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Orca at sunset, a snapshot of wildlife photography decision making.

Orca at sunset, a snapshot of wildlife photography decision making.
A large male orca glides through the water at sunset.  Photograph by Colin Munro, available as a fine art print or wall art at Colin Munro Images https://www.colinmunroimages.com/Prints-for-Sale/i-2Bp3WgP
Male Orca at sunset, New Zealand South Island, East of Stewart Island.

Orca are hugely impressive animals. They have come to symbolise power, intelligence, grace and – sometimes – ferocity. Often known as killer whales, largely due to the way they would attack harpooned baleen whales, or harry and gradually wear down larger whales in a similar fashion to wolves on land, they are in fact large dolphins. Few of us will not have seen the BBC footage of orca powering on to beaches in Peninsula Valdes in Patagonia to grab unwary elephant seals. The power of these animals is quite awe-inspiring. Large individuals may weigh up to 11 tonnes, and females may life to be at least 80 years old. We now think of orca as a highly variable species, or species complex, with up to nine different types recognised. Advances in science may eventually split these into sub-species, or possibly separate species.

I took this photograph a few miles off the coast neat the southern tip of New Zealand South Island. We were sailing from Stewart Island, the small, rugged island to the south of South Island, heading towards the city of Dunedin. It was a perfect evening in mid-November, summer in the southern hemisphere, around 8.30pm. The sun was already almost touching the horizon, creating deep shadows in the troughs of the ripples pushed along by the light breeze. The orcas approached our bow from the northeast, then passed close by on our port side. This was going to be the best shot I would get, before he disappeared towards our stern. However the low sun was directly behind him, casting his curved back and giant dorsal fin almost in silhouette. I had a couple of seconds to decide. I could ramp up the camera ISO and expose my shot to bring out the details on the orca’s back, but doing so – shooting straight in to the sun – would blow out all detail in the water around him, or… I could do the opposite. I could aim for silhouettes and shapes, patterns and texture on the water. If this were a studio shot it would be termed ‘low key’; but of course this was not a studio, there would be no posing, no running around with a hand held light meter, no test shots. I dialled down the ISO, ramped up the shutter speed, quick check of the viewfinder light meter …. focus… and click, click, click. And that was it. I watched as the dorsal fin slipped beneath the water, to reappear several minutes later, far behind us. The sun was dipping beneath the horizon, and the light was gone.

I find wildlife photography is often like this. Animals don’t appear on que, they don’t appear when you’re standing waiting with your camera gear all set correctly, they don’t appear in the right place or the right conditions and often they don’t allow you time to think through your choices and your settings. This is where practice and experience comes in. After years of taking shots in all sorts of conditions, you learn to instantly recognise situations, and dial in settings almost with muscle memory. Not that you can ever become complacent. Camera technology is constantly improving; that means that the rules that you automatically followed three years ago may no longer be the best way. Advances in technology may mean that the settings you used last year may now be improved upon by turning them on their head. So successful wildlife is a continual process of learning, practice, relearning, practice..repeat.

Art prints and downloads

The orca picture shown here is one of my images I have selected to make available as fine art prints. These are available as stretched canvas, canvas wraps, flat canvas, dye-infused aluminium prints and acrylic on alumimium in a range of sizes and crops. They can be ordered directly from my website colinmunroimages.com. Default printing is my Bay Photos professional fine art printers in California. For orders from the UK, contact me directly and these can be supplied by Loxley professional printers in the UK. It can also be downloaded as a digital file, for private or commercial use, in a range of file sizes.

The basking shark

Large basking shark feeding

Large basking shark feeding

Large basking shark feeding

I clearly remember my first in-water encounter with a basking shark.  Quite a few years ago now, I had gone out specifically to try and video a basker underwater.  After a couple of hours we spotted a pair slowly circling a ball of plankton.  I slipped mask, fins and snorkel on and slid in to the water.  Basking sharks can be sometimes be wary and dive when one gets close, but these two seemed quite unconcerned by my presence.  I floated on the edge of the plankton ball and watched them circling.  As one approached out of the gloom I started to swim towards it.  Even through you know it’s quite harmless it is still a strange feeling watching a six metre long shark swimming straight towards you with its mouth wide open.  A mouth I could easily fit inside.  At the last moment the shark would alter course slightly and cruise past me.  The experience was similar to standing too close to the edge of the platform watching a train go past.  Again and again the sharks would circle and cruise past, sweeping by less than a metre from me.  Just me and two large sharks.  It was a mesmerising experience, but I could not help thinking ‘this is so easy!’ Little did I realise at the time quite how lucky my encounter was.  Several years and quite a few attempts would pass before I was able to repeat the experience.

