Contributors on this forum often state that they can focus closer than the manufacturers' specifications, but the attainable close focus is just as personal as the individual focus or dioptre setting and is also determined by the user's ability to accommodate.
I assume that manufacturers' specifications are calculated values for the shortest focusable distance where parallel "rays" (i.e. image at infinity) emerge from the eyepiece, so most users will be able to undercut this.
On another thread a desire for variable speed focus was expressed and I not only question the sense of this, but also the extremely close focus offered on many recent roof prism binoculars. There is a tendency to compete on specification figures that have no relevance to birding situations. I have an owned a 7x42 Swarovski SLC with 4 m close focus for the past 14 years and the number of times I have hit the bottom limit could be counted on the fingers of one hand. In fact, I can only recall one instance where I used around 2 m and that was to view a rare Swallowtail butterfly. For those applications, though, there are specialists (Pentax Papilo).
Much as I appreciate some of the qualities of my 10x42 EL SV, it does try to be an "Eierlegendewollmilchsau" (egg-laying woolly milking pig). A close focus of 1,5 m is as if I were viewing at 15 cm and even after reducing the IPD by 5 mm the view is uncomfortable because the objective spacing is still 66 mm (objective spacing larger than eyepiece spacing).
Holger Merlitz has often lamented the cost and complexity of many modern binoculars. Close focus capability demands either a more powerful focussing lens or longer travel. Both of these solutions are going to be detrimental to chromatic and spherical aberration over much of the focussing range.
In retrospect, Swarovski's "downgrading" of the 42 mm SLC HD to a close focus of 3,2 m made a lot of sense.
John
I assume that manufacturers' specifications are calculated values for the shortest focusable distance where parallel "rays" (i.e. image at infinity) emerge from the eyepiece, so most users will be able to undercut this.
On another thread a desire for variable speed focus was expressed and I not only question the sense of this, but also the extremely close focus offered on many recent roof prism binoculars. There is a tendency to compete on specification figures that have no relevance to birding situations. I have an owned a 7x42 Swarovski SLC with 4 m close focus for the past 14 years and the number of times I have hit the bottom limit could be counted on the fingers of one hand. In fact, I can only recall one instance where I used around 2 m and that was to view a rare Swallowtail butterfly. For those applications, though, there are specialists (Pentax Papilo).
Much as I appreciate some of the qualities of my 10x42 EL SV, it does try to be an "Eierlegendewollmilchsau" (egg-laying woolly milking pig). A close focus of 1,5 m is as if I were viewing at 15 cm and even after reducing the IPD by 5 mm the view is uncomfortable because the objective spacing is still 66 mm (objective spacing larger than eyepiece spacing).
Holger Merlitz has often lamented the cost and complexity of many modern binoculars. Close focus capability demands either a more powerful focussing lens or longer travel. Both of these solutions are going to be detrimental to chromatic and spherical aberration over much of the focussing range.
In retrospect, Swarovski's "downgrading" of the 42 mm SLC HD to a close focus of 3,2 m made a lot of sense.
John