Interchangeable lens, camera system, imaging apparatus, control method of camera system, and control method of imaging apparatus in which the size of an image circle varies inversely to the focal distance

1. A camera system having an interchangeable lens and an imaging apparatus which the interchangeable lens is attached to or removed from,

the interchangeable lens comprising

an optical system which is variable in focal distance and in which a size of an image circle varies by the focal distance, the image circle being an effective image formation region of an optical image of a subject, the optical system having a wide-angle end and a tele-angle end, the focal distance being shortest at the wide angle end,

a lens data storage unit which stores data indicating a correspondence between the focal distance and a value of the size of the image circle, and

a lens interface unit which sends data indicating the correspondence to the imaging apparatus,

the imaging apparatus comprising

an imaging unit which obtains image data from the optical image formed on an image pickup device via the optical system,

an apparatus interface unit which receives the data indicating the correspondence from the lens interface unit, and

an image processing unit which cuts out image data corresponding to the image circle among image data obtained by the imaging unit on the basis of the data indicating the correspondence received by the apparatus interface unit and subjects the cut-out image data to changing processing having a magnification based on the data indicating the correspondence received by the apparatus interface unit,

wherein the optical system comprises a plurality of lens groups and is configured such that the size of the image circle is inversely proportional to the focal distance throughout a variable range of the focal distance, the variable range extending from the wide-angle end of the optical system to the tele-angle end of the optical system,

and

wherein the variable range of the focal distance throughout which the size of the image circle is inversely proportional to the focal distance.

2. The camera system according to claim 1 , wherein the image processing unit cuts out image data in a relatively small region corresponding to a relatively high focal distance, and subjects the cut-out image data to changing processing having a relatively high magnification.

3. The camera system according to claim 1 , wherein the image processing unit performs the changing processing so that the number of pixels in the cut-out image data is a predetermined number of pixels regardless of the focal distance.

4. The camera system according to claim 1 , wherein a diameter of a lens group that is closest to the subject among the plurality of lens groups is smaller than in a case where an optical system is configured to maintain a size of an image circle within a variable range of focal distance, and

wherein the optical system of the interchangeable lens has a length that is shorter than in a case where an optical system is configured to maintain a size of an image circle within a variable range of focal distance.

5. The camera system according to claim 1 , wherein a relationship of the size of the image circle to the focal distance throughout the variable range of the focal distance is stored as a table in the lens data storage unit.

6. The camera system according to claim 1 , wherein a relationship of the size of the image circle to the focal distance throughout the variable range of the focal distance is stored as a linear equation in the lens data storage unit.

7. The camera system according to claim 1 , wherein a relationship of the size of the image circle to the focal distance throughout the variable range of the focal distance is stored as a curve equation in the lens data storage unit.

8. An imaging apparatus comprising:

an optical system which is variable in focal distance and in which a size of an image circle varies by the focal distance, the image circle being an effective image formation region of an optical image of a subject, the optical system having a wide-angle end and a tele-angle end the focal distance being shortest at the wide-angle end;

a data storage unit which stores data indicating a correspondence between a value of the focal distance and the size of the image circle;

an imaging unit which obtains image data from the optical image formed on an image pickup device via the optical system; and

an image processing unit which cuts out image data corresponding to the image circle among image data obtained by the imaging unit on the basis of the data indicating the correspondence and subjects the cut-out image data to changing processing having a magnification based on the data indicating the correspondence,

wherein the optical system comprises a plurality of lens groups and is configured such that the size of the image circle is inversely proportional to the focal distance throughout a variable range of the focal distance, the variable range extending from the wide-angle end of the optical system to the tele-angle end of the optical system,

and

wherein the variable range of the focal distance throughout which the size of the image circle is inversely proportional to the focal distance.

9. The imaging apparatus according to claim 8 , wherein the image processing unit cuts out image data in a relatively small region corresponding to a relatively high focal distance, and subjects the cut-out image data to changing processing having a relatively high magnification.

10. The imaging apparatus according to claim 8 , characterized in that the image processing unit performs the changing processing so that the number of pixels in the cut-out image data is a predetermined number of pixels regardless of the focal distance.

