US3629490A
Expired / Lapsed
US
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Method for electronic color correction
Assignee: RUDOLF HELL KG
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Filing: 1969-04-09
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Granted: 1971-12-21
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Expires: 1989-04-09
Abstract
Abstract A method for the electronic color correction of an electrical signal representing a color record employing a secondary correction signal derived by difference formation from a primary color separation signal to be corrected and a primary color correction signal of the same grey gradation, wherein the secondary correction signal disappears for grey tones, and in which the color separation signal to be corrected and the signals to be used for the difference formation are transformed according to respective different preferably nonlinear functions lying between logarithmic and linear functions, with the curve of the color separation signal to be corrected more closely approaching a logarithmic function and the curve of the signals to be used for difference formation more closely approaching a linear function.
Inventors
- 👤 Hans Keller
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 19:56
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/46; H04N1/56; H04N1/60
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
179 words
A method for electronic color correction in the production of colored reproductions of colored originals, by the use of respective electrical primary color separation signals, in which a secondary correction signal, which disappears for gray tones, is formed from an uncorrected primary color separation signal; and another signal of the same gray contrast containing color correction information, by forming the difference, comprising the steps of transforming the respective primary color separation signals concerned, which are proportional to the respective colors of the colored original, and the signals to be used for the difference formations according to respective, different, preferably nonlinear functions lying between a linear and a logarithmic function, effecting transformation of the respective primary color separation signals according to functions more closely approaching a logarithmic function, effecting transformation of the respective signals to be used for the difference formations according to functions more closely approaching a linear function, combining a selected pair of said last-mentioned signals to produce a secondary correction signal, and combining a transformed primary color separation signal with at least one such secondary correction signal.
Claim 2
Independent Claim
179 words
A method for electronic color correction in the production of colored reproductions of colored originals, by the use of respective electrical primary color separation signals, in which a secondary correction signal, which disappears for gray tones, is formed from an uncorrected primary color separation signal; and another signal of the same gray contrast containing color correction information, by forming the difference, comprising the steps of transforming the respective primary color separation signals concerned, which are proportional to the respective colors of the colored original, and the signals to be used for the difference formations according to respective, different, preferably nonlinear functions lying between a linear and a logarithmic function, effecting transformation of the respective primary color separation signals according to functions more closely approaching a logarithmic function, effecting transformation of the respective signals to be used for the difference formations according to functions more closely approaching a linear function, combining a selected pair of said last-mentioned signals to produce a secondary correction signal, and combining a transformed primary color separation signal with at least one such secondary correction signal.
Claim 3
Dependent Claim
64 words
A method according to claim 1, comprising deriving a first secondary correction signal predominantly for the light color tones and a second secondary signal predominantly for the dark color tones, and transforming the color separation signals participating in the difference formation for deriving the second secondary correction signal according to functions with less difference than those employed in deriving the first secondary correction signal.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-12-20 | 1975-06-21 | 1975-12-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-12-20 | 1979-06-21 | 1979-12-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-12-20 | 1983-06-21 | 1983-12-21 | $7700.00 | Window Closed / Lapsed |