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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.

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.

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.

How and why: creating a customised Copyright Logo in Photoshop

How and why: creating a customised Copyright Logo in Photoshop

A clear but unobtrusive logo helps identify the image as yours.

Why add a copyright logo?
Posting images online is a great way to get your images seen but (there’s always a but) it does leave you open to image theft and unauthorised use. While there are various tricks around – disabling right-clicking, placing images in Flash displays etc., if someone knows what they are doing and are prepared to put a tiny bit of effort ito it they can lift your image. For a photographer it is not always desirable anyway to prevent people doing this; potential buyers may want to store a copy of some images to browse later or as a reminder. In this way photographs can be like business cards, and we don’t ask for those back as we leave the conference hall do we? But like any form of advertising we want the (potential) client to remember where the image came and, most importantly, who it belongs to. Now this can (and should) be done adding to the image metadata, however this is not immediately obvious and must be actively searched for (it can also be stripped out, unintentionally or otherwise, by some programmes). A simply logo has the advantage that it is immediately obvious so is like branding – the more your image is shared around the more people associate it with your name and or website.
What should it include?
There is more than one way to do so, this just happens to be my preferred way. Thekey information I want included are 1. my name; 2. clear identification of my copyright 3. a quickway the viewer can locate me, and 4. a quick way for the viewer to find more of my images. This obviously has to be done as succinctly as possible, no-one wants to look at an image covered in screeds of text. 1 and 2 are easy to combine as (C) Colin Munro Photography; it helps in my case that my business name includes my own name so there is no confusion as to exactly where the copyright lies and no need to repeat both seperately. With 3 and 4 I could include both my email and website, but as my email is very clearly displayed on my website I chose to keep things compact and just go with my website.
Ok, so to creating a logo.
These instructions apply to Photoshop, however the workflow is similar in other editing packages. You have you final image, resized for the web and suitably sharpened. Decide on the colour you want the text to be (generally white or black) and set this as the foreground colour using the set foreground and background colours icon in the toolbar. Click on the Horizontal Type Tool. The icon is a capital T, located in the toolbar. This will change the horizontal toolbar at the top of the window to change and display font, font size, formattint etc. Select the approximate font size you’d like (you may have to experiment here). Clicking on the type tool will also create a new layer (visible in the layers sidebar) which will be the active layer in which text will be created. Then simply position the cursor approximately where you’d like the text to start and begin typing. Once your text is all typed out it may not be ideally positioned, or it may appear slightly too large or too small. To rectify this click on the ‘move’ tool (the cross with arrowheads at all four compass points). This will make the text a selection which can be be moved, shrunk or expanded using the cursor. However if you do re-size you will need to apply the transformation (by clicking again on the move tool and then selecting ‘apply transformation’ in the pop-up box) before you can complete other tasks. Sometimes you may not want your copyright logo too prominent; one way to change this is to reduce the opacity, making is partially transparent. This can be done using the opacity slider in the layers dialogue sidebar. Once your text is suitably sized, positioned and has the right level of opacity, your final task is to flatten the image, merging your text with the underlying picture. Simply click on the layers tab; right at the bottom of the drop-down menu you will see ‘flatten image’. Select this, save and your image is ready to upload. Of course we can automate this process by creating batch processing actions in Photoshop, but that’s for another blog. For those based in Exeter, Devon, I am currently running Digital Photography classes later this month and will also be running Photoshop classes subject to demand.


The advantages of winter photography

The advantages of winter photography

A friend of mine recently complained that she wished winter would hurry up and end so she could get out and start taking photographs again. No, no! I contradicted, winter is a fantastic time for taking photographs; all those heavy, brooding skies, the low sun, those stormy seas and frost-coated landscapes. It’s true I’ve never been a fan bright sunny scenes; give me grey, moody, atmospheric vistas any day. A sun high in the sky rarely makes for great photographs, even in summer landscapes generally appear more interesting shortly after dawn or close to sunset when the sun is low.

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

Dawn over Cockwood Harbour on a frosty December morning.

In winter the sun follows a lower arc across the sky, thus a greater proportion of the available daylight produces what is, in my view, a more interesting light. A corollary of this is that the sun rises later and sets earlier, thus one does not have to drag oneself out of bed at five in the morning, or hang around until almost 10pm, to get those sunrise and sunset shots. It is true that some wildlife shots become trickier when one has to work with slower shutter speeds and wider apertures, and sometimes one has to rely on a tripod, not exactly condusive to high mobility for stalking some flighty subject. However, on the flip side, many animals become markedly less wary in winter, when hunger overrides normal timidity.

Heavy rain clouds above Teignmouth Pier, Teignmouth, Devon, England, UK.

A long exposure shot of Teignmouth Pier on a winter’s afternoon. Teignmouth, Devon.

I have always been fond of long exposure shots of moving water, producing beautiful soft, fluid and slightly surreal effects on waterfalls or waves on the beach. This does require low light levels entering the camera though, and in summer (even at minimum apertures) one must either stack neutral density filters in front of the lens, or get up really early or wait really late to get those shots around dawn or dusk. In winter it is so much easier, light levels are much lower anyway and as the sun rises and sets at a more acute angle to the horizon so the period of gloomy light lasts that much longer. This can be crucial if you are rushing between spots to try and find the best angle for you ‘money shot’. So dig out the winter boots and woolly hat and make the most of these chilly and gloomy landscapes. If nothing else it’s such a great excuse to eat lots of chocolate and warm up in a pub afterwards.