By Jill Smith
An Adobe Photoshop ® tutorial
This is a colour correcting technique that may be employed in Adobe Photoshop ® using the Curves contrast adjustment tool in conjunction with LAB colour mode. Convert an image to LAB colour mode, and apply curves to the channels individually to knock out extreme colour casts, boost colour and even make very specific changes to colours all in one fell swoop.
A LITTLE ABOUT CURVES:
The Curves dialogue box is another graph mapping all of the tonal values on a straight diagonal line. The steeper the curve, the more contrast between the tonal values in the steep part of the curve; the flatter the curve, the flatter the contrast in the tones of that area of the curve.
Click within the image, and a small circle will appear on the curve where that tonal value is represented. You can set a point on this line by clicking on the line directly, or by Ctrl-clicking within the image to plot that specific value on the line of the curve. Up to 14 control points can be added to the curve; this allows for very precise control when adjusting contrast. Each point may be edited separately.
A LITTLE ABOUT LAB COLOUR MODE:
LAB Colour mode consists of 3 channels much like RGB; however, the similarities end there.
The LAB channels:
First, let’s illustrate the concept of LAB with this jacket to help us understand using Curves with the LAB channels better.
We have decided to change this image of a blue and black jacket to a red and black jacket.
The image has been converted to LAB Colour Mode (Image > Mode > Lab Colour), and the Curves dialogue box is open - Image > Adjustments > Curves (Ctrl - M for PC /Command –M for Mac).
Note: Both of these Curves graphs plot the colour values along the diagonal line (top graph is for "a" channel, bottom graph is for "b" channel). Adjustments in a and b will affect colour, but not contrast.
About "a" channel curve: Values that are plotted on the mid-neutral line in the center are neutral (neither green nor magenta). Values plotted above the neutral line are more magenta than green, increasing in intensity the higher it goes. Conversely, values plotted below the mid line are more green than magenta.
About "b" channel curve: Values that are plotted on the mid-neutral line in the center are neutral (neither blue nor yellow). Values plotted above the neutral line are more yellow than blue, increasing in intensity the higher it goes. Conversely, values plotted below the mid line are more blue than yellow.
Top Right ("a" channel curve):
Above the graph display the Channel selection (drop-down box) has been changed from "Lightness" to "a" (I am satisfied with the brightness and contrast of this image, so I am not going to adjust curves on the Lightness channel).
The "a" channel contains all of the green and magenta colour information. There are two values plotted on the graph. The top one was selected by Ctrl-clicking (Command-clicking for Mac) a good representation of the black fabric around the shoulders and the neck (do not take the sample from either the highlights or the shadows). It is seen plotted on the mid-neutral line of the graph, meaning it is neither magenta nor green. The bottom value was plotted by Ctrl-clicking a good representation of the blue fabric (neither highlight nor shadow). This value is plotted well above the mid-neutral line, indicating there is more magenta than green in the colour of the jacket. The red arrow on the graph shows the direction we are going to take this value when we edit (next).
Bottom Right ("b" channel curve):
The bottom curve shows the graph for the "b" channel containing all of the blue and yellow colour information. Again, a value representing the black has been plotted on this graph-line by Ctrl-clicking a good representation of that tone in the image. This time, the value is not plotted exactly on the mid-neutral line, but a little bit below, indicating either a blue colour cast, or perhaps the true colour of the fabric is navy blue.
Below that (still see the figure above, the graph below the "a" graph), is another point that has been plotted on the line to represent the blue values in the jacket, and again, the red arrow on the graph illustrates the direction this value is going to be moved when we edit.
Editing the Value Points:
Now let's edit those points.
That's it, look Ma, no selections! This is an easy example, because the background is blank and relatively neutral, but it is a great image to introduce the concepts. Now let's colour correct an underwater image.
Applying Curves with LAB Colour Mode in an Underwater Image
I've never met an underwater image that didn't need some help, and this image can do with some pretty drastic adjustments in LAB. This Honeycomb Trunkfish and small yellow remora riding under him, is underexposed, and the colour cast is very cyan. At a glance, the water in the background looks like it has too much magenta in it too.
First step is to open the image and convert to LAB (Image > Mode > LAB colour). Then open Curves (Image > Adjustments > Curves, or Ctrl-M/Command M for keyboard shortcut). The default Channel selected is the Lightness channel. That is where we will start.
