RSS Understanding the photography triad: ISO, aperture and shutter speed

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  1. MASA Admin

    MASA Admin Moderator

    8 May 2007
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    As aquarium owners, we are often very proud of our creations and want to capture them in pictures. Perhaps it’s that Acropora that you’ve been growing, or that fish that you love so much. Photography is a great way to document and digitalise your day to day hobby activities. Photography is an art, and there is no right or wrong. What works for me may not work for you, and vice versa. There is absolutely nothing wrong with a phone or digital camera, and as long as it brings you happiness, that is all that matters. 

    However in this day and age where fancy high-tech SLR cameras are getting more prevalent, knowing a thing or two about them might not be such a bad thing after all. Perhaps your neighbour or a friend has one and you’ve been thinking about borrowing it for your own use, but don’t quite know how to get around using it. Here are some little helpful notes that you may find useful for photography in general. Throughout this post there are many examples of subjects not related to just the reef aquarium, emphasising that the rules and theories can be applied in any scenario on any subject.

    [​IMG]Macro photography is a great way to capture small details like the tentacles of this Euphyllia. Playing with the depth of field allows you to selectively throw certain portions out of focus.

    Before I begin, I would just like to point out that i’m no expert in the craft of photography. It’s just a hobby comprising 50% fumbling and 50% actual camera know-how. There are tons of photographic geniuses and post-processing photo editing wizards out there who may be reading this, and so if you might have any helpful tips yourself, please feel free to correct or add on in the comments at the end of this article.

    A digital SLR camera is a versatile tool with a myriad of different lenses serving different purposes. Majority of the examples used in this article will focus on a macro lens with a short focal length, primarily used for close up or macro imaging. This allows you to shoot small targets with greater emphasis on the subject rather than the background.

    [​IMG]A macro shot of a sunflower.

    Lenses and equipment aside, there are three main important pillars of photography that you need to know. They are ISO, aperture and shutter speed. The pictures you see here are all shot in manual mode, with direct manipulation of these three components including a mount on external camera flash. An important point to take note with regards to these three components is that they all directly affect each other in one very important aspect. Lighting. This article will also touch very briefly on the role of camera flash. But before we get there, let’s see what each of these settings actually do.

    [​IMG]A low ISO will yield a darker image, which can be compensated with the use of camera flash. In this scenario, a dimmer background with the subject lit up will create a contrasting effect.


    ISO is the first major aspect of the photography triad. To put it in very simple terms, ISO is the level of sensitivity of your camera to available light. The lower the ISO, the less sensitive it is to light. The higher the ISO, the more sensitive it is to light. At a higher ISO setting, the camera’s sensor increases its sensitivity and produces a brighter image, allowing photos to be taken in dim settings without the use of supplemental flash. However, this comes at a cost. Higher ISO settings often lead to grainy, or noisy photos.

    [​IMG]A Tigerpyge hybrid at ISO 300. Notice the lack of noise and grain in this photo. This picture was also taken with the combination of a large aperture at f/4, which isolates the subject and blurs the background. More about aperture later on.

    Lower ISO settings are therefore always preferred, and in instances where ambient lighting is very strong, a low ISO is enough as lighting can be compensated by the environment. Every camera has a base ISO, which is the lowest ISO number on your camera capable of producing the best image quality without any noise or grain compromise. For my camera model, the base ISO is 100, but it differs from camera to camera. It is optimal to stick with the lowest base ISO to get the best optimal images, but in the world of photography, this is not always possible, especially when shooting in low light conditions. Remember, a low ISO makes the camera less sensitive to light, and therefore dims the image. This would be counterproductive in conditions of low light.

    [​IMG]The same fish at ISO 2000. Note the graininess and noise produced in the background. This was taken with a small aperture of f/9, which keeps much of the background in focus. Compare this with the previous image. More on aperture later on.

