An image pickup apparatus, comprising: an image sensor to perform photoelectric conversion on incident light to generate an electric signal, the image sensor including a plurality of non-overlapping focus detection regions (290, 210, 230, 250, 270) each comprising image pickup pixels and focus detection pixels, the plurality of non-overlapping focus detection regions being separated from each other by a further region comprising only image pickup pixels; the focus detection pixels comprising at least first pixels (410; 430; 450; 470) and second pixels (420; 440; 460; 480), and each of the first and second pixels comprising: a lens having an optical axis (Ll), a first light receiving element configured to convert light from the lens into an electric signal, a second light receiving element configured to convert light from the lens into an electric signal, and an element separation area between the first light receiving element and the second light receiving element; each image pickup pixel comprising: a lens having an optical axis (Ll), and a third light receiving element configured to convert light from the lens into an electric signal, wherein the image pickup pixel does not include light receiving elements separated by an element separation area, wherein: the optical axis of the lens of the first pixel is offset from a center of the element separation area of the first pixel; the optical axis of the lens of the second pixel is offset from a center of the element separation area of the second pixel; and within each of the focus detection regions the image pickup pixels are disposed between the focus detection pixels; wherein within each of the focus detection regions the image sensor provides a two dimensional array of pixels formed from a two dimensional array of the image pickup pixels and a two dimensional array of the focus detection pixels, the image pickup pixels being disposed such that, in each of the two dimensions, each focus detection pixel is separated from an adjacent focus detection pixel by an image pickup pixel; wherein within each focus detection region, an orientation of the first and second light receiving elements within the first and second pixels is dependent on a relative location of the focus detection region within the image sensor. an image sensor to perform photoelectric conversion on incident light to generate an electric signal, the image sensor including a plurality of non-overlapping focus detection regions (290, 210, 230, 250, 270) each comprising image pickup pixels and focus detection pixels, the plurality of non-overlapping focus detection regions being separated from each other by a further region comprising only image pickup pixels; the focus detection pixels comprising at least first pixels (410; 430; 450; 470) and second pixels (420; 440; 460; 480), and each of the first and second pixels comprising: a lens having an optical axis (Ll), a first light receiving element configured to convert light from the lens into an electric signal, a second light receiving element configured to convert light from the lens into an electric signal, and an element separation area between the first light receiving element and the second light receiving element; a lens having an optical axis (Ll), a first light receiving element configured to convert light from the lens into an electric signal, a second light receiving element configured to convert light from the lens into an electric signal, and an element separation area between the first light receiving element and the second light receiving element; each image pickup pixel comprising: a lens having an optical axis (Ll), and a third light receiving element configured to convert light from the lens into an electric signal, wherein the image pickup pixel does not include light receiving elements separated by an element separation area, a lens having an optical axis (Ll), and a third light receiving element configured to convert light from the lens into an electric signal, wherein the image pickup pixel does not include light receiving elements separated by an element separation area, the optical axis of the lens of the first pixel is offset from a center of the element separation area of the first pixel; the optical axis of the lens of the second pixel is offset from a center of the element separation area of the second pixel; and within each of the focus detection regions the image pickup pixels are disposed between the focus detection pixels; wherein within each of the focus detection regions the image sensor provides a two dimensional array of pixels formed from a two dimensional array of the image pickup pixels and a two dimensional array of the focus detection pixels, the image pickup pixels being disposed such that, in each of the two dimensions, each focus detection pixel is separated from an adjacent focus detection pixel by an image pickup pixel; wherein within each focus detection region, an orientation of the first and second light receiving elements within the first and second pixels is dependent on a relative location of the focus detection region within the image sensor.