Phase Correction in Binoculars
Article | Posted by Best Binocular Reviews 
Phase Correction on Binoculars
After the light travels through the objective lenses on a roof prism binocular, it then reflects off the surfaces of the prism. These multiple internal reflections on the prism and because of a phenomenon known as Brewster’s or the polarization angle, cause the light to become partly polarized and the light splits into two slightly out-of-phase beams.
Left uncorrected, this "phase shift" will produce an image with less contrast and a lower resolution. So to prevent this and thus increase the image quality and contrast, better quality binoculars have special multilayer phase-correction coatings applied to one of the roof surfaces which forces the split light back into phase so that they now both have essentially the same phase shift and thus there is no longer any interference to degrade the view.
To produce these very thin coatings on the prism surface, they are usually deposited using a process known as chemical vapor deposition. If you are interested in seeing this process, take a look at this article and video on how binoculars are made.
Note: Phase correction coatings are only needed on roof prism binoculars as this phase shift does not occur on a porro prism.
Best Lower Cost Phase Corrected Binoculars
Whilst you can safely assume that all these high end and the very top tier expensive roof prism binoculars are phase corrected, not all of the lower tier and slightly cheaper models are. The price of bins with high end features continues to drop, but as of yet, I have not reviewed any really cheap binoculars that are phase corrected.
So if you are on a budget and to help with your search below is a selection of some of the best cheaper (Mid priced) roof prism binoculars with phase-correction coatings that I have reviewed and which I have rated very highly:
Low Cost Binoculars
Meade 8x42 Rainforest Pro Binoculars
A well made water and fog proof body does a great job of protecting the fully multi-coated optical system that includes BaK-4, silver and phase coated roof prisms. From here it is easy to see how these Meade binoculars were awarded the title of Best Low Cost Binocular for 2015.
Add to this a very wide field of view and great quality image and you have a very versatile pair of optics, but ones that are particularly strong in the areas of birding and wildlife observation.
Important Stats:
Field of View: 395ft at 1,000 yards
Eye Relief: 17mm
Close Focus Distance: 6.6ft
Hawke Nature-Trek 8x42 Binoculars
With all their high end features, components and great stats, it is easy to see how these excellent Hawke binoculars won the award for Best Low Cost Binocular in 2014 and an all round excellent value for money bin.
As well as having mirror coated, phase corrected BaK-4 prisms, the optics are fully multi-coated, which at this price is superb.
The polycarbonate body is completely sealed and filled with nitrogen gas making them both fog and waterproof.
Important Stats:
Field of View: 388ft at 1,000 yards
Eye Relief: 18mm
Close Focus Distance: 6.6ft
Mid Price Binoculars
Hawke Endurance ED 8x32 Binoculars
As a mid-priced, mid sized binocular, this Hawke Endurance ED really does rank up there with the very best within their class.
As well as phase correction coatings, the roof prisms on the Endurance is made from quality BaK-4 glass. Optics are also fully multi coated and the lenses contain an ED glass element which helps reduce some aberrations even further. The result is a quality of view that far exceeds any expectations that I have at this price range – a truly excellent pair of mid sized binoculars.
Important Stats:
Field of View: 388ft at 1,000 yards
Eye Relief: 18mm
Close Focus Distance: 6.6ft
Pentax DCF BC 9x32 Binoculars
Winner of the award for the Best Lower Cost Safari & Travel Binocular in 2012, these mid sized Pentax binoculars come with a somewhat different 9x magnification giving you a great compromise between a wide field of view and Image detail.
The BAK-4 roof prisms have phase correction and highly reflective silver-evaporated coatings that help to transmit more light than the aluminium coatings used on many binoculars in this price range.
Important Stats:
Field of View: 351ft at 1,000 yards
Eye Relief: 16mm
Close Focus Distance: 8.2ft
Carson 3D Series 10x42 Binoculars
These Carson binoculars come with ED glass, fully multi-coated optics and Bak-4 phase corrected roof prisms to produce an image that far outperforms their price tag.
Also included is a binocular harness and their excellent wrap around BinoArmor case, which is one of the best carry cases I have ever used.
Important Stats:
Field of View: 314ft at 1,000 yards
Eye Relief: 16mm
Close Focus Distance: 6.2ft
Vanguard 10x42 Spirit ED Binoculars
Winner Best Value for Money Binocular in 2011, these Vanguard binoculars prove that you don’t have to spend huge sums of money to get many of the features found on the very best binoculars.
Optical highlights include phase corrected prisms, fully multicoated optics with ED lenses, whist the waterproof and fogproof body has a tough rubber armor for protection.
Important Stats:
Field of View: 315ft at 1,000 yards
Eye Relief: 16mm
Close Focus Distance: 9.2ft
Mid-High Value Binoculars
Vanguard Endeavor ED 10x42 Binoculars
These phase corrected binoculars scored an outstanding 85% when I reviewed them and eventually went on to win the award for the Best Value for Money binocular in 2012.
Other high end features include a fully waterproof body with a lightweight open bridge design. Inside you find fully multi-coated optics with ED glass elements in their objective lenses to reduce color fringing. The prisms are phase corrected and silver mirror coated to further improve light transmission.
Important Stats:
Field of View: 342ft at 1,000 yards
Eye Relief: 16.5mm
Close Focus Distance: 8.2ft
Vortex Viper HD 8x42 Binoculars
Like the Vanguards above these Vortex binoculars scored an outstanding 85% on the BBR scale, which included a near perfect 9/10 for their Image Quality.
Helping to achieve this, they have fully multi-coated optics, ED glass in their lenses and phase corrected Bak-4 roof prisms. ArmorTek scratch-resistant coatings have also been added to the exterior lenses.
Important Stats:
Field of View: 347ft at 1,000 yards
Eye Relief: 20mm
Close Focus Distance: 5.1ft
Celestron Granite 9x33 Binoculars
If you are looking for a slightly smaller binocular than the two listed above then you may wish to consider these mid-sized Celestron Granite binoculars.
Bak-4 Roof prisms with phase correction coatings also include dielectric coatings to help produce the highest levels of transmittance possible. Combine this with Fully Multi-Coated Optics with ED glass and a Lightweight Open-hinge Magnesium Alloy Body and you have a great pair of binoculars.
Important Stats:
Field of View: 378 feet at 1000 yards
Eye Relief: 14.1mm
Close Focus Distance: 8.2ft
More
For some more great binoculars take a look at the following links:
Categories: Binocular Terms, Technical | 
Tags: Coatings, Phase Correction | 
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