How Good is the E-M1's Sensor? How About Overexposing at least 1 stop and Underexposing 4 to 5 Full Stops and Still Make a Good Image!

Beartown State Park, West Virginia (click to enlarge)

We all know how good the sensor is in Olympus' E-M1.  We all know it is capable of making excellent digital images.  That is a given.  But I wanted to know, if I were a really bad photographer, could the sensor save my images?  Read on, I think you will be amazed!

I decided to conduct an experiment.  I set up my tripod with my E-M1 and Olympus 12-40mm lens mounted, set the ISO for base (200), and pointed the camera at a subject that had areas of full sunlight as well as deep shadows.  I would determine the "best" or "nominal" exposure, then with the camera in manual mode, underexpose by 1 stop, 2 stops, 3 stops, 4 stops, 5 stops and 6 stops.  I would also overexpose by a stop to see how the sensor handled that condition.

The first image below is the subject, right out of the camera, with a nominal exposure of 1/400th @ f/4, ISO 200 with the camera set to record RAW files.  In actuality, the scene exceeded the dynamic range of the histogram, as viewed in the Lightroom 5.6 develop module.  The develop module was used to view the histogram as, in my experience, the grid module does not accurately show the histogram, nor the actual image sharpness. Just FYI. The dynamic range slightly extended beyond the both edges of the histogram, i.e., both ends of the histogram showed some clipping.   That does not mean that the scene exceeded the capability of the sensor as you have to remember that you are looking at a JPEG rendering of the raw file. The data is there.  The second image shows a slight highlight and shadow correction to "normalize" the image and keep it within the confines of the histogram so there is a baseline for reference and matching.

Nominal Exposure, no corrections (click to enlarge)

Nominal Exposure, slight highlight and shadow recovery (click to enlarge)

Using the same camera settings, I then made several exposures; -1 stop, -2 stops, -3 stops, -4 stops, -5 stops and -6 stops.  Below are the original underexposed images along side the same image corrected to somewhat match the one directly above.  I didn't spend a lot of time trying to match the image exactly, but wanted to see how the sensor handled underexposures.

-1 Stop on left, corrected to match image above on right (click to enlarge)

-2 Stops on left, corrected to match image above on right (click to enlarge)

-3 Stops on left, corrected to match image above on right (click to enlarge)

-4 Stops on left, corrected to match image above on right (click to enlarge)

-5 Stops on left, corrected to match image above on right (click to enlarge)

-6 Stops on left, corrected to match image above on right (click to enlarge)

Here is the image at 1 stop overexposed.  Not a stretch for this sensor in any way.

+1 Stop on left, corrected to match image above on right (click to enlarge)

In my assessment, -4 stops is very usable, even for a print, maybe 8" X 10" in size.  When you underexpose by 5 stops, the image, in my opinion would still be usable for the web.  The bottom image, -6 stops is really pushing it., but if you really, really need to use, it you could work hard to make it at least acceptable for web use.

Now, I don't think these images are what you want to create on a regular basis, and are not what I would classify as technically great images, and I surely don't recommend underexposing your images at all, but if you accidentally did, I think you could get a salvaged image of acceptable quality—for a variety of uses, but not every use.

At -4 stops, I detected a slight shift in shadow color.  At -5 and -6 stops I started to see a larger color shift to red,especially in the shadows.  At -4 stops, the shadows were decent as far as detail and contrast.  At -5 and -6, the shadows were pretty weak, but again with a lot of work, they could be improved with more time than I wanted to spend on them.

Below, I wanted to give you a look at the nominally exposed image directly along side of the underexposed, but corrected image.  Again, I could have spent more time matching the nominal image exactly, but decided it wouldn't serve my purposes for this test.

Nominal Exposure on the left, -1 stop corrected on the right (click to enlarge)

Nominal Exposure on the left, -2 stops corrected on the right (click to enlarge)

Nominal Exposure on the left, -3 stops corrected on the right (click to enlarge)

Nominal Exposure on the left, -4 stops corrected on the right (click to enlarge)

Nominal Exposure on the left, -5 stops corrected on the right (click to enlarge)

Nominal Exposure on the left, -6 stops corrected on the right (click to enlarge)

This test was not meant to be the be all to end all.  It is more of an informal test for me to learn the capabilities of the sensor for this camera.  Whether an image is a stop overexposed or quite underexposed, the E-M1 sensor was able to pull out the detail in the highlights and shadows.  The next question I have for myself is, "What is the visual difference between increasing the ISO and underexposing the image?"  Will one method produce a better end result over the other or no practical difference?  That test is for the future, so stay tuned.

If you think about it, it is quite remarkable that one can significantly underexpose an image and still have the ability to tame the highlights as well as draw detail out of the shadow.  Not only have we come a long way in the realm of digital sensors, but the capabilities in smaller sized sensors.

Those of you who used to shoot film, well, this should knock your socks off!  It does mine. You old film shooters will remember with slide film, if you underexposed, you lost your shadow detail forever.  With negative film, if you underexposed, your shadows looked really muddy.  They weren't black and had no micro contrast.  Same with highlights.  With slide film, all you had was clear acetate.  With negative film, you highlights became so dense you could hardly print the image.

I just can't see ever going back to film as digital photography produces such better images under such a variety of situations that film could never handle.  It can even make up for photographer's mistakes!

Thanks for looking.  Enjoy!

Dennis Mook

Many of my images can be found at www.dennismook.com.  Please pay it a visit.  I add new images regularly.  Thank you.


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