Fundamentals of Photography: Optimum Exposure (Part 3)

Ready to take control of your camera? In the previous two tutorials we touched on the settings that contribute to photographic exposure – ISO, aperture, shutter speed – and the relationships between them. In this concluding part we will explore various ways you can control exposure and be sure you are creating exactly what you want to create.

 

Shooting Modes

 

health spa pool at night

 

Stepping in at the deep end, manual exposure mode requires you to set ISO, aperture and shutter speed to achieve your desired exposure. So you control everything – but the camera’s inbuilt light meter can still guide you – check your manual to see how exposure information is displayed on your camera.

typical camera meter display
A typical camera meter reading will look something like this. Under-exposure or over-exposure may be indicated in increments of 1/2 or 1/3 of a stop.

 

Some people will find manual the most creatively satisfying shooting mode to work with. The beauty of digital is that you can shoot away until you get the settings just right –  but if you are inexperienced you might take time finding the best combination and risk missing the shot altogether!  Back at the paddling end of the pool, fully automatic exposure (possibly augmented by a range of specific scene options such as portrait, landscape, macro, snow, action etc) may do a good job some of the time, but may also get it wrong – and if you’ve read this far these are the very modes you are seeking to escape!

Between auto and manual many cameras offer two modes that allow you to alter ISO and either aperture or shutter speed creatively whilst the camera still determines the exposure by adjusting the other setting for you.

 

Aperture priority is the mode of choice for many photographers. I use it for most location photography since depth of field is usually of primary importance to me. If your subject is stationary this is usually the mode to use.

a nut
This nut was shot at an aperture of f8. Note that distance between camera, subject and background also influences depth of field.

 

Shutter priority comes into play when you are shooting moving subjects such as the local fun run, your dog bounding across a meadow, fast flowing water etc. You will want to control the amount of motion blur in the image – using the shutter speed.

Blur can also occur when your hand moves whilst shooting – this is called camera shake. You would think that holding a camera still for one second wouldn’t be difficult – try it and look at the resulting picture on a computer. A tenner says its blurred. Even with VR (vibration reduction) lenses you will likely need shutter speeds of under half a second to avoid camera shake. So use shutter priority mode to be sure of a fast shutter speed when shooting hand-held (or, better still, purchase a monopod or tripod to support the camera).

 

panning street scene
A long exposure during which the camera was deliberately moved to create motion blur.

In manual, aperture priority and shutter priority you normally adjust the aperture and/or shutter speed via the camera’s command dial(s) – details vary with camera make and model, so check your manual for precise details of how to work in these modes.

Whatever the shooting mode, ISO can be left on auto-ISO although I only use that in situations where light levels are changing very rapidly – such as a live performance under theatrical lighting.

Under most circumstances, you check and (if necessary) adjust ISO manually when you start shooting a scene, then leave it alone until the light level changes significantly (for example, when moving outside from indoors).

Set the lowest ISO you can, as that will render the best quality image. In low light environments where a tripod cannot be used you may need to increase the ISO.

 

noisy low light environment
Click on the image to see the ugly “noise” that resulted from a high ISO setting.

 

Exposure Compensation

 

You have probably noted that the camera still exerts some control over exposure in every shooting mode apart from manual.

What if the camera gets it wrong?

What if your interpretation of a scene does not correspond with the correct exposure determined by the camera?

In other words, how do you achieve your optimum exposure without switching to fully manual mode?

There is another feature that overrides the camera’s choices in automatic or semi-automatic modes, and that is the exposure compensation button.

 

high key frozen beauty

 

With this function you force the camera to increase or decrease overall exposure. This can usually be done in increments of 1/3 or 1/2 stop. Adjustments of up to plus/minus 3 – 5 stops can be made, but each stop is a doubling or halving of the amount of light hitting the sensor – so this is a control that usual responds best to a gentle touch.

In automatic modes you don’t know which setting (aperture or shutter speed) the camera will alter to affect compensation. In aperture priority the camera will change the shutter speed when exposure compensation is invoked and in shutter priority it will alter the aperture. In manual mode it does nothing at all.

