Posted by: kerryl29 | March 7, 2013

Approaching the Scene

Recently, I’ve received a number of e-mails asking how I deal with exposure settings in the field.  These aren’t “how do you meter” questions; the queries fall more in line with the notion of “what part of the exposure settings triad do you prioritize” when approaching a particular scene, and why?

The broad answer (and I’m sure you saw this coming) is, “it depends.”  And, to respond to a question that often accompanies the one detailed above–“how will I know what to do?”–it comes with experience.

I’ve had enough of these questions that I thought a dedicated entry covering the subject was warranted.  What I’m laying out here is second nature to experienced photographers, so I apologize to those of you reading this who already know this stuff, but for relative newbies–and even some intermediate photographers who have largely let their cameras choose their settings–this may be somewhat helpful.  Note that, as alluded to above, this isn’t a primer on how to meter a scene per se; it’s more about how to go about prioritizing the process of setting your exposure benchmarks.

The Exposure Triad

Just to clarify, when I use the term “exposure triad,” I’m referring to the basic set of three adjustable settings that impact exposure in combination with one another.  They are, in no particular order:

  1. Shutter Speed
  2. Aperture (f-stop)
  3. ISO

You should be familiar with all of these concepts already and understand that, in the most fundamental sense, all three can be used interchangeably, in equal increments, to impact image exposure in either direction (i.e. make the image lighter or darker).

(That’s as much as I’m planning to say about the true exposure basics in this piece, because I sense that most readers of this blog already understand the fundamentals.  If there are readers out there who would like a basic primer about how the exposure triad functions, let me know, in the comments and/or by e-mail, and I’ll prepare something on that subject down the road.)

The “Correct” Exposure:  A Brief Cautionary Tale

I want to briefly touch upon a related topic:  the notion of the “correct” exposure.  The entire phrase is a bit of a misnomer because the correct exposure for any given scene is the one that establishes the look you’re trying to achieve, whatever that may be.  The classic example would be trying to render a silhouette of some foreground object against a bright sky, or trying to show detail in a foreground object against that same sky.  (Even leaving out the possibilities of multi-image blends and HDR; with many, if not most, current DSLRs, both options are typically available to you.)  The “correct” exposure in this instance depends on your intent.

Totem Pole at Sunrise, Monument Valley Tribal Park, Navajo Reservation, Arizona

Totem Pole at Sunrise, Monument Valley Tribal Park, Navajo Reservation, Arizona

So don’t buy into the notion that there’s a single “correct” exposure for a given scene.  The exposure of choice is the one that enables you to render your vision in the resulting image.

Examples

Here are some images that will illustrate the point of different exposure triad priorities.  I’ll show the image and then explain what my priorities were and why, and how I went about implementing them.  Note that in many cases there are multiple priorities.

Oaks and Maples, Morton Arboretum, Illinois

Oaks and Maples, Morton Arboretum, Illinois

Background:  It was a windy, overcast day.  The breezy conditions meant that the foliage was blowing around quite a bit, and my goal was to freeze the leaves.  Based on a bit of brief experimentation, that meant a minimum shutter speed of 1/30 of a second.  It could be faster than that, but no slower.  The problem was that, given how relatively dark it was (remember, it was completely overcast), achieving those shutter speeds at base ISO (200, with the D700 I was using at the time), meant a fairly wide aperture–less than f/8.  But in this instance, f/8 didn’t provide an adequate depth of field to render the entire scene acceptably sharp from front to back.  I needed f/11…and I couldn’t even get f/8!  Focus stacking, using a wider aperture, was out because the movement of the foliage would make compiling a single image from multiple frames impossible (i.e. the elements wouldn’t line up).  What to do?

Raise the ISO.  I always shoot at base ISO when I can…but generally speaking with the last few generations of digital sensors, almost nothing in the way of image quality is surrendered by raising the ISO a few stops.  If you need to do it, it’s there.  In this case, I was able to boost the ISO to 400 and achieve the minimally acceptable shutter speed (though I also waited for a lull in the breeze, just to be sure).