By clicking and dragging the cursor over the image it is possible to see where the values are plotted on the curve; note the lightest area of the image with detail (mouth of the trunkfish), and where that resides on the curve. Instead of Ctrl-clicking though, I click a value on the line above the lightness values of the mouth. This is because I want to keep the detail of mouth in the steepest part of the curve for contrast and detail (I don't count spectral highlights as important detail - there aren't any in this image anyway). The highlight point is dragged up significantly to lighten the image, and increase contrast, while watching the mouth area to make sure it isn't being clipped. To set the shadow, find the darkest values of the area of interest, and see where that value lives on the curve. Then manually click a point below that, and lower it to darken shadows and increase contrast.
The curve now has an "S" shape, and all of the values of the image that are important detail, reside in the steep part of the S, creating more contrast. At the extreme bottom and top of the S, the darkest shadows and the lightest highlights are actually flattened and have less contrast. It may be helpful to remember that when adjusting the curve for contrast, while one part of the curve is made steeper to increase it, another part of it will be flattened, decreasing it.
Above is the Curves adjustment for "a" channel (selected from the dropdown Channel menu):
For now, 3 points plotted is enough, although plotting a point for the sandy area roughly on the same plane as our fish would not be a bad idea either, but we'll check those values after we make some adjustments.
Clicking the water value, pull it straight down to the green. Push the Trunkfish's skin value to the neutral, and drag the remora's yellow value up towards yellow. At this point, check the sand value near the fish , and try to keep it close to neutral, or even slightly warm in the magenta, but not too much. The sand in the distance may retain some blue values, and that is acceptable because it is natural-looking. The colour still doesn't look right, and that is ok, because we haven't adjusted any colour in yellow/blue yet.
Above is the Curves adjustment for "b" channel (selected from the dropdown Channel menu):
The remora yellow may be raised a bit to make it a more intense yellow, but care must be taken to not introduce too much yellow to the sand. The sand may be a little yellow, but should not be as intense as our little remora. If the sand became too yellow, it may be plotted on the curve and pulled down a little. You have so much control here!
If sharpening is desired, sharpen on the Lightness channel before converting back to RGB to avoid colour distortion around edges. Then I do any minor tweaking in RGB, and I'm done!
I do love that I can control the colour and the intensity of a colour in an image using LAB and Curves; even two colours that are very similar may be pulled apart to be made more distinctive.
I hope you find this colour mode to be useful to you; it has become one of my favourite tools in more ways than one.
This is a pretty quick and dirty introduction to a very comprehensive colour mode/topic. Want to learn more? Here is a great resource written by one of my favourite instructors, Dan Margulis (now semi-retired):
Margulis, D.2006.Photoshop LAB Color: The Canyon Conundrum and Other Adventures in the Most Powerful Colorspace.California:Peachpit Press.
By Jill Smith
Chromatic Aberrations are those ugly, coloured halos that may outline contrasted edges in an image. They are often bright blues and yellows, or magentas and greens. The colours of light (yes, white light is made up of colours; all the colours of the rainbow - same principles apply), don't all behave and bend the same way. That is why we get to see and enjoy rainbows (nice), but also why we have these gross distortions (not so nice). Here are two quick and dirty ways to banish them (one way is quicker and dirtier than the other, but it may not always be the answer).
RAW images - If your images have been shot in RAW file format, they may be opened in Camera Raw, and possibly corrected very easily there. Go to the Lens Corrections tab, and click the “Remove Chromatic Aberration” box at the top of the panel. Most of the time this will do a good job. That was easy.
The following Chromatic Aberration Removal technique may be employed in the event that the Camera Raw feature did not completely remove the aberration, or if there is no RAW image to work with.
This image sports arguably the most grotesque chromatic aberration I have ever seen. Notice how the distortion becomes more severe further away from the centre of the image. The distortion here is so terrible for a couple of reasons:
This part of the process will be numbered to correspond with the figure below.
While the nasty colours have been taken care of, this particular image (and this section taken near the edge) was an extreme example, and I can still see the contrast on the edges. If I first ran this image through Camera Raw and checked the "Remove Chromatic Aberrations" box, they would have been largely removed, and the above method would have cleaned the rest up beautifully....but for this method, we wanted to work with the worst case scenario.
Happy Shooting and Editing!
by Jill Smith
The decision to do this for myself was without a doubt one of the best decisions I have ever made; I shall never, ever forget it.
Words cannot express how beautiful it was to experience the Caribbean Reef Sharks "up close and personal"! I have been dreaming of this very special trip for some time, and will always treasure the memory of standing in the middle of a swirling group of graceful reef sharks. Oh, my...
