Focus v.

Pples. focused, -ing; in England commonly, but irregularly, written focussed, -ing. [f. prec. sb.]

  1.  trans. To draw to a focus; to cause to converge to or as to a focus.

1875.  Bedford, Sailor’s Pocket-bk., v. (ed. 2), 132. The catoptric system has the further advantage over the dioptric of facility in erection, at a distance from where skilled mechanics are obtainable, requiring less delicacy in putting up and focussing the light, and being less liable to be put out of adjustment by volcanic or other disturbances.

1881.  A. G. Bell, Sound by Radiant Energy, 2. A beam of sunlight was focussed into one end of an open tube, the ear being placed at the other end.

1895.  H. W. Burrows, Sound in Its Relation to Buildings, in Jrnl. R. Inst. Brit. Archit., II. 28 March, 353. One finds a flat wall a source of echo and annoyance, and promptly proceeds to build a curved one as a remedy, perhaps only to find that he has plunged into a worse difficulty by focussing and concentrating the sound into one or more points in his building.

  fig.  1807.  Uti Possidetis, xxx.

1862.  W. M. Rossetti, in Fraser’s Mag., LXVI. Aug., 195–6. If now, focussing our observation to a single point, we endeavour to arrive at some conclusion as to the general march of the fine art of the present day in all forms and all schools collectively, we feel at first almost overwhelmed by its immense variety.

1863.  J. Brown, Horæ Subs. (ed. 3), 80. This remarkable man, inferior to my father in learning, in intensity, in compactness and in power of—so to speak—focussing himself.

1888.  Burgon, Lives of Twelve Good Men, I. iii. 331. If you were suddenly to ask him [Charles Marriott] a profound question in Divinity, he could,—and with evident pleasure would,—instantly focus his thoughts, and proceed to explain.

  c.  intr. for refl. To converge to or as to a focus.

1863.  Thornbury, True as Steel, I. 148. Light flashing and focussing on armour.

1888.  L. Hearn, Chita: A Memory of Last Island, in Harper’s Mag., LXXVI. April, 764. Silent seconds passed; and still the eyes stared—flamed as if the life of the man had centralized and focussed within them.

  2.  To adjust the focus of (the eye, a lens, etc.).

1814.  W. Taylor, in Monthly Mag., XXXVIII. 214/1. Painted landscapes are divided into close or open, accordingly as the eye is supposed to be focussed for seeing the foreground or the distance.

c. 1865.  J. Wylde, in Circ. Sc., I. 66/2. Arrangements are required for focussing the lenses; or, in other words, to enable them to present the best possible image to the eye of the observer, by regulating their mutual distance.

1881.  Tylor, Anthropol., ii. 47. The eagle’s eyes are focussed to see small objects far beyond man’s range.

1885.  Illustr. Lond. News, May, 491/3. Austell focussed his eye-glass on his wife.

  absol.  1853.  Hand-bk. Photogr., 13. It is well in focusing to make the first adjustment by placing the lens midway, i. e., so as to stand one half out of the sliding tube.

1890.  Woodbury, Encycl. Photogr., 294. Focus upon some distinct object about 150 or 200 yards away.

  3.  To bring into focus; to bring (the image, etc.) to the proper focus.

1775.  S. J. Pratt, Liberal Opinions (1783), III. 8. Sir Charles Crazy focuss’d her through an opera-glass.

1858.  A B C of Photogr. (ed. 10), 57. Having focussed the right-hand view, half of the sensitive plate is first impressed, then the cap placed on the lens.

c. 1865.  J. Wylde, in Circ. Sc. I. 143/1. The image received on the ground-glass plate … is focussed in this form of camera, by moving or adjusting the lens contained in the tube.

1879.  Cassell’s Techn. Educ., III. 97. Too much care cannot be taken with this part of the work, as unless the picture be accurately focussed, it will appear blurred and ‘out of sharp.’