How the O4B Scorecard Works

Instructions

Looking at binocular pages one at a time, it gets difficult to remember specifications to make comparisons. To facilitate that process, the Optics4Birding Scorecard allows you to select up to four binoculars and compare them side by side. Select binoculars while surfing the site, or from the menus on the scorecard page. All binoculars have certain specifications such as minimum close focus, eye relief or such. We took all the specifications that apply to binoculars and gave each rating within the range of values possible for that specification, a score from 1 (lowest) to 10 indicating our evaluation how that binocular ranks for that specification. The Scorecard then totals all the scores for each binocular selected, giving an overall comparison. Since not everyone has the same preferences in binocular traits, the O4B Scorecard lets you apply your own preference factor for each specification. Preference factors range from 10 (most important) to 0 (irrelevant). On your first visit, the preference factors will all be set to 5, the intermediate score. You can change these factors to fit what you want in a binocular. The raw scores are multiplied by the preference factors, personalizing the scores to the way you use your binoculars. Note: the Scorecard does not apply to image-stabilization binoculars, whose weight and cost (among other factors) is governed by the image-stabilization technology in ways that invalidate the scoring mechanism.

Setting Preference Factors

When setting your preference factors, it is essential to remember that all binocular designs are a set of compromises required by the physical laws that govern optics. For example, it is impossible to get very short close focus, wide angle of view, and long eye relief at the same time, or to make a binocular with a large objective lens and low weight without using expensive materials. Set your preference factors high for the parameters that are important to you. Don't set them all to 10 to try and find the perfect binocular. We divide the total score by the number of non-zero preference factors, so setting them all to 10 gives the same relative score as setting them all to any other number.

On every visit, you will be able to check a box to save your current preferences in a cookie so they are there the next time you visit. (Optics4Birding believes that cookies should be for the convenience of visitors only. We use the information in cookies only to make your visit easier. We do not set cookies without your permission, and do not use the data in the cookies for any other purpose.)

Scoring Criteria

Each parameter in the O4B Scorecard is scored by a method appropriate for that parameter. For some, we were able to write an equation that describes how we think the scores should fall. For others, scores have to change at different rates in different parts of the range. For these, we decided on scores and entered them into a reference table. Either way, we feel these scores are representative of how most birders knowledgeable about optics would judge each parameter. To help you determine which parameters are (or should be) important to you, each parameter links to its respective discussion in the All About Optics section of this website.

Eye Relief

Eye relief for all binoculars, of any magnification, ranges from about 10mm up to 25mm. Eye relief longer than 22mm has negative side effects, making it harder to keep ones eyes aligned with the image. Eyeglass wearers need a bit more eye relief, but too much still has the same problem. We therefore use reference tables with different scales depending on whether you wear eyeglasses.

When using the scorecard, set the importance factor to 0 for any parameter that doesn't apply to you.

Close Focus

Outstanding binoculars, usable for insect study, can focus as closely as 3 feet, but anything below 6 feet is exceptional. Marine binoculars and other field glasses can only focus to 20 feet or more. This range is normalized so that 5 feet or less scores 10 and 23 feet scores 1, with the formula:

12½ - (CF / 2)

Weight

Higher power binoculars tend to be heavier than lower power binoculars, but weight can also add stability if the binocular is well balanced. Regardless, too much weight can cause fatigue after a long day in the field. Our scoring function is non-linear and discontinuous, so we address it with a reference table.

Field of View

The field of view is usually measured by the width (in feet) of the visible field at 1,000 yards distance. This field is directly related to power, so that higher power binoculars have a narrower field of view. To compare binoculars of differing magnification, we can calculate the apparent angle of view, which is the angle the observer sees when as if standing at the actual distance divided by the magnification rather than looking through the binoculars. Except for subcompact binoculars, this apparent angle ranges from about 45° to about 70° (with 65º and above being considered “wide angle”). Field of view is given a discontinuous scoring system for several reasons. First, while having a wide field of view can be useful, it isn’t necessarily an unmixed blessing. Frequently, truly wide-angle binoculars suffer somewhat in clarity and sharpness because of the optical compromise made in the design in order to provide that panoramic field. Accordingly, we have given the widest field binoculars somewhat lower scores to reflect this tendency.

Waterproofing

The levels of waterproofing are not a continuum, but discrete levels. Porro prisms get lower scores at the same level of waterproofing because their external focusing mechanisms cause wear to the waterproofing seals. Thus, we assign the following scores:

none = 1
shower-proof = 3
waterproof porros = 5
waterproof roofs = 7
nitrogen-purged porro = 7
waterproof and nitrogen-purged roofs = 10
waterproof and argon-purged roofs = 10

Eyecups

Eyecups are rated for durability, comfort, and adjustability.

rubber = 3
slide-up = 4
slide-up and lock = 5
twist-up = 7
wrap-around = 8 (if not an eyeglass wearer)
twist-up with detents = 10

Lens coating

Lens coatings are rated by the number or percentage of lens surfaces that are coated.

none = 1
coated = 4
fully coated = 5
multi-coated = 7
fully multi-coated = 10

Prisms

With prisms, ratings evaluate both the material in the glass and the coatings.

BK-7 = 3
BaK-4 = 6
Phase Coated BaK-4 = 8
Exotic Phase Coated BaK-4 = 10

Class

Scaled from 0.2 (lowest quality) to 1.0 (top quality) in steps of 0.2, this factor is used to give a balance between optical quality class and price, and is multiplied by the score from all the other factors to give a final score. In most cases, Class is determined by manufacturer’s suggested retail price (MSRP), binoculars of scopes that are particularly better or worse than their MSRP might indicate they have their Class adjusted to the appropriate level.

Scorecard | Introduction