Mike Gerken: Evolution Underwater Imaging

Within this gallery you will find a compilation of entrees offering great underwater photographic advice.

Scroll down to see the variety of topics covered such as:

•Shooting Macro •Black & Whites •Ambient Light •Composition

Photo Tip of the Week

April 28, 2015

Shooting Super Macro

Recently, I visited Dumaguete, Philippines with the Hampton Dive Center as their photo pro for a week in February. (Read more about it at my Dive Blog Report, Dumaguete Muck: "A Small But Savage World".) I wasn't a serious super macro photographer before this trip but I am now. I had a great time shooting many small and unusual critters in the muck. Here are a few tips for nailing great super macro shots:

1- Due to the increased magnification of a super macro lens, such as the Nikkor 105mm, holding the camera steady is never more important than now. The smallest move or shake of the camera will cause your subject to jump and bob around the viewfinder considerably more than shooting wide. Practice, practice, practice is my only advice for learning to hold the camera steady.

Flamboyant Cuttlefish

A flamboyant cuttlefish fills the frame of my 105mm lens.

2 - Buoyancy control is important for underwater photography and even more so with muck diving. They don't call it muck because the bottom is made of course white sand. Usually you will find very fine dark or even black silt. The slightest fin kick or contact in general will silt out your shooting area. Keep your knees, fins and hands off the bottom. Learn to be an expert at hovering and you will keep the muck out of your macro shots.

3 - Finding good subjects to shoot is half the battle so follow the dive guides. Most of the guides at the resorts in Dumaguete are eagle eyes when it comes to spotting the small stuff. Too often they would call me over and point to a critter with there long pointers. After getting close, I still could see what it was they were trying to show me until I got really up-close. There would be a frog fish, for example, smaller than my pinky nail laying in the silt. I could only shake my head and ask myself, "how did they see that?".

Painted Frog Fish w/ Feather Duster

This clown frog fish was nearly impossible to see hiding beneath this small christmas tree worm.

4 - Composition is critical for taking a compelling super macro image. Rather than concentrating on the critter by itself, try to find subjects that are situated with interesting backgrounds otherwise known as negative space. The entire scene should be appealing and not just the fish or creature. Many times I will turn my back on an interesting critter because the scene as a whole just does not work. Also, please do not become one of those photographers who manipulates and harasses marine life to get "the shot".

The sponge in the background was no mistake in the composing of this shot. The continuous pattern helps highlight the features on this ornate ghost pipefish.

5 - Shooting animal behavior is usually more fascinating than shots without it. If you can nail critters actually doing something such as feeding, hunting, tending to eggs or dens then you have a superior shot and great conversation piece to boot. Doing this is easier said than done and requires research and patience in understanding and finding behaviors but the rewards are worth the extra work.

A symbiotic relationship between this goby and bulldozer shrimp catches interesting animal behavior in a still image. The shrimp burrows the home while the goby keeps watch.

6 - Lighting is everything with photography. In the case of macro photography, you will primarily be utilizing strobes as your primary light source. Ambient light is not usually used for super macro very often. Experiment with strobe strength and quantity. Most often you will discover a particular subject will look better with the use of a single strobe rather than two. A single strobe will cast shadows and create a more two-dimensional image.

Female Harlequin Shrimp

Note the shadows cast across the body of this Harlequin Shrimp due to the use of a single strobe.

If you are interested in learning more about macro photography, contact [email protected] and ask about the photo courses available.

April 15, 2014

Composition

Composition is a topic I could write about for hours but, I do not have the space here in to do so. Here is a quick tip to hold you over for taking better photos.

Rather than chase a subject around with your camera hoping to get a shot of it, such as a sand tiger shark on a wreck in North Carolina or an anemone fish in its host, why not set up a shot with an interesting background and wait for your subject to swim in to your shot. I understand that this is easier said than done in some circumstances. Sometimes subjects just don't do what you want them to do. Here are a few steps to take to improve your odds:

1 - Do your homework and learn about fish or animal behavior before you jump in to the water.

