Lens Reviews / Nikon Lenses i Lab tested

24mm	$2,197 average price

SLRgear Review
December 22, 2008
by Andrew Alexander

Tilt-shift lenses provide a very unique function for photography, allowing the photographer to adjust the direction of the lens relative to the image plane. This practice provides very interesting results, allowing the photographer to correct image perspective as well as have much greater control over depth of field. Nikon calls this type of lens a ''Perspective control'' lens. It's a little bit beyond the scope of this review to explain how tilt-shift lenses work; if you need to know, I suggest reading this excellent article in the Wikipedia.

Until 2008, Nikon lagged behind other manufacturers in its output of Tilt-shift lenses. Now that has changed, with their introduction of 24mm, 45mm and 85mm PC-E lenses. All Nikon PC-E lenses cover the 35mm film or FX frame; on a DX-sensor body the 24mm ƒ/3.5 PC-E will give an equivalent coverage of 36mm.

The 24mm ƒ/3.5 PC-E comes standard with a bayonet-mounted bowl-shaped lens hood, a lens pouch, and a price tag just shy of $2,000.

Update (February 2, 2009): We've removed the DX(D200) data.

Sharpness
The 24mm ƒ/3.5 PC-E is a very sharp lens, but for $2,000, you'd expect it to be. However, before we examine the sharpness of the lens we need to devote a paragraph or two to our testing methodology with this lens.

In short, it wasn't an easy lens to test. Our testing software, DxO Analyzer, works by analyzing JPEG images of a test chart shot with a given lens. For most of the time, we feed fairly easy images into Analyzer; sometimes however, we create images of those charts on which Analyzer will choke. The 24mm ƒ/3.5 PC-E was no exception.

Our original intention was to shoot the lens in its various shifted and tilted positions and see if there was a substantial degradation in quality. Our plans were foiled in various ways - mainly, it was just that Analyzer refused to analyze some of the images we attempted to feed it. In the end, try as we might, we could not get data for a tilted image. We did, however, get data by shifting the lens to the left and right ends of the spectrum.

With the lens in its default position, it's pretty obvious to see that it's very, very sharp. The results of the lens on the full-frame D3 shows a performance reminiscent of regular prime lenses; sharp, to be sure, when used wide open at ƒ/3.5, but with increasing sharpness as you stop down and hitting an optimal setting of ƒ/5.6. Diffraction limiting seems to set in after this point, losing accuity as the lens is stopped down, but still under 2 blur units by ƒ/22. At ƒ/32, it's just over 3.

But using this lens without shifting or tilting would be like buying a Ferrari to use as a commuter car. There is some definite corner softness in the shifted corner. On the full-frame D3, the lens seems to be capable of producing extremely sharp images on this platform. When used wide open at ƒ/3.5, ''central sharpness'' - or what would be central if the lens wasn't shifted - is still very good, at 1 blur unit, with the corners on the shifted side rising up to about four blur units. Sharpness improves dramatically at ƒ/5.6, and is almost tack-sharp at ƒ/8. Diffraction limiting again sets in at ƒ/11, with a small drop in sharpness, but even at ƒ/22 the lens doesn't exceed 2 blur units. At ƒ/32, we see between 3 and 4 blur units.

Chromatic Aberration
Because the D3 applies chromatic aberration correction to in-camera JPEG images, we also shoot RAW and process those images through Bibble with minimal corrections to give a more ''accurate'' picture of how a lens is performing.

On the full-frame D3, chromatic aberration is slightly prominent, even with CA reduction inherent in the camera. Average CA is still virtually non-existent, meaning you're just going to see aberration in the corners, if at all. CA is good wide open at ƒ/3.5, is at its worst around ƒ/11 (at around 5/100ths of a percent of frame height), but gets better as the lens is stopped down towards ƒ/32. Looking at the RAW images processed through Bibble, we can see the D3 is definitely earning its keep to reduce the CA present in the image.

Shifted, the lens produces substantial chromatic aberration on the D3, but the CA reduction kicks into overdrive and ensures aberrations are kept to a minimum. CA seems to be acceptably low on average - only popping up in the corners. The lenses fare slightly better when used wide open at ƒ/3.5, getting to the worst of it by ƒ/8.

Shading (''Vignetting'')
Our Analyzer software had a particularly difficult time figuring out light falloff when the lens was shifted; we really only have accurate results for the default non-shifted, non-tilted position. On the D3, we see a conventional spread of data for light falloff - some with the lens wide-open at ƒ/3.5 (1/2 EV), with an improvement by ƒ/5.6 (1/4 EV) that is maintained all the way to ƒ/32.