11. A control method of a camera system having an interchangeable lens and an imaging apparatus which the interchangeable lens is attached to or removed from,

the interchangeable lens comprising an optical system which is variable in focal distance and in which a size of an image circle varies by the focal distance, the image circle being an effective image formation region of an optical image of a subject, and the optical system having a wide-angle end and a tele-angle end, the focal distance being shortest at the wide-angle end, and

a lens data storage unit which stores data indicating a correspondence between the focal distance and a value of the size of the image circle,

the imaging apparatus comprising an imaging unit which obtains image data from the optical image formed on an image pickup device via the optical system,

the control method comprising:

cutting out image data corresponding to the size of the image circle among image data obtained by the imaging unit on the basis of the data indicating the correspondence received by the apparatus interface unit and the focal distance of the optical system; and

subjecting the cut-out image data to changing processing having a magnification based on the data indicating the correspondence,

wherein the optical system comprises a plurality of lens groups and is configured such that the size of the image circle is inversely proportional to the focal distance throughout a variable range of the focal distance, the variable range extending from the wide-angle end of the optical system to the tele-angle end of the optical system,

and

wherein the variable range of the focal distance throughout which the size of the image circle is inversely proportional to the focal distance.

12. The control method of the camera system according to claim 11 , wherein in the changing processing, image data in a relatively small region corresponding to a relatively high focal distance is cut out, and the cut-out image data is subjected to changing processing having a relatively high magnification.

13. The control method of the camera system according to claim 11 , wherein the changing processing is performed in the changing processing, so that the number of pixels in the cut-out image data is a predetermined number of pixels regardless of the focal distance.

14. A control method of an imaging apparatus including an imaging unit which obtains image data from an optical image formed on an image pickup device,

the imaging apparatus comprising an optical system which is variable in focal distance and in which a size of an image circle varies by the focal distance, the image circle being an effective image formation region of an optical image of a subject, and the optical system having a wide-angle end and a tele-angle end, the focal distance being shortest at the wide-angle end and

a lens data storage unit which stores data indicating a correspondence between the focal distance and a value of the size of the image circle,

the control method comprising:

cutting out image data corresponding to the image circle among image data obtained by the imaging unit on the basis of the data indicating the correspondence and the focal distance of the optical system; and

subjecting the cut-out image data to changing processing having a magnification based on the data indicating the correspondence,

wherein the optical system comprises a plurality of lens groups and is configured such that the size of the image circle is inversely proportional to the focal distance throughout a variable range of the focal distance, the variable range extending from the wide-angle end of the optical system to the tele-angle end of the optical system,

and

wherein the variable range of the focal distance throughout which the size of the image circle is inversely proportional to the focal distance.

15. The control method of the imaging apparatus according to claim 14 , wherein in the changing processing, image data in a relatively small region corresponding to a relatively high focal distance is cut out, and the cut-out image data is subjected to changing processing having a relatively high magnification.

16. The control method of the imaging apparatus according to claim 14 , wherein the changing processing is performed in the changing processing, so that the number of pixels in the cut-out image data is a predetermined number of pixels regardless of the focal distance.

17. A control method of an imaging apparatus which obtains image data from an optical image formed on an image pickup device,

the imaging apparatus comprising an optical system which forms an optical image on the image pickup device and which is variable in focal distance and in which a size of an image circle varies by the focal distance, the image circle being an effective image formation region of an optical image of a subject, and the optical system having a wide-angle end and a tele-angle end, the focal distance being shortest at the wide-angle end,

the control method comprising:

cutting out image data in a relatively small region corresponding to a relatively high focal distance; and

subjecting the cut-out image data to changing processing having a relatively high magnification,

wherein the optical system comprises a plurality of lens groups and is configured such that the size of the image circle is inversely proportional to the focal distance throughout a variable range of the focal distance,

and

wherein the variable range of the focal distance throughout which the size of the image circle is inversely proportional to the focal distance.

18. The control method of the imaging apparatus according to claim 17 , wherein the changing processing is performed in the changing processing, so that the number of pixels in the cut-out image data is a predetermined number of pixels regardless of the focal distance.