2 - Have a plan in your head as to the shot(s) you would like to get.

3 - Upon arriving at your dive site underwater, pause for a moment to study the fish/animal behavior. Determine if it is doing what you want it to. If yes, move on to the next step.

4 - Set up your shot based on the witnessed behavior, compose with interesting background or negative space and fire off test shots to check your exposure.

5 - Wait for your subject to swim in to your scene or near the scene and begin to fire away.

6 - Take as many shots as the subject will allow.

7 - Do not harass your subject(s). It is likely they will swim away and ruin a chance for you or anyone else getting the photo.

8 - If the subject matter is not there or not doing what you hoped, abandon your plan and move to plan B. Then plan C etc.

Here are a few examples of where this technique proved successful for me:

This sand tiger shark on the wreck of the USCGC Spar swam right in to my frame with the bulk of the super structure in the background. I noticed the sharks swimming round and round on the foredeck and knew it was a matter of time before one would swim in to my shot.

Duo

Watching this pair of pink anemone fish swim round this magnificent sea anemone, I noticed there was a pattern to their swimming. I waited for the surge to pull back the mantle of the anemone and the fish to appear beneath it as I had witnessed before firing off this shot. Luck may have been a factor as well.

October 2013

Shooting Video w/DSLR

Being that I shoot both video and still images underwater, I was excited years ago at the development of DSLR cameras that could do both. Unfortunately, the video aspect for these early dual SLRs was not very proficient and lagged in quality and functionality. I decided to wait until technology had produced a better SLR for shooting HD video. That day finally came for me when I purchased the Nikon D800 DSLR. Although there is still much room for improvement, this camera, like other cameras in it's league performs very well.

Advantages

First off the advantages of shooting both video and stills with the same camera are many. The cost savings alone in having to purchase a single camera and single housing are obvious and need not much elaboration here. No longer do you need to purchase, maintain and travel with a whole other system.

In addition, being able to utilize your arsenal of DSLR lenses to shoot video is also a huge savings. For example, a super wide angle dome port for a designated video housing can run between $3-$6000+. A wide angle lens for a Nikon SLR like the 16-35mm 2.8 will cost a mere $1200-$1400 and can be used for both video and stills. The quality of this piece of glass is stunning. Not happy with the 16-35mm. No problem. Pop a 16mm fisheye ($900) on and away you go.

Another big advantage is the capability to shoot both video and stills at the flick of a switch on the camera without having to return to the boat to get your other system. This can be a disadvantage if you are not mentally focused on a single task, but otherwise, if you descend and discover conditions are not conducive for the task you had planned, then you can merely switch and make a new plan on the fly. It is even possible to mount both underwater strobes and underwater video lights on the same set of arms. This can be a little cumbersome, but the first time I tried this I had great results as you can see by the video below.

This video and the still image at the top of this web page were shot during the same dive the first time I ever attempted to shoot both photo and video. Needless to say, I was very satisfied with the results and continue to equip my housing to shoot video and photo on most dives. There are occasions where I will shoot only one or the other and cross over takes only a matter of minutes topside.

Disadvantages

The disadvantages of using a DSLR such as the D800 to shoot video is setting the exposure. There is a bit more to it than say a consumer or pro-sumer camcorder. Shooting on auto exposure is a bit tricky, if not impossible and produce quality shots. I found it is best to shoot on aperture priority where the camera will determine your shutter speed (which should be between 1/30 and 1/60 of a second) while the aperture is adjusted by the photographer. This is of course not as simple as a point and shoot, but the results will be more desirable. Shooting on manual mode is also a very desirable method to shoot where you can be certain to get the best exposure for each shot. This requires a bit more training and I will save these tips for another blog report.

The auto focus on the D800 shooting video is about useless. One must always shoot manual focus and take care when doing so. I have had several great shots ruined because I did not focus the camera properly before recording.

