JP7273642B2 - Image processing device and its control method and program - Google Patents

Description

The present invention relates to a technique for adjusting exposure during imaging.

HDR (High Dynamic Range) video signal systems such as ITU-R BT.2100 (Non-Patent Document 1), which have been proposed in recent years, can reproduce gradations in high-luminance areas with a contrast close to that of the subject. On the other hand, the peak brightness of the output monitor may change the reproducible brightness gradation. Therefore, when shooting and developing HDR video signals with a camera, if it is possible to check how the subject being shot will be reproduced on the final viewing monitor, it will be possible to reflect the user's drawing intentions. make it easier to Conventionally, as an exposure determination method for an image processing device that supports HDR, a method has been proposed in which the reference exposure at the time of shooting is determined based on the absolute brightness value obtained by converting the representative brightness value in the image based on the input/output characteristics of the output device. (For example, Patent Document 1).

JP 2018-56702 A

Recommendation ITU-R BT.2100-2 (07/2018)

In Patent Document 1, when the user wants to change the reference exposure according to the dynamic range of the shooting scene or the intention of drawing, the exposure range is grasped to be appropriately reproduced in the luminance reproduction range of the final output monitor. you can't. Also, when shooting with exposure bracketing to check the correct exposure settings, if the brightness range of the display device in the camera is different from the brightness range that can be reproduced on the output monitor for viewing, It is difficult to confirm whether the camera settings are appropriate from the displayed image.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a technique that allows a user to adjust exposure in consideration of the luminance range of a viewing monitor when shooting an image.

In order to solve this problem, for example, the image processing apparatus of the present invention has the following configuration. i.e.
An image processing device that presents information to a user for adjusting exposure of an imaging means,
detection means for detecting representative luminance values of bright and dark areas based on the luminance distribution of image data captured by the imaging means based on initial exposure settings;
setting means for setting a display dynamic range representing a target luminance range of a display device;
a comparing means for comparing an input dynamic range representing a luminance range captured by the imaging means with the display dynamic range;
determining an adjustable range of exposure using the representative luminance values of the bright and dark areas detected by the detecting means based on the result of the comparison by the comparing means; and providing a user interface for adjusting the exposure within the determined range. and processing means for presenting the

According to the present invention, it is possible for the user to adjust the exposure in consideration of the luminance range of the viewing monitor when shooting the video.

1 is a block configuration diagram of an image processing apparatus according to an embodiment; FIG. 4 is a flowchart showing a processing procedure of the image processing apparatus according to the embodiment; 4 is a flow chart showing a processing procedure of an exposure adjustment range determination unit; FIG. 5 is a diagram for explaining the processing contents of an exposure correction range determination unit; FIG. 5 is a diagram for explaining the processing contents of an exposure correction range determination unit; FIG. 5 is a diagram for explaining the processing contents of an exposure correction range determination unit; FIG. 4 is a diagram showing a display example of a user interface for exposure correction; A histogram showing the luminance distribution of the input image.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. It should be noted that the following embodiments do not limit the invention according to the scope of claims. Although multiple features are described in the embodiments, not all of these multiple features are essential to the invention, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same or similar configurations are denoted by the same reference numerals, and redundant description is omitted.

[First embodiment]
The present embodiment relates to an image processing apparatus that performs development processing corresponding to the HDR standard such as ITU-R BT.2100 and encodes a video signal on a captured image to record an image with a wide dynamic range. Therefore, it is assumed that the video signal shot and developed by this image processing apparatus will be reproduced and displayed on an external monitor compatible with the HDR standard. Furthermore, it is assumed that the internal display unit (rear liquid crystal panel, electronic viewfinder, etc.) for checking the image during shooting with this image processing apparatus may have a different luminance reproduction range from that of the external monitor.

FIG. 1 is a block configuration diagram of an image processing apparatus according to an embodiment, showing a configuration when applied to an imaging apparatus.

In FIG. 1, an optical system 101 includes a lens group including a zoom lens and a focus lens, an aperture adjustment device, and a shutter device. This optical system 101 adjusts the magnification, focus position, or amount of light of a subject image formed on the image sensor 102 . The imaging element 102 is composed of a photoelectric conversion element such as a CCD or CMOS sensor, and photoelectrically converts the light flux of the imaged object that has passed through the optical system 101, converts it into an electric signal, and outputs the electric signal. The A/D conversion unit 103 converts the video signal per pixel input from the image sensor 102 into a digital image with a predetermined number of bits (for example, 14 bits) and outputs the digital image.