The Shark Handling course
The instructor, a highly accomplished shark consultant, and conservationist - Cristina Zenato. I have been following Cristina on social media for a couple of years (I like to think of it as research, rather than stalking, haha), and was impressed with all of the work she does in the interest of ocean conservation and saving sharks; I knew I wanted to learn more, and I was excited to meet this interesting and amazing lady!
This course includes classroom time with Cristina, learning about shark behaviour, biology, and how to interact and feed them on the upcoming dives with her. After that, it is time to get ready to dive; a total of 5 shark dives near Freeport, Grand Bahamas, to provide you with the experience of a lifetime!
So we made it happen, and before I knew it, Cristina was helping me with my chain mail, and we were jumping into the turquoise waters to meet her babies. Cristina visits them often (see below to learn more about her work), so as we descended, they were already swimming nearby. We arrived at our spot by an overturned wreck, and removed our fins at a depth of about 45 feet. I was surprised how balanced and stable I felt walking on the ocean floor in chainmail. It was far more comfortable than I expected.
We spent a few minutes just breathing and relaxing there, while they swam around us. Holding a feeding tube full of dead fish in my left hand, I simply watched them all around me. I needed about ten eyeballs to take it all in. I didn’t want to miss a thing.
Remembering what Cristina had taught me in the classroom, I reached out to place my hand on the top their heads, and let my hand trail down the length of their bodies. This motion is meant to replicate the way I will feed, and build my confidence.
It was just amazing. I was in awe the entire time. There I was, standing in the middle of circling sharks with dead fish in my left hand, and they weren’t attacking me. Sometimes they bumped into me. Sometimes they would swim between my legs. Over my shoulder. In front of my face. Everywhere. I loved it. Every minute.
I kissed a shark, and I liked it…
I found that some sharks will not tolerate touch. So you don’t touch. Some allow it. Some seem to seek touch. On one of my last dives, Foggy Eye (she has an injured, scarred right eye), swam right into my belly. I lightly stroked the top of her head, and she immediately relaxed and began to sink. Cristina came over right away to assist, and she was gently lowered to the ocean floor. Cristina pointed to her dorsal fin which was slightly curved, and demonstrated very light stroking on the top of her head. After a couple of minutes, Cristina pointed to the dorsal fin pointing straight up, and indicated that Foggy Eye was “out”, meaning that she was sleeping, if not extremely relaxed. I bent over to look at her face. Her bottom jaw was working to take in water, and it was being pushed over her gills for respiration. Her good eye remained open (meaning her nictitating membrane was not closed over her eye), and I could see the “pores” of ampullai lorenzini on her face (electroreceptors), that help her sense electric fields in the water.
And then I kissed her! The denticles of her skin are smooth (ish) when you stroke “with the grain”, but rougher if you were to stroke the skin “against the grain” – feeling a little like sandpaper.
My first attempt at feeding a shark was not only clumsy, but I broke the golden rule: do not drop the fish. When feeding, you choose the right shark, and feed that shark, and everybody is happy. If you drop the fish, they all get agitated looking for the fish. They really aren’t as adept at locating their food source and eating it as I would have thought.
When I decided to feed a shark, I leaned down and reached into the feeding tube. I grasped the dead fish as I had been instructed, and I prepared to feed. I had my eye on the shark that was going to get his snack, and pulled the fish out, only to panic at the last second and fling it at his face! OY! I knew I wasn’t supposed to do that, but it happened. And she missed it. I didn’t see who finally got it, probably one of the horse-eyed jacks that were prowling around (they are fast)! In fact, my second attempt at feeding resulted in a jack stealing the fish right out of my hand! It is good that Cristina is a very patient woman!
But I did finally do it correctly, and fed a couple of sharks the right way. It was so exciting! The video frame grab above has some motion blur, but it shows the jaws right after they have closed around the fish!
Ooops, Shark bite!
My very last dive, and I was feeling great. I reached out to touch the top of an approaching shark’s head, and I guess the nature of the movement led a shark approaching from the side to believe that maybe I was offering fish. I saw the jaws extend up and out, and chomp down on my right hand! Before I could even process what happened, she had realized that I wasn’t fish, released me, and was swimming on her way. I had felt the squeeze of pressure when she bit me, but the chainmail did its job, and I was not injured. WOW! That was pretty incredible!
Unfortunately, my event did not get captured on video I would have liked to see the look on my face...damn!
Cristina removed a fishing hook...
