referring now to the drawings , and in particular to fig1 there is illustrated a block diagram of a white balance circuit of a color video camera . in this embodiment , 1 is a lens for receiving an optical image from an object . two is a iris controlled by a signal level detector described hereinafter for varying exposure of an optical image from the lens 1 . three is an image pick - up device such as a ccd ( charge coupled device .) four is an automatic gain control circuit ( agc ) controlled by a signal level detector 10 described hereinafter for amplifying output signals from the image pick - up device . five is a matrix circuit for separating an output of the agc 4 into r ( red ), g ( green ) and b ( blue ) color signals . six , seven and eight are white balance amplifiers supplied with the r , g and b color signals , respectively . the gain of the white balance amplifier 7 , supplied with the color signal g , is maintained at a predetermined level . the gain of the white balance amplifiers 6 and 8 are controlled by a microprocessor based controller 12 described hereinafter . nine is a signal processing circuit for generating a video signal . the signal level detector 10 described above includes a wave detector . the signal level detector 10 integrates each amplitude level of the color signals r , g , b when an amplitude level of the color signal g is within a predetermined range . in this case , a luminance signal can be used instead of the color signal g . color difference signals can be used instead of color signals r and b . the predetermined range of the amplitude of color signal g is set up by the microprocessor 12 . eleven is a sensor for detecting position of the iris 2 and for outputting position data to the micro processor 12 . the position data is used by the microprocessor 12 to represent how much light can pass through the iris 2 . as position sensor 11 , a hall effect device may be used , for example . other position sensing mechanisms may equally well be used . twelve is a microprocessor for calculating the most suitable white balance control data in accordance with the output of the signal level detector and the position data of the iris 2 . referring to fig3 a calculating method for white balance data in microprocessor is described hereinafter . fig3 represents the color signal g within a duration of one horizontal scanning period . s h and s l are upper and lower slice levels of a limiter ( not shown ) set up by the microprocessor 12 , respectively . for example , the limiter is established in the signal level detector 10 . when the amplitude level of the color signal g is more than s h or less than s l , the microprocessor 12 controls the signal level detector 10 to inhibit each integrating operation of the amplitude levels of the color signals r , g , b . namely , integration is inhibited in the marked areas 1 and 2 in fig3 . when the amplitude level of the color signal g is between s l and s h , the microprocessor 12 controls the signal level detector 10 to carry out each integrating operation of the amplitude levels of the color signals r , g , b . referring to fig3 the areas shaded with oblique lines are integrated . then , the amplitude level of each color signal is integrated in the signal level detector 10 , and integrating data is output to the microprocessor 12 . the microprocessor 12 changes the upper and lower limits of the slice levels s h , s l respectively , to generate two sets of integrating data which are described hereinafter . the upper limit s h is set up to eliminate a saturated part of the output of the image pick up device . this is because accurate color information is not included in the saturated part of the outputs of the image pick up device . the lower limit s l is set up at about 5 % to 10 % of the integral value of one whole image where s l is zero . as explained above , the integral value for the high luminance portion is based on the integral calculation of the color signals where the color signals are between the upper and lower limits , s h and s l . the upper limit s hm is set up to the lower level s l which is set up in high luminance portion . the lower limit s lm is set up to zero . namely , except for the high luminance portions described above ( s h ˜ s l ), the signal level detector 10 integrates the amplitude level of each color signal r , g , b so as to obtain a integrated value of middle luminance portions . according to this embodiment , a method for obtaining the most suitable white balance data is described as follows . the microprocessor 12 generates the most suitable white balance control data d h and d m in accordance with the integrated values of the high luminance portion and middle luminance portion of the color signals r , g and b respectively . moreover , the microprocessor 12 sets up white balance data d s corresponding to the previous color temperature of outdoors . the white balance data d s are compared to white balance data d h , d m . for example , the white balance data d s is set at a color temperature of about 5800 ± 500 k . microprocessor 12 determines whether it is outdoors or indoors , based upon the position information of the iris which corresponds to the surrounding illuminance . this process is illustrated in fig4 . for example , microprocessor 12 inspects the position of the iris to determine an illumination value at step 20 . it determines that it is an outdoor image at step 22 when the illuminance is more than a particular threshold , e . g ., 800 lux . it determines , at step 24 , that it is an indoor image when the illuminance value is less than a second threshold , e . g ., 500 lux . it determines that it is same as before ( outdoor or indoor ) at step 26 when in between these values . if the image is determined by the above process to be an outdoor image , that is an image illuminated by sunlight , microprocessor 12 carries out the following process . those skilled in the art will appreciate that the order of the steps below may be interchanged without departing from the invention . 1 . when white balance control data d h and / or d m is near the color temperature 5800 k at step 30 , the process chooses the white balance control data which is closer to the color temperature at step 34 . 5800 k is used because the color temperature 5800 k is the center of color temperature outdoors . if the data obtained is near the color temperature 5800 k , it is very probable that the image is an outdoor image . 2 . when white balance control data d h and d m are at both sides of the color temperature 5800 k ( except when condition 1 is satisfied ) at step 36 , it is highly probable that the video camera is shooting a mixed scene . for example , the scene could include bright sunlight having low color temperature and shade having high color temperature ( for example , at sunset on a fine day ) or a mixture scene of blue sky and red ground . therefore , if one of white balance control data d h and d m is selected and used , the resulting image will be too red or too blue . to avoid this result , an average of d h and d m is used as white balance data at step 40 . 3 . when both white balance control data d h and d m are on the same side of the color temperature 5800 k at step 36 , the video camera is very likely to be shooting either a shade scene or bright sunlight scene having low color temperature . in this case , the one of the white balance control data d h and d m which is closer to the color temperature 5800 k is selected as a white balance data at step 42 . on the other hand , if the microprocessor 12 determines that it is an indoor scene based upon the illuminance values according to the process above at step 24 , it selects one of white balance control data d h and d m which is closer to the present white balance data at step 44 . in the above described system , white balance data are obtained based on the shot image . therefore , if the image includes a large colored object or very bright object with color temperature different from the surrounding one ( like a tv screen ), the camera is not adversely affected . even if bright sunlight and shade co - exist in one image , optimum white balance can be obtained . fig2 shows another embodiment according to the present invention . in this second embodiment , the present invention is applied to a digital video camera . in fig2 elements common to fig1 have same reference numbers and explanation of those elements will be omitted . in fig2 an image of an object passes through lens 1 and iris 2 for controlling exposure and is focused on a surface of an image sensor 3 . the output of image sensor 3 is amplified by automatic gain control amplifier 4 and then converted to a digital signal by analog - to - digital converter 13 . the output of analog - to - digital converter 13 is supplied to a signal processing circuit 9 which produces a video signal in a desired form . the output of analog - to - digital converter 13 is also sent to a signal level detector 10 which integrates each color video signal r , g and b respectively . this integration calculation is controlled by a microprocessor 12 . the calculation is done based on the luminance level as done in the first embodiment . the integral values of each color video signal are then sent to microprocessor 12 . sensor 11 sends position information of iris 2 to microprocessor 12 . microprocessor 12 calculates the optimum white balance data according to the integral values of each color video signal and the position information of iris 2 . this calculation of the optimum white balance data is the same as shown in the first embodiment . finally , microprocessor 12 controls signal processing circuit 9 according to the optimum white balance data so that proper white balance is achieved by signal processing circuit 9 . a variety of modifications are possible to which the present invention , and thus the invention is not limited to these particular embodiments shown in this specification .