The image processing unit 104 performs development processing on the output signal from the A/D conversion unit 103 . Specifically, the image processing unit 104 performs development processing including noise suppression, demosaicing, gradation conversion, color correction, contour compensation, etc. on the signal from the A/D conversion unit 103, and converts the luminance signal and the color signal into to generate Further, the image processing unit 104 can perform similar image processing not only on the signal output from the A/D conversion unit 103 but also on the image data read from the recording unit 110 .

The input image analysis unit 105 analyzes the signal level of the input image and generates evaluation values for controlling control parameters of the optical system 101 , imaging unit 102 and image processing unit 104 .

An assumed luminance reproduction range determination unit 106 determines a luminance range that can be reproduced when an HDR-compatible video signal recorded by the image processing apparatus is displayed on an external monitor as a user's target.

The exposure adjustment range determination unit 107 determines an exposure adjustable range for the scene being photographed based on the determination result of the assumed brightness reproduction range determination unit 106 and the evaluation value of the analysis result from the input image analysis unit 105. do.

The display processing unit 109 functions as an electronic viewfinder (EVF) by sequentially displaying video signals output from the image processing unit 104 on a display member such as a liquid crystal panel. The recording processing unit 108 has a function of recording the video signal output from the image processing unit 104, and may include, for example, an information recording medium such as a memory card equipped with a semiconductor memory. A user instruction unit 110 includes a touch panel and buttons, and is a user interface for the user to specify processing contents of the image processing apparatus such as exposure settings and development settings.

The system control unit 111 includes a CPU, a ROM storing programs executed by the CPU, and a RAM functioning as a work area for the CPU. The system control unit 111 is connected to each processing unit of the image processing apparatus of the embodiment, and controls the operation of the entire image processing apparatus via image signals and control signals.

Next, the processing flow of the image processing apparatus of this embodiment will be described with reference to the flowchart of FIG.

In S100, system control unit 111 determines the input dynamic range of the image processing apparatus.

Here, the input dynamic range indicates the luminance range of an object that can be obtained and reproduced by the image sensor 102 . The lower limit value Cmin (nits or cd/m ² ) of the input dynamic range corresponds to a state in which no light enters the image sensor 102, and Cmin=0 is always obtained regardless of the dynamic range setting. The upper limit value Cmax (nits or cd/m ² ) of the input dynamic range corresponds to subject luminance at which the imaging device is saturated. Also, in this embodiment, it is assumed that the brightness of a subject with a reflectance of 100% is 100 nits. For example, it is assumed that there are three levels of dynamic range settings, and the level of object luminance at which the imaging device is saturated is Cmax={200nits, 400nits, or 800nits}.

The input dynamic range is set by the user according to the dynamic range of the scene to be shot, or automatically set by the image processing apparatus based on the analysis result of the input image analysis unit 105 . When the input dynamic range is set, the system control unit 111 sets the aperture and shutter speed of the optical system 101 and the ISO sensitivity of the image sensor 102 so that the image sensor 102 is saturated at a saturation level corresponding to the input dynamic range. conduct.

In S101, the system control unit 111 controls the assumed luminance reproduction range determination unit 105 to set the assumed luminance reproduction range based on the user's instruction.

Specifically, the maximum luminance value Dmax (nits or cd/m ² ) and the minimum luminance value Dmin (nits or cd/m ² ) of the display dynamic range of the output monitor for viewing that the user ultimately assumes, the output Sets the HDR signal encoding method supported by the monitor (PQ (Perceptual Quantization), HLG (Hybrid Log-Gamma), etc.).

Note that the maximum luminance value Dmax, the minimum luminance value Dmin, and the encoding method referred to here are set by the user by operating the user instruction unit 110 . However, information for specifying various monitors (for example, manufacturer name, model name), maximum luminance value Dmax, minimum luminance value Dmin, (in some cases Further, the encoding method) may be stored in advance as a table, and the user may select one of them from the user instruction section 110 . Also, the information may be obtained from a network via a communication unit (not shown). Also, if the user does not set the final output monitor, the system control unit 111 sets the initial value. For example, it is assumed that the assumed brightness reproduction range setting unit sets information that the maximum brightness Dmax=600 nits, the minimum brightness Dmin=0 nits, and the HDR signal encoding method is PQ.

