This is a 2 part review. The first part is dedicated to the Nikon D7000 camera and the second part is an in depth look at the Aquatica AD7000 housing.
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By Keri Wilk
Aquatica phoned me here at ReefNet at the end of December 2010, and asked me if I’d be willing to field test and publicly review a prototype of their AD7000 housing for the newly-released Nikon D7000. The review was to be honest, candid, and to include all positive and negative aspects of the system. It was clear to me that Aquatica was more interested in honest user feedback and constructive criticism than an overly positive advertorial.
I accepted their offer and booked a trip to Dominica to put the system through its paces. Aquatica generously covered my trip expenses, and I (reluctantly) sent back the prototype upon my return.
The newest Aquatica housing that I had used before this review was my father’s AD300 (for the Nikon D300) which was released in 2008. Since then, I’ve watched from the sidelines at dive shows across the US, as their line of housings has grown, in both quantity and quality. Many advances and innovations had been made by Aquatica since the AD300, which made me all the more eager to get in the water with the AD7000.
When the D7000 box arrived at my house, I put the battery to charge immediately, and starting paging through the user manual. The 1200 USD price tag became more and more shocking to me as I read on, considering the long list of newly-developed and pro features packed into this consumer-level body. Nikon has set the bar incredibly high with this new release, which makes you wonder what the next pro body is going to have under its hood (D800? D400?).
16.2MP APS-C (DX) sensor
The D7000’s new sensor has roughly 30% more pixels than the 12MP D90, D300/s, D700, and D3, and is only topped in resolution by one body in the Nikon range - the professional D3X, at 24MP. With those extra 4 million pixels, you can print an image 15% taller and wider, for a given DPI. This may not seem like much, and is probably a moot point to many of you, but I certainly appreciate the extra resolution compared to my D300. This pixel-dense sensor, combined with a 14 bit A/D converter (discussed below) and a new EXPEED 2 processing engine are capable of reproducing beautifully rich colors, incredibly sharp details, and buttery smooth tonal gradients.
Dual SD slots (SDXC compatible)
The D7000’s 14-bit RAW and JPEG images sometimes tip the scales at over 25MB and 9MB, respectively, and its 1080p HD videos average around 2MB per second, so storage space can be eaten up very quickly. Thankfully, the D7000 has two SD card slots, so single-card capacity issues can be avoided.
I used a pair of Sandisk 16GB Extreme Pro cards, which was more than enough to let me shoot worry-free for a full day of 3 or 4 dives. I probably could’ve managed with just a single 16GB (or pair of 8GB), but the last thing I want to do is waste time underwater deleting photos.
The second slot can be used as extra storage, or as an automatic backup destination, on the off chance that data from one of the cards is lost (I’ve had a couple of no-name cards go completely belly up before). Videos can be directed to either card slot, but once that card is full, you need to manually switch destinations (SHOOTING MENU>Movie settings>Destination). You can also send RAW images to one card, and JPEGS to the other, but I find this feature useless.
Usually a pro-body feature, a 100% coverage viewfinder allows precise in-camera framing, potentially eliminating the need for future cropping. Underwater, this feature is relevant only when using an external viewfinder, like Aquatica’s Aqua View (discussed below), since it’s nearly impossible to see the entire frame through any housing manufacturer’s stock viewfinders.
1/320s flash sync speed
A disappointing aspect of digital sensors is their inability to capture highlights in the same way that film does.
Sensors are comprised of an array of pixels, which collect and record photons. These pixels and photons can be thought of as buckets and water droplets, respectively. Nothing prevents water from entering the buckets, so they can get filled as fast as water is poured into them.
Now, consider slide film, which is comprised of a plastic substrate coated with grains of light-sensitive silver-halide. Each grain can still be thought of as a bucket, but with a small funnel attached that the water must first travel through. Average quantities of water can pass through the funnel without restriction, but, when faced with large amounts, the funnel will overflow, only letting a portion of the water into the bucket.
In other words, digital sensors are much more sensitive to high-intensity light than film.
What this means for underwater photographers is that shooting into the sun will often result in an unsightly stark-white ball in your images, usually encircled by an equally unattractive cyan ring.
To expose the sun more pleasingly, a very high shutter speed, small aperture, and low ISO are typically required, but this usually results in extreme underexposure of the foreground, which isn’t always desirable (unless shooting silhouettes). Ideally, you’d just turn on your strobes, crank up their power and illuminate the underexposed area, but DSLRs are limited by something called the “maximum flash synchronization speed” which prevents strobes from being used past a particular shutter speed. The higher this limiting shutter speed, the more these sunballs can be kept under control, so having a camera with a high sync speed is very desirable. The D7000 can sync up to 1/320s, which is the fastest in Nikon’s DSLR range, other than the lower grade D70/s and D50 which sync up to 1/500s.
