Lens Overview

General Information

The on-camera zoom lens covers focal length from 8.9mm to 71.2mm as marked on the lens:

The 35mm equivalent of 8.9mm-71.2mm is 35mm-280mm, which covers not-so-wide-angle to telephoto. This is a variable aperture zoom lens, which means the maximum aperture changes as the lens zooms. The lens marking shows that the wide side (i.e., 8.9mm) has maximum aperture F2.8, and the tele side (i.e., 71.2mm) has maximum aperture F4.2. The effect of zooming-in or -out can be viewed on both the electronic viewfinder (EVF) and LCD monitor. One must be very careful in handling 5700's lens. When the camera is powered off, the lens retracts into the barrel of the camera body. However, when the camera is powered on, the lens extends. The left image below shows the configuration when the 5700 lens is at the wide angle end, while the right one shows the fully extended lens. Thus, one must be very careful not to hit and/or bend the lens when power is on.

In what follows, we shall provide a very general overview of a number of concepts and the meaning of some terms.

Focal Lengths

When you change focal length, you will notice two important effects: angle of view and magnification. When the focal length becomes smaller (resp., larger), the coverage of the scene is wider (resp., narrower). It would be very helpful if you know the correspondence between the 35mm focal length and the focal length of 5700's on-camera lens. Assuming that the focal length of the 5700 changes linearly, which may not exactly be the case but close enough, the following gives an approximation of this conversion. If you need a simpler way, you can multiply the 5700 focal length by 4 to get its 35mm equivalent. On the other hand, dividing a 35mm focal length by 4 yields the 5700 equivalent.

The following images show the coverage of commonly used focal lengths. They are 28mm, 35mm, 50mm, 100mm, 135mm, 200mm, 280mm, 334mm and 420mm (35mm equivalent). The 5700 on-camera lens covers focal length from 35mm to 280mm. The 28mm image was shot with Nikon's WC-E80 wide angle converter. The 334mm and 420mm images were shot with Nikon's TC-E15ED tele converter. With the TC-E15ED, the focal length 334mm is the lowest focal length without vignetting. In other words, if the camera lens zooms back to below 334mm, vignetting will occur. Hence, there is a focal length gap between 280mm and 334mm.

28mm	35mm	50mm	100mm	135mm

200mm	280mm	334mm	420mm
Click on the image to see a larger one

Angle of View

The angle of view of a lens is the maximum angle of acceptance of that lens which is capable of producing an image of usable quality on the film or image sensor. Keep in mind that the angle of view is measured along the diagonal of the image because this diagonal can "maximize" the angle of view. The following table shows the focal lengths of 5700, their 35mm equivalents, and corresponding angles of view.

Lens Hood

Nikon has a lens hood HR-E5700 for the 5700. It is understandably big, because it must provide a very wide coverage from 35mm to 280mm. The left image below shows the lens in wide angle position. It is clear that the lens hood provides a very good protection. The right image shows the lens in the tele position. Obviously, it is insufficient for blocking stray light from hitting the lens, and, of course, lens flare is possible.

If you prefer to shield the telephoto end better, you might want to consider an adapter tube such as the Coolfix 5700 (below left) and a telephoto type lens hood such as Nikon's NH-30 (middle). The result is shown in the right image below. With this setup, the on-camera lens must be zoomed to at least 18.8mm or 73.9mm to avoid vignetting.

Lens Attachments/Accessories

The on-camera lens provides the most commonly used focal range (i.e., 35mm - 280mm). If the desired focal length is not in this range (i.e., wider than 35mm to cover a wider area or longer than 280mm to bring distant subjects closer), you have to use lens converters. Nikon manufactures a fisheye converter (FC-E9), a 0.8X wide angle converter that can bring the focal length down to 28mm (WC-E80), and a 1.5X tele converter that extends the focal length to 420mm (TC-E15ED), Click here for an overview of these lens converters.

The lens of 5700 does not have thread for using filters. If you wish to use filters on a 5700, a special adapter tube is required. Click here for an overview of using filters.

Lens Flare and Ghost

Flare occurs due to light bouncing off the glass surfaces of a lens (i.e., internal reflection) rather than transmitting through. Because of this internal reflection, image contrast and tonality are reduced. When you point the lens close to the sun or a very strong light source, lens flare and/or ghost may occur in your image. In the left image below, the sun is near the upper-right corner, and the upper right portion of the image is somewhat washed out. The middle image below even include the sun in the image. The area near the bright spot (i.e., the sun) is washed out completely.