The last disadvantage to shooting video with the D800 is the image quality itself. The cameras processor compresses the video files to a format that is not recognized by certain editing softwares such as Final Cut Pro. A conversion of the file is necessary, but the image loss cannot be recovered. If you were to play the compressed video from a D800 and compare to an uncompressed file you might have a hard time noticing the difference.

So unless you plan on shooting broadcast/theatre quality footage, I would not worry about this compression. Besides, there is a solution to this problem anyway. One can purchase an external video recorder that doubles as a video monitor, such as the Atomos Ninja 2 thus bypassing the SLR compression algorithm. This is exactly what I have done. Stay tuned for a full review of this monitor/recorder system.

So if your wondering if it is time to move in to the world of photography and video with the same camera, I can say that I am very content with these new age cameras and look forward to the exciting future developments to come. With a few basic tips and techniques you can be off to shooting high quality HD video with a DSLR.

Photo Tip of the Week

RAW Files

To shoot RAW or not to shoot RAW, that is the question. When I get asked that, as I do on a regular basis, I always answer, "if you want to get the most out of your photography then shoot RAW and learn to process your images". RAW files, otherwise known as the digital negative, are uncompressed files of your photos that require a certain amount of post processing with softwares such as Photoshop and Lightroom. The RAW image may lack contrast, color saturation and sharpness to name but a few. It is up to the processor to add the elements back in to the image and recreate the scene with which they saw.

These RAW files are only suitable for photographers who plan on processing their files after shooting them. If you are not one of these people then be content on shooting JPEG files and having images that will be less than what they can be. JPEG's are compressed files with a loss of data each time your save the file. They are not suitable for fine art photography but more for snapshots and posting images on the web or sending via email since they are smaller files.

Also, processing digital images is not cheating when done correctly. I have written about this in previous blogs and won't dwell on the ethics of Photoshop in this post. Let me remind you though that Ansel Adams, the world famous landscape film photographer of yore, did his finest work in the darkroom.

So in short, shoot RAW and sign up for a Lightroom or Photoshop course and learn to make the most of your images. Your photography will love you for it.

Photo Tip of the Week

Backing Up Your Images

When I used to work on liveaboards in Truk Lagoon every so often someone would come up to me with a large frown on there face holding a camera with water dripping off of it. In the digital age there is little than can be done to save a camera that has been immersed in water. I would ask them, "Do you have insurance?". Sometimes they would answer yes, but that didn't seem to matter. What they were most upset about was all of their photos from the entire week were on the storage card inside the now wet camera and completely lost. I then would ask, "Did you back up your files?" Inevitably, many would shake their head and frown even more. Not only did they not back up their photos but they never even downloaded them off the camera in the first place.

At the end of a dive or at the least, at the end of a dive day, one should always download their images on to an external source such as a laptop. Once that is complete back them up on to another hard drive. Then you can format your storage card and get ready for another photo shoot. You should never use a storage card as a long term place to store your images. They are not reliable enough and every time you take your camera in the water you run the inherent risk of flooding and thus destroying the storage card as well.

Your files should exist in two separate places at any given time always! I take it a step further and keep another hard drive in a separate home and update it every so often. There are also internet services out there where you can upload and store unlimited data on external sites for a small yearly fee and access them easily enough when you are logged in to the net. Whatever you decide to do be sure to back your images up and then back them up again. You will be grateful you did so if a catastrophe should occur.

Photo Tip of the Week

Ambient Light Exposures

Although strobe lighting is critical for achieving well exposed images underwater, there are circumstances where you should shut them off and experiment with just the ambient light available. When should you shut your strobes? Here are a few tips:

1 - Most strobes are only effective with lighting up the foreground of your image within several feet to maybe 12 feet away depending on the strength of your strobe units. If your subject happens to be out of range of the strength of your strobe, then it is pointless to keep them on. Shut them off and try shooting ambient. All the strobe will do is illuminate suspended particles in the water and create complications. It is important to understand just how powerful your strobes are by spending time out testing them on a subject at different strengths and distances with varying exposure settings.

The Fumitzuki destroyer from Truk Lagoon, was too
far away for strobes to be effective.