In S102, the system control unit 111 controls the optical system 101 and the image pickup device 102 to start photographing, thereby starting to capture an image.

In S103, the system control unit 111 controls the input image analysis unit 105, analyzes the signal level of the image output from the A/D conversion unit 103, and calculates the dynamic range of the shooting scene in the following procedure.

First, the input image analysis unit 105 divides an input image into a plurality of block regions and calculates the average luminance value of each block. Then, the input image analysis unit 105 creates a brightness histogram as shown in FIG. 8 based on the calculated average brightness value. Next, the input image analysis unit 105 refers to the created luminance histogram, and obtains the representative luminance value Smax (nits or cd/m ² ) of the bright portion of the shooting scene, the representative luminance value Smin (nits or cd/m 2 ) of the dark portion of the shooting scene, /m ² ), and the difference between Smax and Smin is set as the dynamic range of the shooting scene. Smax is the average luminance value of the upper luminance area LH in the luminance histogram, and Smin is the average luminance value of the lower luminance area LL in the luminance histogram. For LH and LL, a predetermined range shall be set in advance. Specifically, the average luminance value of the top 10% of the distribution indicated by the luminance histogram is LH, and the average luminance value of the bottom 10% is LL. It should be understood that the figure of 10% shown here is only an example. This is because the user may appropriately set or select from the user instruction section 110 .

In the above description, the representative luminance Smin, Smax is detected from the shooting scene. Alternatively, a user-desired area (for example, a person's face) in the shooting scene is set, and the luminance is obtained from the image within the set area. Also good.

In S104, the system control unit 111 controls the exposure adjustment range determination unit 107, refers to the outputs of the assumed brightness reproduction range determination unit 106 and the input image analysis unit 105, and determines the exposure adjustable range in the scene being photographed. to decide. Then, the exposure is adjusted within that range, and the imaging process is performed.

In S<b>105 , the system control unit 111 controls the image processing unit 104 to perform development processing on the output signal of the A/D conversion unit 103 .

In S106, the system control unit 111 controls the display processing unit 109 and the recording processing unit 108 to receive the output signal of the image processing unit 104 and perform processing related to display and recording. The display processing unit 109 displays incidental information such as the optical system of the imaging device, the imaging device, and development setting values at the time of shooting, and a histogram indicating image characteristics, in association with the output image of the development processing unit 104 . A recording processing unit 108 records the output image of the development processing unit 104 in association with incidental information during shooting.

Here, the maximum brightness that can be displayed by the display processing unit 109 may be lower than the maximum brightness of an external monitor that generates a video signal shot and developed by this image processing apparatus.

This is because the devices of the external monitor and the display processing unit 109 are different, and in addition, in order to suppress power consumption, control is performed to lower the display brightness in the display processing unit 109 during the imaging operation. there is Under such conditions, it is difficult for the user to determine whether or not to set the exposure while viewing the developed image displayed on the display processing unit 109 during imaging. Therefore, in this embodiment, in the exposure adjustment range determination unit 107, the user can change the exposure setting with respect to the reference exposure set at the time of shooting in consideration of the luminance display performance of the final output monitor and the encoding method of the HDR signal. Calculate the range and determine the information to display.

Next, with reference to the flowchart of FIG. 3 and the schematic diagrams of FIGS. 4, 5, and 6, processing details of the exposure adjustment range determination unit 107 under the control of the system control unit 111, which is a feature of the present embodiment, will be described. will be explained.

4, 5, and 6 are schematic diagrams showing an example of magnitude relationships among the input dynamic range, the assumed luminance reproduction range, and the luminance distribution information of the photographing scene.

In FIG. 3, in S200, S201, and S202, the exposure adjustment range determination unit 107 determines the input dynamic range Cmin, Cmax of the image processing apparatus, the assumed brightness reproduction range Dmin, Dmax of the final output monitor, the HDR signal encoding method, the shooting Input the luminance distribution information Smin, Smax of the scene.

