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Understanding the D800

Simon Stafford offers some further observations on the Nikon D800 & D800E

The announcement of the D800 had two predictable consequences; for many hours following the news breaking web servers were slowed down, in some cases to the point that sucking concrete through a straw would have been quicker, as photographers around the world sought as much information as possible about the new camera, while now, inevitably, some misunderstandings and misconceptions about it have begun to percolate the Internet. The latter issue is hardly surprising given the specification of the camera, in particular its 36.3-megapixel resolution, and the option of the D800E that has no anti-aliasing filtration, both of which are uncharted waters for Nikon D-SLR users.

Before I attempt to set the record straight on a few points concerning the D800 and D800E, let me quickly recap the core features of the two models. Setting aside the matter of the newly developed sensor, which is common to both, they each share exactly the same specification with the only exception being the lack of anti-aliasingfiltration in the D800E.

Click for larger imageThe D800E
Click for larger imageThe D800

Both cameras inherit the same enhanced TTL metering and AF systems from the recently announced D4, together with the same Expeed 3 in-camera processing and, essentially, the same video capabilities. Likewise, they benefit from the same 8 cm (3.2 inch) monitor screen, and re-engineering of the shutter unit to improve power efficiency and provide a slicker performance in Live View, although the shutter of the D800 is tested to only 200,000 cycles (the D4 is tested to 400,000 cycles). Attributes of its predecessor, the D700, are also mirrored in the new camera, including a built-in flash, similar robust build quality, and extensive environmental sealing, all in a body that is virtually identical in size and shape as the D700, yet weighs 95 g (2 oz) less.

Now to those misunderstandings:

Misunderstanding 1: The D800 is a medium format camera

Weaved throughout the promotional material for the D800/D800E issued by the Nikon Corporation are comparisons to medium format image quality, which is not the same as saying that the D800 is a medium format camera! Just because the sensor of the D800 has 36.3 million image-forming pixels, which is comparable to the number of pixels in some of the digital backs available for current medium format cameras, it does not mean the D800 offers the same potential advantages of a medium format camera, including having to magnify the image less to achieve an equivalent print size, the ability to use lenses with leaf shutters, and significantly larger pixels, which will be inherently better at capturing photons of light and thus produce a cleaner signal off the sensor.

Misunderstanding 2: The D800 is pointless because it will out-resolve my lenses

Not true! Regardless of the lens used you will see a higher resolution, but it is the degree to which the resolution is increased and, in turn, how this will impact on the appearance of an image that needs to be considered. Most modern lenses provide a very high level of optical performance at, or close to the central area of the image field, so here at least the higher number of pixels on the sensor of the D800 will provide greater resolution of detail. It will be at the periphery of the image that the differences between individual lenses will be most telling, and the D800 is going to be very unforgiving with any lens that exhibits an appreciably lower optical performance in this area compared to its centre. However, jumping from a 12, 16, or even 24-million pixel camera to the D800, or D800E, will require the use of the very best Nikkor lenses in order to realize the full potential of the gain in resolution they offer.

If you have taken a look at the 14 high-resolution sample images released by Nikon (see links below), seven-a-piece for the D800 and D800E, you might have noticed that in each case bar one, the available light portrait shot of the bride, the lens aperture was set to f/8, or f/10 – which is no coincidence and should tell you something. If you do not know what that something is, I would suggest the D800, or D800E is probably not a camera for you!

The seven D800 sample images can be viewed here.

The seven D800E sample images can be viewed here.

Misunderstanding 3: Apart from its sensor the D800 is not significantly different to the D700

If you have read this far I would hope by now you have changed your opinion on this point. If not, I would invite you to re-read the summary of the D800 specification set out above; externally, the D700 and D800 could (almost) be identical twins, internally the differences are as chalk is to cheese, with the D800 promising D4 like performance in terms of metering, AF, video, and image processing.

Misunderstanding 4: The D800E should not be more expensive than the D800

The filter array located in front of the sensor of many digital cameras is a finely tuned piece of optical engineering, typically comprising an anti-aliasing filter, and infrared blocking filter, a layer of micro lenses, and Bayer-pattern filter. Simply removing one of these components would alter the properties of the filter array in such a way that light passing through it would no longer be brought to a proper point of focus; hence, the filter array in the D800E, which lacks any anti-aliasing properties, is an entirely different filter to the one used in the D800.

d800_olpf_diagram

The following is a brief synopsis of how the anti-aliasing, or optical low-pass filter (OLPF) of the D800 and D800E work and thus differ. In the diagram above (courtesy of the Nikon Corporation) the top section shows the light path through the OLPF of the D800, which is typical of a conventional OLPF used in many digital cameras. An OLPF contains material that causes a double refraction of the light passing through it, which splits a single ray of light in to two rays. Here, the first OLPF splits the incoming light rays in to two, offsetting them horizontally, so they remain parallel to each other. The degree of the offset is miniscule, typically less than the pixel pitch of the camera, which in the D800 / D800E is around 4.9-microns. The second OLPF then splits these two light rays, this time offsetting them vertically, so that four light rays continue on to the sensor. This results in four identical copies of the image each fractionally out of resister with each other, so that the image projected on to the surface of the sensor appears very slightly blurred. Ideally this blurring is just sufficient to prevent any moiré patterns occurring, but not too strong to the point that resolution of fine detail is compromised.

