WES DEASON wrote:
Hello everyone. I'm just trying to get a better understanding of converting images from RGB to CMYK. I know that this is the ideal mode for images that will be intended for print but I've also read that this is no longer necessary. Is this true?

This is a really tricky question.  To be able to view an accurate color gamut, absolutely, convert your images to CYMK as soon as you open them, and make all color corrections in CYMK.  Now that's for full accuracy, keeping in mind that you keep your system calibrated, which needs to be done every 3 months or so and are really picky about your work.  Now, for most people who print at home, or even send your work out to a lab to be printed, you don't need too because most printer drivers convert pretty accurately.  So, is it still necessary, I'd say yes, if you really want to be accurate with your color.  But for the most part, most people don't need to convert.

Legacys 7 wrote:
Not for ink jet printers. In most cases, it's Adobe 98. The only time that I seen or use CMYK is for when I send pdf files out to a high end printing company that will print out my business cards. You have to convert it to a CMYK for that.

If you are having your images printed, you are MUCH better off having the printer convert the images to CMYK. They know their equipment and what settings are needed. If you convert and don't like the color on the proofs, you will probably end up paying for color corrections. All programs that convert do not do it the same, and some colors are better than others on different softwares. Converting to CMYK and then trying to evaluate it on an RGB monitor is not a great idea unless you understand CMYK, and can visualize screen builds.

J O H N  A L L A N wrote:
I believe that's (CMYK versus RGB) only true if doing offset printing. During the 90s I would do my own separations sometimes for magazine publishing - which is offset.

Like 'giclee', the word 'offset' doesn't really mean anything anymore. Most of the time you hear that these days it's digital offset, which is just a glorified drylab. Its usually a really good drylab, but it's still a drylab.

I've had some books printed, and they always use CMYK. However, I've never worked with  'real' printer that didn't offer to do it for me, usually at a reasonable rate. I recommend letting them handle it, so you can complain about it if its wrong when you get your proofs. If you do it yourself, assuming you're not awesome at it, there's nobody to blame if it isn't perfect, even if it's not your fault.

Essential Image wrote:

If you are having your images printed, you are MUCH better off having the printer convert the images to CMYK. They know their equipment and what settings are needed. If you convert and don't like the color on the proofs, you will probably end up paying for color corrections. All programs that convert do not do it the same, and some colors are better than others on different softwares. Converting to CMYK and then trying to evaluate it on an RGB monitor is not a great idea unless you understand CMYK, and can visualize screen builds.

That's not true. A couple of things. I understand CMYK very well. If you're going to send off your prints to an outside source to print, you're better off sending them the ICC profile. A company knowing their equipment isn't going to equate to a print that will print the way that you want it to look, due the fact that you don't give them a color profile and they will print it the way that they feel it needs to be printed.

CMYK. I've only send CMYK when I'm printing non prints. Business cards, post cards, brochures and like. Proof in the pudding. If your monitor is calibrated correct, when you send the proof to them and they send it back to make sure that the color matches, that's when you know all is fine. I haven't had any issues with this. It's always consistent.

Legacys 7 wrote:

That's not true. A couple of things. I understand CMYK very well. If you're going to send off your prints to an outside source to print, you're better off sending them the ICC profile. A company knowing their equipment isn't going to equate to a print that will print the way that you want it to look, due the fact that you don't give them a color profile and they will print it the way that they feel it needs to be printed.

CMYK. I've only send CMYK when I'm printing non prints. Business cards, post cards, brochures and like. Proof in the pudding. If your monitor is calibrated correct, when you send the proof to them and they send it back to make sure that the color matches, that's when you know all is fine. I haven't had any issues with this. It's always consistent.

Well, the only problem with that is that the printer most likely has alreday created their own ICC profiles for their printers.  At least the company I worked for did.  We even went as far as creating one for each printer and paper type.  But, I'm not sure how many printers do this anymore.  If you're doing it at home, and you want to convert to cymk, I'd make sure that I'm using Photoshops color space and not the printers.

Isaiah Brink wrote:

Well, the only problem with that is that the printer most likely has alreday created their own ICC profiles for their printers.  At least the company I worked for did.  We even went as far as creating one for each printer and paper type.  But, I'm not sure how many printers do this anymore.  If you're doing it at home, and you want to convert to cymk, I'd make sure that I'm using Photoshops color space and not the printers.

