6 Replies Latest reply on Feb 12, 2014 3:13 PM by Herbert2001

    Grayscale among color

    KenWK Level 1

      Hello! I do OK in Photoshop but as this question undoubtedly reveals, I'm no expert.


      I have book to reproduce with a page that looks like this:


      The client doesn't want to have to proof read and retypeset everything. The blue text at the top changes colors and is sometimes black. The black text at the bottom, the art lables and the horizontal rules will  be scanned 600 dpi on a document feeder, then straightened and placed in InDesign with a script that will plunk them all on the page and we'll tweak manually to ensure the position is OK. The color and gray scale images in the middle of the page will be done in a separate Photoshop file with no background.


      My question comes with the color and gray art in the middle. My first inclination was to have the gray scales separate from the color scans. But is that really necessary from a printing-on-a-press perspective?


      Hoping to keep just one image for the color and gray, in Photoshop I've tried cutting the grayscale images from the color to a new file, converting to grayscale and pasting back in to the color image. But instead of being shades of black (as I'd hoped) Photoshop converts them them CMYK values. Is there any way in Photoshop to get the gray scales "converted" to be shades of black within a CMYK image?


      Many thanks,


        • 1. Re: Grayscale among color
          DrStrik9 Level 4

          To put grayscale images in a color (CMYK) document, copy the grayscale image to a channel (paste in place), invert the channel, load it as a selection, and then on a layer, with only the BLACK channel activated in the channel palette, fill the selection with black. Now all other colors are present (CMY), but the grayscale image only shows up as it should, black only.

          • 2. Re: Grayscale among color
            KenWK Level 1

            Thanks for replying! I'm afraid I'm more than a little lost though, I've not dealt with color hardly at all, only grayscales.


            I'm starting with just the 1 color scan. I assume I need to cut what I want to turn into black only out of the color scan to a new document and make it gray scale.


            Do I create a new channel on which to paste in place the grayscale image?

            By invert the channel do you mean invert the selection or the actual color?

            I assume I need to make a new layer? How do I do the fill?


            Sorry to be so thick here and thanks again.

            • 3. Re: Grayscale among color
              DrStrik9 Level 4

              So by color, can I assume you mean RGB? I thought that since you're doing a color document for print, that your color model would be CMYK. -- ?  What I suggested will only work in a CMYK environment, because it has a black channel (RGB does not have a black channel). Whether a document shoud be RGB or CMYK will depend entirely on the printing process you intend to use. If it is a printing press (digital or traditional), then CMYK is what you want; if it is an inkjet printer, then RGB usually works fine, and the grayscale parts of the image can remain in RGB.


              Are you going to print this on a printing press (CMYK), or on an inkjet printer (RGB)?


              The typical scan is RGB. In Photoshop, convert the image to grayscale (Image > Mode > Grayscale), or alternatively, use an adjustment layer: Black & White, which allows you to adjust the darkness of various grays based on the colors in the original RGB image. This allows more control over the conversion from color to grayscale. However, for the image you attached, a straight grayscale conversion will probably be fine.  But if your document will be RGB, this conversion is probably not needed.


              If your document will be CMYK, then yes, create a new channel to contain the grayscale image (pasted in place). If RGB, then just make sure your "gray" image parts are balanced to gray via adjustment layer.


              I based my suggestion to invert the channel with the pasted grayscale image on the assumption that under Chanel Options, "Color indicates Masked Areas." In other words, what will be selected for black fill (in a CMYK document) will be white (seen as "clear" or "fillable" by the selection) in the channel. Invert the channel (without selection) if this is how your Channel Options are set up.


              CMYK only: Before you load the channel and fill a new layer with black, first fill that new layer with white. In the channel palette, turn off all color channels except black. Make your foreground color CMKY Black (C0, M0, Y0, K100). Select the black channel in the channel palette, and choose your new white layer in the layers palette. You can fill a the channel selection by choosing Edit > Fill, Foreground Color 100% Normal blending. Drop the selection, and you have a grayscale layer containing your grayscale image in black only, inside your CMYK document.


