The best binoculars are hard to find – particularly if you aren’t much aware of them. You should do more research, find more tips, and read a whole lot before you get. But is everything that they are telling you true?
In our previous weblog post, we’ve discussed how exactly to determine quality binoculars. Today we are going to discuss a number of the binoculars hype that’s costing you money. They are things that you wish you knew before purchasing the next binoculars. Hang within and let’s go for a ride.
So, you have observed some cool things printed on your own next binocular’s cover plate. They are enticing…right? They are Fully Multi-Coated (FMC), BAK4 prisms, high magnification power, large objective lens, etc.
Well, don’t be deceived by those specifications. Forget even the web forums and leave alone the cool binocular’s cover-plates.
Why Do I Say So?
First, there are incredibly many important things that the cool binocular’s cover-plates or the vendors don’t fill you in. Especially, when it comes to Fully Multi-Coated (FMC) lenses or the BAK4 prisms such as for example these:
- Edge distortion
- Prism housings
- Smoothness of focus
- Field curvature
- Size of fully illuminated field of view
- Spherical aberration
- Quality internal light-baffling
- Type and quality of the eyepieces
- Crispness of focus
- Construction/Build quality
- Chromatic aberration
So, How about Coatings and Prisms?
Fully Multi-Coated Optics
When the coating is performed properly, multi-coated optics will transmit more light when compared to single-coated or uncoated optics. It’ll be much more when all of the lenses are coated – as in fully multi-coated optics.
To achieve a perfect transmission of light, the coatings should be applied evenly and to the right thickness. In the event they are unevenly applied or if the application form is even but with the wrong thickness, it’s as effective as the regular toy bino.
How to Identify
Uneven-application of coatings might look “blotchy” but not always. Worse off is that without the correct testing tools, you won’t have the ability to find out if the proper thicknesses are ideal. In a nutshell, you be based upon trust.
You ‘re going with quality control and hoping that you get the proper optics. But quality control can be relative and while many persons complain about the product quality it is the truth:
To improve the quality and consistency of optics production needs additional time. It also needs better glass selection, more training and assembling time, and more resources. This way, an increased quality binocular can be designed. However, the final cost will be high and many people will shy off again.
To say the truth, we are in an age where in fact the “accountants are in control” rather than the engineers. Forget about input in products. We concentrate more on the price of production, affordability to almost all, and that’s just it.
We give a budget prior to the optic was created. We don’t design a binocular first and attach a price tag to it later. No. Why? Because we fear the end cost might be too much for anyone to afford and low sales mean losses.
Fully Multi-Coated: EXACTLY WHAT IT Mean Today
In short, the term “Fully Multi-Coated” can be relative. Exactly like “affordable” FMC can now mean that all the glass-to-air surfaces of the objectives and eyepieces lenses and the transmissive prism faces all have the 7 layer interference coatings with proper application and thickness.
Or additionally, it may mean that only the glass-to-air surfaces have significantly more when compared to a layer interference coating. So, yes, you never quite really know very well what you are buying unless the manufacture gives more details.
Magnification Power and Aperture
A”10×50″ that’s printed on a binos cover plate means 10× magnification power and 50mm objective lens diameter/ aperture.
So it’s logical to assume that when you measure your exit pupil, it’ll be 5mm (50mm ÷10)? I measured a few models and I was disappointed. I came across 4.2 mm instead. It means that your binocular is effectively the 10×42.
But why say it’s a 50mm which transmits 1½ times much light compared to the 42mm? Here is what I think.
When the target lenses are ground poorly, the edges are affected mostly. So, the light coming from the lens edges produces distorted images. In order for these distorted images not to occur the manufacturers use a diaphragm among the objective lenses and the eyepieces. The diaphragms stop the light coming from the edges to the eyepiece. This makes a 50mm objective lens to a 42mm and even lower. Knowing only the target lens diameter, therefore, does not tell us just how much light a binocular can gather to make a bright image.
Moreover, if indeed they stop the aperture down to 42mm they could just escape with the use of smaller prisms. Small prisms often require a smaller housing. In addition, it demands lesser fixing.
In addition to that, going down to 42mm will also increase the optics effective focal ratio to about f/4.2 from about f/3.5, which demands lower eyepiece quality. It also improves the color correction and the edge performance.
In short, leaving since it were will cost more to create a top-rated bino. Stepping it down may be the shortcut to getting what they want. Less cost, lower quality optics, and main goal achieved. It really is that bad.
Bak4 glass hails from Germany. The BaK in the BaK4 means “BaritleichKron” which is “Barium Crown” in German.
BaK4 is often found in high-end binoculars prisms. Its advantage is that it has higher refractive index over the BK7 glass.
In short, BaK4 is impressive when found in any binocular to supply more light. It permits additional light to pass from the border of your field of view, through the prisms, and eventually into the eyepieces.
This action provides a brighter edge of field. However, there won’t be any effort to make the middle of the field brighter. Nonetheless, persons have observed it as desirable because of this simple analogy.
WHAT YOU OUGHT TO Know
There are international professional optics standards that determine what kind of BaK4 glass that needs to be used. For example, the international BaK4 standard designation is 569561 with the first three digits telling the refractive index (1.569) and the remaining three telling you the Abbé number (56.1).
Glass Type Refractive Index Critical Angle Dispersion
Schott BaK4 1.5688 39.6° – 0.0523μm -1
Chinese BAK4 1.5525 40.1° – 0.0452 μm -1
Scott BK7 1.5168 41.2° – 0.0418 μm -1
The Abbe indicates how much light which will disperse into its constituent colors. The bigger your Abbé number the lesser the dispersion.
However, the “BAK4” glass on the Chinese optics isn’t the original Schott BaK4. The Chinese binoculars use phosphate crown glass rather than the Barium Crown. Phosphate crown has lower refractive index, dispersion, and skills compared to the Schott BaK4.
What the Bak4 on The Cover Plate Don’t Say
- The Bak4 prints on bino covers don’t let you know the following:
- That if your prisms are under-sized they cut some light out.
- What precision the prism’s flat surfaces are polished too.
- If the prisms have grooved hypotenuses that decrease the spurious reflections
- If the sides of the prism are blackened, shielded to avoid the entry of non-imaging light
- The mechanism used to secure the prisms into the bino housing.
No one tells all these things. Many of them, you may never discover a solution to. Nonetheless, they are costing you money. You will wrap up with an excellent optic device on the cover and lower quality in reality – during use. My suggestion is simple – start learning more about optics now.