The basking shark, Cetorhinus maximus, is the second largest fish in the World. Mature adults commonly reach between six and and seven metres in length, occasionally reaching around nine metres. Despite their massive size basking sharks are quite harmless. They are gentle filter feeders. During summer in the north-east Atlantic they can often be seen swimming close to the surface with their mouths gaping wide. A baskers’ gape can be over a metre top to bottom, so that’s pretty wide. As they swim forwards water is forced in to their mouths, passing across their gills where oxygen is extracted, and out through their large gill slits. This water flow serves a dual purpose. The arches between the gill slits are covered in long stiff bristles called gill rakers. These gill rakers sieve the water flow, retaining planktonic organisms. This is the food of basking sharks. In northern Atlantic waters they feed especially on copepods (planktonic crustaceans) particularly those of the genus Calanus, which occur in enormous numbers in the North Atlantic. Large numbers of such tiny creatures are required to sustain something as large as a basking shark.  Therefore baskers need to filter very large volumes of water.  It has been estimated that around 1.3 million litres of water will pass through the mouth and over the gill rakers of a large basking shark every hour.

Basking shark feeding, showing large gill slits the almost encircle its head

Basking shark feeding, showing large gill slits the almost encircle its head

In the North East Atlantic basking sharks start to appear off the tip of Cornwall (SW England) in early May.  This co-incides with what local fishermen call ‘May-water’, where the coastal seas turn green and turbid due to the seasonal population explosion of plankton.  Throughout the summer months sharks will move northwards through the Irish Sea and around the west coast of Ireland.  In the years immediately following WWII the author Gavin Maxwell ran a basking shark fishery from the island of Soay in the Inner Hebrides, exploiting this northward seasonal migration. The operation was beset with problems and drove him to the edge of bankruptcy.  Basking sharks were hunted by Norwegian and Irish boats also. Due to concern over dwindling numbers, the basking shark received full legal protection in  U.K. waters in 1998.  The last British shark fisherman, a larger than life character called Howard McCrindle, ceased operations a year earlier.  The basking shark is now protected throughout E.U. waters. In 2006 hunting also ended in Norwegian waters.

A basking shark swimming through plankton rich waters off Southwest England

A basking shark swimming through plankton rich waters off Southwest England

Despite their large size, relatively slow movement and surface feeding habits there is much that remains unknown about the life history of basking sharks. Each year the they appear in late spring, then disappear again at the end of September.  Where they go and how they live for the rest of the year has been a mystery, and remains so today, though we are starting to get tantalising clues as to the the answer.  Occasionally, basking sharks would be caught in trawl nets during the winter months.  Some of these were found to have shed their gill rakers, suggesting they were not feeding.  This lead to the theory that they became dormant in winter, hibernating on the seabed.  This theory had a certain plausibility to it.  Basking sharks have enormous oil-filled livers.  The liver can be 25% of the sharks body mass (the low density oil gives the shark buoyancy, allowing it to swim efficiently at the surface; it was also this high quality oil for which they were hunted). It was suggested that this enormous store of liver oil could sustain the shark for months without feeding. Recent research using data logging tags has begun to shed light on shark behaviour during the winter months.  The tags used detach after a predetermined time and float to the surface, where they transmit the data data to satellites. The data at the time of writing indicates that basking sharks are active all year round, but spent much of their time at considerable depth, 200 and 1,000 metres.  It also seems they are highly migratory.  One 5 metre female nicknamed ‘Banba’, was tagged off Malin Head, the most northerly point of Ireland, in the summer of 2012.  On the 13th December 2012 the tag popped off and was located by satellite – just west of the Cape Verde islands 5000km to the south.  The still sparse, but growing, body of evidence now suggests that – in the North East Atlantic move in to coastal waters from deep water in April or May.  As the water warms and daylight lengthens (and so plankton blooms) there is an erratic movement northwards.  At the end of the summer they return to deeper water, heading west away from the British isles and mail and Europe, and some probably heading south also.  So in reality we should maybe consider the basking shark as a deep water species that happens to congregate in shallow water during the summer months in pursuit of rich feeding.