In S203, the exposure adjustment range determination unit 107 refers to the luminance analysis result of the input image and determines the reference level Save (nits or cd/m2) for exposure adjustment. The reference value for exposure adjustment may be the average luminance value of a predetermined area in the center of the input image, or may be the average luminance value within a rectangular area in the image selected by the user.

In S204 to S209, the exposure adjustment range determination unit 107 determines the exposure adjustment range based on the assumed luminance reproduction range, input dynamic range, HDR signal encoding method, and luminance distribution information of the shooting scene.

First, in S204, the exposure adjustment range determination unit 107 compares the assumed luminance reproduction range and the input dynamic range, and if the assumed luminance reproduction range is equal to or greater than the input dynamic range, the process proceeds to S205. Also, if the assumed brightness reproduction range is less than the input dynamic range, the exposure adjustment range determination unit 107 advances the process to S206.

In S205, the exposure adjustment range determination unit 107 calculates the exposure adjustment amounts ΔEV+ and ΔEV- by Equations (1) and (2) so that the luminance distribution of the shooting scene does not exceed the input dynamic range.

Here, ΔEV+ indicates the upper limit correction amount (nits or cd/m ² ) that can positively correct the exposure with respect to the exposure adjustment reference level Save determined in S203. ΔEV− indicates the lower limit correction amount (nits or cd/m ² ) that allows negative correction of the exposure with respect to the exposure adjustment reference level Save determined in S203.

As shown in the schematic diagram of FIG. 4, the difference between the representative luminance value Smin of the dark part of the shooting scene and the minimum luminance level Cmin that the imaging device 102 can output is ΔEV-. Also, the difference between the representative luminance value Smax of the bright portion of the shooting scene and the maximum luminance level Cmax that can be output by the image sensor 102 is ΔEV+, ΔEV−=Smin−Cmin (1)
ΔEV+ = Cmax - Smax (2)

In S206 and S208, the exposure adjustment range determination unit 107 switches the exposure adjustment range setting method according to the encoding method of the HDR signal.

The exposure adjustment range determination unit 107 branches the processing to S207 if the encoding method of the HDR signal is the PQ method, to S209 if the encoding method of the HDR signal is the HLG method, and to S205 otherwise.

The HDR signal encoding method, the PQ method is the method described in Non-Patent Document 1 (p.5 TABEL4 Reference PQ OETF), and the HLG method is the method described in Non-Patent Document 1 (p.6 TABLE5 HLG Reference OETF). This is the encoding method described in . As another method, a log format encoding method is assumed as an example, but other encoding methods may be used.

In S207, the exposure adjustment range determination unit 107 determines the exposure adjustment range when the encoding method of the HDR signal is PQ.

In the PQ method, the brightness of the scene is encoded by associating it with the absolute luminance of the monitor display. , can be reproduced correctly when displayed on a monitor.

Therefore, the upper limit value ΔEV+ and the lower limit value ΔEV− of the exposure adjustment amount are determined by equations (3) and (4) so that the luminance distribution of the shooting scene does not exceed the assumed luminance reproduction range.

ΔEV+ indicates the upper limit correction amount (nits or cd/m ² ) that can positively correct the exposure with respect to the exposure adjustment reference level Save determined in S203. ΔEV− indicates the lower limit correction amount (nits or cd/m 2 ) at which the exposure can be negatively corrected with respect to the exposure adjustment reference level Save determined in S203.
ΔEV- = Smin - Dmin (3)
ΔEV+ = Dmax - Smax (4)

As shown in the schematic diagram of FIG. 5, ΔEV- is the difference between the representative luminance value Smin of the dark part of the scene and the minimum luminance level Dmin reproducible on the output monitor for viewing. Also, the difference between the representative luminance value Smax of the bright part of the shooting scene and the maximum luminance level Dmax reproducible by the output monitor for viewing is ΔEV+. Determines the exposure adjustment range when the encoding method of is HLG.

The HLG method performs encoding in which the maximum luminance of scene brightness is relatively associated with the maximum luminance of monitor display. Therefore, when the upper limit luminance value of the output monitor for viewing is low with respect to the input dynamic range of the image processing apparatus, the object in the dark to intermediate luminance range may become dark.

