Abstract: A virtual reality instrument measures the refraction and aberrations of the eye in an automatic way, and includes a portable part which is a virtual reality headset foreseen of a detailed screen per eye and at least one background screen, both virtual. The detailed screen has a resolution multiple times the foveal resolution of the eye and the background screen has the resolution similar to the peripheral resolution of the eye. The virtual reality instrument also includes at least one pupil camera, a system to manipulate the phase of the light coming from the detailed screen, a wavefront sensor and light source to measure the wavefront using a wavelength of at least 400 nm.

Abstract: Virtual reality instrument to measure the refraction and aberrations of the eye in an automatic way. Virtual reality instrument to measure the refraction and aberrations of the eye in an automatic way consisting of a portable part which is a virtual reality headset foreseen of a detailed screen (9) per eye and at least one background screen (19), both virtual, where the detailed screen has a resolution multiple times the foveal resolution of the eye and the background screen has the resolution similar to the peripheral resolution of the eye.

Abstract: Electron donor compounds of the formula I are effective to reduce non-diffusing reducible color providing compounds which when reduced release under the photographic development conditions a diffusible dye.R.sup.1 (--L.sup.1 .dbd.L.sup.2).sub.n --NH--SO.sub.2 --X (I)in whichL.sup.1, L.sup.2 represent methine groups which may be part of a carbocyclic or heterocyclic ringR.sup.1 represents --OR.sup.2, --SR.sup.2 or --NHR.sup.3R.sup.2 represents H or a hydrolysable groupR.sup.3 represents H, alkyl, aryl, acyl including a group that together with L.sup.1 completes a ringn=1 or 2X represents a non-colored organic group.

Abstract: Photographic color elements are described wherein one of the emulsion layers comprise a 4-phenylazo-2-pyrazolin-5-one coupler, the phenylazo group of which carries a p-alkoxy group of the formula:--O--Alk--X--Rwherein:Alk represents a straight-chain or branched-chain alkylene group, which may carry an aryl substituent,X represents a linking group, andR represents an aryl group.

Abstract: A compound of the following formula and use of this compound in a photographic material and a photographic diffusion transfer process for the production of color images: ##STR1## wherein R represents a hydrogen atom or an alkyl group with 1 to 4 C atoms;A represents an oxyalkylene group, such as --CH.sub.2 --CH.sub.2 --O--;n represents 1 or 2;X represents a residue of a dye or a dye precursor, which either directly or by means of an intermediate link Z is linked to the SO.sub.2 -group;Z represents an alkylene group of 1 to 6 C atoms, an arylene group, or a heterocyclic group, which is linked to the residue X either directly or by means of --O--, --S--, --SO.sub.2 --, --NR-- (R being hydrogen or an alkyl group), --CO--, --CO--NH--, or --SO.sub.2 --NH--;R.sup.1 represents --OR.sup.2, --SR.sup.2 or ##STR2## R.sup.2 being hydrogen, an alkyl group with 1 to 22 C atoms, a cycloalkyl group or an aryl group wherein said alkyl, cycloalkyl and aryl groups may be further substituted, R.sup.