26th September 2003, 10:19 PM
The lens is an AF-S, the 'S' denotes the Silent Wave Motor from Nikon (like the USM-Ultra Sonic Motor for Canon)
Originally Posted by TME
The AF-S lens have a quieter and faster focusing speed than the non AF-S lens.
I am not referring to the aperature (i.e. f/2.8...etc) when I mentioned 'fast'.
I mean it's focusing speed is faster not the f-stops.
BTW, chromatic abberations is not kept in check by aspherical lens elements.
The Aspherical lens is useful in correcting the distortion of wideangle lenses.
Hence you will find it mostly on wide angle lenses or lenses starting from 24mm or 28mm, like the 24-135 and 24-85.
You will not find aspherical lens element in telephoto lens like 70-200mm, 80-200mm, 50mm, 85mm etc
Chormatic aberration is corrected with ED (nikon), UD(canon), LD(tamron), SLD(sigma)....etc elements.
It makes the light rays of different wavelengths converge together to eliminate chormatic abbertion.
The Tamron 24-135 has LD elements for that, while the Nikon 24-85 has ED elements for that.
"Nikon's new series of AF lenses, involves the intergration of coreless motors into their super telephoto lenses. This gives these lenses quick, ultra quiet autofocus operations."
Last edited by Winston; 26th September 2003 at 11:06 PM.
28th September 2003, 01:08 AM
Originally Posted by Winston
Sorry my mistake. Anyawy I thought chromatic abberations were corrected with APO glass - apochromatic? The ED, LD, SLD, etc are all low dispersions glass..... is that the same at APO? Or is APO only for telezooms? BTW, the 24-135 comes with AD glass. Whatever that means. Can't seem to find what it refers to on my lens manual.
28th September 2003, 09:41 AM
APO is Sigma lens terminlogly
Originally Posted by TME
APO lenses These lenses use apochromatic design and Special Low Dispersion glass (SLD) for minimum color aberration and ultimate telephoto image quality, improving contrast and sharpness.
Apochromatic (APO) telephoto lenses greatly minimize color aberration, a phenomenon created by different wave lengths of light refracting at different angles. This causes each color to have a slightly different imaging point, resulting in poor image quality.
APO glass is not the same as the ED, UD, SD, SLD, LD....etc glass
The 'AD' in the Tamron's 24-135 does not refer to Aspherical lenses.
Though the 24-135 does have Aspherical lens element in their design.
"Anomalous Dispersion" glass is a type of optical glass material that delivers an abnormally larger partial dispersion ratio (amount of dispersion at a given wavelength area within visible light range) relative to a specific wavelength zone. Combined use of AD glass with other optical glass material (s) different dispersion characteristics serves the purpose of optimising the dispersion character of an optical system at a specific wavelength. Thus, it helps to compensate for on-axis chromatic aberration on telephoto lenses, or for lateral chromatic aberration on wideangle lenses.
Chromatic aberration is a form of optical noise that undermines the sharpness of an image. An LD (Low Dispersion) glass element is composed of special glass materials that possess low refractive and dispersion, indices (characteristics that separate a ray of light into seven rainbow colours) for effectively compensating for the chromatic aberration, especially at the telephoto end.
These lens makers all patented their respective lens terms and hence it is a hassle to remember what they are and what terms in Nikon is similar to what terms in Tamron/Sigma/Tokina...etc
Last edited by Winston; 28th September 2003 at 09:48 AM.
28th September 2003, 09:57 PM
Thanks for the links. I dun think APO is exclusive to Sigma only. It's a type of glass design/material/way of manufacturing glass, etc...... it's used mainly on telephotos as far as I know...... I have seen in on my own Minolta 10-400APO, the Tokina ATX-II 80-400mm, and other similar lens.......
From what the Tamron website gave, I guess the AD allows the incorporation of the wide 24mm and tele 135mm with little optical distortions and other abberations within a single lens lar....... maybe one day we'll see a 17-400mm lens....... hiopefully lar........ saves one a lot of trouble switching lens........
28th September 2003, 10:19 PM
APO is just a general term for apochromatic lens design. This means that the manufacturer has taken steps to ensure the diffraction of colour has been properly controlled in the lens.
What ED,SLD,LD..etc are just manufacturer specific terms for the type of glass used to achieve apochromatic design. In any case, most of the lens material used in Tokina/Tamron/Sigma lenses are made by Hoya anyway.