As a final aside it is often written that basking sharks are toothless filter feeders. Basking sharks are filter feeders utilising gill rakers in a similar fashion to the baleen plates of great whales to trap small planktonic creatures but surprisingly they also teeth.  In fact they have hundreds of tiny, backward-pointing teeth.  What, if any, purpose these teeth serve is not known.  They may be a vestige from a more predatory ancestry; equally there may be more still to learn of the basking sharks feeding habits.

You can see more of my shark images here

The extraordinary life cycle of the lion’s mane jellyfish

Lion's mane jellyfish, Cyanea capillata, underwater clearly showing tentacles trailing in many directions. Colin Munro Photography

Jellyfish, or sea jellies as they are now often called (clearly they are not fish) are amongst the most ancient of multi-organ animals.  Fossils of jellyfish (or scyphozoans, to give them their scientific name) are found only rarely as they contain no hard structures within their bodies, which are 95% water.  However, under the right conditions fossils of soft bodied creatures will form; current fossil evidence suggests they first evolved at least 500 million years ago.

Lion's mane jellyfish, Cyanea capillata, underwater clearly showing tentacles trailing in many directions. Colin Munro Photography

The lion’s mane jellyfish, Cyanea capillata, is the largest known species. The bell of individuals in colder northern waters can reach two metres across.

The lion’s mane jellyfish (Cyanea capillata) common throughout the North Atlantic, epitomises this image of a large, slowly pulsing, gelatinous bell (or medusa) and long trailing tentacles that pack a powerful sting, but this is in fact only one stage of a complex life cycle.  Lion’s mane medusae begin to appear in April or May in the Northern Atlantic, but are quite tiny at that stage.  These jellies are voracious predators and grow rapidly through the summer.  By August the medusae are commonly one third to half a metre across, with trailing tentacles many metres long.  However there is considerable variability;  large specimens have been reported at over two metres across with tentacles up to 37 metres long, though these generally occur within the more northern parts  of their range.  As they grow large in late summer they will often drift, under the influence of wind and tides, in to sheltered bays where they may aggregate in large numbers. This is when sperm is release and egg fertilisation takes place.  In common with most scyphozoans (the taxonomic group to which jellyfish belong) the sexes are separate; lion’s mane jellies are either male or female.  Sperm is released from the mouth of male jellies and drifts in the current, some reaching female jellies, where the eggs are fertilised. Fertilised eggs are stored in the oral tentacles of the female, where thy develop in to tiny planulae larvae. Once fully developed the planulae larvae detach and, after drifting for a short time, settle on the seabed.  Here they metamorphose into a polyp, not dissimilar to tiny sea anemones or coral polyps (both of which are relatives of jellyfish).  These polyps then grow, taking on a layered appearance until they resemble a stack of wavy-edged pancakes.  Each one of these ‘pancake layers’ will then separate from the parent polyp, once again becoming free living and drifting with the currents.  The ‘pancakes’, more properly ephyra larvae, will grow throughout the summer into the giant lion’s mane jellies and the cycle is complete.  With a lifespan on only one year, during which they can grow to be as long (possibly even longer) than blue whale, lion’s mane jellies need to catch and consume considerable amount of prey.  Each trailing tentacle is packed full of vast numbers of stinging cells, known as nematocysts.  When touched these cells fire out a harpoon-like structure which pumps toxins in to the hapless victim (this is what causes the painful sting from jellyfish).  These toxins incapacitate the prey, which is then drawn up towards the mouth of the jellyfish.  A large lion’s mane may have over 1,000 tentacles trailing far behind them.  Many SCUBA divers in Scotland and Scandinavia have experienced the situation where, having completed their dive on a sunken wreck and returned to the buoy line they planned to ascent to the surface, only to look up and see numerous lion’s mane jellies strung out along the line.  As the current sweeps the jellies along so their tentacles catch on the buoy line, leaving the divers with the unpleasant prospect of ascending through thousands of jellyfish tentacles.

