Wednesday, 29 May 2013

How exposure affects miniature photography

Before you can improve on your miniature photographing skills, it is crucial to get to grips with a basic concept i.e. exposure, which is a measure of how much light the camera's image sensor is exposed to during a shot. In simple terms - an underexposed shot is one that is too dark while an overexposed shot is one that is too bright. For a better understanding of exposure, you will have to explore all the elements involved - ISO, aperture and shutter speed - or the exposure triangle in short.  

Before I get to the more practical aspects of how to utilise the exposure triangle to get the shots that you want of your miniatures, let us first have a quick look, individually, at the three components of exposure as well as some basic theory of how they relate to one another.

Exposure Triangle in a nutshell
a) ISO is the sensitivity of camera sensor to light in which the higher the ISO setting, the more sensitive the camera sensor is to light so less light is required when taking the shot. Too high an ISO setting may introduce noise (grainy patterns) into your shots. General rule of thumb is to keep ISO as low as possible but the latest DSLR cameras are able to take good quality shots at high ISOs.

b) Aperture is an opening at the camera lens which controls how much light passes through to the camera sensor. While a bigger aperture size allows more light into the camera, the trade-off is a lower depth of field. Aperture size is measured in f-stops in which the larger the f-stop number, the smaller the opening (this takes a bit of getting used to) so f4 is a larger aperture opening than f8.

c) Shutter speed controls the length of time light is allowed to hit the camera sensor. At high shutter speeds, less light is allowed into the camera but your shots won't be affected by shaky hands (something important to consider when you are taking shots with a dedicated macro lens). While a high shutter speed also allows you to freeze-motion-capture a fast moving object, this is not an important consideration when taking shots of stationary miniatures.

So how do they all tie together? Well, when you change any one component in the exposure triangle you will most likely need to amend one or both of the other components. For example, you have just taken a perfect shot at the correct exposure and then decided to increase the depth of field by using a smaller aperture opening. Now less light will hit the camera sensor (shot is underexposed). To regain the correct exposure, you will need to use either a slower shutter speed which increases the length of time that the light hits the sensor, or set a higher ISO to increase the sensor's sensitivity to light.

In general, when taking photographs of miniatures, I prefer a high depth of field so as to take in as much detail of the miniature(s) as possible. This means the lowest aperture size I can get away with before a lack of light becomes a hindrance. I also try not to set the shutter speed too low because although I use a tripod to take shots which can help mitigate against shaky hands, at a low enough shutter speed, the act of just pressing the shutter button itself can shake camera slightly and spoil your shot. This can be solved by using a camera trigger cable but I don't have one yet.  

Practical application of the Exposure Triangle
To show the effects of the exposure triangle when taking shots of miniatures, I decided to use two Word Bearers Anointed minis placed side-by-side but with one slightly behind the other. There was no editing done with any image software so the photos are WYSIWYG.

Shot 1: Shutter speed 1/500th of a second, Aperture at f4, ISO 400

Low depth of field at 1/500 - f4 - ISO 400
In my first shot, I used a low aperture setting of f4 which meant a very low depth of field, the effect of which is the blurred out miniature in the background, on the right.

Shot 2: Shutter speed 1/60th of a second, Aperture at f11, ISO 400

Better depth of field but still not good enough - 1/60 - f11 - ISO 400

To get a better depth of field I made use of an important concept in the exposure triangle i.e. reciprocal exposure. To keep it simple, reciprocity refers to the fact that shutter speed and aperture can be adjusted by the same amount in opposite directions to get the same exposure. In this case, I adjusted the shutter speed by three stops (one stop is a measure of light) from 1/500 to 1/60 while the aperture was also adjusted by three stops in the opposite direction from f4 to f11. (A quick search online should give you a chart showing various reciprocal exposure settings).

To explain further, I had reduced the shutter speed which allows more light into the sensor while lowering the aperture size (better depth of field) which reduces the amount of light that hits the sensor. End result is the same exposure as Shot 1 is maintained but at different shutter speed and aperture settings. Note that the ISO value is maintained at 400 so it is the constant variable here.

Shot 3: Shutter speed 1/30th of a second, Aperture at f16, ISO 400

Much better depth of field at 1/30 - f16 - ISO 400

While the depth of field on Shot 2 was much better, it was still not good enough as the miniature behind was still a bit blurry. Using the reciprocity rules, I increased depth of field and compensated with a lower shutter speed. But the shutter speed was so low that any slight vibrations of the camera would have resulted in a blurry picture. So a better solution if you do not have a tripod-camera cable trigger combo would be to take the shot at a shutter speed of 1/60. To get a better depth of field at even lower aperture settings, we will have to change the one thing kept constant so far - ISO. 

Shot 4: Shutter speed 1/60th of a second, Aperture at f22, ISO 1600 

Required depth of field at 1/60 - f22 - ISO 1600

Using the settings of Shot 2 as the base to work from, the aperture was set as low as the lighting conditions allowed which was f22. As I wanted to maintain the shutter speed at 1/60 that meant I had to change the ISO. Under the reciprocity rules, I set the ISO at 1600 to ensure that the exposure stayed the same as (or at least close to) all the other shots so far. Now the differences in the depth of field might not be substantial enough to necessitate reducing aperture settings to as low as f22 but that's a judgement call the photographer will have to take depending on the way the minis are set up.

Next up for macro photography: Achieving the perfect black background in your shots


  1. Nice write up dude. We need to meet soon so I can get all this in person :)

    1. Thanks man! Hopefully I can work something out and visit Legio Malaysia on Friday more often. =)


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