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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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Split image (above and below the surface) shots of swimmers

Over under shot of a girl in a blue patterned bikini swimming front crawl in an outdoor pool. The shot is half above and half below the waterline and uses a combination of monochrome, reduced colour saturation and selective colour. Image copyright Colin Munro Photography

I’ve been taking a few split image shots recently, where the image recorded is partly above and partly below the waters’ surface.  These are sometimes termed over under shots, sometimes half anfd half shots.

Over under shot of a girl in a blue patterned bikini swimming front crawl in an outdoor pool.  The shot is half above and half below the waterline and uses a combination of monochrome, reduced colour saturation and selective colour. Image copyright Colin Munro Photography

Over under shot of a girl in a blue patterned bikini swimming front crawl in an outdoor pool. The shot is half above and half below the waterline.

The technique can be quite challenging when working with fast moving subjects. To ensure crisp images the subject must be very close to the camera, in the above case the girl’s hand was around 10-20cm in front of the camera dome port at the time of the shot.

Over under shot of a girl in a blue patterned bikini swimming front crawl in an outdoor pool. Colin Munro Photography

Over under shot of a girl in a blue patterned bikini swimming front crawl in an outdoor pool.

Keeping the port clear of large water droplets often involves dipping the entire camera housing below the surface, then raising it at the last moment thus ensuring the image is recorded before droplets can form. Needless to say this normally involves a lot of luck and a LOT of takes to get the right image. However, when it works well the effect can be quite dramatic. I will be making this image, and some others, available as fine art prints.  They can be printed on a range of art media, canvas or 300gsm art paper, up to 24 inches across.  So if you are interested in a print for your studio, office, fitness centre or lounge, please get in touch with your requirements and I’ll get back to you with a quote.

You can contact me directly email me

More women and water images on my http://colinmunro.photoshelter.com site.
More split images (above and below) on my photoshelter site here.
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Photographing Blue sharks off Cornwall

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

A few days ago I was fortunate enough to get in to the water off Cornwall with a couple of blue sharks (Prionace glauca).  Getting some good images of blues had been high on my ‘to do’ list for several years, but for one reason or another it had not happened. In part this was a result of the dreadful summers we have had in the UK for the past few years; wet and windy and severely limiting the number of days when it was possible to spend all day offshore in a small boat (and limiting even more the number of days one would want to). This summer has so far been perfect, high temperates and light winds.

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

Blue sharks are highly migratory, with strong evidence for there being a single well-mixed population within the Atlantic Ocean and seasonal trans-Atlantic migration.  Some studies indicate a crosswise annual migration across the temperate zone of the Atlantic but evidence for this is inconclusive.  What we do know is that blue sharks start to appear off the tip of Cornwall in early July and remain around Southwest England until late September.

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

Off the tip of Cornwall is one of the best areas to see blues; it also has the advantage of exceptionally clear water.  Most are found at least five miles offshore, so with the longish drive an early start was required.  By 10a.m. we were drifting with the current, a nice fish oil slick trailing from our chum bag, cameras ready and waiting.  The sky was blue, the sun hot, the sea ruffled by a light breeze and our spirits were high.  And we waited.  Mid-afternoon a brief flurry of excitement: two sharks arrived within the space of an hour, grabbed our mackerel bait….. and disappeared.  By 4.30pm our hopes were fading and our thoughts turning to when we could schedule the next trip.  Suddenly at 4.45pm a third shark arrived.  A smallish female, probably around 5ft, but most importantly she showed none of the skittishness of the previous two. She was interested in the fishy smell from our chum bag and she was hanging around.  It took a real effort of will to stay calm, remain on the boat and allow her time to settle – what if she also suddenly disappeared?  However, after a few minutes Charles, the boat skipper, gave us the nod and Richie and I slipped gently and quietly in to the water.  As we swum towards her she showed no fear at all, appearing quite curious about us, to the extent that she temporarily lost interest in the chum bag and began cicling us as we drifted slowly from the boat.  Time and again we would swing around to make close passes, to the extent that she occasionally had to be gently pushed away as she came nose to nose.  A more obliging photographic model I could not have wished for.  Around 20 minutes passed in a flash, at which point she became bored with us and disappeared.  Yet no sooner had we climbed back in to the boat than a larger female arrived.  She definately wasn’t timid; before anyone could react she had grabbed the chum bag and was tearing it to pieces.  Within seconds the water around the boat was a murky brown from the contents of the chum bag and the bag itself shredded.