2 - Sometimes there is nothing in the foreground of your image that requires the use of artificial light. The subject may be drab, lacking color and generally not an important element to the overall shot.

A foreground lacking subject matter and color required I
shut the strobes off. Fujikawa Maru 2006©

3 - Maybe your camera set up doesn't even have strobes on it. Understand the limitations of your gear and seek subject matter where ambient light exposures would work well. ie, colorful reef systems may not work well, but wide angle shipwreck shots would.

No strobes required here. Plenty of
ambient light and little foreground to
light up. Fujikawa Maru 2006©.

Experiment and try different situations and over time you will begin to see what works and what doesn't.

Photo Tip of the Week

Shooting Black White

First off, let me clarify one thing. One should never shoot an image in the black and white mode on their cameras. Shoot in color and convert to black and white later in post processing instead. By shooting in color you are creating more data in the image that when converted to B & W will yield more dynamic range or in other words, a larger palette of gray tones from shadows to highlights. You will also find more latitude in processing your image when shooting in color and the ability to add greater contrast. Lots of contrast is most often a desirable result when converting to B & W. Some would say it adds dramatic effect or to put it simply, it just looks better.

When should one shoot in B &W? This decision is subjective and in the eye of the beholder. Some people love black and white photography, while others do not. Convert an image to B & W and hold side by side with its color version and see how you feel about it. I show many of people both versions of an image and most often the opinions are split down the middle as too which one they prefer.

Generally speaking though, I would recommend converting to B & W under these circumstances:

1) When you want to achieve an alternate mood in your photo such as one of boldness, antiquity, or mystery to name a few.

Which one do you prefer?
The engine room of the Fujikawa Maru, Truk Lagoon©

2) When the underwater scene is green or having a lot of suspended particulates. Rather than create a blue image where there was none; convert to black and white and the green is no longer there and the specks now add character to the image.

Rather than try to save the green cast image with low visibility I converted to B & W.
Sand tiger shark of North Carolina©.

3) When your image is monotone or when color is not a factor in the photo.

Monotone images are prime candidates for B &W conversion. Color is not a dominate factor in this image.
Sand tiger sharks on the USCGC Spar, NC©.

I hope this tid bit of information will inspire you to dabble with your post processing conversion of color to awesome Black and White images.

Photo Tip of the Week

Negative Space

I have heard that the famed photographer and film maker, Howard Hall had first coined the term, 'Negative Space' when describing the part of your image that was not your primary or even secondary subject but the background. How one uses negative space in their composition may determine the outcome of the photo. One can have a fantastic subject in front of there lens, but not look at what is around or behind this subject. It is of utmost importance that you do so and utilize this space correctly.

Here are a few quick rules as to how to effectively use negative space:

1- The Negative Space of you image should contrast greatly from your subject. What good is your subject if you can't see it. (unless your trying to show animal behavior such as camouflage).

Getting low and shooting the bright white belly of sharks is a good way
to add contrast to your subject not too mention include his 'pearly whites' in the shot.

2- Negative space should have compelling color, texture and or shape. A hodgepodge of patterns and color may not carry the image.

This ornate patterned anemone was what caught my eye.
The Clark's anemone fish were an added bonus.

3- Negative space should highlight your subject and not detract from it.

High contrast accentuates the plate and the silty negative space
adds to the 'where' and the 'what' of the image.

4- Too much Negative Space is a bad thing. Scale your subject to proper size and practice the rule of thirds.

Wrecks make for ideal background or negative space when shooting
marine life such as sand tiger sharks.

So the next time you look in to a view finder be sure to take a gander over the shoulder of whatever or whoever you are shooting and fill that negative space with some positive looking stuff. Your photos will love you for it.