This is more dangerous than the feeding of sharks, so I observed from the sidelines. Not all sharks wish to go to sleep with some well-placed strokes, so Cristina aggressively entices the hooked victim in to her with fish, feeds her, and then tries to pull the hook out. Of course, it hurts, and the shark flails and escapes to avoid the pain, yet I was surprised to see it return to Cristina over and over again, until finally the large hook was removed from its mouth. Pretty incredible to watch! Cristina loves these sharks so dearly, she really tries to do whatever she can to help them. She lamented that it saddens her to see them injured or sick, and she is unable to do anything to make it better; while she can take her dogs to the vet if they are ill, these sharks are pretty much on their own. And mother nature is a cruel B%#$!
And so ends a beautiful dream… thankfully my memories remain. Every time I see these sharks I love them even more.
What differentiates a shark from other fish?
Sharks may be identified by their cartilaginous skeleton (only the dentical-type structure of their teeth hardens like bone when exposed to salt-water), large exposed gill slits on the side (usually 5), and unlike other fish, sharks do not have a swim-bladder for buoyancy control, but rather an oil-filled liver.
The swim bladders of fish allow them control of movement and position in the water (like our BCD’s), but because sharks lack this, if they stop swimming, they sink.
All sharks swim to move water through their mouths, and over their gills (ram ventilation method), thus absorbing the oxygen from the water. Some species can only respire this way, and must swim continuously to get the oxygen they need (white sharks, mako sharks, and whale sharks). Some species have spiracles (holes behind the eyes of some species), to assist in taking in water to move over the gills.
Others also use the “buccal pumping” method to draw water into their mouths using muscles of their lower jaw, and over their gills while resting on the ocean floor (nurse sharks, angel sharks and even reef sharks can do this, to name a few).
Although it is commonly believed that sharks have poor eyesight, they do in fact, have excellent eyesight. Behind the retina is a tissue of mirrored crystals called “tapetum lucidum”. It enables the shark to contract and dilate its pupils much like humans do. Other bony fish do not have this. Instead of light entering the eye being absorbed, the mirrored crystals reflect it back to the retina, lending the shark much better vision in darkness. Further, a shark’s underwater vision can be up to 10 times better than humans!
With over 500 known species in our oceans, these incredible animals are so much more than the imagined picture people often “see” when they hear the word “shark” – all too often associated with a strong, negative emotion. Yet, the word “shark” can refer to a species as small and benign as a dwarf lantern shark, fitting into the palm of your hand at 7 cm, or a school-bus sized whale shark, filter feeding in plankton-rich waters.
Many species are now endangered or threatened with extinction; their numbers have dropped worldwide by over 80%, and despite their bad reputation (thank-you Hollywood), they are a critical part of maintaining the health of our reefs and the ocean. Sharks clean the reefs and oceans of sick, injured and dying or dead fish, and keep other strong predators in check. As shark populations are on the decline, our oceans are in grave danger. Our oceans must be healthy to sustain life on land; it’s all a big circle, and we are all connected!
PADI Course Director, NSS-CDS Full Cave Instructor, and TDI Extended Range and Advanced Nitrox with Decompression Procedures Instructor. Inducted into the Women’s Scuba Hall of fame in 2011. Public Speaker and advocate for ocean and shark conservation.
Cristina is a dive operation manager, and instructs recreational, technical, and shark courses. She is shark consultant, and participates in shark research around the world. Aside from removing hooks and parasites from the sharks she loves so much, she collects data and cartilage samples periodically for marine scientists to support research. She is the first woman to have connected a fresh water inland cave with a salt-water ocean system.
Cristina has developed a Caribbean Reef Shark Awareness Distinctive Specialty and was the initiator of a campaign that resulted in the complete protection for all species of sharks in the entire Bahamas. No wonder Bahamas reef systems are so healthy!
Most of all, her goal is to change the negative perception that people have about sharks. She works tirelessly to save sharks and support conservation efforts around the world. Even Singapore invited her to attend a conference to speak about the necessity of protecting sharks, and how detrimental the practice of “shark finning” is to world’s oceans.
A big thank-you to Cristina for working so hard to save our sharks and keep our oceans healthy!
What is finning?
Every year, thousands of sharks die a slow, agonizing death because of finning. Sharks are captured, their fins are brutally hacked off, and they are carelessly tossed back into the water where they drown or starve; they are helpless. Their fins fetch a good price, and shark fin soup is considered a delicacy in Asia, served at restaurants and weddings.
The video below is thirteen and half minutes long (cut down from well over an hour). It is still pretty long...if you are interested in what it would be like to take the shark handling course, it may help give you an idea. If you would like to fast forward to near the end, there is a resting shark, and you can watch the buccal pumping respiration as she rests on the ocean floor.
