My Take on Exposure: Part Four

NB: This series of posts will convey my understanding of photographic exposures. While I hope it serves a useful purpose, I by no means describe this series as a be-all, end-all resource on exposure. As ever, if you feel I have made a factual error, please correct me.

Exposure is a combination of how long and how much light an imager (digital sensor or film) is exposed to by the lens and shutter. ISO/ASA (and less commonly nowadays DIN) is the standardised measure of an imager’s light sensitivity (i.e. sensitivity dictates how much light and how long for). In Part Four of this series, I shall attempt to integrate these three elements.

Somebody walking through campus on a miserable day. The yellow umbrella caught my attention. The 1/4 shutter speed accentuates how quickly they want to get where they're going. The f/8 aperture provided enough depth of field to put them in the context of their surroundings. ISO 200 was necessary to achieve this effect.
Somebody walking through campus on a miserable day. The yellow umbrella caught my attention. The 1/4 shutter speed accentuates how quickly they want to get where they’re going. The f/8 aperture provided enough depth of field to put them in the context of their surroundings. ISO 200 was necessary to achieve this effect. Exposure is biased to the highlight areas; note the lack of detail in the tree at left, whose silhouette helps frame the main subject.

Sitting down to write this, the phrase “personal preference” is coursing wildly through my mind. At the end of the day, the way in which you expose a photograph is as much a reflection of your thoughts as the composition. In fact, when you consider that depth of field, noise/grain and depiction of movement are directly related to your chosen exposure, I posit that composition itself hangs upon a well-chosen exposure.

A nice yellow flower. The f/11 aperture means most of it is well defined; due to the close range, it is still separate from the background. Captured at ISO 400 for a hand-holdable shutter speed, and 1/160 second to under-expose, thus further isolating it from the darker background.
A nice yellow flower. The f/11 aperture means most of it is well defined; due to the close range, it is still separate from the background. Captured at ISO 400 for a hand-holdable shutter speed, and 1/160 second to under-expose, thus further isolating it from the darker background. Not how the shadow areas have darkened, but highlight detail is well preserved.

As well as the aforementioned factors, there are, broadly speaking, three exposure levels: under- (deeper shadows and more detailed highlights), “normal-” (evenly balanced shadows and highlights) and over-exposure (lighter shadows and less detailed highlights). These are useful for changing or setting a mood, such as under-exposing for a moodier atmosphere, or over-exposing for a much happier one.

Someone crossing a bridge on campus in the rain. ISO 320 allowed me 1/60 second at f/2.8. This was enough to freeze the slow walker, whilst focusing on the foreground foliage
Someone crossing a bridge on campus in the rain. ISO 320 allowed me 1/60 second, which was enough to mostly freeze the slow walker. Focusing on the foreground foliage at f/2.8 limited the depth of field to here, somewhat blurring them, as if they were a distant memory passing (or your own interpretation). The “normal” exposure gives a good balance between highlight and shadow detail, which helps the faded aesthetic to a point (or however it fits your own interpretation).

Rather than exploiting my typical verbosity, I think I’ll let my pictures (and their captions) do the explaining this week. There are justifications for choosing just about any exposure in any circumstance, so the best advice I can give is to try out the different settings, and experience how they change the way you depict things. You may find you prefer particular styles for particular subjects, or, that your choices vary depending on your mood or the weather. It’s not untoward to use several different sorts of exposure between successive photos at all.

Autumn oak leaves. It was bright, so I ran my lowest sensitivity (ISO 200). To limit depth of field to the foreground leaves, I set an aperture of f/4, which led to a shutter speed of 1/160 second. This has been underexposed slightly to enhance the vibrant colours (see the blue of the sky) in the background).
Autumn oak leaves. It was bright, so I ran my lowest sensitivity (ISO 200). To limit depth of field to the foreground leaves, I set an aperture of f/4, which led to a shutter speed of 1/160 second. This has been underexposed slightly to enhance the vibrant colours (see the blue of the sky) in the background). The translucent nature of the leaves has given relatively even illumination in spite of this.

To summarise, each element of exposure affects the way your image depicts the subject. You can use these elements in combination to craft your image in the way you see fit. Personal preference in the creation of the image is what makes it yours. If there is anything you want to ask about, feel free to e-mail or comment, and I’ll reply as promptly as possible.

A bike stand at the rear of the Registry Building, University of Otago, Dunedin. Since I wanted to focus on them primarily, I used an f/4 aperture. This rendered the person in the background out of focus; to further blur them, I used a slower shutter speed of 1/25. This forced an ISO of 400. The good balance between shadows and highlights is from a "normal" exposure, helped by the diffuse lighting from the rainclouds.
A bike stand at the rear of the Registry Building, University of Otago, Dunedin. Since I wanted to focus  primarily on the bikes, I used an f/4 aperture. This rendered the person in the background out of focus; to further blur them, I used a slower shutter speed of 1/25. This forced an ISO of 400. The good balance between shadows and highlights is from a “normal” exposure, helped by the diffuse lighting from the rainclouds.
A peach coloured flower of some description. Due to the bright lighting, I used ISO 200. To limit my depth of field and focus on this single group of flowers, I set an aperture of f/2.8. Using a shutter speed of 1/2000 second, I managed to overexpose a little, which softened the colours and helped to wash some more detail out of the background.
A peach coloured flower of some description. Due to the bright lighting, I used ISO 200. To limit my depth of field and focus on the foremost flowerhead, I set an aperture of f/2.8. Using a shutter speed of 1/2000 second, I managed to overexpose a little, which softened the colours and helped to wash some more detail out of the background. This is the reason for the sparse areas of light in the background. Overexposing also softened the shadows cast by other flowers on the plant.
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