    ISO numbers typically start at 100/200, and then increase in the power of twos. Generally, it goes as follows. 100, 200, 400, 800, 1600, 3200, 6400 and so on and so forth. More powerful cameras with better image sensors will offer ISO levels far greater than normal, as well as produce images with very low noise levels at the use of higher level ISOs. What you need to know is that each step of increment doubles the sensitivity of your camera to light. Therefore, ISO 400 is twice as sensitive as ISO 200, and four times more sensitive as compared to ISO 100.

    So what does it mean when ISO 400 is four times more sensitive than ISO 100? It means that it takes four times less time to capture an image.

    Example of ISO speeds

    ISO 100 – 1 second
    ISO 200 – 1/2 of a second
    ISO 400 – 1/4 of a second
    ISO 800 – 1/8 of a second
    ISO 1600 – 1/16 of a second
    ISO 3200 – 1/32 of a second

    So when do you use a low ISO setting, and when do you use a high ISO setting? When there is plenty of light, for example in a brightly lit room or outdoors, try to stick with a low ISO. The lower the better. Conversely, ISO can be increased in dim environments to compensate for the lack of light. A higher ISO will also enable you to capture faster moving objects, so take that into consideration as well.

    [​IMG]Not a fish, but this photo demonstrates the ability to throw the background completely out of focus with a large aperture. At f/4, the vegetation in the background is reduced to a green slate. The subject on a camera lens is pun intended.


    Aperture is the second pillar of the photography triangle, and adds dimension to your images. Depending on the setting, aperture allows you to keep the subject and its background in focus, or throw everything out of focus and create a creamy backdrop. The aperture is a hole in your camera lens which allows light to pass through to the camera body. Much like the human eye, the pupil is akin to a camera’a aperture.

    When the pupils in the eye dilates, more light is allowed to enter. This is the same for a camera’s aperture setting. A smaller aperture will let lesser light in compared to a larger aperture. In photography, aperture is measured in f-numbers, otherwise known as f-stops. A smaller f-stop will mean a larger aperture, and a larger f-stop will mean a smaller aperture. This is a little confusing since it’s an inverse use of language, but this pictorial will allow you to visualise better.

    [​IMG]F-stops and their aperture sizes. The smaller the f-stop, the larger the opening, and thus more light enters. Photo from Wikipedia.

    An important thing to note here regarding aperture is its direct relation to depth of field. Depth of field is the area of an image which appears sharp, or in focused. A large f stop (which means a small aperture) will bring all background and foreground in focus compared to a small f stop (which means a big aperture). The latter will keep the subject in focused while throwing the background into a blur. Take a look at the butterfly image two photos above, with an aperture of f/4.

    [​IMG]Conversely, increasing the depth of field will retain detail in foreground and background. This photo was shot at f/11.

    Conversely, by closing the aperture and increasing the f-stop, you retain detail in the fore and background. The photo above of Genicanthus semifasciatus was shot at f/11, and the subject is framed by the background in focus. Depending on the effect you want, manipulation of the aperture and depth of field is a highly important and useful tool in photography.

    The lens and your subject also plays a part in depths of field. With a macro lens especially, if the subject is big, you would have to increase your focal length to accommodate everything in the frame. A longer focal length increases the depth of field, and even with the biggest aperture, the background may still be in focus.

    [​IMG]Even with an aperture of f/4, the background remains much in focus because of the increased focal length used to accommodate a large subject.

    Compare this photo above of a Genicanthus watanabei measuring 6 inches, and again with the butterfly above measuring in at 2 inches. Although both were shot in the same aperture of f/4, the smaller subject (butterfly) was able to have its background thrown out of focus while the fish was not. Because a macro lens has a very short focal length, you would have to stand pretty far back to accommodate a large subject. This increase in distance would compromise your ability to throw the background out of focus. Therefore the type of lens is also very important in determining what kind of composition you are aiming for.

    [​IMG]A shutter speed of 5 seconds produces a motion blur effect, which makes this water fall in Bali look soft and in movement.