So again…the scene required a minimum shutter speed (to freeze the foliage) and a maximum aperture (for depth of field purposes).  I knew the minimally acceptable settings.  When I found that they couldn’t be achieved with the base ISO, I adjusted the third element of the triad to achieve the required settings.

Virgin River, Zion Canyon, Zion National Park, Utah

Virgin River, Zion Canyon, Zion National Park, Utah

This one was fairly easy.  I was trying to achieve a simplified hard (rock)/soft (water), yin-yang contrast.  I wanted to slow the shutter speed down a great deal, to get as detail-free a look in the water as possible.  Depth of field was no consideration at all here.  So, I dropped the ISO to it’s lowest level (the equivalent of 100).  I closed the aperture down to f/16.  I put a polarizing filter on the lens.  I still wasn’t getting a slow enough shutter speed.  So I pulled out one of my neutral density filters (a three-stop) and, removing the polarizer, placed that on the lens, then stacked the polarizer on top of that.  Bingo.

Again, this was all about obtaining a very slow shutter speed (in this instance, 15 seconds)–that was essentially the only priority here–and I used all three elements of the triad–plus filters–to realize the goal.

Clingman's Dome Sunset, Great Smoky Mountains National Park, Tennessee/North Carolina

Clingman’s Dome Sunset, Great Smoky Mountains National Park, Tennessee/North Carolina

In this case I was just trying to get an exposure that would retain detail throughout the image, so the goal was to expose this as brightly as possible without blowing the highlights (with the possible exception of the sun itself).  I started with a middling aperture (f/8), the base ISO (100, with the D200 I was using at the time) and whatever shutter speed (1/20 sec. in this case) would do the trick, with f/8 and ISO 100 as the other components.  I was perfectly happy to let the foreground ridge go black since this was fundamentally a layered image.   There were plenty of other exposure setting combinations that would have provided an equivalent result.

Mill Creek Rapids, Cataract Falls State Recreation Area, Indiana

Mill Creek Rapids, Cataract Falls State Recreation Area, Indiana

This situation is similar to the first example, but not identical because I was looking at a narrow range of acceptable shutter speeds, rather than a minimum.  Two equally important priorities played a role here.  Because of the foreground objects (the leaf and the rocks), depth of field was a major consideration.  I was looking at f/11 or so.  This image was shot with the D800E and, frankly, diffraction becomes apparent at f/8 with this camera, but sometimes, you need something narrower than f/8 to achieve the desired depth of field.  I’d rather shoot for the necessary DOF and deal with any elements of diffraction, but I do try to keep the aperture as close to f/7.1 as possible.  This scene might have lent itself to focus stacking, but I chose not to go that route.

Every bit as important as depth of field here was the chosen shutter speed.  I was looking for some water blur, but not too much (i.e. nothing like what I was aiming for in the Virgin River example above).  I had the polarizer on the lens and, with a bit of tweaking, I was able to get a shutter speed in the 1/6 of a second range at f/11, using base ISO (100 on the D800E) which was more or less what I was looking for.  That allowed me to render the water the way I wanted to and obtain the necessary depth of field.

Summing Up

You can see that prioritization of the exposure triad depends on what you’re trying to accomplish (which itself will vary depending on the scene you’re dealing with).  With a minimal amount of experience, these kinds of decisions will become instinctive.  If they’re not second nature to you yet, spend some more time in the field.  What better assignment could a photographer ask for?

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Responses

  1. Gorgeous sample shots!

  2. I hate to repeat myself every time you do a post, but your photographs just blow me away!

    I think that your opening premise, the notion of the “correct” exposure, may be the most important part of this post, and often misunderstood by many people just getting started in photography. Very often you can use two completely different settings, and come up with two acceptable photos, although different from each other in overall appearance, each can be very good in its own right. I think that most of us without your experience are best off by shooting the same scene multiple times using several different combinations of settings.

    • Thanks very much for the kind words.

