Olympus WideView 10x25 Porro Compact Binocular

Rating:
Summary: Fantastic
Review: Binoculars are great for concerts and outdoors

Rating:
Summary: Love it
Review: Binoculars are great for concerts and the outdoors.

Rating:
Summary: Excellent small binoculars
Review: Very nice portable/compact binoculars. Very high quality given the necessary tradeoffs between price of the lens/prism system and the size of the overall unit. I have had very bad experiences with other "compact" binoculars in the past. Either they seem to have bad optics, a narrow field of view, a high price tag, or all of the above. But this Olympus has really made a believer out of me.

The most important things I appreciate about these binocs are:

1. that they have a wide field of view (72 deg), which is useful in framing your subject and in compensating for the minor hand jitter attendant in a 10x mag binoc;

2. that they are reasonably small, portable and durable (they were effortless to carry with me when I went India earlier in the year, and very useful for spotting and identifying the birds wheeling over the city, and I didn't feel like the binocs were too fragile/expensive to carry around with me);

3. the field of view is flat and well-focused from edge to edge.

Additionally, it is worth mentioning that the tradeoff made in these binocs for optic quality versus total size (i.e. they are not among the smallest of the 'compact' binocs out there) was a good one. The bottom line is that you want the binocs to be small, but not to the extent that the image is poor. The porro prism design of this Olympus model adds a little bit of size to the binocs, but in return you get better optics. I have experienced many problems with other "compact" binocs in the inexpensive (<$) price range because of the common use of cheap roof prism systems. Convergence problems sometimes manifest themselves in roof prism binocs; recognizable as vertical misalignment of the left and right eye images. This causes eyestrain. This Olympus model gives me a very clear image across the entire field of view with no convergence problems whatsoever.

Rating:
Summary: Live and Learn
Review: Well, you live and learn. These binoculars are ergonomic, look great and will perform well in bright light. However, out in the woods at dusk, the image just isn't bright enough.

Binoculars all advertise a strange-looking formula, such as 7x35, 8x40 or 10x45. This formula is one of the key elements in judging a particular binocular, but few of us understand how to do so.

Most of us know that the first number in the formula is the magnification power, such as 7, 8 or 10. Something 1000 yards away looks as if it were only 100 yards away when viewed through a 10-power magnification. However, the amount of magnification is not an indicator of how good a binocular is. You pick the magnification based on your needs, keeping in mind that the higher the magnification, the more shake will appear in the image. The use of magnifications greater than 10 or so often requires a tripod for a steady image.

And, of course, the second number in the formula is the diameter of the objective lens in millimeters. The size of the objective lens controls the image received -- how much light is gathered. Also, larger objective lenses generally offer larger fields of view, or the width of the image that you see at a given distance, for example 350 feet at 1000 yards.

But it turns out that these two numbers can be used to calculate a third--and very important--one: the exit pupil diameter. The exit pupil diameter influences the brightness of the image that is transmitted to the eyes. All other things being equal, larger is better, especially in low light. In bright light, the viewer's pupils contract, making the size of the binocular's exit pupil less important. In these conditions, the brightness of the image is limited more by the size of the viewer's pupils. But in low-light situations, such as at dawn or dusk and in areas of heavy tree cover, the size of the exit pupil is very important.

The diameter of the exit pupil in millimeters can be calculated by the formula: D / P, where D is the diameter of the objective lens and P is the magnification power.

So a 10x25 binocular has an exit pupil of only 2.5mm, while a 10x50 binocular has an exit pupil of 5mm. This means that several times more light is passed to the eye with the latter than with the former. (Although the 10x50s will tend to be larger and heavier)

Keep in mind that there are additional variables that play a role, such as optical quality, coatings and prism type. With all other things being equal--say between a Tasco 7x42 and a Leica 7x42--the better quality binoculars will out-perform the lower quality ones. -- Scott Loban