Photo Tip of the Week

Dive Briefings

If you want to know the where, what and when's of photographic subject matter on a dive site, I highly recommend you listen to the dive briefing if you don't already. Listening to the guys and gals who know the dive sites like the back of their hand is a sure fire way to find out what is hot and what is not. Most often the person briefing (that would be me in this case) is a keen photographer or videographer who is willing to share some of their secrets with you. Even if the person is not a photographer they will have enough knowledge to assist you in finding what you seek. It is also imperative to ask as many questions as the dive leader or person doing the briefing will answer. ie Where is the best place to find sharks? Is the wreck intact? What is the most photogenic part of the wreck? etc etc. Don't be afraid to find out the important details that will benefit you photography and maximize your bottom time. I know for one that I will share what I know in the name of photography.

Over the years, I am astonished at how few questions photographers on my boats ask me about subject matter and how to find it. I once volunteered information unsolicited, but stopped doing so when most were not interested. This isn't always the case though. Surprisingly, it is usually the most accomplished professional photographers who seek local knowledge of a dive site from me. These photographers have learned over the years that it is the locals who can steer you in the right direction towards award winning publishing quality images. The same goes for me as well.

When I dived the Maldives in 2008, it was a local dive guide and photographer, Moosa, who worked on board the liveaboard dive vessel, Manthiri, who was invaluable to me in obtaining some great images. I picked his brain as much as I could during the week long stay on board. I knew this guy had a strong knowledge of the region and I wanted a piece of it. "What lens should I shoot on this dive?", I would ask Moosa beforehand. He would say, "use your 16mm fisheye. There is a large Napolean Wrasse down there that loves having his photo taken". Sure enough I had a field day shooting 'George' a tame wrasse the size of a Toyota Prius. One of the photos that I took landed on the cover of Sport Diver Magazine in Aug of 2010. If I had brought my 60mm or even my 10.5mm fisheye I may not have gotten the shot I wanted. Thanks Moosa!

The cover of Sport Diver Magazine.
Aug 2010 Edition.

In short, do your homework, learn a dive site before you get there, read books, talk to other photographers and most of all listen to the dive briefings and ask lots of questions. Besides, the briefings are not just for dive information, but have lots of important safety advice as well. I may regret ever posting this piece since I may get inundated with questions now, but that's ok since I love talking shop. One word of warning though, once you get me rambling on about photography you may have a hard time getting me to shut up.

Photo Tip of the Week

Buddies

Underwater photographers make the worst dive buddies. There, I said it; I'm a terrible dive buddy. There is nothing more distracting to a photographer who has to constantly look over their shoulder to check on their buddy or to race to keep up with a dive group. Your ability to focus on your task is considerably hindered. Maintaining healthy dive buddy relationships is very difficult. Many dive couples have been ruined from this conflict in interest. A diver not shooting wants to swim, explore and see it all and I can't say as I blame them. A photographer wants to be methodical, move slow, study and work a subject until he or she has nailed it. What a disaster for both. As a photographer, either you need to find a dive buddy that can tolerate your hobby and hang out with you without getting in the way or, best yet, a dive buddy that will model for you. Otherwise, you need to find a new buddy for your buddy and get a new one yourself. When I travel, if a dive operator insists on having a dive buddy I request to hire a private guide so I can do my own thing without the pressure of others to deal with.

If you absolutely positively cannot find a new buddy for your buddy then you need to make some sacrifices and learn to shoot on the fly while keeping up with the buddy. You may notice a serious drop in the quality of your images, but at least your buddy will be still speaking to you and maybe even allowing you to share your bed while on vacation. There are trade offs in life everywhere.

The other reality is many photographers simply dive alone when operators allow it. I myself prefer it, but I am trained to deal with emergencies on my own if they should occur and I do not place myself at risk in situations where I cannot help myself. This piece is not a debate on solo diving though and I do not recommend anyone do so without proper training, certifications and permission to do so from the dive operator.

If anyone out there needs a dive buddy, I am for hire. You just need contact me to find out what I charge. One hint though, I don't work for food anymore.

Photo Tip of the Week

Lanyards

I received a Facebook message recently from a dive enthusiast asking me what to do with his camera when descending and ascending from a dive with current. I wanted to respond with a short answer by telling him to simply use a lanyard, but then it occurred to me that using lanyards for your photo/video gear is a little more involved than a sentence answer.