For those interested, here is a brief explanation of why this limitation exists:
Focal plane shutters in DSLRs consist of 2 “curtains” – front and rear. The front curtain blocks the sensor until the shutter release is triggered, and then moves fully out of the way. The sensor remains exposed for the selected duration (i.e. the shutter speed), then the rear curtain quickly springs into place, ending the exposure. At a high enough shutter speed the second curtain cannot move quickly enough to provide the correct exposure. This mechanical limitation of independently-moving curtains is overcome by having the curtains move together in the form of a slit that pans across the sensor. The shutter speed is now determined by the slit’s fixed travel time and its width ---the narrower the slit, the faster the effective shutter speed. This mode of shutter operation presents a problem for flash photography. If a short strobe burst (typically 1/1000-1/50000s) occurs while the slit is passing over the sensor, only that part of the image under the slit will “see” the flash, and the rest of the frame will be dark. The flash must therefore be triggered while the shutter curtains are moving independently. The maximum shutter speed at which this occurs is the camera’s sync speed. [Note: Some newer cameras extend the sync speed to higher values by rapid pulsing of the dedicated flash while the slit is travelling, but this significantly diminishes the flash power].
In addition to being essential for suppressing sunballs, high sync speeds are also a key element in creating jet-black backgrounds. When shooting against bright backgrounds, like sand, seagrass, or coral, it can be difficult to eliminate all of the ambient light, so the higher the camera’s sync speed, the better.
2016 pixel RGB sensor for metering
After 14 years of using their 1005 segment RGB meter (first seen in the F5), Nikon released a newly developed 2016 segment metering system in the D7000. Since the new metering module has more than twice the number of RGB segments of its predecessor, and because it’s combined with the new (presumably more powerful) EXPEED 2 processor, it certainly seems like Nikon’s new metering system is a step forward. I never took the camera out of manual (M) mode, and used manually controlled Ikelite DS160 strobes (no TTL), so I didn’t actually test this system underwater.
100-6400 ISO range (expandable to 25600 equivalent)
The first thing I did when I turned on the D7000 was shoot at high ISOs to compare with my D300. To say that I was shocked is an understatement – flabbergasted is more like it. Even though the D7000’s sensor has 25% more pixels than the D300 over the same area, it exhibits significantly less noise at high ISOs. Equally surprising is how well this sensor compares to the D700’s FX sensor. I don’t have a D700 to test against, but if merit is given to the DXO Mark tests, then the noise levels of the D7000 are only one stop behind it… with a sensor having 50% less area AND 25% more pixels!
This is an incredible step forward in sensor technology. It’s certainly going to be interesting to see the noise levels that the next generation FX sensors produce using this same technology – I’m sure we’ll see soon enough!
I arrived in Dominica on schedule, but my bags didn’t make it with me. All of my strobes were in those bags, but I did have the D7000 housing, Aquatica’s 9.25” Megadome, and my trusty Magic Filters, so I was stuck shooting with ambient light day after day until my bags arrived. This gave me a chance to play with the camera’s low light capabilities, and I was very pleasantly surprised time and time again. Finally, a Nikon DX camera with a usable ISO range!
As you can see from the above comparison, noise increases incrementally with ISO. The level of noise that one considers “too much” is a highly subjective matter, depending mainly on personal preference and an image’s intended use.
I enter a lot of photo contests, and print 12” x 18” images for friends and family regularly, and I’d feel comfortable doing both with images shot at up to ISO 3200-6400. If you’re only publishing images online, then the entire range is very usable… when viewed at screen resolution, the full ISO 100 shot above is only marginally cleaner than the ISO 12800 shot!
Multi-cam 4800DX autofocus sensor
Another new feature being debuted in the D7000 is Nikon’s Multi-CAM 4800DX autofocus module. It has 39 focus points (9 of which are the more accurate cross-type sensors), and is capable of more accurate 3D tracking than previous models, when combined with the 2016-segment RGB metering module and EXPEED 2 processor. I’ve done a number of very unscientific focus tests between the D300 and D7000, and it seems to me that the D7000 wins every time in terms of speed and low contrast performance. The edge that the D300’s Multi-CAM 3500DX autofocus system has is 12 more focus points (6 more cross-type) spread over a larger portion of the frame.
