You can find specific information on which cameras are supported in your installed release of Capture One in the release note that comes with the installation files.
RAW file support
Capture One 4.8.3 DB supports RAW files from the following digital backs/cameras:
Phase One: P 65+, P 45+, P 40+, P 30+, P 25+, P 21+, P 20+, P 45, P 30, P 25, P 21, P 20, H 25, H 20, H 10, H 101, H 5, LightPhase
Mamiya: M31, M22, M18
Additionally Capture One 4.8.3 / 4.8.3 PRO supports RAW files from the following digital backs/cameras:
Canon: 1Ds Mark III, 1D Mark III, 1D Mark II N, 1Ds Mark II, 1D Mark II, 1Ds, 1D,
5D Mark II, 5D, 50D, 40D, 30D, 20D, 10D, 500D/Rebel T1i, 450D/Rebel XSi, 400D/Rebel XTi, 350D/Rebel XT, 300D/Rebel, 1000D, D60, D30, Pro 1, G10, G9, G6, G5, G3, G2
Epson: R-D1s, R-D1
Fuji: S5 Pro, S3 Pro, S2 Pro
Konica Minolta: Alpha 5 D / Maxxum 5 D / Dynax 5 D, Alpha 7 D / Maxxum 7 D / Dynax 7 D, A1, A2
Leica: M9, M8, D-LUX 4, Digilux 3, Digital Module R for R8 and R9 cameras
Mamiya: MZD, ZD Back
Nikon: D3X, D3, D2Xs, D2X, D2Hs, D2H, D1X, D1H, D700, D300, D200, D100, D90, D80, D70s, D70, D60, D50, D40X, D40
Olympus: E-620, E-3, E-520, E-510, E-420, E-410, E-500, E-1, E-10, E-20, E-30, E-330, E-300, E-400, C- 7070, C-8080
Pentax: K20D, K10D, K200D, K110D, K100D Super, K100D, K2000/K-m, *istDL2, *istDL, *istD, *istDS2, *istDS
(Only PEF files supported)
Sony: DSLR-A900, DSLR-A700, DSLR-A350, DSLR-A300, DSLR-A200, DSLR-A100, DSC-R1
Adobe: DNG (raw DNG support only). The DNG support is not optimized for specific cameras.
Tethered camera support
Capture One 4.8.3 PRO/DB has tethered support for the following digital backs/cameras:
Phase One: P 65+, P 40+, P 45+, P 30+, P 21+, P 25+, P 20+
P 45, P 30, P 25, P 21, P 20, H 25, H 20, H 101, H 10, H 5, LightPhase
Mamiya: M31, M22, M18
Additionally Capture One 4.8.3 PRO has tethered support for the following cameras:
Canon: 1Ds Mark III, 1D Mark III, 1D Mark II N, 1Ds Mark II, 1D Mark II,
5D Mark II, 5D, 40D, 30D, 20D, 450D/Rebel XSi, 400D/Rebel XTi, 350D/Rebel XT, 1000D
Nikon: D3X, D3, D700, D300, D200, D90, D80, D60, D40x, D40