Sunday, May 3, 2009

Nikon Teleconverters

Teleconverters are optical extenders which will magnify the image and effectively increase the focal length of a lens. My experience is limited to the latest Nikon TC-XXE II teleconverters and Kenko pro TCs. I will be discussing my experiences with TCs and compare Nikon and kenko. I will also discuss my experiences of using TCs with Nikon 70-200mm VR, Nikon 70-300mm VR, Nikon 300mm AFS lenses and a comparison of these lenses with TCs.

TCs were available for along time (since 1976 for Nikon to be exact). They have their followers with some touting as most useful photographic accessory to others claiming total waste of their time and precious space in their camera bags. There are basically 3 different TCs which magnify the images to 1.4x, 1.7x and 2x. I am going give some basic facts about teleconverters before I go into their uses with different lenses.

Basic facts:

1. The most important fact is to realise what you are trying to achieve with this. TCs achieve longer focal length with existing lenses. These must be used for obtaining very long focal lengths where the original focal length lens is very expensive or simply not available like 300mm or longer lenses. If you buy a TC to use with a 50mm lens to make it 100mm it makes no sense either economically or photographically since the TC itself is more or almost as expensive as 100mm lens and it decreases the quality and aperture of the original lens. Whereas use it on a 500mm lens to get 700mm or longer lens then the effort is worthwhile since there are no primary lenses longer than 600. You can also use it on a $5000 300mm lens to convert it to a 600mm lens which costs $10,000, thereby justifying the savings to slight decrease in image quality.

2. TCs are designed for prime lenses. All TCs result in loss of image quality. If the original lens has extremely high resolution and sharpness, especially one that exceeds the sensor resolution, then TCs will not cause noticeable or unacceptable decrease in IQ. But there are few lenses which have this kind of resolution and they are mostly primes.

3. All TCs cause decrease the amount of light transmitted. A 1.4x TC loses 1 stop, 1.7x TC loss 1.5 stops and a 2x TC loses 2 stops of light. This also affects AF ability and speed. So your lens aperture should be f/2.8 or atleast f/4 to get the best out of the TC. For most current camera systems you need atleast f/5.6 for good AF so if your TC makes your lens slower than f/5.6 the AF is going to be seriously affected.

4. All TCs decease the depth of field. So you need to stop down more than you normally would to achieve the same depth of field.

Advantages include

1. Longer reach for your lenses. This is very important of you are a bird, wildlife or sports photographer.

2. The minimum focusing distance is the same, meaning you get magnification with an increase in focal length. This may not substitute for a macro lens but does give closeup effects to a certain degree.

Next I will blog about my experiences with the 1.4x TCs both Nikon and Kenko. Stay Tuned.

1 comment:

  1. Hi
    Your blog is very informative, I read it regularly..(i mean each post..)

    could you post few of photos related to device you explore ?