I always use Adobe color space. I don't convert to cmyk in photoshop because I do my own printing.  Again, my only use for cmyk is when I'm sending off a pdf file to have business cards and like printed. I use Illustrator for that.

Legacys 7 wrote:

I always use Adobe color space. I don't convert to cmyk in photoshop because I do my own printing.  Again, my only use for cmyk is when I'm sending off a pdf file to have business cards and like printed. I use Illustrator for that.

8 or 16 bits per channel?

Do your contain colors outside the sRGB gamut, or do you just want the headroom?



I am curious as there are both advantages and disadvantages to using a wide gamut colorspace.  I am curious as to how others deal with the tradeoffs.

Legacys 7 wrote:

I always use Adobe color space. I don't convert to cmyk in photoshop because I do my own printing.  Again, my only use for cmyk is when I'm sending off a pdf file to have business cards and like printed. I use Illustrator for that.

Well, pdf's are used extensively in the printing world because it keeps things separated, and in your case, 4 channels.  One thing that I never liked about files that were used when I worked on the printing press is that it had a 4 color black versus a 1 color black which made registration for the blacks more difficult.  An .eps still gives you a 4 color separation, but only a 1 color black.  But since you're just doing business cards, primarily with text only, it's not going to be that huge of a deal.  In your case, the person doing it may actually be more of a typesetter than a printer like what I was doing on an offset press, but it wouldn't hurt to ask what file type the prefer.  A good thing about the .pdf's is that they embed the ICC color profile in the file itself so you wouldn't have to send that with the file that you're having printed, it's already going.  But an .eps has the benefit that they can apply their own color profile for their inks, their papers, their presses, and not what you are using on your computer, which tend to be more of the standard ICC profiles, and allows them to make more accurate color corrections on site.

Michael Fryd wrote:

8 or 16 bits per channel?

Do your contain colors outside the sRGB gamut, or do you just want the headroom?



I am curious as there are both advantages and disadvantages to using a wide gamut colorspace.  I am curious as to how others deal with the tradeoffs.

When I save my image for printing, it's Adobe 98. I print my own images.

Isaiah Brink wrote:

Well, pdf's are used extensively in the printing world because it keeps things separated, and in your case, 4 channels.  One thing that I never liked about files that were used when I worked on the printing press is that it had a 4 color black versus a 1 color black which made registration for the blacks more difficult.  An .eps still gives you a 4 color separation, but only a 1 color black.  But since you're just doing business cards, primarily with text only, it's not going to be that huge of a deal.  In your case, the person doing it may actually be more of a typesetter than a printer like what I was doing on an offset press, but it wouldn't hurt to ask what file type the prefer.  A good thing about the .pdf's is that they embed the ICC color profile in the file itself so you wouldn't have to send that with the file that you're having printed, it's already going.  But an .eps has the benefit that they can apply their own color profile for their inks, their papers, their presses, and not what you are using on your computer, which tend to be more of the standard ICC profiles, and allows them to make more accurate color corrections on site.

My designs vary. Example. My last design for a client front side was primarily a logo. The logo was the person on the card who I'd designed it for. I drew an image of them and put it on the card. So the only thing that was really needed was making sure that the font was outlined for the offset printer.

Legacys 7 wrote:

When I save my image for printing, it's Adobe 98. I print my own images.

OK.  But do you save in 8 bits per channel or 16 bits per channel? 

Why do you use Adobe 98?  Do your images routinely exceed the sRGB color gamut?

Isaiah Brink wrote:

Well, pdf's are used extensively in the printing world because it keeps things separated, and in your case, 4 channels.  One thing that I never liked about files that were used when I worked on the printing press is that it had a 4 color black versus a 1 color black which made registration for the blacks more difficult.  An .eps still gives you a 4 color separation, but only a 1 color black.  But since you're just doing business cards, primarily with text only, it's not going to be that huge of a deal.  In your case, the person doing it may actually be more of a typesetter than a printer like what I was doing on an offset press, but it wouldn't hurt to ask what file type the prefer.  A good thing about the .pdf's is that they embed the ICC color profile in the file itself so you wouldn't have to send that with the file that you're having printed, it's already going.  But an .eps has the benefit that they can apply their own color profile for their inks, their papers, their presses, and not what you are using on your computer, which tend to be more of the standard ICC profiles, and allows them to make more accurate color corrections on site.

