Application profiles for hand-held binoculars

In a series of binocular reviews I have tried to characterize the binocular's performance by comparison with others of similar specifications. In order to display the performance spectrum as transparent as possible, I have introduced rankings for features like angle of field, image sharpness, stray light suppression, ghost image suppression, low light performance, image color rendition and quality of mechanical construction. The results were summarized in a table, containing relative scorings for each of these disciplines and a final score, computed as the sum of all single scores. I also added a warning not to take the final score too serious, instead to take the time to study the individual scores and find out the adequate field of application for each binocular.

Since then I have been receiving e-mails from readers with questions like: "I am hunter - which of these features are actually of relevance for me? Which binocular is best suited for my needs?" Obviously, there will always be a factor of individual taste involved when trying to find 'the best' instrument for one's needs, but in fact a couple of rules of general validity can be compiled to guide somebody onto the right track. To give a set of examples, I have been thinking about typical situations of binocular use by hunters, sailors, soldiers, astronomers, birders and travelers. Each application then produces a profile of features which should be present in the binocular of choice. In the following table, 'X' indicates a feature of rather high importance, while '0' means that this feature is of less importance (which doesn't mean it were useless) for that particular application:

  Angle of Image Stray Ghost Low Image Mechanical Central Example for
  field sharpness light image light color construction Focuser device in use:
Hunter 0 X X 0 X 0 X X Docter 8x50 Nobilem
Sailor 0 X X X X 0 X 0 Fujinon 7x50 FMTR-SX
Soldier X 0 X X 0 0 X 0 IOR-SA 7x40
Astronomer X X 0 X 0 X 0 0 Fujinon 10x50 FMTR-SX
Birder 0 0 X 0 0 X 0 X Docter 10x42 B/CF
Traveler X 0 0 0 0 X X X Nikon 8x32 SE

A few general remarks: Regarding the feature of 'image sharpness', I should add that, of course, every binocular of moderate quality provides a sharp image in the central region of the field. The binoculars I have tested were different in their image quality far outside the center. Therefore, 'image sharpness' in our case rather refers to the close to edge performance of the glass. The feature 'mechanical construction' essentially refers to resistance against water, dust and mechanical impact. The examples I have added in the last column should be seen as an orientation only. I am aware of the fact that other specifications are successfully employed in those applications. Generally, Porro prism types are preferred if a good stereoscopic view is of relevance and the extra weight (compared to roof prism binoculars) can be tolerated. In what follows I provide a few explanations to justify the conclusions shown in the table:

Hunter: The binocular is mostly used in low light. Stray light suppression is critical here, because the sky is usually brighter than the forest and a high contrast is required for the dark areas between the trees. These night glasses have narrow fields of view, therefore image sharpness close to the edge is of some relevance. Mechanical ruggedness is a must and the glass has to survive rainy weather and work under low temperatures. A central focuser is useful because objects at varying distances have to be put into focus.

Sailor: Water resistance is a must to avoid salty water corroding the instrument. It has to work under low light conditions, internal reflections (ghost images) have to be suppressed when the sun is causing bright reflections on the water surface. Again, image sharpness close to the edge is relevant because these night glasses have narrow fields of view. When the ship is rolling, a low magnification and large exit pupils come handy to achieve stable observation conditions.

Soldier: A wide field helps to control the area, and a high contrast is needed under any light conditions, for example when identifying a vehicle with headlights on. Therefore, ghost image and stray light suppression are mandatory. Although low light performance seems to be desirable, it would increase the weight of the device and also have a negative impact on the field of view (binoculars with large exit pupils are either heavy or show a narrow field). For night use, a modern army is employing electronically amplified goggles instead.

Astronomer: Stars immediately display any image degradation, therefore a wide but sharp to the edge image is desirable. To observe bright objects, ghost image suppression is of relevance. For a proper determination of star magnitudes, a neutral color rendition is required. A night glass is not always a good solution for the astronomer: Many people are living close to the cities so that the sky is never completely dark. A night glass would then amplify the residual background illumination so that faint objects would loose any contrast. Therefore, exit pupils of 4-5mm are often a better choice.

Birder: Birds often hide in shady places inside trees so that a stray light suppression is required for a good contrast. A neutral color rendition is needed as is a central focuser, because the objects of desire are rather close and frequently change position. For bird watching, a rather high magnification like 10x is wanted, therefore the device should preferably be of roof prism type with low weight.

Traveler: To enjoy the mountain views, the binocular should have a wide field of view and provide a neutral image color. Trekking and hiking can be tough so that the glass should be of solid construction but as light-weight as possible. Here one has to decide whether a roof prism (low weight but less stereoscopic view) or a small Porro prism is a better solution.

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