It is important to remember that exposure compensation remains set until you physically unset it. If you forget to do this after shooting, and then just switch on and start shooting a few days later, you will probably end up with some very badly exposed shots indeed!

Check your manual again to see how you implement exposure compensation on your camera.

 

Viewing Modes

 

When playing back the images you shot there are two further features digital cameras provide that make achieving optimum exposure easy for creative photographers – the highlights view and histogram view (names may differ on your camera; rotate through viewing options until you find the functions described below; very basic cameras may not offer these features).

If you over-expose a scene the brightest areas may be reduced to pure white. The highlights view shows such clipped highlights as flashing areas in the LCD display. It will, however, not tell you when there is shadow clipping (where dark areas are under-exposed to pure black). This is probably because clipped highlights are generally considered to be more undesirable than clipped shadows.

The histogram view is a more sophisticated tool. It takes the form of a graph depicting the range of tones (shadows – mid-tones – highlights) within the image.

 

histogram
The histogram in Photoshop’s levels tool is essentially the same as the histogram your camera displays. Both show the dispersal of light, dark and mid-tone pixels.

If the graph bunches at the far left of the horizontal axis, or does not reach the right edge, you may have under-exposed the scene. If it bunches at the far right, or does not stretch to the left edge, you may have over-exposed the scene. Adjust ISO, aperture or shutter speed to compensate, and shoot again – unless such under- or over-exposure was your intent. This tool is just a guide – there is no such thing as the perfect histogram.

 

This has been a very small introduction to a very big subject. Until you put things into practice it will probably remain a bit of a blur; learn to control exposure by playing with the functions described above. Shoot a scene (any scene, but ideally one where you do not immediately achieve great results) with a variety of settings and compare the results – it will all start coming into focus.

To chat about photography or Photoshop tuition, call me on 07757 259390 or send me a message via email.

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Restoring St Mary’s Church, Wivenhoe

Saxon in origin, the church that currently provides a hub (cultural as well as spiritual) in Wivenhoe is a primarily Victorian construction. Many photographers love snapping churches, and I was delighted when a representative of St Mary’s asked me to document some of the restoration work currently being undertaken there.

 

st marys Wivenhoe exterior colour

 

The main part of my work will involve before-and-after shots of exterior masonry, along with some wide angle contextualising shots. Most of the exterior restoration work is on the south and west sides of the building, and access to diagrams of the areas being restored allowed me to determine some of the more visually interesting sections to photograph. On the inside, it is sometimes quite obvious where some TLC is required, such as where the plaster work has fallen away below.

plaster missing from ceiling

 

The majority of shots here, however, simply show various areas of the church with the scaffolding erected. This is not a commercial commission, and there is some room for artistic licence above and beyond the documentary requirement.

 

stained glass window and ladder

 

One of the more obvious beauties of photographing church interiors is the light coming through the stained glass windows; I chose to rely entirely on ambient light to capture the interior scaffolding. Much of the window light was blocked out by the wooden boards that provided a platform for workinmg on the ceiling; a tripod enabled me to keep the ISO down to a relatively noise-free 400 by facilitating a slow shutter speed of around about half a second.

 

scaffolding near rafters inside church

 

Had this been a strictly documentary task, I may have used a bit of flash to brighten the interior of the church without blowing out the windows. However, with licence to play, I went for a high contrast look that relied on window light alone to really make the scaffolding stand out from the surroundings.

scaffolding and church pews

 

The tripod came in handy again when getting a view along the scaffolding,  level with the bottom of the window in the background. With the tripod fully extended and balancing on the pews a two second delay on the shutter release ensured there was no camera shake with the long-ish exposures still being employed.

 

scaffolding and window

 

I ended the afternoon with a bit of abstraction, contrasting the scaffolding with the stained glass. Removing the colour from a stained glass window may seem a little counter-intuitive, but it helped balance the elements in the shot.

 

scaffold and window abstract

 

To learn more about St Mary’s Church, including the ongoing restoration work, visit stmaryswivenhoe.org.

 

St Marys Wivenhoe exterior black and white

 

Some more examples of my location photography can be found here or to discuss your own unique requirements, just drop me a line.

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