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Basics – Lens Selection

Lens Selection

Lens selection suggestion can be broken down into two simple words, It Depends. It depends on the given situation, typical digital camera or full frame digital camera, the subject, the subject distance, available light, depth of field required and composition. Another factor would be whether your digital camera is a standard digital camera or a Full Frame digital camera.

Typical Digital camera or Full Frame Digital Camera

All digital cameras and lenses are referenced to a standard 35mm camera film size (Unless the sensor is considered Medium or Large format. A standard digital camera has a sensor smaller than the area of 35mm film. All camera lenses are marked as to their focal length based on focusing light on a digital sensor equivalent to the area of 35mm film. So, unless you are shooting with a “Full Frame” sensored digital camera, the focal length on the barrel of the lens may not be true to the actual focal length due to the reduced size of typical digital camera sensors with exception of full frame cameras.

So what happens? If shooting with a reduced size digital sensor the focal length of the lens is greater than as indicated on the barrel of the lens and one must accommodate for this when selecting the proper lens. For example, a 50 mm lens is actually a 75mm lens. The image produced by a 50mm lens is greater than the sensor size so the resulting image is that as if you used a 75mm lens.

For non full frame digital cameras you should use a mutiplication factor of roughly 1.5 times the focal length as indicated on the barrel of the lens. This would also be true for zoom lens where the focal length of the lens can change based on zooming in and out. For example a 70-200mm zoom lens is roughly a 105-300mm zoom lens.

The Subject

Different lenses are manufactured for different purposes.

WIDE ANGLE  – “These lens are typically less than 50mm (Full Frame) or 32mm for digital. (Remember that 32mm x 1.5 would equate to 50mm for digital). These types of lenses are called wide angle as the smaller the focal length the wider an area both horizontally and vertically the lens will cover. It is amazing how much area these lens will cover. Watch and make sure your shoes are not in the shot! These types of lens are mostly used for landscapes as the cover a very large area and keep the entire subject are in focus as the depth of field is broad and deep. Objects with this lens will appear smaller and much further away.

NORMAL  – The 50mm lens (32mm for digital) is considered to be the standard workhorse lens. It shows a normal field of view. Is is typically a very inexpensive lens and is typically fast (small f/stop). It is typicall used for standard full length shots for people or typical standard distance shooting.

MEDIUM TELEPHOTO – Greater then 50mm to 150mm (32mm to 100mm for digital) Telephoto lens come in the form of prime lenses (fixed focal length) or medium telephoto zooms that have focal lengths in the range of medium telephoto. These lenses are most often used for portrait shots. This lens allow sufficient distance between the photographer and the subject in order not to crowd the subject. They also produce a short depth of field, many times with great bokeh. This lens is most often used for portraits.

TELEPHOTO –  Greater than 150mm (100mm for digital) This type of lens is usually used for wildlife and sports. It has the ability to get an up close shot when the photographer is unable to get close to the subject due to limitations such when shooting sports or capturing wildlife with causing the creature to run or be alerted to the photographers presence. This type of lens can also capure only a small area of the scene and isolate the subject. Telephoto lenses are usually expensive and very expensive if a fast lens is required to shorten the depth of field.

ZOOM – Various ranges Zoom lenses can be adjusted for a range of focal lengths. This type of lens can be a wide variety of focal lengths and have a zoom range such as 70-200mm. Composition can easily be adjusted by zooming in and out the focal length. In addition, they are very useful when the subject is moving and the focal length required is constantly changing. This variety of focal lengths within one given lens allows the phographer to shoot with one lens instead of constantly changes lenses as the subject moves or the composition requirements change.

MACRO/MICRO – The most important factor of Macro/Micro lenses is its ability to create a 1:1 ratio of the subject as to what is captured on the sensor. It produced a real life image of the subject. Thus a subject 10cm in size can be easily reproduced on the sensor 10cm in size. These lenses allow the photographer to get VERY close to the subject and still achieve focus. Two important factors to consider are that the depth of field is very small and that it helps greatly to keep the lens/sensor on the “Same Plane” as the parts of the subject that the photographer requires to be in focus. These lenses come in a wide variety of focal lengths.

Other Specialty Lenses/Adapters:

TILT/SHIFT (Perspective Control) – These types of lenses are used to correct many elements of the image but most widely used to correct perspective and depth of field. The Lens can actually be tilted or shifted as to create an angle between the lens and the film sensor. By Shiting the lens the photographer can correct perspective or converging lins in a image such as shooting a building where the sides of the building converging as you move up the sensor are not desired. By using a shift lens one can stay close to the subject and maintain excellent perspective as if the image was shot from a great distance. By Tilting the lens one can correct depth of field issues whereby the photographer desires to maintain sufficient in focus detail for up close subjects as well as the background.

TELE-CONVERTERS – Tele-converters are made to lengthen the focal length of a given lens by a multiplication factor of 1.x. For example, Nikon makes Tele-Converters in 1.4x, 1.7x and 2.0x factors of the lens focal length. The converter mounts in between the camera body and the lens. A 2.0x converter would change the focal length of a 200mm lens to a 400mm lens. It is important to remember that a tele-converter comes at a price. The use of such will reduce the lower f/stop by one or more stops. So a 2.8 fast lens with a tele-converter may actually become a 4.5 f/stop lens. Typically the higher the factor of tele-converter results in an increase of f/stops lost on the low end as the f/stop typically increases by the same factor of the tele-converter.

Suggested Nikon Lenses:

Nikon Normal AF Nikkor 50mm f/1.4D Autofocus Lens

Nikon Telephoto AF Nikkor 85mm f/1.4D IF Autofocus Lens

Nikon AF-S Zoom Nikkor 14-24mm f/2.8G ED AF Lens

Nikon AF-S Nikkor 70-200mm f/2.8G ED VR II Lens

Nikon AF-S NIKKOR 300mm f/2.8G ED VR II Lens

Nikon Zoom Telephoto AF Zoom Nikkor 200-400mm f/4 G-AFS ED-IF VR (Vibration Reduction) Autofocus Lens

Nikon AF Micro-Nikkor 60mm f/2.8D Lens

Nikon PC-E Micro Nikkor 45mm f/2.8D ED Manual Focus Lens

Nikon TC-14E II 1.4x Teleconverter for D-AF-S & AF-I Lenses ONLY

Suggested Canon Lenses:

Canon Normal EF 50mm f/1.2L USM Autofocus Lens

Canon EF 85mm f/1.2L II USM Autofocus Lens

Canon Zoom Super Wide Angle EF 16-35mm f/2.8L II USM Autofocus Lens

Canon EF 70-200mm f/2.8L IS II USM Lens

Canon Telephoto EF 300mm f/2.8L IS Image Stabilizer USM Autofocus Lens

Canon 1.4x EF Extender II (Teleconverter)

Canon TS-E 45mm f/2.8 Normal Tilt Shift Manual Focus Lens for EOS

Copyright Robert Shreve Photography

[Chapter 7]

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