advise please

[9-point]

hello to all, I am new here,and have just figured out the importance of quality optics, I was given a pretty old pair of kowa binoculars by my uncle, they are about 50-60yrs old,prominar type with each eyepeice having its own adjustment dial they are also 7x50pwr. someone said they might be made of flourite crystals?? dont know what these are any help would be greatly appreciated

 

[Buffalobob]

There are about four parts to an optical system.

The housing which is the outside body and internal mechanisms and lens holding systems.

There is the design of the system of lens themselves which was very good long ago for high quality optics but very poor for low quality optics. The new cheap high speed computers have allowed the low quality optics to catch up for a cheap price on the design however the high quality optics still have high paid lens designers who earn their money.

There is the coatings on the lenses which are proprietary and expensive to develop and so when you pay a lot of money you expect really good optical coatings on the lenses.

There is the quality of the glass used to make the lens and its characteristics. High quality glass was and is expensive. Fluorite has different characteristic from regular glass for colors.

The refraction of light differs depending on the wavelength. The point of focus therefore differs depending on the different wavelengths or colors. When the different wavelengths are focused at different points, the colors look smeared. This is called chromatic aberration. The longer the focal length, the more pronounced chromatic aberration becomes. Usually, an achromatic element is used in a lens to correct chromatic aberration. However, normal optical glass can only be corrected for two primary spectral colors. An exception to this limitation is Fluorite, an ideal material. Fluorite, which is crystalline, has abnormally low refraction and dispersion characteristics, which optical glass cannot achieve. It also has anomalous dispersion from the green to blue wavelengths. Canon developed production technologies to manufacture fluorite. By incorporating Fluorite in lenses, the points of focus of the three primary spectral colors of red, green and blue all meet at one point for ideal correction of chromatic aberration. There is also UD-glass, which is a special type of optical glass whose properties nearly match those of Fluorite. The effect of two UD-glass elements gives almost the same effect as one Fluorite element. And one super-UD-glass element gives almost the same effect as one Fluorite element

My advice is to take the binoculars out and look at some things about 500-700 yards away with them rested and still. Check the quality of the image near the outside edge. Check the sharpness of detail. Take a piece of cardboard and shade the binocular objectives from the sun and while things should be slightly darker (less whiteness) they should be clearer and more definitive in detail. All of the whiteness is from glare and is an indication of the qualities of the optical coatings and the lens design. Depending on your age this will be OK or it will be really bothersome.

Just after sundown go out and look at some red/brown objects and some blue objects. See how long things are resolvable. You will notice the new Luepold VL scopes offer dawn/dusk lenses with special blue/green transmission. This is a good thing but it is too bad that the deer are red/brown!.

Take at look at the lens and see if they are scratched or the coatings are gone.


There is nothing that says an old set of optics is not just fine so you just need to check them out now before you go hunting with them. But and however, as your vision ages you will need better and better optics and these might be jsut great.