Lens flare and ghost
Click on the picture to see a full size one

The right image above illustrates another effect, ghost, a string of color dots appearing in the image. The washed-out effect (i.e., flare) is still there near the upper-left corner, but is not as strong as in the middle one. However, there is a string of dots, usually in green, purple or violet, appears in the image. These dots have the shape of the aperture of the lens and are not part of the actual scene. Therefore, they are called ghosts! Most low cost zoom and wide angle lenses suffer this problem. The image below shows flare, ghost and severe washed-out. Sun light comes in from the upper-left corner, and, as a result, you can see the shape of the aperture there. The washed-out bottom portion is caused by water reflection. With a better lens, surfaces of glasses are multicoated with special anti-reflection chemicals to prevent flare and ghost. However, even though with a multicoated lens like the on-camera one, flare and ghost cannot be eliminated completely. See Coated or Non-Coated for more details about lens coating.

Lens flare, ghost and severe washed-out

Click on the picture to see a full size one

To overcome this problem, do not point the lens directly toward or near a strong light source. If this cannot be avoided because it is your favorite scene, try to hold a piece of paper or use your hand or a lens hood to block the incoming light. It usually partially solves this problem. See the above lens hood section, or click here for more details.

Distortions

There are two types of distortions: barrel and pincushion. Both types are slightly visible with 5700's on-camera zoom lens. Barrel distortion means straight lines in real world bow outward in images. The closer to the image edges, the worse the barrel distortion. Barrel distortion usually occurs in the wide angle side. On the other hand, pincushion distortion means straight lines in real world bow inward in images. Similar to barrel distortion, the closer to the image edge, the worse the pincushion distortion. Pincushion distortion usually occurs in the tele side.

Click on the picture to see a larger one

The left image above shows an example of barrel distortion. Parallel lines on the wall are no more parallel. Instead, they bow outward. The middle image also show the same barrel distortion. The right image above shows an example of pincushion distortion. A yellow line connecting the two endpoints of the roof is drawn. Comparing this line and the edge of the roof, you should see pincushion distortion. The 5700 lens has noticeable barrel distortion, especially when the wide angle converter WC-E80 is used. However, pincushion distortion is well under control.

Chromatic Aberration

The refractive index of a transparent material varies with wavelength. It means a lens, in general, is not able to focus all three primary colors (i.e., red, green and blue) at the same point without optical correction. A lens in which two primary colors are corrected and united so that they focus at a common image point is said to be achromatic, while if all three primary colors are corrected and united is said to be apochromatic. A lens in which the primary colors are not brought to the same image point suffers chromatic aberration. Therefore, the image produced by such a lens frequently contains color fringes that are not part of the actual scene. In digital cameras, the image capturing devices (e.g., CCDs) also contribute come degree of aberration. Because the photosites of an image capturing device are densely packed, it is possible that the color captured by one photosite may "propagate" to its neighbors. In the worst case, an over-charged photosite (i.e., over-exposed) may have its charge ``leaking'' to its neighboring photosites. This an effect, which is similar to chromatic aberration, is usually referred to as blooming.

Chromatic aberration is an universal problem of all camera lenses. Cheap lenses and lenses of large zoom ratio frequently suffer from chromatic aberration. The following image shows some typical chromatic aberration.

Click on the image to see a larger one

Usually, one can easily find chromatic aberration along borders of two high contrast areas. The left image below is a 100% crop from the area in the top border of the image above. Dark leaves and bright sky are of very high contrast, and, as a result, dark leaves are no more black but become purple, which is a commonly seen form of chromatic aberration. The lower left crop is shown in the right image below. In addition to a purple touch of the image, we also see green fringes along high contrast areas. In general, purple and green fringes are the two commonly seen chromatic aberration problems.

The lower right crop is shown below, which is resized and rotated 90 degree. This crop does not include high contrast areas. However, you still can see green and purple fringes along the silhouette of the tree trunk.

Click on the image to see the original one

Fortunately, the 5700 lens performs much better than the lens used to take the above image. However, it does not mean one will not see any chromatic aberration. Occasionally, along high contrast areas you still see purple and green fringes.

What Is Ahead?

Nikon Coolpix 5700 supports two types of zooms, Optical Zoom and Digital Zoom. The latter provides a way to blow up the center part of a captured image using software algorithms, thereby offering a digital equivalent of telephoto lens with lower image quality. Also refer to Lens Converter Overview for more information.

Technical Data

The following lens technical information are taken from Nikon's manual.