      I think the exposure choices really come down to intent on the part of the the photographer. It can be thought of as akin to two of the different shooting modes that accompany most cameras: shutter priority and aperture priority. The thought process that goes into selecting the right shooting mode can easily be adapted and transferred to taking full control of exposure settings in manual mode; you simply start as if you were shooting in A or S, establish the appropriate benchmark, and then establish the other settings of the triad (including ISO) accordingly.

      Once you correctly associate the different options with different visual outputs, this entire procedure becomes second nature and takes almost no time at all to implement.

  3. Very informative and well-written, Kerry, and excellent examples to illustrate your points. Absolutely right–one never knows which settings will render the image that the photographer envisions until getting down to process the recorded data. In short–if you love what you’re shooting, bracket at different settings so that the best will be available when you need it!

    • Thank you kindly for the comments.

      There’s absolutely nothing wrong with bracketing–I used to do it religiously when I was shooting slide film–but I have to concede that unless I’m deliberately preserving blending or HDR options…or if I’m experimenting with different “looks” (as in the case of moving water, for instance) I don’t do it very often with digital capture. The built-in digital capability to conclusively determine that I’ve “got the shot” has, I think, led me away from this approach. But as I said, there isn’t a thing at all wrong with doing it, even in the digital age.

  4. This is a wonderful tutorial, worth coming back to. You explain the settings very clearly.

    • Thanks very much!

  5. Thanks, Kerry, I enjoyed going over this. It is always a good reminder and helps me to think about and get the results that I want.

    • Thanks very much, Jane. Always happy to help, if I can.

  6. Thank you for this post. As it has already been said, you explain everything very well 🙂

    • Thanks very much.

  7. Kerry, I love when you do these type of posts. You are able to so clearly describe your thinking process illustrated by your gorgeous photos – you’ve got it all going on! I go through much the same process – I love shooting digitally since it allows the manipulation of ISO, something impossible in the film days. I was glad you addressed the neutral density filters. I was hoping that maybe I could just lower the ISO enough for shooting in the field when I want a slower speed for shooting stills of water, or for matching frame speed when I’m shooting video, but I suspect I will need more control than that. Do you recommend a set of separate stackable ND filters or a combined 3 stop (or more)? I’ve read a lot about both options but still can’t make up my mind.
    Great post, Kerry, as always! Still planning that “silent” post.

    • Thanks, Lynn. Yeah, changing ISO back in the film era meant shooting out the roll and inserting a different speed of film with the new roll. Not quite as flexible as being able to adjust the sensitivity setting on the fly on a shot-by-shot basis. 🙂

      Regarding your ND filter question…keep in mind that a polarizing filter can serve as a functional 1-2 stop ND filter if you’re trying to slow things down (but be sure to watch out for uneven polarization if you’re shooting with a wide angle lens and include the sky in your shot). I have a pair of dedicated ND fliters, which, in combination with one another and/or a polarizer give me every combination from one stop to 11 stops. If I stack filters I do have to be on the lookout for vignetting. A variable ND filter–Singh Ray makes one and Lee has one as well–are much more convenient because you can dial in from two to approximately eight stops with a single filter, but these filters can be extremely expensive and you can run into some issues with them sometimes at the upper level of density. My two B+W ND filters ran me less than half the cost of the Singh Ray variable ND, so I went with the less expensive option. I really don’t use ND filters all that often, so I couldn’t justify the higher cost. Your mileage may vary, of course.

      • Thanks, Kerry, that’s very helpful. Less expensive is better, especially since I don’t expect to need them all of the time. Many thanks for the advice!

        • Just wanted to add one thing that works in the favor of the vari-ND option: if you need to experiment to find just the right amount of neutral density to get the look you’re after, it’s far, far more convenient to do that by simply adjusting the dial on the filter that’s already on your lens than it is to play around with adding/removing different filters from your lens. Whether it’s worth the trouble or not is in the eye of the beholder, of course, and likely related to how often you apply ND filters in the first place.

  8. Great info! Thank you 🙂

  9. […] or less equal priority and waterfall/creekside shooting is a good example of such an occasion. In this entry on my own blog I discuss in-the-field shooting considerations covering a variety of situations, […]


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