Exercise – concentrating light

Keeping the set-up from the previous exercise on lighting angle, the next photographs taken were using a concentrated light rather than diffused. Fig.01 shows the result when a large, diffused light source is used close to the subject. Soft-edged shadows are present, providing visual clues to the texture, form and shape of the figure. The light is next to the camera and looking down at approximately 45 degrees, meaning that the whole figure is evenly lit with good detail and colour information.

Fig. 05 - Light in front and 45 degree above

Fig. 01 – Light in front and 45 degree above

If the intent  is to draw attention to only a limited part of the scene, then one option is to concentrate the light produced by the light source – a speedlight in this example. So instead of a diffuser that is much bigger than the light source, an inverted cone is used that effectively funnels the light. These snoots can be bought to fit over the flash gun, or made from card and attached to the light. Fig.02 shows the effect of this lighting with the light in a similar position as the picture above. Only a small area is lit and because of the absence of any diffusion, shadows are very hard (under the cravat for example). There is a small amount of light that has bled onto the white box that the figure is sitting on and we can just about make out his hands. The edges of the pool of light are slightly soft.

Concentrated

Fig. 02 – Concentrated

Further concentration is possible by using a honeycombed grid in the front of the snoot (fig.03). This is an array of hexagonal channels fitted to the front of the snoot down which the light shines. Where normally light beams would be able to spread into a wide pattern, here they can only travel in a reduced spread, straight down the channels. Even though the material used is matt black, some light does bounce off the walls of the tubes causing softening of the edges of the spot of light. These grids are often used in low-key portrait photography for just this effect.

Concentrated Grid

Fig. 03 – Concentrated with grid

Exercise – Contrast and shadow fill

Having learnt to soften light using diffusers in the previous exercise, this explores how we can change the contrast in a scene that is lit by photographic lighting by filling the shadows and reducing the difference between light and shade.

The camera was mounted on a tripod with a 100mm lens looking at a pile of junk on my shed floor carefully constructed still-life arrangement with the flash 90cm to the right of the shot and slightly higher than the subject, set at full power. Camera settings remained the same throughout the shoot.

Naked flash only - Canon 5d2, iso 200, 100mm, 0ev, f/16, 1/100s

Naked flash only – Canon 5d2, iso 200, 100mm, 0ev, f/16, 1/100s

First off, I photographed the scene with the flash gun only. As seen previously, this high-contrast light gives sharp-edged shadows and high contrast – that is a big difference between the lightest highlights and darkest shadows. It means that any part of the scene that is in the shadow of the saddle and cogs to the right of the image are invisible in shadow.

Diffuser - Canon 5d2, iso 200, 100mm, 0ev, f/16, 1/100s

Diffuser – Canon 5d2, iso 200, 100mm, 0ev, f/16, 1/100s

Next up, I fitted the same 60cm square diffuser used in the previous exercise. It softens the edges of the shadows and because the size of the light source is bigger, it is able to light areas that were in shadow when only using the flash. The contrast is reduced, but at the same time, because the same exposure settings were used, the image is slightly darker overall.

Reflector 90cm - Canon 5d2, iso 200, 100mm, 0ev, f/16, 1/100s

Reflector 90cm – Canon 5d2, iso 200, 100mm, 0ev, f/16, 1/100s

For the third image, a circular reflector was positioned to the left of the scene, opposite the flash at about 90cm from the saddle, roughly the same distance as the flash is to the right. The reflector was white material with a matt finish but reflects enough light to begin to give some detail in the shadows. For example, we can now see some shape in the front part of the saddle and the curve of the leather.

Reflector 50cm - Canon 5d2, iso 200, 100mm, 0ev, f/16, 1/100s

Reflector 50cm – Canon 5d2, iso 200, 100mm, 0ev, f/16, 1/100s

Next, the same reflector was then moved closer, to around 50cm from the saddle. The intensity of a diffuse reflection, such as the one bounced from the reflector, follows the inverse square law meaning that a source at any particular distance will light an object with and intensity four times as bright at the same source, twice as far away. Or more simply, move the reflector closer, it’ll have a greater effect. This is demonstrated in the image above that is now much more balanced with good detail in the areas of the image that are not lit by the main light.

Silver reflector - Canon 5d2, iso 200, 100mm, 0ev, f/16, 1/100s

Silver reflector – Canon 5d2, iso 200, 100mm, 0ev, f/16, 1/100s

The white reflector was then swapped for a silver reflector with a shiny surface, meaning that even more light is being reflected back towards the scene from the main light. There is still a gradient (the flash is still brighter than the reflected light) but the balance is much better. We can now see colour and form in the saddle and highlights on the rails showing is that they are a tubular shape. We can now identify each individual part in the scene.

Gold reflector - Canon 5d2, iso 200, 100mm, 0ev, f/16, 1/100s

Gold reflector – Canon 5d2, iso 200, 100mm, 0ev, f/16, 1/100s

Swapping the reflector for a gold coloured shiny surface means that all of the reflected light is now coloured. This demonstrates what we have learned above in that all area lit only by the reflector are gold. Surfaces lit by both are less coloured and to greater or lesser extent.


 

Fill flash full power - Canon 5d2, iso 200, 100mm, 0ev, f/16, 1/100s

Fill flash full power – Canon 5d2, iso 200, 100mm, 0ev, f/16, 1/100s

Rather than using reflectors, the same effect can be achieved by using a second light source. Here, I positioned a second flash gun opposite the first, at the same distance from the scene and used a hand held diffuser in front of it. Guide numbers of flash guns is probably a topic for another time, but suffice to say, the Canon light on the right, used as the main light (guide number 43) is slightly brighter than the Jessops unit on the left (GN36). The resulting image is well balanced and pleasantly lit. There are still some areas of shadow, but they are very soft edged. It is the lowest contrast image of the set.