A diver warily watches a large lion's mane jellyfish (Cyanea capillata) drift past. Isle of Arran, West Scotland.

A diver warily watches a large lion’s mane jellyfish (Cyanea capillata) drift past. Isle of Arran, West Scotland.

Not every creature lives in fear of lion’s mane jellies however.  Leatherback turtles, the only species of marine turtle that can tolerate the cold waters these jellies inhabit, consume them with relish, apparently oblivious to the stinging tentacles.  Lion’s mane jellies can make up 80-100% of a leatherback’s diet.  When you consider that a full grown leatherback weighs up to 800kg and may consume up to its own weight in jellyfish daily (bear in mind jellyfish are 95% water) then that equates to pretty large numbers of jellyfish being eaten.

As summer wanes and autumn approaches the lion’s mane jellies begin to die.  This provides a feeding bonanza for many scavengers.  On the surface seabirds will peck away at the gelatinous bell, whilst those that sink are often torn to shreds by shore crabs (Carcinus meanus) and velvet swimming crabs (Necora puber).

Dying lion's mane jellyfish (Cyanea capillata) that has sunk to the seabed being eaten by a velvet swimming crab (Necora puber).

Dying lion’s mane jellyfish (Cyanea capillata) that has sunk to the seabed being eaten by a velvet swimming crab (Necora puber).

At the other end of the scale these deadly tentacles can provide refuge to some unlikely creatures.  Juvenile whiting (Gadus melangus) have long been known to swim underneath the bell of lion’s mane jellies, apparently unconcerned by the curtain of tentacles they weave between. In fact they have been observed to rush into the mane of tentacles when startled by predators.  A series of fascinating experiments by the Swedish zoologist Erik Dahl in the late 1950s showed that, compared to other fish species, juvenile whiting were able to adapt their movements such that even when surrounded by tentacles they rarely came in to contact with them.  Also, unlike other fish species, when they did brush against them it seemed to cause them little concern. Biopsies of the tissue of whiting where they had contacted tentacles showed that very few if any stinging nematocysts had fired into the fish’s body; this compared to hundreds per square millimetre for other fish species.  We still don’t understand the mechanism behind this protection. So does the lion’s mane get anything in return for the refuge afforded the young whiting?  Well another creature found on lion’s mane jellies is the tiny planktonic amphipod (a type of crustacean) Hyperia galba. Hyperia is, for the jellies, a rather irritating ectoparasite. It lives on the outside of the jellies’ bell, nibbling away at it.  Now whiting don’t appear to like the taste of lion’s mane jellies, instead they are rather partial to planktonic crustaceans; in particular (you’ve guessed this already) Hyperia galba.   It is these elegant little symbiotic collaborations that make nature so beautiful.

These, and many more of my images, can be found at colinmunroimages.com

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Blue sharks, graceful sea wolves

Blue shark, Prionace glauca. A female blue shark swimming close to the surface off Southwest Cornwall, UK.

The blue shark, Prionace glauca, is possibly the most beautiful of sharks.  It is a slender, fast and graceful shark, but it is the vivid, almost electric blue colouration that is most striking.

Blue shark, Prionace glauca. A female blue shark swimming close to the surface off Southwest Cornwall, UK.

A blue shark passes close by.