By Jill Smith
While we were in Cancun this July for our annual whale shark swim, we experienced something new, wonderful, and unexpected! We did not realize that the eastern facing beach in Cancun where our resort (the Golden Parnassus) was located, had a sea turtle conservation program working in full swing due to the high volume of mama tortugas (turtles) coming onto the beach at night to lay their precious eggs.
Nearly all species of sea turtles are labelled as endangered; without the help of the resorts who gladly participate in sea turtle conservation program (the Mexican people love their ocean, and are so happy to help their marine wildlife), these nests might otherwise be destroyed. While unintentional, tourist life on the beach is a hazard to the survival of these nests (think about beach volleyball, tractors raking and grooming the beaches every day, etc), not to mention the natural hazards of land and sea-bird predators. We did wake up one morning to find that a sea turtle had nested in the middle of the volleyball court during the night, leaving a fairly deep 3 foot in diametre hole. Adorable!
Many resorts along this strip, including our own, had fenced nurseries, where they re-bury the eggs after mama has laid them. They are protected from foot traffic and predators, and each nest is labelled with the date the eggs were laid, the species of turtle, and number of eggs. We saw nests posted of eggs from Caguama tortugas (loggerhead), Blanca (white sea-turtle), and Chelonia mydas (green sea-turtle). It’s wonderful to see this effort on the turtles’ behalf.
Jody and I had lots of questions for the lifeguard, who participates in the program. He was very patient to answer them all, and actually, I think they are just as interested and happy to share. A little later, he approached me, and asked, “Would you like to see a nest of white baby sea-turtles hatching?”
“Ummmmmm let me think… DOES A WHALE SHIT IN THE OCEAN??? HELL YES!!!”
He advised us to meet him by the nursery in 20 minutes. I wasn’t letting him out of my sight though, so I stalked him back to the nesting area. We were SOOOOOOO excited, I can’t even tell you! WOW! OH BOY OH BOY OH BOY!
Reading the plaque, I could see that the eggs were laid on June 1st. It was now July 21st - 50 days have passed. The lifeguard starts digging down, very gently, and soon, we catch the first glimpse of a turtle fin! I asked why they don’t allow them to dig out on their own when they are ready, but he says, they want to collect them, keep them safe, and release them when the pelicans and sea-birds aren’t a threat (just after dark). And soon the hole is erupting with all of these wiggly, beautiful, perfect little sea-turtles! Even the markings on their faces are already there. Collected in a sandy basket, we had to wait a couple of hours for the sun to go down, and then we took them to the ocean to let them go. Part of me didn’t want to release them, because I know most of them are facing certain death out there (maybe only 10% will survive), but that is the nature of things…
Hopefully they have been given their best chance!
But that’s not all.
After dinner, around 10:30, Jody and I go for a walk on the beach, and don’t we come across a mama loggerhead sea-turtle making her way up the beach to find a place to lay her eggs. Seriously, how amazingly crazy is that? I thought my head would pop off from the shear excitement of it all. We stayed well back, and sat on a beach chair to observe quietly from a distance. The conservation guy (Fernando) was also there, standing back to observe, so we got to whisper our questions to him. We couldn’t take pictures, because flashes and lights will scare a mama back into the ocean before she has laid her eggs, so we could only squint and watch in the dark.
It took her a little while to decide where she wanted to nest, but she finally decided that under the lifeguard station was a good spot. Her powerful front fins can really throw sand! We saw sand flying several feet into the air as she dug a bed for herself. Soon, she was so deep in the hole that she was just below the sand surface. That is when she starts scooping out a hole with her back fins. Fernando says that her back fins can scoop much like our hands can (cupped). After the sand was no longer flying, and she was still and quiet, he said, “Come with me, we are going to check her now. Quietly.” OHMYGOSH!!! He and his colleague used red lights to see, as this is the least disturbing to mama turtle. Fernando handed Jody a pair of gloves to wear to help collect the eggs, while I took pictures the best I could in the darkness. I got to stroke her shell; Oh my gosh I love her. A mama sea-turtle can lay 50-200 eggs at a time, though we were carefully collecting them and placing them in a bucket for re-burying, and did not count them at that time. Presumably they are counted as they are placed in the new nest.
We thanked Fernando and started walking back to our resort, and we came across several large holes in the sand, and there was even another mama turtle in one of them! Jody ran back to tell Fernando, and he came with a flag to mark the spot so they could retrieve them later. There were still more sea turtles coming up onto the beach to lay…so many!
What an experience!
Best day ever!
Bravo to the Mexican Conservation Authority and the Resorts that are invested in this program! Let's hope that the efforts made today make the sea turtle populations and oceans healthier tomorrow.