Replacing all instances of one color with another on a jpg image

[rayfritzu]

Hi, I'm afraid I'm a complete Photoshop newbee. I have a scanned jpg image (its actually a letter printed on headed paper) and I'm trying to make the background of the image completely white as it appears greyish following the scan. Someone advised me to try using the 'Threshold' command in Photoshop CS3 in order to do this, but the problem with this is that although it does indeed make the background white it also turns the header and footer of the image black and white where I need it to preserve the colour, and there also seems to a significant loss in the sharpness of the text in the image when adjusting Threshold.

Is there any facility in Photoshop CS3 that will allow me to effectively set it to find all instances of the greyish colour in the background and replace it with white?

Hope someone can spare the time to respond - any help would be greatly appreciated.

-Ray

 

[blpanther]

in some instances select - color range may help

 

[rayfritzu]

Thanks for your response - I seem to have worked around this by playing with the curve, levels and contrast and I think it looks a great deal better than it did.