Fill flash half power - Canon 5d2, iso 200, 100mm, 0ev, f/16, 1/100s

Fill flash half power – Canon 5d2, iso 200, 100mm, 0ev, f/16, 1/100s

This time, the second flash was not diffused, but reduced to half-power. The highlights (on the inner curve of the leather) are bright and some detail is lost.

Fill Flash 1/16th - Canon 5d2, iso 200, 100mm, 0ev, f/16, 1/100s

Fill Flash 1/16th – Canon 5d2, iso 200, 100mm, 0ev, f/16, 1/100s

Finally, the same arrangement but with the flash at 1/16th power. The small, high contrast light source does little to to reduce the contrast of the scene or soften shadows. It only contributes some highlights and edge lighting (to the spanner for example), improving from the earlier single diffused light picture.

This was an extremely useful and satisfying exercise. A high contrast image can be powerful and useful to show outline and shape, but often at the expense of detail that will show us form and colour. Understanding how to reduce contrast is valuable.

The set-up

2014-07-12 13.24.52

References

Hunter, F et al. (2012) Light – Science and magic. An introduction to photographic lighting. Oxford; Elsevier Inc.

Exercise – Focus At Different Apertures

Another exercise to help us get to know the camera and another to get us used to the effect that aperture has on depth of field.

I had a walk down to the Great Central Railway and took some cheesy pictures of steam trains. While waiting for the next to arrive, I took these shots of the oil-soaked fence that runs next to the spot where the locomotives stop and then take the strain once more to haul their load towards Leicester.

I didn’t use a tripod and should really have considered having equal range in the foreground and beyond the focus point. Also, because I’m looking down on the subject, rather than (only) along it, finding the ‘slice’ that is in focus is more difficult. I used a 100mm lens and had the camera in aperture priority (Av) mode so that the shutter speed changed automatically to suit the aperture. If I’d been doing this manually, I’d have needed to slow the shutter as the aperture size got smaller (and f-number bigger).

OCA (2)

The focus spot is obviously the centre of the sign. The first shot was at using my largest aperture f2. The in focus area is limited to just a couple of letters in the centre of the sign. While you can see that the sign is attached to a fence, it is difficult to be sure what is beyond the fence and many other details are completely lost. The ground is simply grey, brown and green shapes with our brain filling in the gaps to suggest to us that the shades of grey under the fence are probably stones or gravel.

This view does however, focus the eye onto the sign. There is no doubt about what the picture is of, or which direction the trains are. This very shallow depth of field is an effect that I like and use for many subjects, even though lenses are often not nearly as sharp at these apertures as they may be when stopped down a little.

OCA (1)The second shot is taken midway across the aperture range at f8. Now, much more of the scene is in focus. We can now see a little more of the fence – two of the thinner uprights are in focus, approximately 3 feet apart. We can also see and identify the track and sleepers in the top left corner of the picture and gaps between the slabs on the path on the safer side of the fence. In the top right, a brown shape on the path that because of the others on the floor, can be assumed to be an autumn leaf. The centre of the image is very sharp, even at full size.

OCAThe final shot (I took pictures at more aperture settings than I’ve included here) was shot at the lens’s minimum aperture, f22. Almost all of the image is sharp and every detail can be identified. The slabs can be counted individually, the leaf in top right is clear enough to imagine the crunch if you were to step on it.

The final step in the exercise was to print out the pictures and draw lines at the limits of focus. Here’s where I realised that I’d made things trickier by shooting down upon, as well as along the fence. This meant that I could not draw 2 parallel lines from top to bottom but rather a slice made up of parts of the subject that were the same distance from the camera.

Aperture Exercise Printed

The maximum width of these sections on the printed images were 10mm (3.5% of the overall width), 50mm (18%) and 200mm (71%) respectively.

As I said earlier, I’d usually go for a limited depth of field, unless shooting landscapes or needing to show an entire scene in detail. I’d leave the viewer to do some of the work and think for him or herself what might be contained in the out of focus areas. Also, as demonstrated here, the narrow depth of field concentrates they eye of the viewer onto the area of the picture that I want to show them.

Finally, here’s another picture of the same sign, but this time in the out of focus area of the image. This picture has a slightly smaller aperture (f3.5) and the subject is further away, meaning a much greater area is in focus.To The Trains

Exercise – Focus With A Set Aperture

In this exercise, aimed at helping us to understand the effects of aperture on the image, the aperture remains fixed but the focus point changes.

I used a 100mm lens at f2. This is a lovely portrait lens because of how well it isolates the subject with a narrow depth of field and how good the out of focus parts of the image look. You can read an awful lot about these out of focus areas, or bokeh, and the ways in which various lenses recreate it. In my experience, it is more about the subject than the equipment.

OCA (7)The depth of field on this lens is so shallow that in the first picture, we can tell that someone is holding an apple, but would be guessing to identify who – my guess is the Mona Lisa…

OCA (6)…I was wrong! The second picture has the same depth of field but with a different focus point. The apple held at arms length is enough to give this huge amount of blurring to areas other than those focussed upon.

This exercise teaches us that a part of the image can be isolated using the aperture to bring attention to that aspect. The eye is drawn to the objects or areas that are in focus, maybe because it has less work to do to understand what is hidden in the bokeh. If I was selling apples, the first picture may be the one I’d choose. As it’s my wife in the picture however, I much prefer the second one of course.

If I had been taking this picture for something other than the exercise, I’d choose an aperture a little smaller, but leave the focus on the apple, reducing the blur on Gosia’s face to a level that still identifies it as her but not as extreme as the first picture.