Actually, the advantages you attribute to PDF are optional features of PDF, and are also available in JPEG files.    PDFs allow you to supply files ready to print.   They do not enforce it.



Both PDFs and JPEGs can have embedded colorspaces, and both can be RGB, CMYK, or even greyscale.

For CMYK files (JPEG or PDF) blacks can be 1 color black, or rich black (black ink plus colored ink).

Registration of the colors can be an issue anytime you are mixing colors.  For instance a green line would be Cyan and Yellow ink.  If there are registration issues, there can be Yellow and/or Cyan fringes on around the line.

With a rich black, trapping can be used to keep the colored ink inset a bit from the edges of the black ink.   This gives a rich black, without the color fringe issues.

Trapping, overprinting, and knockouts can be applied by the printer to EPSF or PDF files.   All of the embedded images in the original PostScript language manual were EPSF files.

The advantage of PDF is that it is now a common industry workflow.  It allows for the file to be self contained.  Images, vector art, and text can all be in one file.  The PDF can contain RGB elements along with CMYK elements (although this is not "best practice").  PDFs can contain embedded colorspaces, and embedded fonts.  Embedded fonts allow you to keep text as text (which is more compact, and more accurate than outlines) without worrying about whether or not the recipient has the desired font.

Michael Fryd wrote:

Actually, the advantages you attribute to PDF are optional features of PDF, and are also available in JPEG files.    PDFs allow you to supply files ready to print.   They do not enforce it.



Both PDFs and JPEGs can have embedded colorspaces, and both can be RGB, CMYK, or even greyscale.

For CMYK files (JPEG or PDF) blacks can be 1 color black, or rich black (black ink plus colored ink).

Registration of the colors can be an issue anytime you are mixing colors.  For instance a green line would be Cyan and Yellow ink.  If there are registration issues, there can be Yellow and/or Cyan fringes on around the line.

With a rich black, trapping can be used to keep the colored ink inset a bit from the edges of the black ink.   This gives a rich black, without the color fringe issues.

Trapping, overprinting, and knockouts can be applied by the printer to EPSF or PDF files.   All of the embedded images in the original PostScript language manual were EPSF files.

The advantage of PDF is that it is now a common industry workflow.  It allows for the file to be self contained.  Images, vector art, and text can all be in one file.  The PDF can contain RGB elements along with CMYK elements (although this is not "best practice").  PDFs can contain embedded colorspaces, and embedded fonts.  Embedded fonts allow you to keep text as text (which is more compact, and more accurate than outlines) without worrying about whether or not the recipient has the desired font.

You're correct with the whole common workflow, everybody can use them just about.  But, like I said, when a pdf is used for a separation, they tend to use all 4 colors for black instead of just black for black.  With an offeset press, it's easier to line up a single color than 4 colors.  So it really depends on what type of press you're outputting too.  If it's a laser printer or inkjet or a sheet feed press, then it's a lot easier than on an offset, so, that's where either a 1 or 4 color black makes a difference.

Isaiah Brink wrote:

You're correct with the whole common workflow, everybody can use them just about.  But, like I said, when a pdf is used for a separation, they tend to use all 4 colors for black instead of just black for black.  With an offeset press, it's easier to line up a single color than 4 colors.  So it really depends on what type of press you're outputting too.  If it's a laser printer or inkjet or a sheet feed press, then it's a lot easier than on an offset, so, that's where either a 1 or 4 color black makes a difference.

I don't think PDF implies 1 color black or 4 color black.  I can do either with PDF and either with a CMYK JPEG.

If the black is text or vector art, then it has to do with how you specified the black in your design program.   If the black is in a formerly RGB image, it depends on the RGB to CMYK conversion settings.   If the image is already CMYK, I can directly specify in Photoshop whether I want 1 ink or 4.


If you are printing to a color laserprinter, then it depends on your workflow.  Many software drivers only accept RGB.   If you try to print a CMYK image, it gets converted to RGB, sent to the driver, which converts back to CMYK and then sends that data to the printer.   If you are sending the PDF (or PostScript) directly to the printer, you may be bypassing the print driver and the extra CMYK -> RGB -> CMYK conversions.

If you are using a software RIP and bypassing the standard driver, you likely don't have to worry about an intermediate RGB conversion.


If the workflow includes converting the data to RGB, then you lose the ability to control the inks used for black.   It's not an issue of PDF vs EPSF vs JPEG, it's an issue of workflow.