Training

Imaging: Understanding Your Camera’s Histogram

If you’re not already shooting with the help of your camera’s histogram, it’s time to start. A histogram is a graph that shows the distribution of tonal values from black to white in your image, and it’s a very accurate indicator of overall exposure. If you’re not checking out the histogram as you shoot, your exposures are a guess at best.

ALL DATA ARE NOT COLLECTED EQUALLY

ETTR (exposing to the right) is a RAW-image-capture technique that increases the exposure of an image in order to maximize the amount of data collected by the camera’s sensor.

Because the digital image sensors collect 50 percent of all available data in the single brightest stop, underexposing your photo by even a small amount is tantamount to tossing a significant amount of information out the window. An underexposed shot often looks just dandy on the back of the camera, but in fact, the LCD preview is a terrible predictor of exposure. Use the histogram to analyze what kind of exposure you’re capturing with each shot.

For the sake of this example, let’s say that a camera has five stops of dynamic range (from darkest to brightest) and shoots a 12-bit RAW image, which is capable of recording a total of 4,096 tonal values. You’d think that each of the five stops should be able to record 850 tones — about a fifth of the total — but that’s not how it works. In reality, the brightest stop (farthest to the right on the histogram) collects a weighty 2,048 values, with each subsequent stop to the left (darker) recording half the amount of the previous one. In short, the right side of the histogram holds the data, and the left side holds the noise.

WHEN TO USE ETTR

This technique isn’t something you’ll necessarily use on every shot. It’s not easy to use the ETTR technique when the dynamic range of the camera is already pushed to its limits; for instance, when shooting sun balls or other ultra-high-contrast scenes. ETTR pays of most in moderate- and low- contrast shooting scenarios, where the ultimate goal is to bias your exposure brighter, with the histogram snugged up to the right, but not so far to the right that the highlights get “clipped” by running into the right edge.

DON’T OVERDO IT!

Pay close attention to the camera’s highlight-warning “blinkies.” When you see them start to flash, it’s time to back off. They’re a friendly reminder that you may be in danger of blowing out highlights. Specular highlights, which are reflections of light from shiny surfaces like water, fish scales and critter eyeballs, might not contain enough critical detail to worry about in small amounts, but completely obliterated highlights are not recoverable and spell doom for your picture. A little clipping is OK; a lot is bad.

BASIC POST WORK FLOW FOR ETTR RAW CAPTURES

All ETTR images need work in post. Right out of the camera, ETTR captures often appear washed out or overexposed. All those yummy tones in the brightest part of the image need to be mashed back toward the left of the histogram in order to restore richness, saturation and contrast to the shot.

Remember, the Highlights and Shadows sliders are detail sliders meant to restore detail in bright or dark areas without affecting clipping. The Whites and Blacks sliders establish the actual white and black points in your photo.

  1. In the Basic panel, slide the Highlights slider all the way left.

  2. Slide Exposure toward the left to lower the overall brightness level.

  3. Add Contrast if necessary.

  4. While holding down OPT (Mac) or ALT (PC), click on the handle of the Whites slider. You’ll see a black- clipping preview screen. Slide the handle toward the right until you begin to see small areas of color. Slide back toward the left until just the tiniest pinpoint of light pixels remains. Those light pixels are the white point in your image.

  5. Slide the Shadows slider to the left until the shadow details are as you desire.

  6. While holding down OPT (Mac) or ALT (PC), click on the handle of the Blacks slider. You’ll see a white- clipping preview screen. Slide the handle toward the left until you begin to see small areas of color, then slide back toward the right until just a smidge of dark remains. Those dark pixels represent the black point in your image.

  7. Re-adjust any of the Basic panel sliders as needed.

  8. Move on to the HSL panel (Hue, Saturation and Luminance) and local tools.

Click here for more photo tips, or head to scubadiving.com/photos

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Training Insights… EFR: Who else can you offer Emergency First Response courses to?