Therefore, in S209, the exposure adjustment range determination unit 107 applies a predetermined gain k(ΔL) corresponding to the difference between the input dynamic range and the assumed brightness reproduction range to correct the brightness value of the shooting scene.

In FIG. 6, Smin', Smax', and Save' are obtained by performing exposure correction on the representative luminance value Smin of the dark portion of the shooting scene, the representative luminance value Smax of the bright portion, and the reference exposure Save, respectively.

ΔL is obtained according to equation (5) using the upper limit value of the input dynamic range (maximum luminance level Cmax that can be output by the imaging unit) and the maximum luminance level Dmax that can be reproduced by the output monitor for viewing. The correction gain k is obtained according to Equation (6) using a predetermined coefficient α.
ΔL = Dmax - Cmax (5)
k = ^ΔLα (6)

Even in the case of the HLG method, if the image processing apparatus shoots and develops the image so that the luminance distribution of the photographed scene after exposure correction falls within the luminance range of the output monitor, it can be reproduced correctly when displayed on the monitor.

Therefore, in S210, the exposure adjustment range determination unit 107 adjusts the exposure using equations (7) and (8) so that the luminance distribution information Smin' and Smax' of the shooting scene after exposure correction does not exceed the assumed luminance reproduction range. Determine the upper limit value ΔEV+ and the lower limit value ΔEV- of the quantity.

ΔEV+ indicates the upper limit correction amount (nits or cd/m ² ) that can positively correct the exposure with respect to the exposure adjustment reference level Save′ determined in S209. ΔEV− indicates the lower limit of correction amount (nits or cd/m ² ) that allows minus correction of the exposure with respect to the exposure adjustment reference level Save' determined in S209.
ΔEV-=Smin'-Dmin' (7)
ΔEV+ = Dmax - Smax' (8)

As shown in the schematic diagram of FIG. 6, ΔEV− is the difference between the representative luminance value Smin′ of the dark part of the photographed scene after the reference exposure correction and the minimum luminance level Dmin reproducible on the output monitor for viewing. Also, the difference between the representative luminance value Smax′ of the bright part of the shooting scene after the reference exposure correction and the maximum luminance level Dmax reproducible by the output monitor for viewing is ΔEV+. end the processing of

The system control unit 111 presents a user interface or information related to the exposure adjustment range calculated by the exposure adjustment range determination unit 107 together with the development result via the display processing unit 109 . FIG. 7 shows an example of the display of the user interface presented by the display processing unit 109 here.

In FIG. 7, reference numeral 750 indicates a screen displayed by the display processing unit 109. FIG. Reference numeral 751 indicates an input image that is a captured image. A rectangular area 700 indicates a reference subject area for exposure adjustment in an input image, and a reference exposure level and a slider icon indicating an exposure adjustable range are drawn at the bottom of the image display screen.

Reference numeral 701 indicates the average luminance value of the rectangular area 700 . Reference numeral 702 is a bar indicating the width of the luminance distribution of the shooting scene, and reference numeral 703 (the range of the double-ended arrow) is the exposure adjustment range reproducible on the final output monitor (ΔEV− ~ΔEV+). This exposure adjustment range 703 is determined in consideration of the reproduction range of the final output monitor, as described above, and is a range different from the width of the exposure amount that can be adjusted by the image processing apparatus according to its specifications.

When the user performs an operation to adjust the exposure, the brightness distribution width bar 702 moves left and right, and serves as a guideline for the user to adjust the exposure. The bar 702 is movable only within the exposure adjustment range 703 .

In this embodiment, the bar 702 can be adjusted only within the range of the exposure adjustment range 703, but it may be adjusted beyond that width. This is because there are cases where it is desired to set a desired exposure even if overexposed highlights or blocked up shadows occur in some areas. At this time, for example, in addition to the display showing the bar 702 and the exposure adjustment range 703, an adjustable exposure range (for example, -3 steps to +3 steps) may be displayed according to the specifications of the image processing apparatus. In other words, the screen of FIG. 7 only needs to allow the user to recognize whether the current exposure setting can be reproduced on the final output monitor.

As described above, the exposure adjustment range 703 differs based on the results of the processing described with reference to FIGS. 3-6. In other words, even when the same scene is shot with the same input dynamic range, the exposure adjustment range 703 may differ if the final output monitor is different.

