How Much Exposure Error Can Be Made With The Fuji X-T2 And The Olympus E-M1 Mark II And Still Have A Usable Image? Part I of III

Fuji X-T2, 16-55mm f/2.8 lens @ 33.2mm; 1/400th sec. @ f/8; ISO 200; full winter sun (click to enlarge)
This exposure closely represents the scene as I viewed it for the test

One of the reasons I love photography as a hobby and passion is the ability to balance my particular interests in technology and creativity.  Left brain/right brain stuff. Most of my energy goes into photographing as much as I can but, usually during the winter months, part of my energy goes into exploring the technology behind the gear I own and use.  If I can't get out to photograph in the winter, travel or find something interesting of which to make images, I will turn my attention to exploring my gear to better understand it. I believe if you understand your gear you can fully exploit its capabilities.  The better I know my gear the less I have to think about what it can do and what it can't do and finding, manipulating or changing controls, menus, etc., become second nature.  Sometimes you don't have time to think about how to change particular settings, you just have to know how to do it quickly.  Some of my interest in technology and my camera gear manifests itself as testing my gear to its limits.  That is what this post as well as the next one, is all about.

A few weeks ago I conducted some tests to determine how my Fuji X-T2 and my Olympus E-M1 Mark II differ in rendering color as I had wondered if they could be matched for color or if their color palates were so different that the two cameras couldn't be matched. Tht led me to wonder how Fuji Acros and Olympus Monochrome differed in the tonal renditions of the various colors.  Those being completed, I wanted to conduct one more test to better understand the sensor latitude of both cameras and how much exposure error could be tolerated and still get something usable.  "Usable" and "decent" are very subjective, but I wanted to know the limits of exposure with these two cameras.  I had conducted this particular test on before on my Nikons as well as my original Olympus E-M1.

You can read the color matching test here, the Acros versus Monochrome test here and the results of the Nikon exposure latitude test here and finally the Olympus E-M1 latitude test here.

This is Part I of a three part posting.  Part I will be the testing I conducted with my Fuji X-T2.  Part II will reveal the testing results with the Olympus E-M1 Mark II and Part II will be a summary and comments about these tests and my findings

What is the purpose of this particular test?  Again, I felt it was important for me to fully understand the ability of my cameras' sensors to handle severe underexposure as well as severe overexposure, scenes with extreme tonal ranges and still achieve a decent or usable (the operative words here) image after editing.

Disclaimer:  This is not a scientific test and I don't portray it to be one.  This is a practical assessment based upon visual interpretation and personal judgment.  There was no scientific testing equipment utilized to fully measure contrast, densities or color hues.  I standardized a testing procedure and applied it equally to both cameras to be able to compare each to one another.  In other words, your results may vary if you conducted the same test or your judgment as to what a usable or decent image is may differ from mine.

Several days ago I found the scene depicted in the image at the top of this post. I thought it would make a pretty good subject for testing exposure latitude since it had deep shadows, bright highlights with detail in the bright metal roof piece, a variety of colors, texture and subject detail.  Although it is full winter sun and the sun was at my back. The sky was clear.

I set the cameras on a tripod in sequence, set base ISO of 200 on both cameras, determined a base exposure according to the histogram, then varied the exposures up and down by six stops.  The file format was RAW and all other camera controls were at default.

When I imported the images into Lightroom, I changed the profiles (Calibration Menu in the Develop Module) of both cameras to the ones I generated using the X-Rite Colorchecker Passport. I did this so the two different cameras would have consistency in color and contrast.  I didn't want to use the Fuji film simulations or the (currently only) available Adobe Standard-Beta profile setting as those would render differently with no consistency and I felt that would hinder my ability to compare the two cameras to each other.  The Colorchecker profiles provided consistent images across both cameras.

The images below depict the results and the captions detail what I found.  Your evaluations may differ from mine, but I was looking to find the extremes in pushing the sensors as far as possible and finding the point where there was no way to bring the image back to approximately what I saw in the normal exposure.

The image at the top of this post is what I judged to be how the scene looked to me while standing in front of it, as much as it can represent reality.  We know that is not totally possible as the human eye and brain's interpretation is much different than the literal and/or electronic interpretation of a digital sensor and associated processing algorithms.

(One thing I discovered during the creation of the below side-by-side comparison images in Photoshop is that when the composite image was converted to sRGB from my usual ProPhoto RGB, the shadows darkened somewhat form my original adjustments.  I had never noticed that in prior work but that anomaly slightly changed the shadows in the comparison images.  Just FYI)

This first image below is 1 full stop overexposed.  Let's start there.