Ask any of your customers (divers or non-divers) if they would know what to do if one of their friends or family had a medical emergency, and have the confidence to feel prepared. None of us like to think that … Continue reading

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Interviews with Freediving legends – Annelie Pompe

Start small by exploring the world around you… During the month leading up to the release of the PADI Freediver Program early November at the DEMA show PADI Regional Manager Jonas Samuelsson talked to a few truly inspiring Freedivers and … Continue reading

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Dive Doc: Why Are My Ears “Full” After Diving?

Ear Fullness After Diving

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Scuba’s Diving Doctor explains ear fullness and how post-care tips.

Question: My ears are always “full” after a dive. Do you have some tips for post-dive care?

Answer Perhaps second only to the lungs, the ears are extremely important organs when it comes to diving. The inability to equalize pressure between the middle ear and the environment will keep you on the surface every time. Because the outer ear is exposed to the environment, infections are quite common.

The usual reason for ear “fullness” after a dive is inadequate pressure equalization during the dive. You might be equalizing enough to make it through the dive, but the eardrum might be undergoing mild trauma that will persist as pain or fullness after surfacing. The best way to keep your tympanic membranes happy is to begin gentle equalizing maneuvers immediately after leaving the surface, and clear regularly and frequently during a slow, gradual descent. It’s a good idea to begin equalizing on the surface and assessing if all feels well, even before experiencing any pressure changes. Taking over-the-counter decongestants prior to the dive has been shown to be effective.

Infection is another major issue. Certain bacteria thrive in wet environments and can cause a serious and painful infection known as otitis externa. Antibiotic drops and abstinence from diving are required once infection is present. Prevention includes good ear hygiene such as avoiding any scratches or other breaks in the skin surface lining the ear canal (earplugs and cotton swabs frequently cause trauma). The use of weak acetic acid (vinegar) solutions before and after diving might decrease the risk of infections by eliminating the bacteria and drying the canal.

James L. Caruso is a 30-year veteran of the U.S. Navy, serving as ship’s doctor, undersea medical officer and flight surgeon. His experience includes a fellowship in Diving and Hyperbaric Medicine at Duke University Medical Center; today he is Denver’s chief medical examiner.

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Dive Hacks: Expert Tips for Liveaboard Adventures

Savvy divers know that liveaboards are the ultimate way to travel for maximum water time and major pampering. These floating palaces of dive lust cruise some of the most exotic and prolific regions on the planet, putting their guests into the best possible conditions at optimal times for mind-blowing encounters. When your plush stateroom and gourmet meals are bobbing gently above a world-class dive site, a vacation doesn’t get much easier. All that’s required is to roll out of bed and into your wetsuit, because your gear is already assembled and waiting for you, attached to a full cylinder. Consider enjoying this scenario for seven to 10 days in a row, and the fantasy that is liveaboard diving comes into clear and wonderful focus.

All of this bliss comes at a price, however. This method of travel represents a significant investment, one that frequently cashes out at a more expensive price tag than a land-based alternative. And because you’re typically isolated from civilization, it pays to come prepared with a highly tuned game plan, the right equipment and a few tricks to which only liveaboard veterans are privy. To even the playing field for every diver, I asked Lauren Hill, the New Zealand-born captain of the Aggressor Fleet’s Cayman Aggressor IV, for her expert advice. A veteran of six years at the helm and a half-dozen more as an instructor and guide, Hill is one of the most customer-focused liveaboard hosts I’ve ever encountered; her advice can help you make the most of your luxury-travel investment.

BE THE EARLY BIRD

Diving from a liveaboard means that, more often than not, you’ll be anchored in a prime spot that day boats can take considerable time to reach. And captains know how to maximize local conditions to serve up the best spots on any given day. Advantage: you. So make the most of the opportunity by rising with the sun and being there when the reef comes to life. Piloting the CAIV gives Hill early-bird entry to some of her favorite sites in the Caymans: “Nancy’s Cup of Tea on Little Cayman as a dawn dive is always a ‘wow’ dive when the reef is waking up around you and the reef sharks come in close to check us out.”