    Shutter speed

    Shutter speed is the last component to the photography trinity. While aperture sets the stage for dramatic focused or out of focused images, shutter speed controls the movement aspect. It can freeze an object, or create motion blur depending on your aim. A camera shutter is like a curtain, that remains closed until the camera is fired. When it does, the curtain opens and exposes the sensor to light, allowing it to pass through the lens aperture before closing again.

    How long the opening and closing of the shutter is called shutter speed, or exposure time. At a fast or high shutter speed, the camera is capable of freezing moving objects. At low shutter speeds, the camera creates motion blur. Again, this can be manipulated by adjusting the shutter speed to give you the kind of effect you are looking for. Shutter speed is measured in fractions of a second. For example, 1/4 means a quarter of a second, while 1/200 means two hundredth of a second. Many high end DSLR cameras are able to capture images up to 1/4000 of a second, or more. Conversely, the shutter exposure can also be measured on the other end, in seconds. This is useful for creating motion blur, and shutter speeds up to 30 seconds can be used, but not without the use of a tripod.

    [​IMG]This water cascade in Taiwan on the other hand, was shot at a shutter speed of 1/200th of a second. The individual water particles and beads are frozen in time, and are not appearing in a soft flowing fashion.

    In movement photography, the manipulation of shutter speed is extremely important. Compare the two photos above, both of moving water. In the first waterfall photo, a slow shutter exposure of 5 seconds is used, and this creates motion blur in any moving objects within the camera frame. In this case, the waterfall appears soft while everything else that is not moving remains in focus.

    In the second picture, a faster shutter exposure of 1/200 is used, and this freezes the moving water. If you zoom in, you can see the individual water particles and splashes that do not appear to be moving. A high shutter speed is often very useful for photographing fast moving subjects, such as a bird in flight, or a swimming fish. A low shutter exposure, especially if it is more than a few seconds, will usually require a tripod or a very steady hand to prevent your own movements from creating motion blur.

    [​IMG]A wrasse in display is one of the most challenging subjects to capture as it requires a high shutter speed to capture. A shutter speed of 1/250 was used for this photo.

    In aquarium contexts, a Cirrhilabrus in display is perhaps one of the most beautiful, yet challenging subjects to photograph. The males flash beautiful colours and patterns, but swim at tremendous speed. A high shutter speed to freeze the subject is important, but tracking it through the camera’s viewfinder adds to the challenge.

    The photo above was taken with a shutter speed of 1/250, and was able to full freeze the subject without causing any motion blur. This was combined with an aperture of f/4 to minimise over focusing of the background which keeps the subject in focus without any distractions. ISO 500 was used, which isn’t too high as aquarium lights were sufficient in lighting up the picture. A filled in external camera flash was also mounted to provide additional lighting to the subject.

    [​IMG]Camera flash is a useful tool for providing additional focused lighting, or for bringing out iridescence such as in the fins and face of this Pseudojuloides xanthomos.

    Now we see how everything comes together. Remember right at the beginning we said ISO, aperture and shutter speed all share one thing in common? That is lighting. Each of these three pillars directly influences light. A higher ISO will mean more light gets exposed to the sensor, which makes for a brighter image. A larger aperture would mean more light enters the camera sensor, which also makes for a brighter picture. Likewise a slower shutter speed would allow more exposure time, and thus more light being exposed makes for a brighter photo.

    Controlling each individual aspect with careful consideration of the other factors will ensure you get a properly exposed photo, while keeping everything else you want in check. For example if you want a photo with a blur background, open up your aperture, but this would mean that you would either have to increase your shutter speed or decrease your ISO to prevent over exposure.

    [​IMG]Subjects such as this Plectranthias inermis dwelling in dimly lit crevices can be brightened up with the use of flash.