This was too good an opportunity to miss, all four of us hit the water.  She was a real beauty.  Between 6 and 7 ft long, the most dazzling vivid blue on her dorsal surface with deep indigo patches near her dorsal fin, pure white on her underside.  As she passed close the mating scars left by the males teeth could be clearly seen on her head neck and back.  For more than 30 minutes she hung around. circling us.  It was almost 6pm when we finally climbed out of the water.  Tired but very happy.

passing under a snorkeller

Our trip was on board the RIB of Charles Hood (charleshoodphotography.com).  Charles regularly runs basking shark and blue shark trips from Penzance, Cornwall.  I would heartily recommend him.

All my blue shark photographs are available for licence and some as fine art prints along with all my other stock images at http://colinmunro.photoshelter.com. Or you can contact me directly email me

Signed canvas prints and photographs of my work can be bought through my Etsy Store

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Photoshop Elements: adding text and changing transparency in Photoshop Elements 11.

Working with Photoshop Elements 11.

Photoshop Elements is a hugely powerful tool for the price and one of the nice features of the lastest version, Photoshop Elements 11 making many image editing tasks very easy by introducing the ‘guided’ mode.  The ‘expert’ mode provides the greatest number of features and options, and most closely resembles the full professional version of Photoshop.  One of the most useful features only available in ‘expert’ mode is the layers feature (note, the layers menu is still visible in the top menu bar in both ‘quick’ and ‘guided’ modes, but all options in the drop-down menu are greyed out).

In this blog I’m going to talk about using the Horizontal Type Tool (symbol ‘T’) to create text layer on your image, and then how to modify the text appearance, making it semi-transparent, by changing the layer opacity.

Step 1.  Once you have opened up Photoshop Elements, select Photo Editor mode, then ensure you are in ‘expert’ mode.  Once this has loaded then open the image you wish to add text to.  As my example I have chosen an image of a black swan guarding her nest as the River Exe floods.  I am going to add copyright text to this image, something I often do to identify my images prior to placing them online.

Step 2.  Once your image has loaded, click on the Horizontal Type Tool ‘T’ (highlighted in grey on the lower LHS of the image below).

Adding text to an image in Photoshop elements 11, step one, select the Horizontal Type Tool (T).

Image 1. Adding text to an image in Photoshop elements 11, step one, select the Horizontal Type Tool (T).

You’ll notice that a sub-menu pops up beneath the image. Heer you will find options to change the default font, font size, font style, colour, leading and anti-aliasing. Leading (pronounced ‘ledding’) refers to the spacing between lines in a paragraph, should you be writing more than one line of text. Anti-aliasing (very briefly) smooths jagged edges that can occur around the edges of text; if you’re not familiar with anti-aliasing leave the box checked.

Sub-menu where text font and styles can be edited.

Image 2. Sub-menu where text font and styles can be edited.

Step 3.

Once you have select the style of text you want, move your mouseso the cursor is over the area of the image where you want your text to appear and left click.  You’ll notice that a new layer suddenly appears in the layer palette on the RHS of the image (see image below).  This is the text layer, by default named layer 1.  You can change this simply by going to the layer drop down menu and selecting rename layer.  This is useful if you are creating multiple layers and prefer to name them intuitively.

