Mode change from RGB to grayscale not working

[silver.hunter]

I am using CS6 to import a number of pdf files in RGB then remove a coloured identifying stripe then convert to grayscale before saving as a tif file. This was working ok, using IMAGE>MODE to convert to grayscale, but suddenly this has stopped working and will not convert the coloured image unless I first convert it to indexed colour. The pdf files have been obtained from scanned images using Vuescan.

[Benjamin Root]

I'm not a scan expert, but since you mention the problem occurred recently and abruptly, try a preference reset.

Win: Press and hold Ctrl+Alt+Shift immediately after initiating Photoshop's startup. A box will appear asking if you want to continue with the reset, select "yes." If you don't see this, you weren't fast enough...Try again.

Mac: Press and hold Cmd+Opt+Shift then start Photoshop. A box will appear, asking if you want to continue with the reset, select "yes."

[silver.hunter]

That gave me a message about loading plug-ins. What preference was I supposed to be resetting?

As far as I can see, the problem is not associated with the external scanning program as that has not changed. For various reasons of convenience the files are scanned and saved as a colour tif file, converted to pdf  in Pixillion Image converter. then opened in Photoshop in RGB mode, all necessary clean-up operations performed then converted to grayscale and saved. As a matter of checking I opened an original colour scan file that has already been done and tried to convert it to grayscale (which has already been done successfully) and it would not change, thus it appears to be something that has changed within PS.

[Benjamin Root]

Pardon my lack of clarity. You'll be resetting Photoshop's preferences. If you received a message about plugins, that means only Shift was giving input...Holding Shift while launching Photoshop gives the option to skip loading any third-party plugins.

Photoshop CS6 is not being updated, nor has it been for quite some time. That, along with the sudden behavior change, would seem to indicate Photoshop's preferences have a problem. Can't guarantee this will fix the problem, but quite likely it will.  

[silver.hunter]

I went to the Adobe online help, where it says those keys should be held down when starting PS. As I only have the use of one hand, I got my wife to hold down the keys while I started PS - it started as normal, with no message about preferences. We tried it a few times with the same result.

[D Fosse]

silver.hunter  wrote

For various reasons of convenience the files are scanned and saved as a colour tif file, converted to pdf  in Pixillion Image converter. then opened in Photoshop in RGB mode, all necessary clean-up operations performed then converted to grayscale and saved.

Why the intermediate PDF? Why do you need that? And for that matter, what is Pixillion image converter and why do you need to use that? You can save out a PDF from Photoshop if that's what you need.

Instead of Image > Mode (which just picks your working spaces for Gray/RGB), have you tried the more specific Convert to Profile?

If the end result is grayscale, you should consider which one. Grayscale treatment outside of Photoshop is very arbitrary and unpredictable. There is always a risk of tonal shifts. RGB is much safer.

[silver.hunter]

The reasons for the various file formats relate back to earlier requirements when distributing copies and are irrelevant to the question asked, which is why I did not waste time explaining. The reason for using Pixillion is that it can batch convert a folder full of files to different formats - much quicker than doing one at a time in PS.

Although it is irrelevant to the question asked : The original pages which I am scanning were printed in black and white, many years ago (thus printing quality is poor). They were originally filed as loose leaf documents and are colour coded with stripes of various colours to indicate which original documents each page belongs to. I am scanning in colour so that I can remove the coloured stripes before converting to grayscale to "clean up" and sharpen the original text.

OK?

[silver.hunter]

The reason I am not using "convert to profile" is because I don't understand it, or how to create the settings which I need (or even, what settings I need) and using the grayscale mode works perfectly well for me over the few hundred pages that I have scanned for this project.

Aas far as I am concerned ithe greyscale mode does what I need - ie reduces the file size by typically 60%

[silver.hunter · Accepted solution]

I seem to have found the problem. It seems to lie with the conversion from tif file to pdf done within the Pixillion program.

The earlier files I worked on, the pdfs were created from PS. (Best not get into the reasons, as it would take too much time). I opened one of the Pixillion pdf files in PS and saved it as a pdf from PS. When I opened that new pdf in PS it converted to grayscale without any problem. I also found that converting the imported pdf to a tif file by saving it as a tif allowed the grayscale conversion to work. Thus not a PS problem at all and easily handled for future files.

Thanks to all those who tried to help.

[Benjamin Root]

Glad you got the problem figured out!

As for the Photoshop reset, you have to be extremely fast. There is a manual way to delete the files, but sounds like you don't need that now.