Friday, November 9, 2012

Making sense of all that complicated photo jargon, Part 3!

Now that you’ve got a handle on shutter speeds and apertures, I’ll move on to the third side of the exposure triangle—ISO or film speed.

ISO stands for the International Standards Organization, which replaced our American Standards Association (remember when America had it’s own standards and our film speed was in ASA?), in order to make all things technical, consistent around the world. I guess the ISO is a kind of United Nations for all the anal-techno-geeks seeking conformity in all things man made.

The ISO basics are simple:  in low light you go to a higher ISO value and in bright light you use a lower ISO value if you don’t want to change your shutter speed and aperture.  The common lower ISO’s are 100 or less.  Depending on the digital camera you have a really high ISO ranges from 400 to 800, in a consumer grade camera. In the professional world we use cameras that will create stunning images at 400 ISO and up to 3200 ISO that we don’t use the lower ISO’s much for outside work.

Now that we’re bringing shutter speeds and apertures together a very important aspect to remember is that each whole shutter speed step (eg. 1/30, 1/60, 1/125 etc.) and each whole aperture step (eg. f4.0, f5.6, f8.0 etc.) are equal.  In other words moving from a shutter speed of 1/60 to 1/125 is equal in an exposure change of one-stop. It’s exactly the same exposure change as if you really did change your f-stop from say f5.6 to f8.0 (and in this example either of these changes would allow one-stop less light to reach the film or sensor).  In addition, your whole ISO steps (eg. 100, 200, 400 and so on) are also equal to a one f-stop change in exposure.  See a pattern here? And just to make things more complicated, digital cameras have shutter speeds and f-stops in between the whole numbers.  But it’s all the same—the smaller steps in between are also the same in how they affect your exposure in equivalence to each other.

So, let’s set-up exposure examples to show some equivalent exposures using different f-stops and shutter speeds.

EXAMPLE ONE: Leaving our ISO at 100, your camera meter says that the proper exposure is: aperture at f8.0 with a shutter speed of 1/250th.  What if you want to stop some fast action, at your son’s football game, so going to a faster shutter speed of 1/500 sec. would help—however, to maintain a proper exposure, since now this faster shutter speed is allowing less light to reach your film/sensor, you must change your f-stop one step, in the opposite direction to get more light, to f5.6 (remember with f-stops, the smaller the number, the bigger the opening of its aperture). As a side effect the larger aperture (f5.6) will isolate your son better because you are creating less depth-of-field at this aperture. 

To recap, you went from:  f8.0 @ 1/250 sec. to f5.6 @ 1/500 sec. This maintains the same exposure with a faster shutter speed and less depth-of-field.  You get a two-fer! Now, You’re not just making a proper exposure—you’re making creative decisions that will make the photograph more visually interesting!

EXAMPLE TWO:  The following would apply to situations where the light level stays the same.  Once a proper exposure is set-up; we will use ISO 100, f-stop of f5.6 and shutter speed at 1/125 sec. for this example.

If you change any one of these numbers you must change one of the others by the same amount, but in the opposite direction, to maintain a proper exposure.  If you go to a higher ISO like 200 you must stop down your f-stop to f8.0 and keeping the shutter speed where it was at, 1/125 sec.  OR still at the higher ISO of 200, keeping the f-stop where it was, f5.6, you must go faster on the shutter speed, to 1/250 sec. 

If the situation changes and the light level changes, say the sun is setting, so you have less light, now you only have to change one of the variables in the original set-up (any ONE!).

Now you have three choices:
1)    Higher ISO: ISO 200, same f-stop of f5.6, same shutter speed of 1/125 sec
2)    Same ISO: ISO 100, wider aperture of f4.0, same shutter speed: 1/125 sec
3)    Same ISO: ISO 100, same aperture of f5.6, slower shutter speed of 1/60 sec.

The exposure triangle is really just a way of thinking about how your shutter speed, aperture and ISO are inter-related.  You can check out some examples below.

That will wrap it up for now…till next time. Jerry

Image 1:  Nature
Extremely fine detail and sharp Low ISO: 100 slide film
On a tripod & slow shutter speed: 1/15 sec
For maximum depth-of-field using a very small aperture: f16.0
Lens: 16mm wide-angle

Tuesday, October 23, 2012

Making sense of all that complicated photo jargon, Part 2!

Photography Skills 101
By Jerry W. Venz, PPA Master Photographer

Last month I went over the first part of the exposure triangle, the shutter speed.  I explained that it could reveal, at very short and very long exposures, many things our eyes could not see.  If the shutter speed at it’s best, reveals much, I often use the camera’s aperture (or f-stop) to hide or obscure what is around my subject. But first, lets talk about what your camera’s aperture is and how it works.  Well, it’s a total rip-off of your eyes’ iris!  You know, the little black holes in the center of the eyes that gets so huge when your hippie friends used to smoke…or, how about when your eye doctor puts the drops in your eyes to dilate them?  Remember how sensitive your eyes became to light? That’s because he took your eyes off Auto and put them into the Manual, wide-open, mode. Thank God for THAT Auto mode! When working properly the iris in our eyes are constantly and smoothly, closing or opening, adjusting to lighting levels around us without us so much as breaking a sweat.  OK, maybe some of us need to break-out the sunglasses sometimes—kinda like putting a neutral density filter (to cut down the light) on your camera’s lens.  See we have more in common with our cameras than you thought!