Distortion
At 24mm, the lens does show some barrel distortion, but it is well-optimized considering its wide angle. On the D3, there is about 0.1% barrel distortion throughout the frame, and almost 0.5% barrel distortion in the corners.

When shifted left or right, this distortion is slightly intensified, but only on an order of about 0.1% in the corners, and only a marginal increase on average across the frame.

Autofocus Operation
The 24mm ƒ/3.5 PC-E is a manual focus lens. Moreover, it requires at least a D300, D700 or D3 (or newer) to automatically select apertures, otherwise you will need to manually select an aperture, too.

Macro
The 24mm ƒ/3.5 PC-E provides 0.37x (1:2.7) magnification, with a minimum close-focusing distance of about eight inches (21 cm).

Build Quality and Handling
Given its premium price tag, it's no surprise that the 24mm ƒ/3.5 PC-E pulls out all the stops when it comes to build quality. From the solid textured finish to the delicate slide of the large focus ring, this lens is a delight to use. The lens comes with a 32-page manual in 12 languages; it has a full-page table of what cameras can use this lens, and what functions can be used with each camera. The lens transmits distance information to camera, so full TTL-BL lighting is possible with Nikon's more recent flashes. It is a large lens - over four inches long and three inches in diameter, and almost a pound in weight. Consequently there are warnings in the manual saying not to use the lens hood with a flash and only shoot flash at certain distances.

The diaphragm is made up of 9 rounded blades. PC-E lenses usually require manual operation of the aperture, but when this lens is mounted on a D3 or D300, automatic selection of the aperture is possible. The aperture selection ring is about 1/4-inch wide and made from a textured rubber. It is positioned before the focus ring, but in front of the tilting and shifting mechanism, for obvious reasons.

As a perspective-control lens, the lens can be shifted left or right, up 11.5mm in either direction, by turning the shifting knob. It can also be tilted by up to 8.5 degrees by turning the tilt knob. The lens can be rotated up to 90 degrees left or right, by depressing a button and rotating the main body of the lens through its axis. By revolving the lens, the shift function can be changed to operate on the vertical axis and the tilt function to operate horizontally. Click stops are every 30 degrees when rotating the lens. When tilting or shifting the lens, there is a locking knob to ensure that the lens stays in the position to which it is set. Finally, there are central indents in the lens body for both tilt and shift functions, to let you know you the lens is in its normal position.

The lens is decorated with a few features: a distance scale, marked in feet and meters, as well as a matching depth-of-field scale (with no marked IR index). The tilt feature is marked in individual degree notations, and the shifting feature is marked in 1mm increments.

On the D3 body, the lens balances nicely; on the D200 body, it is a little front heavy, but not overly so. To get the best results from this lens, a tripod is highly recommended. The lens takes 77mm filters.

The manual focus ring is the other main feature of the lens, made from a large, soft rubber 1 1/8 inches wide. It is very smooth to turn, taking about 120 degrees to run through the entire focusing distance. The front element of the lens does not rotate while focusing, making working with polarizers a painless operation. An additional feature of this lens is that two SB-R200 wireless speedlights can be attached to the front of the lens.

The bowl-shaped lens hood is simple in comparison, with a smooth interior. Attaching it will add 3/4-inches to the overall length of the lens, and is recommended to reduce the appearance of flare in images. The lens hood can be reversed for storage.

Alternatives

Really, the only alternatives in this category lens, in the Nikon line-up, are either the 45mm ƒ/2.8D ED PC-E or the 85mm ƒ/2.8D PC-E. Both of these lenses offer essentially the same characteristics, with the only difference being a slightly faster maximum aperture and the focal length.

Conclusion
Unfortunately, this is one of those cases where if you think you need this lens, you probably know almost everything about it and the only real consideration is the sticker price. For getting shots with a unique perspective, or a depth of field impossible with conventional lenses, there is no substitute - the only choice involved is 24mm, 45mm, or 85mm.

Sample Photos

The VFA target should give you a good idea of sharpness in the center and corners, as well as some idea of the extent of barrel or pincushion distortion and chromatic aberration, while the Still Life subject may help in judging contrast and color. We shoot both images using the default JPEG settings and manual white balance of our test bodies, so the images should be quite consistent from lens to lens.

Still Life shot

VFA target

As appropriate, we shoot these with both full-frame and sub-frame bodies, at a range of focal lengths, and at both maximum aperture and ƒ/8. For the ''VFA'' target (the viewfinder accuracy target from Imaging Resource), we also provide sample crops from the center and upper-left corner of each shot, so you can quickly get a sense of relative sharpness, without having to download and inspect the full-res images. To avoid space limitations with the layout of our review pages, indexes to the test shots launch in separate windows.