Blues are oceanic sharks, uncommon in shallow coastal waters.  In the tropics they are normally found in deeper, cooler waters, but in temperate seas they are more likely to be found in surface waters (thus are described as being epipelagic).  This does not mean that in temperate waters they occur only in the warmer surface layers.  Recent data from satellite tags have shown that they blues may regularly undertake dives to more than 1000 metres.  One male blue shark, nicknamed Bodi by the researchers, was logged as having dived to 1250 metres off the Bay of Plenty (New Zealand) three weeks after being tagged in 2013.  An earlier joint British- Portuguese study recorded a female blue shark diving to 1160 metres off the coast of Portugal (Queiroz et al, 2012).   This behaviour is probably linked to hunting activity.  Blue sharks are quite catholic in their diet, eating a wide range of mid-water fish and cephalopods,  but appear to be particularly fond of squid, and of course squid will often undertake marked vertical migrations, with many species occurring at considerable depth.  That this deep diving behaviour of blues is primarily foraging for food is supported by a preponderance of deep water quid species found in the gut of contents of blue sharks caught by long-lines, in particular the wonderfully named vampire squid, Vampyroteuthis infernalis, a small deep-water squid those scientific name literally translates as the vampire squid from hell.

In the northern Atlantic at least, they appear to undertake seasonal migrations. They are unusual amongst ocean sharks in that they will sometimes aggregate in groups, often all same sex, as they roam.  This pack-like activity has lead to them being dubbed the wolves of the sea.  Around Southwest Britain blue sharks start to appear in June each year, and hang around until late October or early November.  Although there have been attacks on humans by blue sharks, aggressive behaviour is relatively rare.  Certainly in British waters, where large blues are rarely seen, most are quite timid and easy to scare off accidentally.  The largest blue caught in UK waters was approximately 2.5 metres long and weighed 107kg. This was caught off Penzance, Cornwall, in 2012 (but was also released).  Blues can grow up to 3.5 metres or more (the largest on record was 3.83 metres long) the females being significantly larger than males.

Blue shark, Prionace glauca. A female blue shark swimming close to the surface off Southwest Cornwall, UK.

Blue shark, Prionace glauca. A female blue shark swimming close to the surface off Southwest Cornwall, UK.

An underwater encounter with a blue shark is a wonderful experience, and provided one takes sensible precautions (i.e. wearing gloves, not wearing shiny bits of equipment and NOT trying to feed them) is normally quite safe.  Blue sharks have been one the shark species hardest hit by the practice of shark fining in various parts of the World and there numbers appear to have declined markedly.  Consequently it’s worth remembering that most blue sharks have far more cause to fear us that vice versa.

The above, and more of my blue shark images, can be found on my stock image website www.colinmunroimages.com. They can be licensed for publication, or purchased as fine art prints and canvas wall art.

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References cited: Queiroz N, Humphries NE, Noble LR, Santos AM, Sims DW (2012) Spatial Dynamics and Expanded Vertical Niche of Blue Sharks in Oceanographic Fronts Reveal Habitat Targets for Conservation. PLoS ONE 7(2): e32374. doi:10.1371/journal.pone.0032374

 

Stock images website: landscape, environment, underwater, wildlife and travel.

Stock images website: landscape, environment, underwater, wildlife and travel.

I now have a new website dedicated to my stock photography up and running.  The site is hosted by Photoshelter and links directly from my colinmunrophotography website, just follow the my stock images link to access it from my home page main menu.  Alternatively you can type in the url www.colinmunrophoto.photoshelter.com to take you directly to the site front page.  Currently I have galleries of sharks, other marine life, seals and sea lions, people (mostly in water), Norway, Scotland, Cape Verde Islands, Senegal, Tonga, Cook Islands, Dartmoor, Devon coastlines and Exeter.  More galleries and many more images will follow shortly.

Close up of a trawl net, full of fish, as it is hauled to the surface. Bottom trawling is one of the most widespread, and most controversial, of fishing methods. colin Munro Photography

Filming trawl nets working underwater

Fine Art Prints and Greeting Cards for sale online at Fine Art America

Sunset creating a dramatic sky of pinks, purples and orange hues. Colin Munro Photography

I’ve recently bit the bullet and created a Fine Art America website to allow a wider audience to view and purchase my photographs.  what’s great about FAA, apart from the ease of use, is the wide range of print styles (canvas, framed, metal, acrylic etc.)and  sizes available.  They also offer images as greeting cards with personalised messages.  but rather than me waffle on, you can check out my new FAA website here.

