilm has overstated the ISO the sensor's light gathering ability by 1 1/3 stop or, once again, the Sunny 16 Rule is out the window for digital cameras.  I don't know.

I knew from previous cameras I've owned that Olympus and Fujifilm would have ISOs that measured differently than my Nikon camera.  It is my recollection that the difference was 1 stop for both.  However, things change and the differences in newer sensors, better image processors, more firmware updates, etc. may have changed things.

Now, its your turn to poke holes in my experiment.  Where did I go wrong?  In the past, I've written and have read many places about camera manufacturers using two different "standards" when publishing ISO numbers.  That is most likely true as shown here.

Does this make a difference?  Not under most circumstances.  The difference may come into play if you try to use the Sunny 16 Rule to set your exposure and not use your histogram and light meter.  If you normally set exposure with your histogram (and keep as much of your histogram to the right as you can without clipping highlights), I suggest you continue to do so as that is that is the best indicator that you will not clip highlights or block shadows.  

ISOs in digital cameras today seem a bit meaningless as many cameras are considered ISO-less, meaning that you can underexpose using a low ISO then raise your exposure in your editing software or raise the camera's ISO.  Basically you will get the same results.  However, some cameras aren't amenable to this.  

I found this little experiment interesting and helpful to me.  I hope you have found it interesting as well.

One last comment.  Take a look at the hue of the blue sky in the Nikon images.  You can easily see what I mean by too much magenta in the blues.  In the Nikon RAW images, it is even worse!  That is what started all of this!  Lol.

Join me over at Instagram @dennisamook or my website, www.dennismook.com. 

Thanks for looking. Enjoy! 

Dennis A. Mook 

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