Text appears as a new layer Colin Munro Photography

Image 3. Text appears as a new layer

The next step is simply to type your text.  I’ve chosen to add copyright text to my image, something I tend to do before uploading any images.

dding copyright text to an image colin munro photography

Image 4. Adding copyright text to an image

Sometimes text can look very intrusive in an image.  One way of reducing this is to change the opacity of your text.  We do this by going back across to our layers menu and clicking on the arrow at the side of the opacity box, immediately above our layers.  This then displays a slider control whereby we can vary the opacity of the active layer (i.e. the one highlighted in blue) in this case out text layer, from between 1-100%.  As you can see in this example I’ve selected 41% opacity.  As an aside, you’ll also note that Elements has changed the name of the layer to the text I’ve typed.  This can also be helpful in allowing us to remeber which layer is which.

Image 5. Changing the opacity of your text

Image 5. Changing the opacity of your text

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Image 6. Text with reduced opacity

Image 6. Text with reduced opacity

Okay, so we’ve got our text written, we’ve reduced the opacity to our liking, only now it’s there we suddenly realise it’s in the wrong part of the image.  Not a problem.  We simply select our ‘Move’ tool.  You should then see a bounding box appear around our text, as in image 7, below.

Image 7. Selecting text with the 'Move' tool

Image 7. Selecting text with the ‘Move’ tool

Moving our mouse over the text, hold down the left button and drag the text to the part of the image where you would like it to be.

Image 8. Our text has now been moved.

Image 8. Our text has now been moved.

 Our final steps and to flatten our image, reducing our two layers back to one, and then save our image.  To flatten our image we open up the Layer drop down menu in the top menu bar and select ‘flatten image’ which should be the option right at the very bottom of the drop down menu.  Once we  click on this you should see that our two layers become one, as in image 9 below.  We can then either save our image or rename it through the ‘save as’ option.

Image 9. Our final step is to flatten our image.

Image 9. Our final step is to flatten our image.

 

Colin Munro

Pic of the Day: Fisherman on a trawler

A fisherman lifts the steel wire warps, that tow the trawl net, in to blocks at the stern of the trawler. Colin Munro Photography

An occasional and erratic series of images.  Today’s is of a fisherman heaving the steel wire warps that tow a trawl net in to blocks suspended from the gantry at the stern of the trawler.  The heavy steel trawl doors that act like hydrofoils, keeping the moth of the net open, can just be seen as the sink beneath the surface.

A fisherman lifts the steel wire warps, that tow the trawl net, in to blocks at the stern of the trawler. Colin Munro Photography

A fisherman lifts the steel wire warps, that tow the trawl net, in to blocks at the stern of the trawler.

Lyme Bay Reefs.

Sunset corals,Leptopsammia pruvoti, growing on the Saw-tooth Ledges Reef, Lyme Bay, Southwest England. Colin Munro Photography. www.colinmunrophotography.com

This blog post about the marine life and importance of Lyme Bay Reefs has moved to my marine biology website: Marine-bio-images.com. You can read it here at:

https://www.marine-bio-images.com/blog/lyme-bay-marine-ecology/lyme-bay-reefs/

Dartmoor images Fine Art prints of Dartmoor

Skull and jawbone on a windswept moorland. Dartmoor, Devon. Colin Munro Photography

 

As Christmas draws near, why not give a photographic art of local landscapesas a gift? My Dartmoor images are available as art prints and cards. These can be purchased dierct from me (see below). As a long term Devon resident, and keen supporter of Devon Wildlife Trust and its work, 10% of all purchases made before Christmas will be donated to the Devon Wildlife Trust. All images on my website are watermarked.  This will NOT appear on the print.

I’ve been taking a few Dartmoor images recently. The moor always looks more interesting as the weather turns colder and the days shorter. This has resulted in a few nights camping out. Sometimes chasing the elusive sunrise that remains hidden behind a thick blanket of grey cloud; sometimes up to mid-thigh in freezing fast-flowing rivers. So I’ve decided to pull a few together, some old, some new. I try and steer clear of well worn styles and try to capture the feel and atmosphere of the moor, the bleak, harsh beauty and the wide open spaces. As ever, all my images are available to purchase as fine art prints, each printed to order to specific requirements. If you’d like to know more then email me here.

Lichen covered granite boulders of a dry stone wall. Dartmoor Devon. Colin Munro Photography. Fine Art prints

Image 1346. Lichen covered granite boulders of a dry stone wall. Dartmoor Devon.