The first time I took an underwater camera beneath the waves was about 18 years ago when I rented a Sea & Sea Motor Marine from my local dive shop on Long Island. I was on a dive trip on a liveaboard in the Bahamas and on my last dive. I was about to climb the ladder to get back on the boat and clipped off the camera to my BC before doing so. Well, at least I thought I did. I let go of the camera, grabbed the ladder and headed up. After getting my gear off I went to un-clip the camera and guess what? It was gone. I searched the bottom under the boat for twenty minutes only to learn that this camera floats. Ugh! Now it was really gone. (Sadly the crew didn't lift a finger in assisting me.)

That was the last time I ever used a lanyard for any of my gear. Today, I do every dive without a lanyard and so far to date I have never dropped or lost my rig. By holding my camera in my hands, firmly, at all times, I know exactly where it is. I'm not suggesting lanyards are bad to use for everyone. I'm just saying I don't like them.

Lanyards are also problematic for other reasons. Some of them are made of coiled stretchy rubber or retractable line that does nothing but get tangled in everything and gets in the way. Others have metal snaps on them that when stretched out and released will snap back at you like a mini missile and put a nice chip in your dome port. Not fun.

A simple home made piece of gear.

I witness time and time again divers on my boat, the Midnight Express struggle with lanyards as I have just described. If you happen to be one of them please don't be offended, but heed my advice. Often a diver will climb on to the ladder on a choppy day with camera attached to them by a long stretchy lanyard. 9 times out of 10 that darn thing gets hung up on the rungs while they are trying to navigate the ladder safely back to the deck of the boat. I hold my breath nervously when I see someone with one hand try to unhook themselves and with the other hand hold on to the ladder while being thrown around like a mechanical bull. If you have to use a lanyard, unclip the gear from your body first, stow the lanyard away properly and then head for the ladder. This technique may save your equipment from damage not to mention your physical well being.

The lanyard I use while diving is an all in one tool that does not get hung up and is very useful for the crew to haul a camera out of the water from the swim deck. I'd seen these used for the first time while working on the liveaoards in Truk Lagoon. This system will work on any type of boat and I guarantee the crew will like it. The best part about it is it costs a few dollars in hardware from the dive shop and hardware store. I have a short length of braided nylon line threaded through a 1/4" rubber hose. On each end there is a brass thumb snap. Each clip attaches to the eye's on the handles of my camera housing. When I jump in the crew will lower the camera to me using this handle to lower it. It keeps the camera and strobes level, making it easy for them to handle the rig and reduces the possibility of your camera getting damaged. Once in the water, I detach the handle and clip it off behind me out of the way on a D ring. Now it doubles as a lanyard if I need it. Since the handle is short and semi rigid, it never gets tangled in anything and I don't even know it's there. If I need it in an emergency, I reach around and recover it easily enough. Otherwise, I do not use it again until I'm ready to pass the camera up to the crew after the dive is over. The crew can recover the camera with the use of one hand and not two. It is safe, cheap and very effective.

Photo Tip of the Week

Using Histograms

Many of you photographers who are new to the hobby may be wondering what that funny looking line graph is on your camera's LCD that accompanies each photo. Some of you may know what it is, but choose to ignore it because it looks too complicated. I say this confidently because I was one of those people who chose to ignore it when I first started shooting. I can now tell you now earnestly that you are making a mistake by paying it no mind. This funny looking graph is called a Histogram. In actuality, it is a very simple representation of the exposure of your image. When you can learn to read a histogram properly you can ascertain wether or not the image is too dark, too light or in between. The y-axis or vertical axis represents the number of pixels. The x-axis or horizontal axis represents the tone from shadows of the left to highlights on the right. Usually histograms are set up where the left side of the x axis is the shadow while the right side is the highlights but this depends on the camera.