Further, the processing in the exposure adjustment range determination unit 107 is performed each time the imaging operation is updated in the imaging unit 102, but the display of the exposure adjustment range in the display processing unit 109 is updated, the brightness distribution of the shooting scene changes significantly, or at predetermined frame intervals.

In the above configuration, when the user operates the bar 702, the exposure for imaging is determined according to the operation. In addition, the user can perform an operation related to imaging, thereby obtaining an image that can reproduce high gradation on the monitor desired by the user.

As described above, according to the present embodiment, when generating a video signal compatible with the HDR standard, the user adjusts the exposure based on the assumed luminance reproduction range of the final output monitor and the signal level of the input image. You can grasp the range and adjust the exposure.

(Other examples)
Although the video signal conforming to the HDR standard has been described in the above embodiment, it is not necessarily limited to the HDR standard. INDUSTRIAL APPLICABILITY The present invention can be applied when there is a difference between the dynamic range of an image obtained by imaging and the dynamic range supported by the final display device.

The present invention supplies a program that implements one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and one or more processors in the computer of the system or device reads and executes the program. It can also be realized by processing to It can also be implemented by a circuit (for example, ASIC) that implements one or more functions.

The invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the claims are appended to make public the scope of the invention.

101... Optical system 102... Imaging unit 103... A/D conversion unit 104... Image processing unit 105... Input image analysis unit 106... Assumed luminance reproduction range determination unit 107... Exposure adjustment range determination unit 108... Recording processing unit 109 Display processing unit 110 User instruction unit 111 System control unit

Claims (9)

An image processing device that presents information to a user for adjusting exposure of an imaging means,
detection means for detecting representative luminance values of bright and dark areas based on the luminance distribution of image data captured by the imaging means based on initial exposure settings;
setting means for setting a display dynamic range representing a target luminance range of a display device;
a comparing means for comparing an input dynamic range representing a luminance range captured by the imaging means with the display dynamic range;
determining an adjustable range of exposure using the representative luminance values of the bright and dark areas detected by the detecting means based on the result of the comparison by the comparing means; and a user interface for adjusting the exposure within the determined range. and a processing means for presenting . The processing means
determining the range indicated by the input dynamic range as the adjustable range of exposure when the comparison result of the comparing means indicates that the display dynamic range is the same as or wider than the input dynamic range. 2. The image processing apparatus according to claim 1. 3. The image processing apparatus according to claim 1, further comprising setting means for setting which one of PQ (Perceptual Quantization) and HLG (Hybrid Log-Gamma) is used as an encoding method. The processing means
When the comparison result of the comparing means indicates that the display dynamic range is narrower than the input dynamic range and the PQ is set as the encoding method, the range indicated by the display dynamic range is , is determined as an adjustable range of exposure. The processing means
When the comparison result of the comparison means indicates that the display dynamic range is narrower than the input dynamic range and the HLG is set as the encoding method, the brightness detected by the detection means 5. The range in which exposure can be adjusted is determined from the corrected representative luminance values and the range indicated by the display dynamic range, by correcting the representative luminance values of the dark and dark areas. image processing device. 6. The image processing apparatus according to any one of claims 1 to 5, further comprising means for developing and recording the captured image based on the exposure adjusted within the adjustable range of exposure. . 7. The detector according to any one of claims 1 to 6, wherein said detector detects representative luminance values of said bright and dark portions from an image within a region set by a user in said image obtained by said imaging means. The image processing device according to . A control method for an image processing device for presenting information for adjusting the exposure of an imaging means to a user, comprising:
a detection step of detecting representative luminance values of bright and dark portions based on the luminance distribution of image data obtained by imaging with the imaging means based on initial exposure settings;
a setting step of setting a display dynamic range representing a target luminance range of a display device;
a comparison step of comparing an input dynamic range representing a luminance range captured by the imaging means with the display dynamic range;
determining an adjustable range of exposure using the representative luminance values of the bright and dark areas detected in the detecting step based on the result of the comparison in the comparing step; and providing a user interface for adjusting exposure within the determined range. A control method for an image processing apparatus, comprising: a processing step of presenting . A program that is read and executed by a computer to cause the computer to perform each step of the method according to claim 8.

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