10X42mm Ultra roof prism

by Swift Print

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This high power Swift Ultra waterproof roof prism binocular weighs only 24 ounces, surprisingly light for a full-size roof prism binocular. It is armored in two-tone dual density grey rubber. The easy-to-hold armor has embossed dimples on its gripping surfaces for a positive hold in wet weather. Thumb grooves molded into the bottom of the barrels position the hands for easy access to the smooth-acting ribbed focusing knob. Its 5.75” length is easy to handle, and its light weight won’t weigh you down during all-day birding. This is an easy-to-carry all-day/all-weather birding bino.

The close focus is 6’ – very good for a 10x binocular. This makes it a surprisingly good choice for observing butterflies, as well as close-in warbler, woodland, and backyard feeder birding.

Even with its excellent close focus capability, its 10x magnification, phase-coated prisms, and the high resolution and brightness of its fully-multicoated 42mm optics make it primarily a long-distance instrument for examining the details and colors of distant birds in open field, lake, and shore-side birding. That said, it is a surprisingly good performer across a wide range of observing conditions, from near to far, from bright sunlight to dim twilight.

Curvature of field and barrel distortion are very modest, and astigmatism is quite low. The result is images that stay usably sharp across most of the field. The sharp images combine with good color rendition and low chromatic aberration for a view that is easy on the eyes during extended observing sessions. Overall, this is an optically and mechanically very good binocular at a very reasonable price. It’s easy on the eyes, easy in the hands, and easy on the budget.

Features of this binocular . . .

  • Roof prism optics. H-body roof prism design with internal center focus. Top-quality BaK-4 prisms for high light transmission.
  • Large aperture fully multicoated optics. Large 42mm objective lenses gather substantial amounts of light for bright images in twilight or overcast conditions. The twilight factor is 20.49, well above the 17 recommended as a minimum for a low light binocular. Its multilayer antireflection coatings have very good light transmission for minimum light loss in dim conditions.
  • Phase coated optics. Phase-correcting roof prism coatings provide very high contrast and resolution. This is particularly visible when looking sunwards, where more color and detail are clearly visible in the shadowed areas of backlit or silhouetted birds.
  • Waterproof. O-ring sealed to be waterproof in all temperature and climate extremes. Designed to operate reliably from rainforest to desert.
  • Armor. Dual-density, dual-color grey rubber armor (dark grey dimpled gripping surfaces with softer-textured medium grey inserts at the front and rear of the barrels) absorbs noise and shock and provides a good grip when wet.
  • Twist-up eyecups. The rubber-rimmed eyecups twist counterclockwise to extend and clockwise to retract. There are stops at four heights to let you match the amount of eye relief to your eyesight.
  • Good eye relief. 12mm of usable eye relief allows only mildly vignetted views for those who must wear eyeglasses while observing due to severe astigmatism.
  • Very close focusing. Little more than one and a half turns of the very smooth and comfortably-large ribbed focus knob moves from an excellent 6’ close focus out to the horizon.
  • Rotary diopter correction. A variable diopter ring with clickstops on the right eyepiece allows you to match the binocular optics to your individual eyesight for a sharp image.
  • Wide neck strap. The comfortable wide woven neck strap makes the lightweight binocular even less of a burden to carry during all-day birding sessions.
  • Tripod adaptable. A standard 1/4”-20 thread socket for attaching an optional tripod adapter is located at the front end of the binocular’s center hinge. A thread-in plastic plate covers the tripod socket when not in use.
  • Supplied accessories. A soft case with a belt loop and a removable shoulder strap is standard. Also included are snap-in objective lens covers and an eyepiece rainguard.
  • Optical Type:
    The optical design of a binocular or spotting scope. A binocular can be either a porro prism (whose objective lenses are off-set and spaced further apart than the eyepieces) or a roof prism (whose objective lenses are in line with the eyepieces). A spotting scope can be either a porro prism or roof prism refractor or a catadioptric (a combination of lenses, mirrors, and prisms).
    Roof Prism
    Field of view:
    The field of view (FOV) is the amount of observable world one can see at any given moment.
    Field of view 1000 yards:
    314'
    Exit Pupil:
    The circular image or beam of light formed by the eyepiece of a telescope. To take full advantage of a scope's light-gathering capacity, the diameter of an eyepiece exit pupil should be no larger than the 7mm diameter of your eye's dark-adapted pupil, so that all of the light collected by the telescope enters your eye. (The eyepiece exit pupil diameter is found by dividing the eyepiece focal length by the telescope focal ratio.) Your eye's ability to dilate declines with increasing age (to a dark-adapted pupil of about 5mm by age 50 or so). For those in this age group, eyepieces with exit pupils larger than their eyes can dilate to simply waste their telescope's light-gathering capacity, as some of the scope's light will fall on their iris instead of entering their eye.
    4.2mm
    Relative Brightness:
    A number used to compare the brightness of binoculars or spotting scopes of similar magnification. The relative brightness is determined by squaring the diameter of the exit pupil. The larger the relative brightness number, the brighter the image.
    17.64
    Twilight Factor:
    A number used to compare the effectiveness of binoculars or spotting scopes used in low light. The twilight factor is found by multiplying the size of the objective lens (in mm) by the magnification and then finding the square root of that result. The larger the twilight factor, the more detail you can see in low light. A twilight factor of 17 or better if usually required for reasonable low light use.
    20.49
    Eye Relief:
    Eye relief is the distance from the last surface of the eye lens of an eyepiece to the plane behind the eyepiece where all the light rays of the exit pupil come to a focus and the circular image is formed, sometimes called the “Ramsden Disk.” This is where your eye should be positioned to see the full field of view of the eyepiece. If you must wear glasses because of astigmatism, you’ll usually need at least 15mm of eye relief or longer if you want to see the full field of view with your glasses on.