PLAN TO TAKE YOUR TIME

Without the pressure land-based operators have to get their guests in the water and back on a schedule, liveaboard divers have the ultimate luxury of time. Whether you’re diving from the yacht or by tender, the relaxed schedule can take some getting used to. “As all our dives are from the mothership, there is no need to take of on a mission swimming 2 miles away underwater,” says Hill. “All our dives are right under the boat, so our guests can slow down and smell the roses — and relax.”

BRING A BACKUP FOR YOUR BACKUP

The glorious isolation of being on a yacht far out at sea is a fantasy many of us share. But it can quickly turn into a nightmare when equipment malfunctions and you can’t hit the local dive store for that key part or replacement piece. “A big mistake our divers make is not testing their gear after having it serviced,” Hill says. “First dive of the week, and we have free-flowing this and malfunctioning that and the cry of, ‘But I just had it serviced.’ Go for a couple of local dives at home before your trip, even if it’s just in the pool.” You can’t always count on the boat staff to have a particular part, so a well-stocked save-a-dive kit is a must.

Hill advises that “having backup equipment if you own an unusual brand, for example, or a spare battery for your flashlight that regular batteries don’t fit,” can help liveaboard guests avoid missing dives when disaster strikes. “And photographers should pack backup fiber-optic cables and strobe connectors, and a backup SD card or hard drive too.”

MIND YOUR CORE

With the availability of up to five dives per day, liveaboard guests can rack up serious bottom time, but they can also chill themselves to the verge of hypothermia — even in tropical waters. Being mindful of your internal body temperature can be the difference between performing at your best and shivering in discomfort.

“I always encourage guests to get completely dry and changed between dives,” Hill says. “Your core temp will warm up faster, and you will probably stay warmer and enjoy the next dive even more.”

MAKE THE BEST OF CLOSE QUARTERS

You’ll be on board with the same group of strangers for an extended period. Even though a common love of diving is a great icebreaker, Hill has seen enough good and bad chemistry experiments to pick up a few best practices. “There are a few key ways to make friends or just get along when you are on a yacht for a week or more,” she says. “In your cabin and on the dive deck, keep your belongings, equipment, and diving and photo gear all in your space. Don’t be that guy or gal who takes over the cabin or the dive deck with all of your worldly possessions.”

Hill’s final piece of advice: “Try not to be a know-it-all,” she says. “It’s great that you are enthusiastic and you have all of this knowledge to share, but don’t force it upon your fellow divers — you’ll only drive them away. Move around the group, sitting with different people at mealtimes, and just be social. Best of all, just relax, bring a sense of humor and enjoy the ride.”

GEAR SOLUTIONS: PACKING LIST

Capt. Lauren Hill’s recommended scuba accessories and common household items to make the most of your liveaboard trip.

A GOOD FLASHLIGHT Think small, bright and rechargeable (or with plenty of extra batteries).

SURFACE-MARKER BUOY Make sure you never dive without one.

TWO OR THREE SWIMSUITS So you’ll always have a dry one.

BATTERIES Bring backups for your computer, camera and everything else that uses them.

SUNSCREEN Nothing is worse than getting fried your first day on board, then suffering the rest of the week
when you strap your BC on sunburned shoulders.

SEASICKNESS MEDS Be proactive about taking them, because when it’s too late, it’s too late.

CONDITIONER Girls or guys with long hair, not all boats supply it (your hair will appreciate it).

PRESENTS FOR THE CAPTAIN AND CREW Bring (and leave on the boat) DVDs of new movies and TV series, books, magazines, etc. The crew will love you.

Click here for liveaboard dive deals and for some of our favorite liveaboard destinations!

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