Two Colour Printing Help

Jed · 15th December 2004

Okay, I'll be the first to admit that I know far too little about CMYK aside from processes. But at any rate, what's happening is that I'm going to need to send a few files to a printer and the guy paying the bill can only afford two colours. In this specific instance, black and yellow.

Does anyone know what the best way is to get Photoshop to ditch the magenta and cyan channels so I don't get any of those colours in the image at all? Basically it's a black and white image which we'd either like to retain a bit of continuous tone yellow, or to burn on a yellow over the existing black and white areas. Or can I literally just ditch the cyan and magenta channels? (in which case, should I start with the greyscale file or the colour file? Assuming I want preferably be able to do greyscale conversion from full colour data rather than just the yellow channel/black channels).

Many thanks for any help.

Sion · 15th December 2004

Set your grey scale photo first and then go to Image - Mode - Duotone (Type: Duotone not Monotone)

Click on Ink 2 to choose your Pentone colour and you could also adjust the curve for tonal control.

Merry Christmas!

Sion · 15th December 2004

Or you can send the printer a CMYK file with blank in Cyan and Magenta channels.

Tell the printer to print Black and Yellow only.

Happy New Year!

ortega · 15th December 2004

That is too simplified. Change your image into a CMYK colour file.
Then adjust your Black and yellow plate to what you need.
Select the cyan plate, select all and delete
do the same for the magenta plate.

Review the composite, to check and save
When you give the file to the Printer/Casting house tell them to cast only Y and K Plate.

Jed · 16th December 2004

Okay hang on. I've tried both methods. With the Duotone method, works great, aside from the fact that the greys go yellow-y. Ditto Ortega's method. What am I doing wrong/not doing? TIA.

ortega · 17th December 2004

for the duotone method you need to adjust the curves for each ink used to balance out the amout of ink used.

For theCMYK method, you must already know what the resulting picture will look like and adjust to get what you want.

Note: You can also cut any other plate and use it as the yellow plate.
You can also use other inks instead of yellow.

ellery · 23rd December 2004

Jed

A word of caution which I learnt from experience for dualtone you need to watch carefully the image of the combined colors - ie there is an overall increase in the amount of ink laid down and a corresponding decrease in contrast - and brightness. If u fail to adjsut properly - murk dull looking repro is the result - that was what the graphics person at one of the film casting houses I used (and no longer use since they were not up to mark).

There is also an issue of dot gain when printing - most cases its about 20% . So a little lighter on the film image can still be darken slightly but not the reverse.

15th December 2004	#1
Jed Senior Member Join Date: Jan 2002 Location: UK Posts: 3,081	Two Colour Printing Help Okay, I'll be the first to admit that I know far too little about CMYK aside from processes. But at any rate, what's happening is that I'm going to need to send a few files to a printer and the guy paying the bill can only afford two colours. In this specific instance, black and yellow. Does anyone know what the best way is to get Photoshop to ditch the magenta and cyan channels so I don't get any of those colours in the image at all? Basically it's a black and white image which we'd either like to retain a bit of continuous tone yellow, or to burn on a yellow over the existing black and white areas. Or can I literally just ditch the cyan and magenta channels? (in which case, should I start with the greyscale file or the colour file? Assuming I want preferably be able to do greyscale conversion from full colour data rather than just the yellow channel/black channels). Many thanks for any help.

15th December 2004	#2
Sion Senior Member Join Date: Jan 2004 Location: 新天地 Posts: 1,014	Set your grey scale photo first and then go to Image - Mode - Duotone (Type: Duotone not Monotone) Click on Ink 2 to choose your Pentone colour and you could also adjust the curve for tonal control. Merry Christmas!

15th December 2004	#4
ortega Moderator Join Date: Nov 2004 Location: NorthEast Posts: 16,507	That is too simplified. Change your image into a CMYK colour file. Then adjust your Black and yellow plate to what you need. Select the cyan plate, select all and delete do the same for the magenta plate. Review the composite, to check and save When you give the file to the Printer/Casting house tell them to cast only Y and K Plate.

16th December 2004	#5
Jed Senior Member Join Date: Jan 2002 Location: UK Posts: 3,081	Okay hang on. I've tried both methods. With the Duotone method, works great, aside from the fact that the greys go yellow-y. Ditto Ortega's method. What am I doing wrong/not doing? TIA.

17th December 2004	#6
ortega Moderator Join Date: Nov 2004 Location: NorthEast Posts: 16,507	for the duotone method you need to adjust the curves for each ink used to balance out the amout of ink used. For theCMYK method, you must already know what the resulting picture will look like and adjust to get what you want. Note: You can also cut any other plate and use it as the yellow plate. You can also use other inks instead of yellow.

23rd December 2004	#7
ellery Member Join Date: Jan 2002 Posts: 785	Jed A word of caution which I learnt from experience for dualtone you need to watch carefully the image of the combined colors - ie there is an overall increase in the amount of ink laid down and a corresponding decrease in contrast - and brightness. If u fail to adjsut properly - murk dull looking repro is the result - that was what the graphics person at one of the film casting houses I used (and no longer use since they were not up to mark). There is also an issue of dot gain when printing - most cases its about 20% . So a little lighter on the film image can still be darken slightly but not the reverse.