In the D800E Nikon has removed the anti-aliasing properties of the sensor's filter array by using two opposing optical low-pass filters. The lower section of the diagram shows how the first OLPF is used to split the in coming light rays vertically, while the second OLPF reverses the effect of the first by recombining the two light rays into a single ray, with the net result that the light passes through the filter array, so a single image with no blurring is projected on to the surface of the sensor, just as though there were no OLPF present.

Currently, Nikon are predicting that the D800E will account for just 10% of the combined D800 / D800E sales. Consequently the unit cost of the D800E is going to be higher than that of the D800, because it will not only be more expensive to manufacture but also cost more in all other respects of a product sold in fewer numbers.

Misunderstanding 5: The D800 has everything the D4 has, but at half the price

While many aspects of the specification of the D800 / D800E can be found in the professional 'flagship' D4 camera, including the same enhanced TTL metering and AF systems, the same Expeed 3 processing and, virtually identical video capabilities, plus other features, such as the in-camera creation of time-lapse video, there are some things that remain exclusive to the D4, such as the following:

  • The D4 offer significantly higher frame rates; 10fps with full support of metering and autofocus operations, and 11 fps with metering and focus set to values for the first frame in any sequence
  • The D4 is compatible for the new Nikon WT-5 wireless transmitter, which is powered directly from the camera, plus the camera has a wide variety of connection options, both wired (the camera has an Ethernet port) and wireless, including its 'HTTP Server' mode that enables remote control of the camera using web browsing software run on a smart phone, tablet, or computer. The D800 is only compatible with the older Nikon WT-4 and has a USB 3 interface, but no Ethernet port, or 'HTTP server' mode.
  • The larger body of the D4 has a full set of duplicate controls for vertical shooting, while it uses a higher capacity battery, the new EN-EL18, rechargeable Lithium-ion battery, which provides a greater shooting capacity from a single battery. The D800 requires the optional MB-D12 Battery Pack/Grip
  • The 'Exposure Delay' item in the Custom Settings menu is limited to a fixed delay duration of 1s in the D800; in the D4 there are options for three different delay periods (1s, 2s, or 3s).
  • In the D4 there is an option to decouple the application of exposure compensation, so it is only applied to the ambient light exposure and does not affect the flash output level; the D800 lacks this option, so just as with all other Nikon D-SLR cameras, exposure compensation is applied to both the ambient exposure and the flash output level when shooting with a compatible Nikon Speedlight.
  • Unlike the D4, the D800 does not offer the option of embedding IPTC metadata into image files as they are recorded.
  • In Live View the D4 has an option for completely silent stills shooting; in this mode the camera can be configured to record JPEG files (up to 1920 x 1080 pixels), at a frame rate of either 12fps or 24fps, and since the reflex mirror remains in its raised position and the exposure time is controlled electronically (the mechanical shutter is not used), the camera does not make a sound. This feature is not available on the D800

Misunderstanding 6: The quality of the Nikkor lenses used with the D800 / D800E is all that needs to be considered as far as achieving the sharpest pictures.

I mentioned above (see, Misunderstanding 2) that in order to realise the full gain in resolution offered by the D800 / D800E it will be necessary to use the very best quality Nikkor lenses; however, I also alluded to another pertinent issue, optical diffraction.

The pixel pitch of the sensor in the D800, which has 36.3-million image forming pixels, is around 4.9-microns, while the sensor of the D700 has a pixel pitch of about 8.5-microns, with 12.1-million image forming pixels. The pixel density of a sensor will influence perceived image sharpness due to the effects of diffraction, because as the pixel pitch of a sensor becomes smaller the aperture value at which the effect of diffraction will begin to manifest, with the result that the image will exhibit a general loss of sharpness, will become larger (i.e. a lower f/# number). While the diffraction limit of the 12-megapixel D700 is around f/13, on the 24-megapixel D3x it is about f/11, while on the D800 the diffraction limit is going to be in the region of f/9. Using an aperture just a little smaller than the point at which the diffraction limit is reached is unlikely to make much difference to image sharpness; however, as the size of the aperture is reduced the effect of diffraction becomes progressively stronger, thus at very small aperture settings, for example f/22, any perceived increase in sharpness achieved through greater depth of field is annulled.

So, assuming all other aspects of your camera technique and lens quality are equal, to make the most of the potential resolution offered by the D800 / D800E, it is very likely that it will be necessary to modify the choice of lens aperture compared with shooting in the same conditions on a D700, or D3x.

Paradoxically, in certain circumstances, very mild diffraction can be a benefit, as it may reduce the incidence of moiré patterns, because the image at the sensor is softened slightly as a result of the divergence of the light rays as they pass through a small aperture opening, so diffraction can be friend and foe!

© Simon Stafford
February 2012

Posted on: Thursday 9 February 2012

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