As a taster, I’ve included a little javascript slideshow of some of the images available through my FAA website.

Art Prints

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Fine art photographic prints, posters and greeting cards for sale on Fine Art America

Sunrise over the Navua River near Beqa Lagoon, Viti Levu, Fiji

I have recently made a number of my photographs available on the Fine Art America website.  Fine Art America has grown markedly over the past couple of years; this is probably due to the ease of use of the website – both for selling and buying artwork, and the wide range of sizes, materials and finishes available. I am particularly impressed with the 30 day money back offer if you decide you are unhappy with the artwork once you receive it. I think this is a great way to inspire confidence in the buyer when buying prints online. My photographs are available on Fine Art America as:

  • stretched canvas prints,
  • standard prints,
  • framed prints (with a vast range of frame styles to choose from)
  • acrylic prints (printed directly on 1/4 inch clear acrylic sheets, ready to mount)
  • metal prints (printed directly on 1/16th inch aluminium, surrounded by a wooden frame),
  • greeting cards (5 x 7 inch, your own personalised message added)

Below you can see a few examples of the images I have for sale as prints on Fine Art America.

 

The Cobb, Lyme Regis, at low water. Lyme Regis harbour. Colin Munro Photography

The Cobb, Lyme Regis, at low water. Lyme Regis harbour. Image 1415, available as a canvas wrap framed print through my Etsy store.

 

Blue shark, Prionace glauca. A female blue shark swimming close to the surface off Southwest Cornwall, UK.

A blue shark passes close by.

 

Sunrise over the Navua River near Beqa Lagoon, Viti Levu, Fiji

Sunrise over the Navua River near Beqa Lagoon, Viti Levu, Fiji

 



Find me on Google+ Colin Munro
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Shutter speed control on digital cameras, what exactly does it do?

The LCD Display on a Digital SLR camera showing the shutter speed (here set to 1/30th of a second). This diplay may be on the top or back of the camera, depending on model. Colin Munro Photography

About a week ago I put up an article looking at looking at what the ISO control on a camera does, so it seems logical to cover the other camera controls that determine image exposure. So logically the place to start is with the first, most basic control, the shutter.  The shutter is basically light-proof barrier placed between the camera’s sensor (or film frame, if you’re old school) and the aperture through which light passes in to the camera.  But, and this is the key aspect, it is a barrier that can be opened for precise durations of time.  Now image exposure is determined by the amount of light hitting the sensor: too much light and the image is overexposed, too little and the image is underexposed, the correct amount and the image is just right (think of Goldilocks and the three bears).  So one way we can control the amount of light hitting the camera’s sensor is by controlling how long the shutter is open and light is allowed to pass through and reach the sensor, rather like controlling the flow of water in to a glass with a tap.

So what does a shutter look like?  various designs have been used over the years with different camera types and as cameras have evolved.  Digital SLR cameras (and film SLRs for that matter) use what is known as a focal plane shutter, that is a shutter placed directly in front of the flat area where the camera sensor (or film) is located.  These consist of a series of overlapping blades that lift and fall as the shutter opens and closes.  Compact, point and shoot, cameras generally do not have a mechanical shutter (as the focal plane shutter is) rather they have an electronic shutter.  Electronic shutters are an integral part of the camera sensor and primarily work by ‘turning off’  reading of the light hitting the sensor.

Focal plane shutter in a film SLR, showing mechanism.  Shutter CLOSED

Focal plane shutter in a film SLR, showing mechanism. Shutter CLOSED

Focal Plane shutter mechanism in a film SLR. Shutter OPEN.

Focal Plane shutter mechanism in a film SLR. Shutter OPEN.

Shutter speed. When we talk about shutter speed that we are actually referring to is the duration the shutter is open and the sensor exposed to light.  In most general photography these durations are only fractions of a second and, despite the spread of decimalisation, we still tend to use common fraction rather than decimal fraction notation (e.g. 1/2, 1/4, 1/8, 1/15th of a second).   Setting the shutter speed on a camera serves two purposes: firstly it determines how much light hits the sensor, and secondly it freezes or blurs movement across the image.

