TO TELL THE TRUTH:

WILL THE REAL "EXPOSURE TRIANGLE" PLEASE STAND UP

Let's talk left brain. This month I'm talking about photographic exposure. So that we are all on the same page, let's define "exposure." There are so many ways to address this technical subject. I'll keep it simple. Cameras (the film or sensor) need light to record a picture.

If the camera receives too much light, the picture will be "overexposed;" "washed out;" "look too bright." If the camera doesn't receive enough light, the picture will be "underexposed:' too dark. If the camera receives just the right amount of light, the picture will be "well exposed."--not too bright; not too dark. Bottom line: we're talking about how much light the film or sensor was exposed to light. That's where the term "exposure" comes from.

Now that we know what we're talking about, the next question is: What factors; what variables affect exposure? In other words, what makes a picture come out too dark, just right, or too bright? Let's take a look at those factors. But first, let's remember that nothing the cameras or lenses do is perfect. We will, and should, make necessary adjustments to our "exposures," as needed. I call it fine-tuning. 

This takes us to the Exposure Triangle. Although most articles refer to the  Exposure Triangle, today I will introduce a second one. But, let's start with the one that is most commonly discussed.

If I shoot in Manual Mode, I am "flying solo," i.e. I have to determine what combination of f/stop, shutter speed, and ISO I need to set to give me a properly exposed image. That's quite a task and may require some "guesstimating" on my part until I get it right.  When shooting in that mode, the "Exposure Triangle" looks like this. 

                                                                             

                                                                                                  

Here are a couple of illustrations shot in Manual Mode. 

                

I shot both images at f/8 and 1/4 shutter speed. For the image on the left, I used an ISO of 200.
It is properly exposed--not too dark not too light. For the image on the right, I doubled the ISO to 400. As you can see, it impacted the exposure; it made it brighter; lighter than the first one. 

The ISO in the Exposure Triangle, however, is not the only factor that can change the exposure. Here is yet another example where I kept the shutter speed the same (1/4) and the ISO the same (200). For this one, I doubled the f/stop, from f/8 to f/16. Notice how underexposed it looks when just that one single factor was changed.

                                                                           

Now let's explore a second Exposure Triangle, one not mentioned much in the literature. It's the 'Triangle' I use for my photography. 

If I shoot in Aperture Priority, rather than Manual Mode, there are still three factors present. When shooting in this mode (Aperture Priority), the three factors are f/stops, shutter speeds, and the (built-in) light meter, or light exposure meter. This Exposure Triangle looks like this.

When shooting with this exposure triangle, in Aperture Priority Mode, I have total control of f/stops, which is my preference. When I change my f/stops, the built-in light meter will "see" that and make adjustments to my shutter speeds. Why? Because it's designed to give me what it thinks is the "correct" exposure. It will decide on its own what the "correct" combination of f/stop and shutter speed should be in order to give me the "correct" exposure. 

As mentioned before, when shooting in Manual Mode, I have three factors to deal with and adjust: f/stops, shutter speeds, and ISO. However, with this exposure triangle, I just have one factor to deal with, which is shutter speeds. For average daytime scenes, I usually don't have to worry about ISO. All I have to do is use the exposure compensation dial on the camera to lighten or darken the image--that's it!  And, if I do need to change the ISO, the exposure remains the same; my images look the same! An example of when I might need to do this is when there's is a strong breeze and the shutter speed has selected for me is too slow to "freeze" my subject. No problem. I just change my ISO from, say, 100 to 200 or 400. Voila! 

Here are three examples of a stationary object, a clock, where all I did is increase the ISO. Two things happened. The shutter speed increased with each change in ISO, but the exposure, the overall look of the image looked relatively the same, i.e., the exposure remained the same. 

Now, you might ask, "But aren't you afraid of also increasing "noise" with each ISO increase? If you asked me that question ten to fifteen years ago, I would have said, "Yes." Today's cameras, however, have improved exponentially in their ability to create great low-noise images at high ISOs, well above 800.  

                                         ISO 100                                               ISO 200       

                     
  

                                         ISO 400                                                 ISO 800        

                        

I like shooting with this exposure triangle at play. I have fewer factors to deal with, which allows me to work faster. And I like working faster because I don't want to miss those one-of-a-kind moments. In photography, timing is everything!  

  

So, I encourage you to experiment on your own. Examine yourself as you shoot in both the 'ISO' Exposure Mode triangle and in the 'Light Meter' Exposure Mode triangle. Then make your own decisions. Experiment with three scenarios. 1) Stagnant subjects where nothing is moving,       
2) Scenarios where wind and motion are problematic, and, 3) Scenarios where changing light is problematic. 

By the way, shooting in Aperture Priority Mode, as opposed to Manual Mode, does not equate to amateur v. professional. 

Have fun with it!!! It doesn't matter how you get there as long as you get there. 

Feel free to contact me if you have any questions or if interested in a ZOOM lesson, on any photography topic.