In Plain Light 02.18 – The Words Issue:
Photography Definitions

Welcome to this month's newsletter!

In this issue: photography definitions from A to Z! Jump to a letter if looking for something special, or scroll down to read all definitions one after another.

A  B  C  D  E  F  G  I  M  N  P  S  V  Z

• Further links
  

Photography isn't exactly a science, but even so, it is rooted in one. With this, and its strong technology links to boot, it is no surprise that it comes with a whole bank of its own terms.

These photography definitions is what we are going to explore in this issue.

Some of them are explained in more detail in dedicated articles within the tutorial and the Tips section. There are direct links to these pages all over the text.

Essential photography definitions

This is also how it is denoted as such: f/8 stands for an aperture of some lens opened to the diameter equal one-eighth its focal length.

This definition lets understand why long lenses with large apertures are so rare and expensive. A 400 mm lens endowed with f/2 would need to somehow embed the entire focal length, and then open to the diameter of 20 cm, or 8". This means rather a lot of glass.

Confusing is that this notation varies in lens specifications, descriptions and reviews. You would find the same aperture value also referred to as 1:8, f8, or simply 8. The two latter spellings are particularly misleading, as they make incomprehensible why a larger number, say 16, would describe a smaller aperture.

Note that this perfectly makes sense when aperture is presented as a fraction.

The maximum aperture of a lens is always present in its denomination. The larger this maximum aperture is, the faster the lens is considered.

APS-C is an image sensor format equal in size to the legacy film Advanced Photo System type-C, approximately 25.1 x 16.7 mm.

APS had been introduced in 1996 as the last significant development in film photography before digital came to replace it. The smaller frame sized at 30.2 x 16.7 mm allowed for three fixed image dimensions. The full APS frame, or APS-H, could be cropped at wish to "classic" APS-C or "panoramic" APS-P, 30.2 x 9.5 mm, when being developed.

The APS-C frame is about 3 times smaller than the 35-mm "full-frame" format and makes smaller and lighter cameras possible. Due to it, lenses also require smaller focal lengths to achieve the same spatial coverage, and thus can be reduced in size, too.

The dimensional factor of 1.5 applies without change to the focal length. An 18 mm APS-C lens has about the same coverage as a 28 mm full-format lens. Conversely, this latter lens will have the coverage of a 42 mm lens when attached to an APS-C camera.

Unlike colour film, which consists of several emulsion layers sensitive to different light wave lengths and hence colours, the vast majority of image sensors in digital chips have only one layer. As a consequence, light-sensitive elements in sensor cells are unable to record the complete colour information in the light reaching them.

Instead, each sensor cell selectively measures the intensity of one dedicated colour channel conducted to it through a filter. The entirety of these filters builds a mosaic pattern whose Bayer variety is the most common one.

This is how a typical digital sensor sees the world. Green cells dominate with 50% of the lot, while red and blue cells make the rest with 25% each. The recorded information in every colour channel is patchy and needs interpolation [read: an educated guess] to calculate missing fragments from the values in their neighbouring cells.

In the image above, each cell only knows the value of its assigned colour component for sure. Green cells have a particularly hard time to tell their real colour, with only two cells of each other kind to help them out.

A true full-colour alternative to Bayer sensors is offered by Sigma with their Foveon chips. A notable workaround for conventional sensors has been developed by Ricoh for their high-end Pentax K camera models (see Pixel Shift Resolution).

Bokeh. The Japanese word stands for the aesthetic quality of the blur created by a specific lens in out-of-focus image areas. Pronounce BOH-kay.

While being of little significance for landscapes, this lens characteristic is quite important for portrait and wildlife photography. The effect can be very irritating when handled badly by the lens, and it can't be easily recovered in post-processing.

I like to think of this as a genuine example of virtual reality, not present in real life and only "dreamed" by the lens.

Composition. The idea of composition isn't exclusive to photography. The concept is known and studied by all visual arts, and its principles are followed—or should be considered, to the very least—by all visual artists.

Composition defines the internal structure of an art object—be it a painting, a sculpture, a graffito, a drama stage, or a photography image—and the relations between its constituting parts. In a photograph, these include the main subject and secondary ones, the fore- and background, negative space, lines and patterns, colours, and how all of it works together—or fails to do that.

When working with wide-angle lenses, landscape photographers' ability to reduce depth of field is very limited—down from f/5.6 pretty much everything will appear sharp in the final image.

Many modern cameras will provide some kind of depth of field preview while composing and focusing.

Distortion. Distortion with regard to a photographic lens defines the latter's inability to render straight lines as such. A square grid photographed with the lens prone to distortion will feature patterns rather resembling a barrel or a cushion.

The EV arithmetic is something to keep an eye on when changing exposure settings. To achieve the same exposure value, eventual tweaks should be counterbalanced by modifying other exposure parameters.

For example, opening up aperture by 1 f-stop (+2 EV) would also require, say, halving both exposure time and ISO (-1 EV each).

Since the underlying scale is logarithmic, the difference of 1 EV is equivalent to doubling or halving the amount of light in question. Underexposing by 0.5 EV, i.e., the difference of -0.5 EV, means reducing the amount of light reaching the sensor by √2, or around 1.4 times.

Exposure. The definition can describe a single shot, like in "I just took two exposures to have the job done", as well as the process of light metering, like in "Lighting conditions made the exact exposure extremely difficult".

In any case, the definition involves setting aperture, shutter speed, and ISO to create a photographic image. The correct exposure, though not the only contribution to a successful picture, is still an indispensable one.