Shutter speed control on a film SLR, showing standard shutter duration increments. Colin Munro Photography

Shutter speed control on a film SLR, showing standard shutter duration increments.

The LCD Display on a Digital SLR camera showing the shutter speed (here set to 1/30th of a second).  This diplay may be on the top or back of the camera, depending on model. Colin Munro Photography

The LCD Display on a Digital SLR camera showing the shutter speed (here set to 1/30th of a second). This diplay may be on the top or back of the camera, depending on model.

Motion blur. Not everything we photograph remains perfectly still. So, the duration the shutter is open will also influence how sharp a moving object is, or whether it is blurred due to it moving across the field of view whilst the shutter is open.  This can be a person, an animal, cars, flowing water etcetera.   Mostly we want our images nice and sharp, with objects frozen in time, but sometimes we will deliberately allow (our induce) motion blur for artistic reasons or to give the impression of movement.  A further consideration here is that motion blur comes not just from objects in front of the camera moving.  If we hand-hold a camera (as opposed to mounting on a tripod) there will always be a slight amount of ‘hand shake’.  At faster shutter speeds this is not noticeably in the captured image but with very slow shutter speeds the camera will wobble slightly in our hands whilst the shutter is open. This results in everything in the image being slightly burred.  A general rule of thumb is to shoot at 1/60th or faster when hand holding your camera, for non-moving objects when using a standard lens (i.e. not a telephoto lens).  When shooting using a telephoto lens, or shooting fast moving objects (maybe motor sports) you will need a significantly faster shutter speed to freeze motion, maybe 1/250th of a second or possibly up to 1/1000th of a second depending on factors such as the focal length of the lens, the speed the subject is moving at and how close you are to the moving subject.

Find me on Google+ Colin Munro

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ISO setting on digital cameras, what exactly does it do?

ISO setting on digital cameras, what exactly does it do?

This is part of an occasional series looking at the basic controls on a camera. It’s here primarily to supplement, and as a taster for, my beginners photography classes and one-to-one sessions. Some of the controls on a camera are fairly intuitive. Zoom, for example, controls the focal length of the lens and so the degree of magnification of the image (we zoom in, or we zoom out). Shutter speed controls the…er…speed of the shutter; well accurately it controls the duration the shutter is open, and so the amount of light allowed to pass through the shutter and impinge on the sensor, which in turn directly influences how bright or dark the image is. But ISO? Knowling that the acronym stands for International Organisation for Standardation doesn’t help that much either, and yes, I know it should be IOS not ISO (there are reasons but truthfully that would simply be too much of a digression to go there now, ask me after class :)). So if we simply accept that the name, ISO, tells us nothing about what the control actually does – then what does the ISO control on a camera do? Essentially the ISO setting works rather like the amplifier on a radio or CD player; it varies the signal gain to produce a brighter (for higher iSO values) or darker (for lower ISO values) without any changes in the amount of light hitting the sensor. Typically ISO values range from 100 (low) to 3,200 or 6,400 (high) on some cameras. These numbers are derived from film; with film cameras the film had a set sensitivity to light. Film that responeded quickly was termed fast film; film that responded slowly …. you’ve guessed already ..slow film. The film’s sensitivity could not be changed, so once it was loaded into the camera the ISO value of that film was then dialled in using the camera ISO control, allowing the film’s sensitivity to be taken in to account when exposure was evaluated by the camera’s light meter (or it would be dialled in to the meter if a hand held light meter was used). The ISO sensitivity in a digital camera is created very differently to in a film camera, but the same numerical values are used and they approximate closely to the changes in sensitivity to light that occurred in film. Essentially, the steps between each ‘standard’ ISO value represents a doubling or a halving in senstivity, depending on whether one goes up or down. So ISO 200 is twice as sensitive as ISO 100; ISO 400 is twice as senstive as ISO 200, and so on. What does this mean in practical terms? Well, if a particular scene was correctly exposed at a shutter speed of 15th of a second at ISO 100, then (all other settings remaining unchanged) the same scene would still be correctly exposed at 30th of a second at ISO 200 (a shorter time the sensor is exposed to light, but a more sensitive ISO value) it would also be correctly exposed at 60th of a second at ISO 400. Okay, so what would the correct ISO setting be if the shutter speed was changed to 500th of a second?
Hopefully this explains how the ISO values influence image exposure, but why do we want this control? Well there are a few situations where it is useful but the fundamental one is that a higher ISO allows us to use faster shutter speeds. If we go back to my first example, a shutter speed of 15th of a second at ISO 100. A 15th of a second is very slow and likely to produce a blurred image, a) due to the slight shakiness in everyone’s hands and b) as people (or animals, cars etc.) move. By selecting a higher ISO value we can then change to a faster shutter speed where these problems will be greatly reduced (for the sake of simplicity I have not considered aperture values and have assumed they remain unchanged).

