Lens Finder

Lens Finder

Optical lens types and coatings

Most lenses are spherical lenses: their two surfaces are parts of the surfaces of spheres.Each surface can be convex (bulging outwards from the lens), concave (depressed into the lens), or planar (flat). Lenses may be cut or ground after manufacturing to give them a different shape or size.

 

Aspheric lenses are more complex. These are lenses where one or both surfaces have a shape that is neither spherical nor cylindrical. Such lenses can produce images with much less aberration than standard simple lenses.

 

Aspheric lenses are also sometimes used for eyeglasses. These are typically designed to give a thinner lens, Aspheric eyeglass lenses typically do not provide better vision than standard "best form" lenses, but rather allow a thinner, flatter lens to be made without compromising the optical

 

A single aspheric lens can often replace a much more complex multi-lens system. The resulting device is smaller and lighter, and possibly cheaper than the multi-lens design. Aspheric elements are used in the design of multi-element wide-angle and fast normal lenses to reduce aberrations.

 

Aberrations

Lenses do not form perfect images, and there is always some degree of distortion or aberration introduced by the lens which causes the image to be an imperfect replica of the object. Careful design of the lens ensure that the aberration is minimized.

 

Dioptric correction is the term used for the adjustment of the optics for a person's eyes. It is the adjustment of one lens to provide compatible focus when the viewer's eyes have different visual capabilities ( left eye vs right eye ).

 

Surprise! Some glasses are still made with lead and used to be radioactive.

Most common glass has other ingredients added to change its properties. Lead glass or flint glass can be more brilliant because the increased refractive index,while boron may be added to change the thermal and electrical properties, as in Pyrex. Barium also increased the refractive index. Thorium oxide was formerly used in producing high-quality lenses, but due to its radioactivity it has been replaced by lanthanum oxide in modern eye glasses.

 

An antireflective coating is applied to the surface of lenses and other optical devices to reduce reflection. This improves the efficiency of the system since less light is lost. Many coatings consist of transparent thin film

The simplest interference AR coating consists of a single quarter-wave layer of transparent material

 

Multicoated photographic lens

By using alternating layers material like silica and a higher-index material it is possible to obtain reflectivities as low as 0.1%.

 

I know most of the above is boring but just maybe it informed you

I hope you enjoyed thanks for reading

About the Author

Dale Coover Live and works in Colorado he like to travel, scuba dive play guitar and take wildlife photos. He visits old cemetery's of outlaws, gunmen and sherriffs and reads western history

tips for using a 50mm lens?

i have a canon rebel 2000. its a film camera
i recently came across a 50mm canon lens.
everytime i take a picture, the view finder goes black and doesnt go back to normal until i take the lens off. can anyone tell me if this is normal, or im doing something wrong? and when are the best times to use this lens? and any tips you have for it? thanks!

Can I assume you don't have this problem with your other lenses ?
If so it sounds like the aperture could be closing down when you make the exposure but it's failing to open up again after. If you're shooting at a small aperture and that is happening then it would have the effect of making the viewfinder appear very dark after taking the shot.
You need to find out if that 50mm lens is actually compatible with your camera, just because they are both made by Canon is no guarantee that it will be especially if it is an older lens.
If compatibility is not an issue then I would suspect a faulty lens rather than a fault in the camera especially if other lenses work fine with it.

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