    A note on our eye relief figures: Quite often, our eye relief figures will differ from those of the manufacturer. This is because we measure the “usable” eye relief, while the manufacturers specify their usually-longer (but technically correct) “designed” eye relief.

    The eye lens of the eyepiece is normally recessed below the rubber eyeguard or rubber rim of the eyepiece to keep the lens from being scratched during use. An eyepiece might have a “designed” eye relief of 15mm (and the eye relief will truly measure 15mm from the eye lens to where the image forms). However, if the eye lens is recessed 3mm below the eye guard, the Ramsden Disk forms only 12mm above the eyepiece body (the 15mm “designed” eye relief, less the 3mm of eye relief made unusable by having the eye lens recessed into the body of the eyepiece). This “usable” eye relief of 12mm (measured from the rolled-down eyeguard – the closest point you can get your eye to the eye lens – to where the image forms) is the eye relief figure we would measure and list in this website.

    Why is it important to list the “usable” eye relief? For those people who don’t wear eyeglasses while observing, a few mm difference between the eye relief they expect from the manufacturer’s literature and the shorter eye relief they actually get in real life doesn’t mean a lot. They can simply move a little closer to the eyepiece to see the full field, and never realize that the eye relief is a little shorter than they expected. However, some people must wear eyeglasses while observing, because of severe astigmatism. These observers can’t move closer to the eyepiece if the eye relief is shorter than expected because their glasses get in the way. For these people, the real life “usable” eye relief is more important than the technically correct but sometimes not fully usable “designed” eye relief. We measure and list the actual usable eye relief so that people in the real world can pick the eyepieces that will work best for them.

    12mm
    Interpupillary Distance:
    55-74mm
    Close Focus:
    How close you can get to an object and still see a sharp image of it in your binocular or spotting scope is called the “close” or “near” focus
    6'
    Height:
    5.75"
    Armored:
    A binocular or spotting scope whose body is clad in rubber or polyurethane armor is said to be armored. Armor can be applied for looks, a better grip, noise-proofing, etc. An armored body does not guarantee that a binocular or spotting scope is waterproof, although most waterproof optics are armored.
    Yes
    Weight:
    The weight of this product.
    24 oz.
    Warranty:
    25 years
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    Swift - 10X42mm Ultra roof prism

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    Swift - 10X42mm Ultra roof prismImage showing binocular with all supplied accessories.
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    Our Product #: SW1042R
    Manufacturer Product #: 930G
    Price: $309.95  FREE ground shipping - Click for more info
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    MSRP: $399.95
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    This light-weight high power Swift Ultra binocular has all the good features you're looking for at a reasonable price. Fully-multicoated and phase-coated optics, an unusually good 6’ close focus, armor, waterproofing, and more . . .





    . . . our 34th year