The glow from a lantern inside a dome tent on a starry, moonlit night on Dartmoor.  Colin Munro Photography.

Image 1002. The glow from a lantern inside a dome tent on a starry, moonlit night on Dartmoor

Icicles and ice formations around a fast flowing stream on the steep-sided Teign Valley, Dartmoor, Devon.  Available as a fine art print. Colin Munro Photography. www.colinmunrophotography.com

Image 1054. Icicles and ice formations around a fast flowing stream on the steep-sided Teign Valley, Dartmoor, Devon.

Boulders and small waterfalls on the East Dart River, high on Dartmoor above Two Bridges. Dartmoor National Park. Fine Art prints for sale. Colin Munro Photography. www.colinmunrophotography.com

Image 1019. Boulders and small waterfalls on the East Dart River, high on Dartmoor above Two Bridges. Dartmoor National Park

Icicles form along the lip of a rocky overhang on the steep sides of the River Teign Valley, East Dartmoor, Dartmoor National Park,  Devon, England.  Fine art prints available. Colin Munro Photography. www.colinmunrophotography.com

Image 1057. Icicles form along the lip of a rocky overhang on the steep sides of the River Teign Valley, East Dartmoor, Dartmoor National Park.

The East Dart River tumbles through a boulder strewn valley, East Dartmoor.  An HDR image.  This image is available as a fine art print to purchase. Colin Munro Photography. www.colinmunrophotography.com

Image 1348. The East Dart River tumbles through a boulder strewn valley, East Dartmoor.

Icicles over a moorland stream, Dartmoor National Park, Devon, England. colin Munro photography

Image 791. Icicles over a moorland stream, Dartmoor National Park, Devon.

Icicles above a small waterfall on the South Teign River, Dartmoor, Devon, England. Colin Munro Photography. www.colinmunrophotography.com

Image 41. Icicles above a small waterfall on the South Teign River, Dartmoor.

Wind dried bones picked clean by ravens and foxes.  Dartmoor National Park. Colin Munro Photography. www.colinmunrophotography.com

Image 1349. Wind dried bones picked clean by ravens and foxes. Dartmoor National Park.

The boulder-strewn steep sided valley of the East Dart River above Two Bridges, Dartmoor National Park, Devon. Colin Munro Photography

Image 1020. The boulder-strewn steep sided valley of the East Dart River above Two Bridges, Dartmoor National Park, Devon

Boulders and small waterfalls on the East Dart River, high on Dartmoor above Two Bridges.  Dartmoor National Park Colin Munro Photography

Image 1021. Boulders and small waterfalls on the East Dart River, high on Dartmoor above Two Bridges. Dartmoor National Park.Fine Art Prints.

FINE ART PRINTS All of the above images can be puchased as Fine Art, archive quality prints on high grade paper or canvas.

Prints up to 10×15 inches (25x38cm) size are produced on Fuji Crystal Archive DP Professional Paper using the latest Fuji Frontier Digital Wet Photographic processing. This system produces rich, vibrant colours and has an archival life of up to 35 years, making ideal for producing long lasting prints. They are available in Pearl or Gloss finish.

8×12 inches (20x30cm) prints are available for only £22 per print.
10×15 inches (25x38cm) prints are available for only £32 per print.

If you are interested in purchasing one or more prints please call or email me stating the finish (pearl or gloss) and the size required. Currently I am happy to accept PayPal, bank transfer, cheque or cash on collection. Cheques will need to clear before delivery.
Please add £2.50 for postage and packaging to mainland UK, worldwide postage on request.

Larger prints, up to 62 inches (1075cm) across are available.
These can be printed on photo gloss or pearl paper, fine art rag paper or on canvas.
Block mounts and backlit
Again the prints can be supplied in block mounts or as a print for backlighting. Please contact me for details and prices.

HOW TO BUY. If you are interested in any of the above options please email or call me, 07926 478 199, stating the Image Number (given in caption), image size, finish (pearl or gloss) and number of images and how you would like to pay.  I will then reply confirming the amount.