 

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The Three Sisters, Bidean nam Bian mountain range, Glen Coe.

The Three Sisters of Glen Coe, Glen Coe, Highlands, Scotland. Colin Munro Photography

The Three Sisters of Glen Coe, Glen Coe, Highlands, Scotland.  Colin Munro Photography

The Three Sisters of Glen Coe, Glen Coe, Highlands, Scotland.

The Three Sisters, Glencoe, Scotland.

The Three sisters are three steep-sided ridges forming part of the mountain complex Bidean nam Bian along southern side of Glen Coe.  These ridges are Gearr Aonach (Short Ridge), Aonach Dubh (Black Ridge) and Beinn Fhada (Long Hill).  The summit of Bidean nam Bian lies at 1150m (3773ft) making it the highest mountain in the former county of Argyll (regional boundary changes in recent years means Argyll no lnger exists as a county).  Bidean nam Bian is popular with walkers and Munro-baggers (Munros are Scottish mountains over 3000ft) summer and winter. The most popular route passes down through the col (low gap between two peaks) between Bidean nam Bian and Stob Coire Sgreamhach, more commonly known as the hidden valley or lost valley.  The name derives from it’s reputation as a hiding place for rustled cattle taken by the Clan Macdonald in earlier times and the fact that the valley is all but hidden from view until one is in it.

Glen Coe is an awe inspiring landscape of looming mountains, the soul of which is most clearly seen on darky and stormy days.  It is sometimes known as the ‘Glen of Weeping’ in reference to the Massacre of Glen Coe in  February 1692 when Thirty-eight men of the Clan MacDonald were killed in the night by soldiers from the Earl of Argyll’s Regiment of Foot who they had accepted in as guests.  Many more died of exposure on the hills as their homes had been burnt down.  The soldier in command of the Foot Regiment was Captain Robert Campbell of GlenLyon; this fact, allied to an existing history of feuding between the Campells and MacDonalds and attempts by the Government of the time to deflect blame and have this seen as no more than inter-clan feuding.  The orders for the massarce were in fact signed by King William II (King Willaim III or England).

The dramatic scenery of Glen Coe has formed the backdrop for many big budget films; these include Highlander, Rob Roy, Braveheart and, more recently, Harry Potter and the Prisoner of Azkaban. In the summer of 2003 vistors to the glen occasionally stumbled across Hadrig’s hut nestly behind the Clachaig Inn.

The picture.  I took this image at 16:45 on the 31st of October 2013 (Hallowe’en).  I was on a brief walking and camping trip with my ten year old son during school half term.  It was a wild day; storm force winds were battering the west coast.  The wind was literally howling down through the glen driving needles of rain before it and forcing me to keep one hand on my camera tripod at all times lest it was blown over.  At 15 minutes to 5pm the sun had just set, though this was not obvious through the thick black cloud overhead, but an already gloomy day was darkening rapidly.  As light was disappearing I dispensed with the polarising filter I had been using earlier but kept the gradient nuetral density filter.  The image is a composite of three seperate exposures, ranging from a 1/60th to a 1/15th of a second duration, to capture detail in both the dark mountain shadows and the clouds overhead.  Between each exposure rain droplets had to be carefully dried off the filter in front of the camera lens and the entire camera covered by my jacket (taking care not to accidentally jostle the camera or tripod) until the next brief gap between squalls allowed another image to be taken.

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