Monday, April 5, 2010

Lenses for Travel Photography - Part VI (Special lenses and lens accessories)

Cutaway of Zoom Telephoto LensThis week in Part VI of my seven part series about lenses for travel photography, I discuss special lenses and lens accessories to consider when choosing lenses for travel. The series is primarily meant for SLR and DSLR camera users, who can attach a variety of lenses to their cameras to support their creativity, and suit the needs of their photographic opportunities.

It’s important to note there are many more lenses and lens accessories available for your consideration than I will discuss below, but the ones I have chosen have utility during travel, and are carried by some travelers, according to their needs.

Three lenses possible lenses for travelers include: fisheye, perspective control, and teleconverter.

There are two kinds of fisheye lenses, the older circular style, and the more modern full frame fisheye.

Circular Fisheye PhotographCircular fisheye lenses take in a 180° hemisphere and project it as a circle within the film or sensor frame. Most circular fisheye lenses cover a smaller image circle than rectilinear lenses, so the corners of the frame will be dark.

With fisheye lenses gaining popularity, manufacturers designed fisheye lenses which enlarged the image circle to cover the entire 35 mm film frame and FX sensor. The full frame fisheye is the most common type of fisheye lens today.

Full Frame Fisheye PhotographThe angle of view (AOV) produced by full frame fisheyes measures 180° along the diagonal angle of view. The horizontal and vertical angles of view will be smaller. For a 16 mm full-frame fisheye, for example, the horizontal AOV will be ~147°, and the vertical AOV will be ~94°. DSLRs with DX sensors need a 10.5 mm lens to achieve the same effect as a 16 mm lens on a camera with full-frame sensor.

Fisheye lenses can produce wonderfully interesting wide angle images which standard wide angle lenses are unable to capture.

Perspective Control LensWe’ve all taken photographs standing at the base of a building to capture its image, only to find the top of the building “pinched-in” compared to the base. That’s called “vertical perspective,” when the parallel lines defining the building’s exterior converge along the height of the building. Perspective control lenses allow the photographer to control the appearance of perspective in the image, by an adjustment which moves the optics parallel to the film or sensor.

I always try to produce the best possible image in the camera I can. While you can correct images in post processing, sometimes you can’t quite post process a photograph to how you’d prefer it to appear. If you take a significant number of cityscapes in close quarters, and many architectural photographs, this lens might be a great travel lens for you, however, most perspective issues, even complex ones, can be beautifully corrected in post processing.

Teleconverters permit you to extend the focal length and therefore the reach and magnification of telephoto lenses. Teleconverters are secondary lenses, mounted between the camera and a photographic lens. Their purpose is to enlarge the image obtained by the main lens.

TeleconverterWith a 1.4x teleconverter you turn a 400mm telephoto lens into a 560mm lens. The focal length extension of a lens via a teleconverter isn’t without a downside. Use of teleconverters cuts back the amount of light reaching the SLR’s film or DSLR’s sensor by one or more f/stops. Teleconverter optics will reduce the sharpness of the lens to which it is attached to some degree. As is true of lenses, all teleconverter optics are not manufactured equally.

If your telephoto lens is fast enough, the use of teleconverter with it, can be an economical alternative to purchasing a longer lens, and is much lighter than an additional long telephoto lens.

While some photographers won’t agree, the UV filter is my top lens accessory. I have one installed on every lens I own.

UV filters reduce atmospheric haziness created by ultraviolet light. They don’t eliminate it. UV filters are mostly transparent to visible light, so they can be left on the lens for nearly all shots. Perhaps more important is the physical protection UV filters provide the lens.

Several years ago in Paris, while walking near the Eiffel Tower, I was accidentally knocked into a metal railing in front of a home. My UV filter was badly smashed, but my lens was unharmed, protected by the filter. It's much less expensive to replace the filter than the lens.

There are other filters which provide excellent aids for travel photographers; polarizing filters, neutral density filters, and graduated neutral density filters.

Polarizing filters can darken blue skies, increase the contrast of partly reflecting subjects, and reduce reflections from non metallic surfaces like glass and water. If you only have enough cash to buy one filter (other than a UV filter which is a must), make it a polarizing filter.

Neutral Density FilterNeutral Density filters (right) reduce the amount of light equally of all wavelengths passing through the filter throughout the entire filter. These filters are often used so that even in bright light the aperture can be opened wide to reduce the image’s depth of field.

For example, on a bright sunny day a Neutral Density filter can be used to help obtain macro photographs of flowers in a garden with a blurry background to enhance the main subject of the image.

Graduated Neutral Density FilterGraduated Neutral Density filters (left) are used when the dynamic range of a scene exceeds the capability of the camera to record detail in both the brightest and darkest parts of the scene. They are often used in landscapes to allow the photographer to catch the detail in a bright sky while simultaneously catching the detail in the darker foreground. They are especially useful when the transition between light and dark is a straight line, something you often see in landscapes and sunrise/sunset photos.

For more detailed information on these filters, read my article, Do filters for digital cameras make sense?

LensPenDon’t forget to have something to clean your lenses. That’s an essential accessory. I use a combination of items.

A very useful device is a LensPen (right). It has a retractable brush to remove dust and a special non-liquid cleaning element, designed to never dry out.

In addition, I always carry a non-woven lens cloth and a high quality liquid optical cleaner.

Each of the above lenses and accessories can serve you well for many situations you encounter while traveling. It’s up to you to choose the ones which make sense for your photography and your travels.


Sam said...

Another amazingly useful article. I can't wait for the conclusion next week.

Charlie said...

I had no idea there were 2 kinds of fisheye lenses. The circular one looks amazing. I can't find a Nikon circular fisheye. Am I missing something?

Ned S. Levi said...

Hi Charlie,

I don't think you're missing anything. Nikon isn't selling one at this point. Sigma has both a DX and FX circular fisheye. They have a Nikon and a Canon mount version.

Bill said...

Really interesting post Ned. I never heard of a "perspective control" lens before. I take lots of city photos. Maybe I'll look at get one.

Ned S. Levi said...

Bill, just so you know, you're looking at a price approaching $2K per lens.

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