    Lastly the use of camera flash is a very important source of additional, focused lighting. All DSLR cameras come with a built in flash, but for more control of the intensity and direction, a mount on external flash can be used. Flash is a powerful lighting option, and when set too strong, can wash out and overexpose a photo. With controlled and clever usage however, flash can add a new dimension to your pictures.

    In subjects such as butterflies or birds, flash can help bring out details not seen by the human eye. Iridescence on scales and feathers for example. In fishes, this can be applied as well. Flash can also be used to light up very dark environments that ambient lighting cannot, for example, in caves or crevices. In the photo above of Plectranthias inermis, a mount on camera flash was set just strong enough to light up the cave it was hiding in partially, without over exposing the image.

    [​IMG]Flash photography helps to bring out the violet and blue markings in this butterfly that would otherwise appear nondescript.

    Camera flash can also be used to overcome challenging light conditions, especially when out in the field. Subjects exposed to light from behind will naturally be shaded by their own shadow. For example, a person standing in front of a sunset would appear dark. This phenomenon is called back light, and in certain instances, intentional backlit photography can be applied for a dramatic contrasting effect to show the dynamics of light.

    In macro photography, backlit scenarios occur frequently as well. An example would be trying to photograph something small like an insect or a flower with direct sunshine coming from behind. The resulting shadow would either cause the subject to appear dark if it is opaque, or see through if the subject is translucent. If this is not what you want, then deployment of your camera flash can be used to overcome backlit scenarios. A camera’s flash casts diffuse lighting in a forward direction with respect to the subject. This brightens up the shadow caused by back light coming in from the opposite direction. An external flash mount provides greater flexibility than an inbuilt flash, and can be manoeuvred in a wide angle of  directions.

    [​IMG]Light coming from behind the subject can be counteracted with a forward directing diffused flash, and in this case it is used just enough to brighten up the subject.

    Using a butterfly as an example again, you can see how deployment of the flash is used to counteract backlighting. In this subject, Pathysa agetes is a naturally slightly translucent insect. In backlit conditions with sun shining from behind, the subject would be rendered almost translucent as the light passes through the hyaline portions of the wings. Those in the opaque portions would be cast in shadow. A medium powered flash was used here to counteract the back light, resulting in brightening of the main subject front. At the same time the flash was intentionally slightly underpowered so as to maintain some of the hyaline quality of the wings.

    [​IMG]Fine details in this porcelain crab brought into prominence with the use of camera flash.

    The most important take home message to budding photographers is to practice. Practice makes perfect. It sounds cliché, but it is nothing but the truth. When I first started out, no one taught me anything so I had to read and figure things out as I go along. Today, I am still learning and there are so many settings I am still unfamiliar with. Play with your camera. Know the settings and eventually, things will become second nature, so much so that you don’t even have to think when it comes to deciding which settings are the best.

    This article covers just the basics, and there will inadvertently be more challenging and confusing terms and equipment you will face along the way. Do not be afraid to ask and experiment. In the digital age, an unwanted picture can be deleted with a press of a button and then you just try again. Good luck and have fun!
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  2. Guest

  3. Reaper


    15 Jun 2007
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    Kuilsriver - Western Cape
    Very good thread!

    I got as far as the ISO - just one thing worth mentioning with regards to ISO, the higher you push the ISO, the more grainy the image will be. By grainy I mean the detail will be less. Almost not noticeable on the standard photo size, but when you start enlarging it will show speckles, depending on the size you enlarge.

    On my camera for instance (a Canon EOS 6D), the ISO can go up to 25600, but then the graininess is even noticeable on a laptop screen, but then again, I can take a picture in nearly complete darkness and it'll look like an overcast day shot. Just my 2 c...
  4. TaahirS

    TaahirS MASA Contributor

    10 Jul 2014
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    Cape Town (southern suburbs)
    Great read! Bookmarked:thumbup:
  5. Reaper


    15 Jun 2007
    Likes Received:
    Kuilsriver - Western Cape
    Agreed - wish I had someone explain it to me this way when I started. I'm a left tought photographer

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