Paypal: To pay for prints by simply log in to paypal and make the payment to colin (at) colinmunrophotography.com.
Bank transfer: To pay by bank transfer simply let me know in your email and I will include the account details in my response.
Cheque: To pay by cheque, let me know and I will include the postal address in my reply. Please note that you will need to allow extra time for cheques to clear on delivery times.
Confirmation:Once I receive payment I will email you confirming this. Prints should then be despatched within five working days.

More prints

You can search my blog for prints for sale by typing ‘Prints for sale’ in the seach box at the top, or simply by clicking this link.

Email me or telephone +44 (0)7926478199 for prices and delivery details.

More... See more of my Devon images fine art prints here

The wreck of an old wooden boat trapped in ice covered mudflats is silhouetted against an ominous sky. Exe Estuary near Turf Locks, Devon, UK. Fine Art Prints for sale. Colin Munro Photography. www.colinmunrophotography.com

Old wooden boat trapped in ice covered mudflats

More of my Dartmoor images are available on Photoshelter, where prints can be bought or images licensed click here
A selection of my images are available on Redbubble (Australia) as prints, posters and cards here

Sunrise over Cockwood Harbour at low tide, Exe Estuary, Devon.

Dawn over Cockwood Harbour on a frosty December morning.

Courses, Classes and Workshops. If you like my Dartmoor images you may be interested in my one day landscape photography courses for individuals and small groups autumn/winter 2012. These will be based around the Exe and Teign Estuaries and East Dartmoor. More info here.

Enfield Bullet 500cc at sunset. Prints for sale, Colin Munro Photography.

Enfield Bullet 500cc at sunset.

Photoshop is an essential part of my toolkit for successful landscape photographs, in the same way we used to dodge and burn prints when working with film.  If you would like to learn more about the potential of Photoshop to enhance your images why not sign up for one of my one to one (or small group) Photoshop sessions.  These are economical and targetted at exactly what you want to learn.  More info here.

Filming over-under shots at sea: the pros and cons of high-end video versus DSLR

An over-under shot of a diver waiting to be picked up at the end of a dive. Colin Munro Photography
An over-under shot of a diver waiting to be picked up at the end of a dive. Colin Munro Photography

An over-under shot of a diver waiting to be picked up at the end of a dive.

I recently completed a short shoot requiring over-under shots at sea; shots of a boat passing by and of a girl who had ‘fallen’ in to the sea. This was UK waters in late September, so conditions were – shall we say – not mirror smooth and crystal clear. If fact we ended up shooting about an hour and a half before sunset with the water darkening and a noticeable sou’westerly breeze creating a bit of a swell; so on the positive side the look was realistic. The shots had been planned for a Sony Alexa, but housing availability and cost considerations pushed the shoot to a DSLR; a Canon 5D MkII to be precise. At first consideration shooting video on a DSLR may seem a big step down from the 2K Alexa, but that’s not necessarily so. The shoot brought a number of these points to mind, so I thought I’d write a short blog on the pros and cons of dedicated high-end video cameras versus DSLRs for shooting over-under or surface shots in open sea. I’m not going to consider or compare camera image quality here; there are plenty of websites reviewing and out there doing just that. Instead I’m going to look purely at usability in this rather problematic situation. Producing good images is not simply a question of image resolution; factors such camera steadiness, ability to focus and frame accurately and freedom from water splash droplets need to be taken in to account also. I’ve randomly selected some well known manufacturers to as examples. This is not to imply the are particularly better or worse than others, simply that they are brands many will be familiar with and the data for them is readily available (and sometimes because I have used them and so have experience and images). Equally, any implied criticism is merely to point out that in this very specific type of shot certain types of equipment have inherent problems. In general, for underwater shoots (which is what they are designed for) they perform excellently.