Exposure compensation is the result of human judgement in the evaluation of one's camera's attempts at exposure—feel free to replace "human" and "one's" with "your". If you are not convinced by the results at hand, or expect current lighting conditions to fool your camera, step in and under- or overexpose deliberately. Most cameras nowadays will allow manual compensation at least from -2 to +2 EV in 1/2 or 1/3 EV steps.

Fixed-focus lenses are in use by disposable and low-end cameras, in phones, webcams, and surveillance cameras, where high image quality is often not a priority.

It is the distance over which parallel rays [from a source in the infinity, like with most landscapes] are brought to the focus. The shorter this distance, the wider is the lens's angle of view.

Though modern lenses consist of several optical elements grouped together, the principle is still the same. Short lenses with wide angle of view are best fit for landscapes, while long, or telephoto, lenses are especially good for portraits or wildlife photography.

The short range usually ends at 35mm, and the long range starts at 85mm. Within these limits lies the standard range.

Focusing is the process of adjusting the camera lens in a manner to render some parts of the image sharp while blurring its other parts.

For objects close to the camera, this process actually involves moving the lens inside its body in order to get a specific scene plane rendered exactly in the lens's focal plane [which coincides with the sensor or film position].

If left to the camera itself, that is, to autofocus, what you get is what your camera thinks you are trying to achieve. The most straightforward approach in deciphering your intentions results in focusing on objects near the image centre. Fancier methods also consider faces within the frame, or particularly bright objects.

If you want/need full control over your camera, learn its handling of manual focus.

Foveon sensor + compact camera model from 2009 (5:39 min.)
YouTube channel by Martynko

While higher ISO values still tend to increase digital noise in the resulting images, the effect gets more and more contained by the year in advanced camera models. Reasonable results at ISO 25600 are not unheard of anymore.

With it enabled, the camera would use lighting information coming from several (many) predefined points throughout the frame and average this information according to some algorithm in its software.

Alternatives to this approach are centre-weighted and spot metering.

When executed right, landscape images with much negative space can be very evocative and emotional.

Pixel Shift Resolution explained (1:01 min.)
YouTube channel by pentaxplus

(Open the [silent] clip in full-screen and see it in HD in order to follow the comparison.)

You can use longer exposure times, or, if you will, slower shutter speeds, to blur moving objects or features, such as water or clouds, in the resulting picture.

Zoom is more convenient, especially when travelling, since you don't need to change lenses often, if at all. However, all-in-one lenses with a huge zoom range usually underperform with regard to image quality, in particular, near the edges of their length bracket.

Didn't find what you were looking for? Ask below! Leave a comment, and I'll add the missing part—consider this work in progress.

Useless knowledge: Don't shoot

Ever wondered why photographers' speak is so rich in words with negative connotations? It never stops to amuse me.

We try to catch the moment, chase the light and the motif, then expose to take, capture, and shoot images, as if they were targets, and every successful one a kill.

As if every photo outing were a safari.

As if we were on the prowl.

The most popular French photo magazine for the last over 40 years is called Chasseur d'Images, "Picture hunter".

Why is that?

“A great photograph is a full expression of what one feels about what is being photographed in the deepest sense, and is, thereby, a true expression of what one feels about life in its entirety.”

Ansel Adams

Can it be a hunt trophy?

Stop shooting—start creating.

Bonus track

It's all about words

Tags: #inplainlight #photographyspeak #comingtoterms #bydefinition

Unattributed images on this page are sourced from public domain via Pixabay and Wikimedia Commons.

Photography definitions explained in detail

Camera exposure and its elements

Understanding camera exposure principles and settings, including exposure compensation, bracketing, and manual exposure.

Aperture and depth of field

Learn what aperture is and how its different settings can change the look of your images.

Shutter speed and motion blur

Learn how exposure time can add dynamic and movement to your images.

ISO and digital noise

Learn how photo noise is related to your chosen ISO value.

Metering modes

Understand different metering modes and when to use them.

Exposure compensation and bracketing

Learn how to overcome shortcomings of your camera's automatic exposure metering.

The sunny 16 rule and manual exposure

Measure up to your camera and take exposure in your own hands with this simple and easy to follow rule.

Photography composition

Composition is ultimately what your photography stands or falls with. Even with the exposure nailed down, if your images don't engage the viewer, nobody will bother. Read here what matters in order to succeed.

Panoramic cameras

Ever wanted to try one? Here are your current options!

Choosing a camera lens

Everything you need to know when looking for a new camera lens, in one place: manufacturers, mounts, formats, types, and how to understand all those mystic lens labels.

Understanding digital camera lenses – and their reviews

Understand how to tell good digital camera lenses from the rest when reading their reviews.

Other resources

Foveon image sensor

If you are curious about this very different sensor, pay a visit to the camera manufacturer who uses it. While at it, take a look at their sample image gallery and some real life shots. The latter are also available at another location. (Images presented are downsized JPEGs—compression may have done some damage to them.)

Pentax K-1 series site

Learn how to obtain full colour information with a ubiquitous Bayer sensor, and what else the brand has to offer.

Previous issue

01.18 – The 2017 review issue

2017 is over but not yet forgotten. To make it stay this way a bit longer, find here the year in review—through archived blog entries.

Following issue

03.18 – The weather issue: How to forecast weather

For those who enjoy—or suffer—planning ahead. Learn how a small Swiss company manages to forecast weather in every place in the world just by studying their own forecasts from the past, why this works, and how you can benefit from their results.

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