Understanding ISO, Aperture, Shutter Speed and Exposure

“To consistently create better images, you need more than luck. You need to build a solid foundation of knowledge from which to draw on in every situation.

Photography is an art form largely based in evolving technology, meaning there will always be something new to figure out, new gear to buy if you’re well off financially (in which case, we should be better friends!), a new technique to perfect and new ideas to try. To absorb all of those innovative ideas, you need to put in the time and effort to learn. We highly recommend starting with the basics because a solid foundation is one of the keys to success.”

The above quote and graphic is an excerpt from our new ebook, “Photography. DUH; A firsthand account of
Landscape Photography and the mistakes NOT to make.”  🙂  The graphic is meant to be a short-hand reference to help you understand how ISO, Aperture, Exposure and Shutter Speed affect an image.  Why, you ask?  Because understanding those basic concepts will allow you to consistently create better images.  And really, who doesn’t want that??

If you’re looking for more easy to understand tips on how to elevate your landscape photography, this ebook is probably (definitely) for you.  Grab your copy HERE today!  It’s on sale for a limited time only for $5.99 (regular price $8.99).

Understanding Aperture

Aperture

As I’ve mentioned before, all of your camera settings work together in concert to create a (hopefully) well-exposed image. The aperture (hole through which light passes on its way to the sensor) can be adjusted, with the larger diameters allowing more light to pass through. It is comparable in function to the pupil of the eye. On a bright sunny day, our pupils shrink to pin-pricks, cutting down the harsh light. Similarly, in bright sunlight, a small aperture will generally allow just enough light to hit a sensor for proper exposure. On the other hand, at dusk, you may need to open the aperture wide to capture as much available light as possible.

The somewhat confusing thing about aperture is not the concept, but the labels. The size of the aperture is designated with an “f/” and a number. That number is the ratio of focal length to effective aperture diameter… <— (Greek?)

Now, I know…most of us aren’t math majors. Ratios? Pssshhaaww! I’m going to simplify this a little. What you need to know is that the f-number will tell you how wide the aperture is open, plain and simple.

Phew! Calculator crisis averted!

Now there is one more tricky thing to remember about aperture. The smaller the number, the wider the aperture, the more light you are letting in. It seems backwards, and personally, I found it difficult to remember when I first dove into photography. If you want more information about the hows and whys of aperture math, the interwebs has plenty of resources. For today’s purposes, however, all you need to know is that “small number = big opening”.

Example: f/4 will allow more light to pass through to a sensor than f/22. Therefore…

• f/4 ::: wider opening ::: allows more light through
• f/22 ::: smaller opening ::: allows less light through

Now that you have an understanding of aperture terminology, let’s talk about the practical effect these setting changes will have on your images! Well…beyond the amount of light it lets in, of course.

Sweet Spot

Every lens has an optimal aperture at which a scene will be sharpest with the least amount of blur (tack-sharp in photography terms). Please note, this refers to sharpness, not depth of field.

The blur is considered to be “defocus” blur on images with wide open apertures (f/1.8, etc) and “diffraction blur” for images with closed, or stopped down, apertures (f/20, etc). The sweet spot on every lens varies – generally it is between f/4 and f/8 – and opinions vary on how noticeable the impact this has on images.

Depth of Field

The larger the diameter of your aperture (smaller f-number), the shallower your depth of field. In laymen’s terms, the bigger the opening, the more blurry your background will be. This is important, because your choice in aperture needs to be suited to the type of shooting you are doing.

For landscape images, you generally want to have as much of the scene as possible in focus, so you would shoot with a larger aperture. Obviously, this will vary depending on lighting conditions, but in my experience, when photographing a landscape I generally shoot between f/8 – f/22.  (The tracks below were shot at f/14. For comparison purposes, the chain was shot at f/5.6.)

Tracks

Chain

However, if I am shooting a subject that I want to isolate from the background, or a portrait, a shallow depth of field is preferable. Similarly, if I want to create background bokeh (out of focus bits, such as circular discs of light in the background of images), I will open the aperture up wide (f/2 for example). It’s important to find the best aperture for the effect you want to create.

When shooting portraits wide open (for example with an f/1.8 lens), it’s especially important that the focus is exact. That depth of field is so shallow that you can easily have one part of the face in focus while another is blurry… At such a wide open aperture, the difference between sharpness and blur is only a matter of inches.

Soft skin is not necessarily a bad thing, but the eyes are the focal point of most subjects.  Generally, it’s important for the eyes to be crisp.  With an f/1.8 lens, if a face is angled, it may be impossible to have both eyes in focus.  In that case, I make sure the eye closest to the camera is sharp to give the viewer a focal point.

Of course, these are guidelines not rules…everyone has their own artistic vision. However, knowing the effect an aperture gives you the ability to drastically change, manipulate or fine-tune an image… Understanding apertures will be one of the greatest tools in your artistic bag!

Starburst

Are delicious! In photography, they are also visually delicious.

Reservoir – Barkhamsted, CT

If I am shooting a scene with street lights, or with the sun partially obscured and I want to create a starburst effect (where you can see beams of light, kind of like when you squint while looking towards a street lamp), I will shoot more towards the f/22 end of the spectrum.  Essentially, this does the same thing as you squinting your eyes. The higher the number, the more defined the light rays will be.

Distortions

Finally, it’s important to keep in mind the effect aperture can have on image distortions. These occur with more frequency at wide open apertures (smaller f-numbers).  At f/1.8 you will see higher incidences of both Chromatic Abberation and Vignetting. You can read about the former here.

The latter – vignetting – occurs because with a larger opening for the light to pass through, the intensity of the light hitting the sensor falls off at the edges of the image. In my mind, I imagine it similar to the intensity of water passing through a hose. If you put your thumb over the end of the hose, the water will hit its target with more intensity.

Conclusion

Obviously, there is more to aperture than just proper image exposure. Even small changes in your aperture settings can drastically affect your final product. Do you want a shallow depth of field, or are you shooting a landscape? Is it a night scene that would benefit from starburst? Are you looking for the sharpest image possible? Understanding the differences between aperture settings is part of mastering your craft…it’s one of the many tools we have to help shape an image.

The best way to become familiar with the various effects that aperture can have on your images t to practice, practice, practice. It’s the only way we make progress!