Achieving RGB values; 3 & 252

<p>How best to achieve this (instructions from a stock agency):<br>

RGB Values<br /> RGB values should be limited with a black point of no less than 3 and white point of no more than 252. This<br /> should be performed at the end of Photoshop editing. In doing this, extreme highlight and shadow detail will<br /> retain all the information needed to print successfully. This also will limit the possibility of color banding and<br /> clipping within the file.<br>

Do I create a Curves adjustment layer and drag the top & bottom points to 3 & 252, or is there a better way to achieve the task?<br>

Thanks,<br>

Frank</p>

<p>as a side note.. i dont think it will make the file retain information or limit color banding.. all it do is that it make your black greyer (3 will make your black around 1-2% less black.. normally for a more secure way people use 5 vs 3) and the 252 will get the white to be printable, or at least have a certain amount of data to be printable.. again, 252 mean around 1-2% in ink.. people use to get this numnber at 245-250, so they could get around 3-4% ink on the white.</p>

<p>Basically, if your image have black and white clipping, you will kind of compress the histogram and create a *kind of* safety net, but if for example your highlight are blowned, you will only create a small amount of grey let say to fill the empty spot, witch instead of being pure white, will be 2-3% of grey.</p>

<p>Its like in the *old* days whe use to add a 1-2% of noise at the end of the process on the entire image to *fix* visually the histogram to make it more smooth looking.. dont do anything to the file itself, but make the histogram look smoother, and expereince user / histogram looking user like to see a smooth histogram ; )</p>