For the "without" case, it is typically assumed that the user would bring the object as close to the eye as possible without it becoming blurry. This point, known as the near point, varies with age. In a young child it can be as close as 5 cm, while in an elderly person it may be as far as one or two metres. Magnifiers are typically characterized using a "standard" value of 0.25 m.
Posted 04/19/2009 6:20 pm
Your question is rather not exactly easy. Remember there are many manufacturers of magnifing devices and also the different materials they are made of. In other words what you buy noted as 10X may be 9X, 9.73X, 10.34X, etc. if made in China and made of plastic. Most manufacturers of products where specific details are not easily detected or able to be disproved know this and don't worry about tolerances. And too, remember that in many industries, there are manufacturing tolerances allowed. For example in steel I beams, it is allowed for a possible +or- 1/2" in many larger sizes.
Plastic type magnification devices are really vague since they are not usually made for accuracy.
Organizations, such a Edmund Scientifics has to produce excessively high quality magnification devices since they are utilized in schools and hospitals. Companies that produce optics for photography also are a little more precise in their statistics.
To sum this up it is not an easy thing to detect the accuracy of an optical device without other accuracy device testing equipment.
Plastic type magnification devices are really vague since they are not usually made for accuracy.
Organizations, such a Edmund Scientifics has to produce excessively high quality magnification devices since they are utilized in schools and hospitals. Companies that produce optics for photography also are a little more precise in their statistics.
To sum this up it is not an easy thing to detect the accuracy of an optical device without other accuracy device testing equipment.
