Archive for the Tutorials Category


Posted in Tutorials with tags , , , , on October 1, 2008 by thtroyer

It’s time to start tackling exposure, and you’ll need to understand what a stop is.

A stop is a dimensionless measurement of light — it needs a reference to be quantified. Stops are most often used to measure relative brightness (“this is 2 stops brighter than that”) and to describe exposures of photos (“that photo was underexposed 1 stop”). The easiest way to see it work is in examples.

So, lets say I have a candle in a dark room. If I add another candle, I would double the light in the room. Doubling or halving the light creates a 1 stop difference.

1 – 2 – 4 – 8 – 16 – 32 – 64 – 128 – 256 – 512 – 1024

If those numbers represented candles in a room, the difference between each number is 1 stop, regardless of where we started and which direction we went.

One stop brighter = light doubled.
One stop darker = light halved.

The shutter is used to allow light through at a certain interval.  On manual cameras, it is often between 1 second to 1/1000th second, and is laid out something like this:

1 – 2 – 4 – 8 – 15 – 30 – 60 – 125 – 250 – 500 – 1000

There is approximately one stop between each number.

Now, you have more control over exposure than just the shutter.  This is where the aperture comes in. I mentioned it in the Depth of Field article. It’s primary purpose is to block light to help one get a correct exposure. The effect on DoF is secondary.

In any case, the aperture value is a ratio of focal length over aperture diameter and represented as f-numbers. The actual size of the aperture isn’t important, but the ratio is — that’s what the f-number is. Important to note: the f-number is a fraction, the smaller the bottom number, the larger the aperture and the more light that is let in. So, f/1.4 is brighter than f/2.8.

The f-numbers on lenses are often arranged in a stop pattern to make them easy to use and understand:
1.4 – 2 – 2.8 – 4 – 5.6 – 8 – 11 – 16

The numbers seem arbitrary — don’t worry about them right now. More importantly is the concept of an f-stop, in that between each of the above numbers is a difference of one stop of light. When dealing with the aperture altering the light one stop, it is called an f-stop. So, the difference between f/4 and f/5.6 is one f-stop.

Finally, there’s one last common variable beyond shutter speed and aperture.  That’s the ISO, or sensitivity of the medium you’re using.  A digital camera can change ISO on the fly, making its sensor more or less sensitive as appropriate.  On a film camera, the film type dictates speed.  Common modern film speeds vary from 50 to 3200 (consumer film is usually between 100 and 400).  The scale looks like this:

50 – 100 – 200 – 400 – 800 – 1600 – 3200

Again, there is one stop difference between them all, meaning that 200 is twice as sensitive to light than 100 (one stop).  1600 is 16 times as sensitive as 100 (4 stops).

There are definite advantages in picking different film speeds.  With faster speed often comes greater grain (noise on digital) and slower speeds capable of higher resolution.  Faster speeds have obvious advantages in low-light, but slow speeds have advantages when wanting a limited depth of field.  There is no obvious hands-down winner because they are all useful for different applications.

Just this morning I just unloaded a roll of Kodak Tri-X I pushed to 3200 to shoot freehand at a night festival and loaded Fuji Velvia 50 that can require a tripod in daylight!

All sorts of combinations can be used to get a proper exposure:
– f/1.4, 1/1000 sec, ISO 400
– f/2, 1/500, ISO 400
– f/2, 1/250, ISO 200
– f/8, 1/60, ISO 800

These would all provide the same exposure given the same scene.  They would not all look the same, given that there are consequences of changing these variables, but the point is, if one was exposed properly, they would all be exposed properly.

Faster (larger) apertures = less depth of field
Slower (smaller) apertures = more depth of field

Faster shutter speeds = more motion stopped
Slower shutter speeds = potential blur from subject/background movement, handshake, camera vibrations

Fast ISO = more grain
Slow ISO = less grain

All of these things can be used creatively — depth of field, grain, blur. However, understanding stops is fundamental to predicting and being able to consistently get the shots you want.