              I hope that's clearer than mud.  :+)

              • 4. Re: Grayscale among color
                KenWK Level 1

                Yes, printing in CMYK.


                I managed to get a new channel that had on it the grayscale image represented in black only. But, I've messed something up with the layers because I don't need the 2nd layer and InDesign doesn't "see" the material on the new channel.


                Going to keep trying things.


                Thanks so much for taking the time for that wonderfully in depth post for us clueless ones.

                • 5. Re: Grayscale among color
                  Herbert2001 Level 4

                  The way I would tackle this (since you mentioned 'printing on press' I take it this will be a press job):


                  1) black and white text/rules: scan at 1200ppi in monochrome (black and white). If you scan at 600ppi and rgb it will look fuzzy and print rubbish. Monochrome work like black text and line work will print fine if scanned at 1200ppi and only working in the K(ey) channel without a raster.


                  2) same for the blue text, - it looks like pure cyan to me (not sure). For best quality scan the blue text parts at 1200ppi in monochrome, and use pure cyan to print.


                  3) scan the images at 600ppi. When you scan images in a book (whether colour or greyscale) you must deal with the moire patterns that will/may occur during printing due to the print raster introduced in the original images when they were printed the first time around.


                  This will look horrible, thus you will need to fix this.


                  That is why you must scan them at 600ppi, and use gaussian blur to remove the print raster, and then scale them down to 300ppi before you use them.  There are lots of techniques to achieve this, but the point is that you will NOT print the images at 600dpi, but at most 300dpi for press work. Also for laser printers in general, btw.



                  The next step would be child's play in Photoline, since any layer can be any image mode in a layer stack. It means merely cutting the greyscale parts of the scan and converting those cut layers into a greyscale layers - done.


                  In Photoshop (presuming this is CMYK press work) you either:

                  A) use the method by DrStrik;


                  B) cut the greyscale images, paste as layers, and then convert those layers to smart objects. Open the smart object, and switch from rgb to greyscale mode. Save, and return to the main document.


                  Option (B) will only work in Photoshop CC - though I am unsure how Photoshop and InDesign deal with this type of placed Photoshop file. You should test and check the cmyk channels in InDesign's seperations preview palette how they come out: if the greyscale parts are pure black channel: great! If not: you may just want to place the greyscale images as a new layer.


                  Honestly, if you are going to bring it all into InDesign, I would forego all this complexity, and just split the image work into two separate files: one for colour work, one for greyscale work.


                  So, scan these two files:

                  1) one monochrome 1200ppi scan black and white for text and line work

                  2) one colour file with rgb at 600ppi for greyscale and colour work


                  Open the monochrome scan.

                  In Photoshop cut the parts for the black and white text in the 1200ppi scan. Save this as a layer for InDesign (tiff).

                  In Photoshop cut the parts for the magenta text in the 1200ppi scan.Save as a layer for InDesign (tiff). In InDesign, open the swatches palette, and drag the Cyan swatch on the blue text - the black will turn cyan, and it will print as such.


                  Both the texts are now printed at high resolution, and no fuzziness.


                  Then open the colour scan.

                  In Photoshop remove the print raster. Scale down to 300ppi.

                  Then create a version without the greyscale images. Save this as a coloured version for InDesign.

                  Then create a version with only the greyscale images. Convert to greyscale mode. Save this as a greyscale file for InDesign.


                  In Indesign you will now have four layers:

                  1) black 1200ppi text and line work

                  2) cyan 1200ppi text and line work

                  3) colour 300ppi images

                  4) greyscale 300ppi images.


                  And during all this, make sure the printed size of all layers remain identical when imported into InDesign.So no cropping or trimming in Photoshop!

                  • 6. Re: Grayscale among color
                    Herbert2001 Level 4

                    Like this (and make certain the white background is saved as transparent)