1 stop overexposed; no other changes (click to enlarge)

1 stop overexposed and corrected by moving the Exposure slider to -1.00 in Lightroom; no other adjustments made.
The image is easily corrected with no loss in shadow or highlight detail.  No noticeable change in color rendition.
(click to enlarge)

Direct comparison of correct exposure and 1 stop overexposed (click to enlarge)

2 stops overexposed; no other changes (click to enlarge)

2 stops overexposed and corrected by moving the Exposure slider in Lightroom to -2.12; no other adjustments made.
At 2 stops over, highlight and shadow detail is still plentiful but starting to see some color shifts, especially
in the blue sky toward cyan. No color shift in shadow detail at this point.  Still looks pretty good.  (click to enlarge)

Direct comparison of correct exposure and 2 stops overexposed (click to enlarge)

3 stops overexposed; no other changes (click to enlarge)

3 stops overexposed and corrected by moving multiple sliders to try to get some sort of decent looking image,  This has
pushed the capability of the sensor too far.  Exposure -2.60, Contrast +42, highlights -100, shadows +8.
At 3 stops over, shadow detail is still plentiful but all detail is lost in the concrete on the front left and the image 
looks pretty bad since highlights can't be adequately recovered and have turned a sickly gray..  (click to enlarge)

2 1/3 stops overexposed; no other changes (click to enlarge)

This is a corrected version of an overexposure of 2 1/3 stops.  This was about as high as I could push it and get an
"adequate" or "reasonable" facsimile of the original image.  There still is detail in the concrete in the left
foreground.  Shadow detail is plentiful.  This turned out to be the upper limit of recovery as another exposure,
just 1/3 stop more, resulted in the same unrecoverable highlight detail as was found in the 3 stops over image.
The adjustments were -1.92 Exposure, highlights -73, shadows -13. I won't say this is a great looking
 image but I think it is usable.  (click to enlarge)

Direct comparison of correct exposure and 2 1/3 stops overexposed, which is amazing in itself!
Think slide film and 1/2 stop overexposure and you forever lose your highlights!  There is some change in
color in the sky and the highlights aren't as crisp and detailed as we would
expect in a properly exposed image, but nonetheless, it is amazing that we could make that kind
of exposure error and recover this much of the image. The sky color can be corrected in Lightroom
utilizing the HSL sliders since there is no other blue in the image, it is relatively straightforward. (click to enlarge)

Now, let's go the other way.  Let's see what happens when we underexpose. 

Underexposure is much more desirable than overexposure and we know we have more latitude in correcting underexposures.  Instead of comparing -1, -2, etc. stops underexposed, which can easily be recovered and matched almost perfectly, let's start with a 4 stop underexposure and go from there.

Here again is the exposure from the top of the post that I am calling closest to how I viewed the scene (click to enlarge)
This is what we are trying to replicate in the over and underexposure tests.

4 stops underexposed; yes there is a pretty good image inside here! (click to enlarge)

Surprise!  Not too bad. There are plenty of details available in the shadows.  The shadows, however, have color
shifted toward green but could be corrected during editing. Also, the sky has slightly shifted toward cyan, also
correctable.  There is quite a bit of digital noise, as you would expect.  However, there is almost no color noise, again, bolstering my contention that Fuji filters it out even in the RAW files.  Even with Lightroom's noise reduction set on 27, very little fine detail has been lost from the original.
I could still tweak the sliders more to change the image in significant ways as there still is a lot of "meat" in the
file for editing purposes. This image is certainly usable. Amazing!  Again, think film.  With slide film
two stops (or less) underexposed and your shadows are lost forever.  In negative film, 2 stops underexposed
and your image is so muddy it was really ugly due to loss of contrast. Digital is so amazing!  (click to enlarge)

Correct exposure on the left and 4 stops underexposed on the right (click to enlarge)

This is 4 2/3 stops underexposed. Five stops was too far. This is right on the very edge of shadow detail being recoverable.  
As you can see in the left bay, the shadows have gone very green, but they can
be corrected with the brush tool in Lightroom.  Contrast is a bit muddy but this image is still kind of usable, but I
probably wouldn't use it unless it was the only image I had. The 4 1/3 stop underexposure does a bit better.
(click to enlarge)

There you have it.  A non-scientific practical application test of what you can expect from the Fuji X-Trans III Pro sensor.  I think the limits of usability are amazing, even for a digital camera.  The only camera that I have owned that has done a bit better, was my Nikon D810.   

In my view, I think the practical limits for the Fuji X-T2 are 2 1/3 stops overexposure and 4 2/3 stops underexposure.  However, to give yourself just a bit of better quality and room for error, I would keep the exposures between 2 stops over and 4 stops under.  That is 7 stops of exposure latitude!

Obviously, it is optimum to precisely expose your image as required by the light and the contents of the scene as that will give you the most flexibility in editing and the best quality.

So what does all this mean?  First, It means we are really fortunate to live in the time of digital photography as opposed to film photography.  Second, it means that the Fuji X-T2 is an amazing tool and, even if you are a pretty incompetent photographer (or photo hack) and really over or underexpose an image because you have no clue as to how to basically operate a camera and refuse to set it on Program, you can pretty much pull an usable image out of your hat to use.  Additionally, you probably don't need to bracket exposures much for HDR images as the latitude built into this sensor along with the X-Trans III Pro processor is amazingly forgiving!

If you see any flaws in my testing, please advise.  I try to logically think my way through these things but I can and do make mistakes.  You should do your own testing under circumstances you may encounter for your particular types of photography and determine your own results.  

I hope you found this educational and interesting.


Thanks for looking. Enjoy! 

Dennis A. Mook 

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