Weight
A key consideration is the overall weight of the rig. Now of course well designed housing-camera combinations are near neutral buoyancy below the surface as the air spaces inside the housing providing positive buoyancy and so compensating for the weight of the metal, glass and perspex of the housing and the camera itself. Close to the surface a large housing with plenty of mass is also a distinct advantage. Swell and surface chop will buffet both cameraman and camera, tending to make the image jump about. A large system with plenty of mass will resist such buffeting and moves more slowly than a little lightweight system, in much the same way as a small rowing boat is tossed about by wave action that has no effect at all on a naval destroyer.

Colin Munro setting up a Sony EX1 in a Gates Underwater housing on the surface prior to a dive. (C) Holly Latham.ll size video housing above the surface

Holding a full size video system partially out of the water requires the strength of Arnie Swarzenegger, even with a trailing line to hang on to. Picture by Holly Latham.

On the surface however, other factors come in to play. That positive buoyancy that balances the weight of the system disappears, and the downward force of the weight of the proportion of the camera and housing above the surface is counteracted only by the upward force applied on the grip handles by the cameraman’s arms. That is damn hard work! As an example, a Gates housing for the Red Epic or Scarlet, in air, weighs in at about 43lbs (19.5kg) including camera. That’s roughly the weigh of a six year old child. It is true that not all of that weight will be felt as not all of the housing will be above the surface; but even if it is only 20lbs for those half and half shots you are going to need pretty impressive biceps and shoulder muscles to hold it up and hold it steady whilst getting that 3rd take of that key shot. You are also going to be finning like hell to counteract the toppling forward effect of the unbalanced weight of the housing held in front of you. Comparing this with a suitable DSLR for video, a 5D MkII in an Aquatica housing (again, given as a representative example) weighs in at around 9lbs (4kg). This is still not much fun in a choppy sea but you don’t have to be built like Arnie to be capable of doing it.

Leverage
Essentially the weight distribution combined with the overall length of the rig. Again, a DSLR wins hands down in the category. A Gates housing for the Sony EX1 is around 17 inches (44cm) long; an Amphibico housing for the Sony EX3 squeezes in at a tad over 20 inches (52cm). For over-under shots one will almost certainly need to be working with a wide angle lens and a big dome port (if you don’t understand why, read the last paragraph). This can mean having something like the exceedingly beautiful and optically wonderful, but extraordinarily heavy Fathom superwide port fitted to the far end of your housing. This will produce stunning images but cause vein-popping strain on your upper body as you attempt to lever this half out of the water. Big glass ports on DSLRs are also heavy (e.g. the fantastic Zen DP-230 9 inch superdome, weighs in at 3.9lbs, 1.8kg) but due to the much shorter length of DSLR housings they are mounted only a couple of inches in front of the grip handles. There is still a forward tilting effect, but it is much less pronounced.

Colin Munro leak testing a Hugyfot housing for a Canon 5D MkII DSLR, during setup prior to filming.

As can be seen in this pic of leak testing a Hugyfot, the dome port is only fractionally in front of the grips handles.

A final consideration is focussing and viewing. Most housings for professional video systems do allow viewing of the camera’s viewfinder, but this is generally small and tricky to use through a housing even in easy conditions. So instead most come equipped with a larger external monitor that can be mounted on top of the housing. This is perfect for underwater, but at the air-water interface simply adds additional weight above the water’s surface, pushing the camera further down. External monitors are also available for DSLR housings, and again they are extremely useful beneath the surface but not at the surface. DSLRs do have the advantage of having a large LCD screen that is much easier to view at the surface of a choppy sea; many housings will also take a 45 degree enlarged viewfinder that can make focussing and framing through the viewfinder a much more practical proposition when floating on the surface.