The histogram that is shaped like a bell curve, where neither the left or the right side of the graph runs off the side and the mid-tones dominate the image, represents a properly exposed image. (See item a.) If the graph runs off the side to the left in the shadows, this is an indication that the photo was under exposed, thus loosing the details in the shadows. (See item b.) If the graph runs off the page to the right this in turn indicates an over exposed image where there is loss of highlights or burning. (See item c.) This clipping, as it is called, is undesirable with most subjects and can easily be compensated for by adjusting your exposure settings such as f-stop or shutter speed (see last weeks Photo Tips). Ascertaining what your image looks like by merely inspecting the LCD is not sufficient. LCD's can be misleading depending on how bright or dim your viewing light or ambient light is. Histograms, however, never lie!

Item a. Proper Exposed: note minimum clipping.

Item b. Under Exposed: note clipping on left.

Item c. Over Exposed: note clipping on right

Sometimes you may be shooting a subject that is strong in the shadows and lacking any highlights. Your Histogram will look like this:

Sometimes you may be shooting a subject that has strong highlights and lacks shadows. Your Histogram will look like this:

Are you starting to see the correlation? Once you do, analyzing your shots while on the fly will be a cinch and save you a lot of time and effort on poorly exposed images. Have faith in this little graph. There is a plethora of information within in it. Good luck!

Note: The top photo is a Pink Anemone Fish and Magnificent Sea Anemone taken in Truk Lagoon, Micronesia. The middle image is a sink and mirror taken on the Heian Maru, Truk Lagoon, Micronesia. The bottom image is the ship builders stamp, Toyo Toki Kaisha, taken from the side of a porcelain sink from the wreck of the Hanakawa Maru in Truk Lagoon, Micronesia. To view more of Mike's images from Truk Lagoon.

Photo Tip of the Week

Bracketing

Bracketing is a technique used to achieve a wider range of photo results by making several exposures of the same subject. This way the odds are more in your favor of yielding a desirable shot that does not contain over or under exposed shadows or highlights. Changing your exposure can be done by stepping up or down your shutter speeds and/or your F-stop. For those of you unsure of what shutter speeds and f-stops are, I can explain them quickly now. The shutter speed is the length of time the cameras shutter is left open allowing light to enter in to the camera and on to the sensor or CCD. Long shutter speeds will yield brighter images, while short ones will yield darker images. F-stops are the size of the aperture or hole leading into the cameras sensor. The higher the number of f-stop the smaller the aperture is letting the least light in. The lower the number f-stop the larger the aperture is etc. By changing your f-stop and/or shutter speed, while shooting the same subject, you will have a wider gamut of exposures to choose from in post-processing. Trying to ascertain what the perfect exposure is underwater may be difficult due to the lighting at the time of day and how it effects your LCD. (Of course learning to read histograms would prevent this problem but that is for another blog).

Overexposed at
F14, 1/1250sec.

Under exposed at
F22, 1/250sec.

Just right at F18, 1/250sec.

By bracketing the shots of this sea fan, from F14 to F18, I succeeded in finding the optimal exposure. F14 was over exposed with highlights 'burned'. F22 was under exposed with the loss of details in the shadows. F18 yielded a better dynamic range from highlights to shadows.

Bracketing can be done manually or automatically. Many cameras, especially SLR's, will have a setting in your menu that will let you create custom auto bracketing exposures by telling the camera how many shots you want to take and how many F-Stops or Shutter Speed settings you want to change up or down, fast or slow. ie Using your light meter, select an exposure setting that you think is correct as your starting point. Let's say I set the camera up to take 5 photos stepping up two and down two starting at F5 with a fixed shutter speed of 1/100. On aperture auto bracketing the results would yield 1 photo each at F5, F5.6, F4.5, F6.3 and F4 (with a Nikon D300). You can do the same for shutter speed and even ISO and white balance but, let me not get ahead of myself. By going up two stops and down two stops from your you are covering a much broader area of exposures. Make sure the strobe units you are using can keep up with the rate at which the camera will fire on auto mode, otherwise do as I do and shoot manual. When you have the time, adjusting your exposure for a photo manually can be as easy as talking a shot, flipping a wheel or control for shutter or aperture and then taking another shot. With practice is gets easier.