Intro to Depth of Field

Posted in Tutorials with tags , , on September 18, 2008 by thtroyer

Minolta XD-11, MD Rokkor-X 50mm 1.4, Vivitar MC 2x teleconverter
Kodak BW400CN

Simply, depth of field (DoF) defines how much of the scene is in focus — both in front of and behind the focus distance. It’s another composition tool available to photographers, but it isn’t incredibly intuitive to pick up, so I’ll touch on the largest determining factors.

The aperture consists of multiple blades which can be closed down to limit the amount of light into the camera (like an eye’s iris). The aperture is the easiest control of depth of field, and the aperture is rated by f-numbers (which is a ratio of the focal length over the aperture diameter). So, the smaller the the f-number, the larger the aperture. For example, a f/2 is larger than a f/4.

The effect of opening or closing the aperture has two side-effects. The most obvious is the amount of light that reaches the film/sensor. For example, one of my lenses can close down 7 stops: f/1.4 is ~128 times brighter than f/16.

Secondly, depth of field is directly affected by the aperture such that a higher f-number results in a larger DoF. Effectively, the smaller the aperture is set, the more that will be in focus. The converse is thus true that a shallow DoF is the result of a larger aperture (lower f-number).

DoF is affected by various other factors that I’ll merely mention. For instance, wide angle lenses typically have greater DoF than standard. Also, the closer you’re focused towards infinity, the larger the DoF. I’ll revisit these ideas again later in an article about understanding and using hyperfocal distance.

Anyway, time for examples:
Ooh... Pretty.
Minolta XD-11, 50mm MD Rokkor-X f1.4, on Fuji Superia 400.

A shallow DoF can be used to isolate the subject from the background for whatever reason — distracting, ugly, etc. In this case, with a large aperture and close focal distance, the trees/yard/road are blurred into oblivion to create a dream-like state.

Yashica Electro 35 GSN, Fuji Superia 200

Controlling DoF can be incredibly useful in portraiture. Here, background blur is present, but not overwhelming. Had the background been sharper, it could become distracting; more blurry, then less interesting.

Minolta XD-11, 28mm MC W.Rokkor-X f2.5, on Kodak Tmax 100.

This is one of my favorites, and it’s a good demonstration that background blur (shallow DoF) is absolutely not necessary for a great photo. There is no “right way” to use DoF — it, like everything else in photography, is merely a tool. No more, no less.

(Not all cameras have access to aperture controls. Some point and shoot digital cameras allow it, but camera/lens design often limits the flexibility of such cameras. Consult camera documentation to see about access to either a manual or aperture priority mode).

Rule of Thirds

Posted in Tutorials with tags , , on September 11, 2008 by thtroyer

Alright.  I figured I’d start out simple.  The “Rule of Thirds” is a universally known rule throughout photography and other visual arts.  It is one of the most basic methods available to compose a shot, and it’s simplicity and effectiveness make it is an excellent place to start.

One of the common pitfalls I see among new photographer (and I was no exception) is a centered subject.  This is one of the few things you want to avoid.  It’s not that all photos with centered subjects are bad, but usually, they could be better.  Centered subjects usually create an awkward or unbalanced feel.  This is where the rule of thirds comes into play.

The concept is that there are stronger places to put the subject (or subjects) than in the middle.  In this case, 4 lines, and specifically, 4 intersections.  It gives you a way to break down the composition and place defining items at these stronger points.  These lines are at 1/3 intervals into the photos, as such.

The lines are common points to place things such as the horizon, buildings, or any other definitive horizontal/vertical lines.  The intersections are excellent places to put the subject, parts of the subject, or otherwise interesting things.  Using this method, it’s perfectly fine to not use all lines/intersections.

Taken with Kodak disposable

Finally, like any rule, this one is meant to be broken — it certainly isn’t the only way to compose a photo, but it’s good to understand what is aesthetically pleasing and why, and the rule of thirds is a great introduction into composition and a guideline that you’ll use for a long time.