Why do we need to use wide-angle lenses and large dome ports?
This is a brief summary of quite a complicated subject. We need to use large dome ports when taking over-under shots for two reasons. The main reason is because light travels at a different speed through air than water. If flat ports are used with wide angle lenses then considerable bending occurs to light rays passing through the port other than those passing through perdicular, significantly distorting all except the central part of the image. However, this change in wave velocity of light passing through the dome (effectively a curved water-air interface) causes the dome to act as a powerful diverging lens below the water surface making objects at infinity appear to be at a distance of slightly less than 4 x dome radius. This is known as the virtual image. Thus using a small dome port, with a small radius, will bring the virtual image very close to the lens entrance pupil. For example, a 4 inch dome port will result in a virtual image approximately 5.5 inches in front of the port. Above the surface, with air on either side of the dome, this effect does not happen and the lens must focus on the actual image to produce sharp images. Consequently a lens with a large depth of field (DoF), i.e. a wide-angle lens, is required. However 5.5 inches to infinity is too great a DoF for almost any lens, thus a larger dome is required, moving the virtual image further away from the front of the dome and so decreasing the required DoF for both underwater and above surface images to be in focus simultaneously. An 8 inch diameter dome is generally considered the minimum necessary to allow simultaneous focussing above and below the surface (a more detailed technical explanation, with calculations and downloadable formulae has been produced by Dave Knight of Cameras Underwater. This can be read here. The example figures I give here also came from Dave’s page). The second consideration is that, if working in a pool with a mirror calm surface, then we can precisely line up the water surface with the middle of the lens even on a tiny dome or flat port. It’s not like that in the sea though; if you are lucky you’ll be working with just a few ripples or maybe a lazy swell passing through, if not you may have 18inch waves slopping through (if you have more than this, give up and go home). A bigger dome gives you more surface area to play with when lining up the camera. It also means that small waves or splashes are less likely to cover the upper half of the dome, leaves droplets visible on the surface. Whilst on the point of droplets and splashes, the biggest curse of trying to shoot half in-half out, although heavier and more expensive, glass domes do have the advantage of shedding water more easily that their acrylic counterparts.

A race against the rising water

A black swan frantically tries to save her nest and eggs as the river water rises following torrential rains. Colin Munro Photography

A black swan tends her eggs in the nest she has constructed along the banks of the River Exe. Colin Munro Photography

A black swan tends her eggs in the nest she has constructed along the banks of the River Exe.


A black swan frantically tries to save her nest and eggs as the river water rises following torrential  rains. Colin Munro Photography

A black swan frantically tries to save her nest and eggs as the river water rises following torrential rains.

The human cost of the wettest summer in 100 years, lost income and damaged property, has been highin the Southwest.  The cost to wildlife has also been high.  The mute swans that gather on the River Exe in the centre of Exeter have failed to raise a single clutch this year.  At the end of September, an Austalian Black Swan (Cygnus atratus) attracted considerable interest as she tried to brood a small clutch of eggs along the riverbank.  The weather was warm, and drier than it had been for most of the summer.  perhaps she might be lucky.  However Sunday and Monday the 23rd and 24th were to test her to the limit.  Around 2am on the morning of the 23rd the rain becan to fall and the wind started to howl.  For more than 30 hours it rained, and as it rained the river rose.  By the early hours of the 24th she was already frantic, trying desperately to shore up her nest.  By 10am the nest was still there, but floating.  Although probably exhausted she moved incessantly, plucking reed blades of the bottom, trying vainly to build up her nest.  The eggs were still same, but became submerged when she sat on the nest.  She was engaged in a desperate race to raise the nest before the eggs lost too much heat. A black swan frantically tries to save her nest and eggs as the river water rises following torrential  rains. Colin Munro Photography

The black swan tries to move her eggs out of the water pooling in the centre of her nest as the river rises.

Although the rains had now stopped, at least temporarily, millions of gallons were still flowing down the river from high ground and so the river was continuing to rise. Passerby stopped to watch, and throw her bread, which is probably all she had time to eat since she had laid her eggs. No-one knew whether the eggs were fertile. She was the only black swan on the river all summer; tagging along at a safe distance with the larger mute swans that congregated along the quayside. But hybrids between mute and black swans were believed to have occurred in captivity. So it was just possible. And although the odds seemed against her, it was still possible her eggs main survive the flood.
This story will me expanded soon – and the whole story of the black swan and her nest will be told.
All images can be licenses from my Photoshelter website here Search black+swan