3. Wetpixel D800 review: Resolution, ISO and tonal range.
As mentioned in the introduction, the D800’s sensor scored 95 out of a possible 100 on the DxO Labs tests. This made it the best sensor tested to date by the organization. DPreview have awarded the camera its “Gold Award” and commented that:
“With its 36MP sensor, the D800 is among the highest resolution cameras we’ve put before our test chart. And as you’d expect its performance here puts it at the head of the class among its DSLR peers.”
From a purely empirical standpoint, the statistics simply state that the camera has more resolution and hence gathers more image information than any other “35mm” format camera currently in production. Yet, when you read further into the tests carried out above, both organizations are at pains to state that the resolution is only achievable by working for it. This involves good technique, as well as excellent lenses and good conditions.
It is perhaps this latter requirement that is potentially the biggest issue for underwater photographers. Shooting underwater is as far from studio conditions as is imaginable. We shoot through water, which degrades our image quality, and often in less than ideal light conditions. We shoot through ports, and sometimes even shoot virtual images just outside of dome ports. Some image quality has to be sacrificed in order to achieve this.
So the question is; although we now have a tool that has the potential to give super high image quality, is it realistic to expect such quality underwater?
The D800’s sensor measures 7360 x 4912 pixels on a sensor that is 35.9 x 24mm in size. By comparison, the Canon 5D Mark III’s sensor is 5760 x 3840 pixels and measures 36 x 24mm. The D800 can shoot an image which can be printed at 200dpi at as big as A1 poster-sized prints (59.4 x 84.1 cm/23.4 x 33.1 in). Is all this really advantageous in an underwater environment?
One of the most frequent concerns expressed about the D800’s resolution is that it will “out-resolve” lenses, causing significant degradation to images. In an underwater context, there is also concern about the ports through which we take images.
In the case of the D800 however, an exploration of the pixel density shows that these concerns are (largely) unfounded. In FX mode, the sensor area is 861.6 Sq. mm. (35.9 x 24). This gives a pixel pitch is 4.88 micron. This is very similar to a DX camera at around 16 megapixel e.g. D7000’s pixel pitch is 4.78 microns. So despite the increase in resolution this is offset by an overall increase in sensor size.
Whilst this type of theoretical comparison is useful, it is in and under the water that is really where things count. Below is a crop of an image shot at 1/320 at f16/ISO 100 using the D800 with a Sigma 15mm and Zen 230mm port. All images have passed through the Lightroom 4 pipeline and been cropped in Photoshop, but have had no noise reduction, exposure or color treatment added.
And this is the original image:
As the final image shows, this was not shot in ideal conditions. Given this, the level of and the resolution of detail in the smallest crop is really quite astounding.
In terms of macro, the following was shot on a very surgy day at St. Abbs, Scotland, using a Nikon 105mm f2.8 VR. 1/320 at f22, ISO 100.
What both these images show is that the cameras resolution is being successfully employed to extract fine detail, even in challenging underwater conditions. Clear, still water will undoubtedly produce stunning results with this camera, and I think it is fair to say that more difficult conditions will challenge it, but this is also true of every other camera out there. The additional resolution gives more creative “head-space” to the photographer, and gives creative potential to scenes and subjects that have probably hitherto not been feasible.
The adoption of larger sensors by Nikon with the D3/700 was largely driven by a demand for better low light performance in digital cameras. The D2 series, very capable DX cameras in many respects, simply could not deliver acceptable image quality at anything over ISO 400. The theory is that FX sized sensors have a greater surface area per pixel, and can hence deal with a greater range of light levels without producing excessive noise.
It is of interest to note that technology also plays a role in this. The Nikon sensors of 2012 (and possibly those of Canon too) are simply better than previous versions. The D7000 was capable of very credible high ISO performance, even though it is a DX format. With the D800, I think we are seeing this evolution develop further. I did a series of pool tests, using this “glass fish” as a subject.
I’m not sure the results show anything particular, except that in a pool environment, noise is apparent. The levels are easily manageable in post-production, even at ISO 3200.
For a more “real world” application of this, please see the following images.
The Capernwray aircraft at 1/60, f7.1 with a green water magic filter and ISO 800. The aircraft lies at 18m (55’) and the weather was very dark, with rain and 100% cloud cover. The combination of the depth, available light and the use of a filter is a really serious test of just what this camera can do. Interestingly, the light conditions were so bad that finding a white balance target to manually white balance the camera proved very difficult.
A crop of the darker cockpit area.
There is noise, but it does not seem excessive.
A quick clean up in the Detail tab in Lightroom produced this:
Another image, taken on the same day. This time, camera settings were 1/40, f9 with magic filter and ISO 2500.
As you would expect, there is more noise in the shadows.
However, once again a quick clean up in Lightroom seems to improve the situation significantly
The D800 is very capable of shooting in low light conditions. As Alex has noted in his D4 review, the ability to shoot at high ISO with minimal image degradation isn’t only for deep, dark and dangerous subjects! Normal wide-angle scenes, when shot at higher ISOs, give the photographer additional creative tools at his or her disposal. Fast moving subjects require a fast shutter speed to freeze their motion, and this can be achieved by pushing the ISO up.
(c) Tonal Range.
The tonal range of a digital image is the number of tones it has to describe the dynamic range. The dynamic range of a sensor is defined by the largest possible signal divided by the smallest possible signal it can generate. DxO has tested the D800’s sensor at 14.4 EV (exposure value), the highest ever tested by them.
As underwater photographers, we frequently attempt to capture a wider tonal range than typical for photographers in general. If you can picture a reef wall, if we look below us, the water column appears black and looking up, the surface appears bright or white. This is complicated by the fact that we often tend to use very wide-angle or fisheye lenses that are, in some cases, capable of capturing this whole range. Until now, options for dealing with this have been limited. People tended to frame images so that the camera could cope with the dynamic range in it, or place an object into or over the sun to silhouette it and prevent the sensor from over exposing.
Sunballs represent an extreme example, and are a subject that has eluded digital image makers so far. Typical results of using a digital sensor to catch a sunball were banding or haloing that showed where the sensor had failed to cope with the dynamic range required to deal with the huge variety of tones in the image. Early in the Wetpixel testing of the D800, it became apparent that, possibly for the first time, this was a tool that could capture a very wide dynamic range.
As is this:
In the days of film, films were often referred to as having more (or less) exposure latitude. Essentially this meant that the film was capable of being under or over exposed and still providing acceptable results. The D800 is, I feel, a digital camera that provides the same thing. The D800, with the ammount of image information contained in each capture seem to be capable of retaining details that can be restored in post processing. In the image on the left below, the shadows have been underexposed. A quick trip into Lightroom 4 using the Highlights and White sliders restores the detail in the image as can be seen in the right hand version.
And here is a somewhat more extreme example:
This ability to capture a broader range of tones will allow photographers to add vibrance and depth to images that arguably may not have been possible before.
- The Nikon D800 body, controls and overview.
- Resolution, ISO and tonal range.
- Image size and “shooting to crop”.
- Autofocus, teleconverters and built-in processing.