An autofocus mode on the D300 that I hadn’t given a chance until now was its AF-C 3D-tracking system. This mode is also present on the D7000, but is now backed by a more powerful RGB metering system, so is presumably more accurate. The system recognizes the colour of the subject of focus, and will track it through the focus area. This simplifies the composing of images, since it eliminates the need to manually position the focus point – it just follows your subject, provided that it’s distinct enough relative to its background.
I usually only use the AF-S servo with a single focus point placed where I want it, but I now found myself using a combination of the AF-C servo with this 3D-tracking mode for shooting mid-range zoom, and macro/super macro shots. When I wanted to fix the plane of focus, I simply held down the AF-L button and then rocked the camera back and forth for fine-tuning.
Less notable is the camera’s AF-A (Auto-autofocus) mode, which decides, based on the subject’s movement (or lack of it), whether AF-S or AF-C is to be used, and sticks with that servo mode until the shutter is fully-depressed or released. This seems good - in theory - but after using it for less than 5 minutes, I got frustrated and switched out of it and never re-visited that mode. Equally useless to me is the “Auto Area AF” focus mode, which lets the camera decide which focus point should be used. This gives you no control whatsoever over what is in focus.
14-bit RAW images
Like the D300s, D700, D3 and other high-end bodies, the D7000 can record RAW files in either 12- or 14-bit format – file sizes of the latter being 20% larger than the former. Here’s a little background info that will help you understand what these formats really mean.
A sensor’s photosites actually record grayscale data, rather than RGB as you might expect. Each photosite has a colour filter that allows either red, blue, or green light to pass through, and the intensity of this light is converted from an analog signal to a simple numerical value. Once data from the entire sensor is collected, the camera’s image processor uses data from adjacent photosites to interpolate a full colour RGB image – a process known as “demosaicing”.
The “bit-depth” of a sensor indicates the range of possible values for the recorded intensity at every photosite. 12-bit sensors have a range of 4096 values (that’s 2 to the 12th power), and 14-bit sensors have a range of 16384 values (2 to the 14th power) – that’s 4 times the range of values. This means that tonal gradients can be recorded more smoothly, fine details can be recorded more accurately, and highlight/shadow areas will contain more information for potent restoration. However, contrary to what some believe, dynamic range is not affected by bit depth, since it is related to the light sensitivity of the sensor, rather than how many levels each pixel is divided into.
Full HD Video capability
This camera can record full HD 1080p videos at 24 fps, or 720p videos at 24 or 30 fps. It compresses them using H.264/MPEG-4 coding – which is the most commonly used format for dealing with HD videos. Video clips max out at 20 minutes, and in-camera trimming and frame-grabbing can be performed by pausing a video clip, pressing the WB button, then selecting the action you’d like to take (Choose start point/Choose end point/Save selected frame).
ISO and shutter speed (minimum 1/30) can be manually adjusted while shooting, but, frustratingly, you have to leave live view to both adjust the aperture and to reset the custom white balance. There are two focus modes to choose from when in live view – single-servo (AF-S) and full-time-servo (AF-F). Each of these modes can be used with any one of the four focus areas (face priority, wide area, normal area, or subject-tracking).
In AF-S mode, autofocus is activated when the shutter is half-depressed, and stays put when released. When in AF-F mode, the camera makes focus adjustments continuously to keep the subject sharp, until the shutter is half-depressed, which momentarily switches it into AF-S mode. On paper, this sounds like an ideal setting for shooting video, but in reality, it’s a little disappointing. The contrast-based autofocus system used in live view mode is not nearly as quick or accurate as the Multi-CAM 4800DX sensor, and left the camera hunting for focus, and getting confused when switching between a close foreground and a distant subject. Sometimes the system seemed to give up altogether, requiring a quick tap of the shutter to jolt it back to life.
I always used either the normal focus area, or the subject-tracking function when shooting videos, since the wide focus area covers too much of the frame, and the face priority function is useless underwater. The subject tracking function is an interesting feature, which is similar to the 3D tracking mode in the camera’s primary autofocus system – simply place the focus box over the subject, press OK, and watch the little focus square follow the subject around. However, again, this is much better in concept than in practice. During my stay in Dominica, I tried to use this feature to track a number of different subjects, but could only get it to work reliably on stationary subjects that stood out from their surroundings.
While the autofocus system was rather disappointing, the quality of the videos was impressive. I didn’t have any video lights, so chose to shoot with ambient light and a magic filter whenever possible. Not only are colours rendered vibrantly, the sensor produced usable videos in even the dimmest conditions, because of its low noise levels at high ISOs.
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