Your camera’s aperture, like the iris in your eyes, is another way to control the amount of light that reaches the film or the camera’s sensor. The smaller the aperture’s opening the less light will pass through your camera’s shutter and onto the sensor or film.  And, the larger the opening… probably guessed that one, right? Just to make something so simple complicated, some engineer decided to call these apertures: f-stops (don’t ask) and attached numbers to them! But, not content with the fractions being used for the shutter speeds they decided to use decimals for the f-stops!  That’s how we ended up with the most confusing and hardest part of the exposure triangle to teach.  So, here are the standard f-stops starting with the LARGEST opening and going down, smaller with each step (even thought the numbers are getting bigger), allowing half as much light in with each step.  The lens widest aperture in this example is f 2.8, followed by f 4.0, f 5.6, f 8.0, f 11, f 16,
and f 22.

If your lens is at f 2.8, the aperture is wide open allowing the most light possible through to the shutter.  As we adjust the lens to the higher numbers the aperture gets smaller allowing less light to the shutter. Got that? Well, you don’t have to like it, but if you can just understand how to control this part of the exposure triangle, you can create images that the human eye could never see. For example, one of the side effects, created by a large aperture, like the aforementioned f 2.8, is my favorite effect when doing portraits of people outside. It’s called shallow depth-of-field in my world.  Depth-of-field in an image is simply how much is apparently in focus in front of and behind the subject you focused on.  So, what’s so hot about that you say? With depth-of-field control I can direct you to where I want you to look first in a photograph by controlling what’s in focus and what’s out-of-focus.

Here’s how it works.  When the aperture is at f 2.8 you get the least amount in focus in an image (often only inches).  When the aperture is at the higher numbers, like f 22, you get the most that the lens can produce in focus—like hundreds of feet to infinity!  The bottom line is what do YOU, as a photographer, want to show the viewer? Often showing our audience everything in focus shows too much—that’s what our eyes do—you can reveal more often by showing less.  It really depends on what the subject is.  Is it the Grand Canyon or the lizard on a rock, on the rim, of the Grand Canyon?  You can decide this when you control the depth-of-field.  The f-stop is the only thing in the exposure triangle that controls depth-of-field.

For you visual types (you wouldn’t be reading this if you weren’t), here are three images I set-up to illustrate depth-of-field at different apertures.

Next month I will wrap-it-up with the third part of the exposure triangle: the ISO or film speed and how the three parts work together. If you missed Part 1 you can view it on the Informer’s website or on our blog.  JV

Thursday, September 13, 2012

Making sense of all that complicated photo jargon!

Photography is all a bout catching “pieces” of light to create an image with a chemical reaction (on film) or an electrical reaction (digitally).  It matters not which medium you use—the basics of controlling light are the same.  If you understand and use these basics you will be a better photographer.  It will allow you to be able to repeat y our successful images instead of them being happy accidents!  These accidentally good images usually happen when you use the Auto modes in your camera.  The auto modes are controlled by a little, tiny, rat-like brain, so you get what you get.  What I’m proposing is that you take back control of your camera by using the big brain—the big lump two feet above your…well you get the picture. Switch your camera into the manual mode.  It’s OK…it will not explode and neither will you!  If you want to ease into this a little at a time you could start with one of the semi-manual modes, like aperture priority or shutter priority, which we will discuss later.

To function in the world of “M” (manual mode) you need to understand the exposure triangle.  The three sides of this triangle are: Shutter Speed, Aperture (or f-stop) and ISO (“film” speed).

Using each side of the triangle either individually or, best of all, in concert with each other can produce stunning images.  But first, you need to understand just what each side of the triangle can do for you.

Shutter Speed
Your camera’s shutter determines how much light reaches the “film” or sensor based on time. The shutter is much like a water faucet (and light is often compared to waves, so it’s not a bad analogy!). The longer the faucet is open the more water flows through it.  The difference is that a whole lot of light can flow through a camera’s shutter in one second, while not much water gets through a faucet in one second.  That’s why most of your camera’s photographs are being done at shutter speeds in fractions of seconds. Oh NO!  Not Fractions! I’ll bet you never though you would really use those outside of high school.  Here are typical shutter speeds you’ll find in your camera’s menu:
1/1000   One/one thousand of a second – FAST!
1/500     One/five hundred of a second – Half as fast
1/250          As we go down the list
1/125          each shutter speed allows
1/60            double the amount of light as the one
1/30            above it because it’s open twice as long.
And so on… 1/15 – 1/8 – 1/4 – 1/2 – 1 second

Your camera’s shutter can reveal much that the human eye alone cannot.  If you set your camera at say, 1/8000 of a second it can stop the fastest things man has made. By using long exposures, holding the shutter open for 30 seconds or more, your camera can gather enough faint light to reveal tens of thousands more star than you’ve ever seen before.  However, to see these wonders at this shutter speed or any shutter speed longer than 1/15 of a second, you’ll need to mount your camera on a tripod for a sharp, clear image.

In the next article we will talk about the second part of the triangle, the aperture or f-stop, and all it’s creative uses.