Low Light; Do You Raise Your ISO Or Get Out The Tripod?

An image such as this needs to have as much dynamic range as possible, depending upon how you want to edit it.  This is
the aircraft carried Dwight D. Eisenhower backlit with some of its 4000+ sailors on the flight deck.  This is pretty much a straight exposure as I envisioned it as a silhouette.  See below for how much dynamic range I was able to extract if I had
wanted a different treatment.(click to enlarge)
Olympus E-M1 Mark II, 12-40mm f/2.8 lens @ 40mm; 1/2000th sec. @ f/5.6; ISO 200

Often times when are out photographing we encounter situations in which the light or circumstances we encounter are such that handholding our cameras might not be prudent as shutter speeds may become very long.  In-body-image-stabilization (IBIS) and lens-based image stabilization (IS) are available on most brand's cameras but even that technology might not be sufficient to guarantee sharp images in some cases.

If we want to capture those images as sharp as possible there are a couple of things we can do.  We can increase the ISO on our digital cameras to get faster shutter speeds or we can get out our tripod and use it, that is if we brought one.  Carrying, getting out and setting up a tripod is the harder option and many photographers don't bring one much of the time.  Raising the ISO seems like the expedient and easy thing to do.  But is that the best course of action? 

Increasing the ISO has at least two noticeable effects.  First, we will most likely see an increase in digital noise.  The amount depends largely on the camera (which includes how new it is, sensor format and its number of pixels) and how high the ISO is set.  Additional noise can be mostly negated (to a point) with sophisticated noise reduction features that are included in most editing software.  For the most part, much of the noise can be dealt with adequately.

The second result, and one that most of us don't think about is that raising the ISO results in a pretty large reduction in dynamic range.  How often you consider that when raising your ISO?  I bet not often.  In every digital camera that I've checked dynamic range is reduced when ISO is raised.  And, it is almost in a directly inverse proportion.  In other words, a straight line down as the ISO is increased.  See the chart below.  The chart has representative current cameras from Nikon, Canon, Olympus, Sony and Panasonic.  All show the same sort of reduction in dynamic range as ISO goes up.

Photons to Photos chart showing the relationship of ISO to dynamic range for the Canon 1D Mark IV, Nikon D850,
Olympus E-M1 Mark II, Panasonic Lumix S1R and the Sony A7rIII.  No matter which camera you own and no matter
what magic is programmed into the camera's processing engine, you lose dynamic range with an increase in ISO.

The pixel wars seem to be largely over.  We have plenty of pixels in our digital sensors if we want them.  However, we still complain about dynamic range and we ask manufacturers to continue to research and develop sensors with additional dynamic range.  So why would we purposefully reduce dynamic range if we don't have to?  Is it due to laziness, ease of turning the ISO dial versus carrying and getting out a tripod or maybe because many of us don't know that dynamic range is reduced dramatically as ISO is increased?  That is why I wanted to bring that fact to your attention with this post.

Next time you think it is easy to just raise your ISO from its base to ISO 400 or 800 or even 1600 in order to get that shot, think about the subject's contrast and if losing 1-2 stops in going from base ISO to ISO 400, another stop or so going to 800 and even another stop of more going to ISO 1600.  By the time you raise your ISO to 3200, you've lost 4 1/2 or more stops of dynamic range!  Will that loss matter to the image you are trying to make?

One interesting observation in the chart above.  The smallest sensored camera, the micro4/3 Olympus E-M1 MKII, with the exception of base ISO, almost equals the "big boys," the cameras with sensors 4X as large when it comes to ISO.  With most of the cameras in the chart the little Olympus shows only about 1/2 stop less of dynamic range at a given ISO.  That camera gives the full frame cameras a run for their money.  That is surprising!

Take a tripod.  Use it.  Maximize the dynamic range you have or don't complain to the camera makers that you want more.  Work smart not fast or easy.

Same image, just opened up the shadows all the way.  If I didn't visualize a silhouette when I made this image, I would
have wanted all the dynamic range I could possible get.

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Thanks for looking. Enjoy! 

Dennis A. Mook 

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