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The settings you see in the screen-grab below are generally accepted as the safest choices (although not necessarily the defaults that you will obtain when you first install Photoshop, so please check), and will enable you to avoid virtually all image data damaging scenarios that you may encounter when opening files from whatever source. One interesting point about Embed Profiles and certainly one to keep in mind. If you deselect the option then Photoshop (so far as I know no other program does this) WILL embed a profile, but this profile will be a special profile indicating to Photoshop that the user made this choice. When you open such an image you will NOT get any warning messages, etc., this is quite deliberate and also a good thing.

 

Image

 

The "Assumed Profile" section is where we tell Photoshop how it should deal with images that contain no embedded profile.  It doesn’t actually do very much other than flag up the "Missing Profile" dialog as shown below, and even this only happens when you open an actual image. Of course if we have set the "Profile Mismatch Handling" section to something other than "Ask When Opening", it will totally ignore the fact that the file has no embedded profile and open the image in a colour space previously specified by you in the "Assumed Profile" RGB pop-up window. So it is important that you ALSO adhere to the following advice on "Profile Mismatch Handling". You should consider the "Missing Profile" and "Profile Mismatch Handling" sections as "safety nets", they're designed to slow you up and make you think.

In the example below the image contains no embedded profile, if you don't know the source then select "Don't Convert". If you do know the source then make that the selection in the "From" pop-down window then choose "Convert". Typically an image scanned outside of Photoshop will cause this dialog to appear. If the appearance of the image changes drastically in colour or density you made the wrong choice, you can use Photoshop "History" to get you back to original image.

 

Image

Example - opening an image with "no" embedded profile

 

The final section of the Profile Setup dialog is the "Profile Mismatch Handling" section. Get the settings in this section wrong and, your image data is very likely to end up in a less than optimal state. For each of the three pop-up windows we have three choices, "Ignore", "Ask When Opening", and "Convert".

Taking each of the options in turn:

  • "Ignore" – This option simply opens the image in your current RGB, CMYK or Grayscale workspace without any conversion of the image data. At first this may appear to be a perfectly reasonable choice, but note, by not allowing a colour space conversion we are in fact changing the "Colorimetric" meaning of the image data thus it will appear on your monitor and print differently from what it would have done on the system in which it was created.
  • "Ask When Opening" – With this option, if you open an image that has the no profile embedded within it, you will be presented with dialog similar to that shown above. If the file has an embedded profile, but it's the wrong profile, then you will get the dialog shown below. It will be displayed in the "From" pop-up window. The "To" pop-down window will usually be "YOUR" actual Photoshop "RGB", "CMYK", or "Grayscale" colour space depending upon which mode, etc. you are currently working.
  • "Convert to ----- C" – This is the most dangerous option in that it allows Photoshop to automatically convert the file you are opening "From" and "To" the colour spaces you specified in the "Assumed Profiles" section. For most this is not the best option for very obvious reasons (e.g. a calibration image will automatically be converted into your current work space thus destroying it).

 

Image

Example - opening an image with the "wrong" embedded profile

 

The example above shows that the embedded profile within the image is "Adobe RGB (1998)", since the Profile Mismatch dialog appeared we must make one of two assumptions depending on the workspace you're actually working in.

1. You are using a colour space other than  "Adobe RGB (1998)", e.g. ColorMatch, sRGB, etc.

2. The profile is NOT what it claims to be. This actually occurred with the original Nikon version of BruceRGB, so don't dismiss it as a possibility.

If the dialog appears, and unless you have very good reason to do otherwise it is recommended that you leave the Engine: at "Built-in", Intent: at "Perceptual Images", and "Black Point Compensation" at "On" at all times.

Remember, the "Missing Profile" and "Profile Mismatch" dialog boxes are designed to WARN you that something is amiss, they will only appear when you open an actual image, and not when you are configuring  "Profile Setup".

5. Profile-to-Profile

Although not specifically part of the Color Settings menu, "Profile-to-Profile" (P-to-P) does form an essential part of the colour management system, and is found under the Image/Mode menu. Profile-to-Profile is a very powerful tool in that it effectively lets you convert an image between any two colour spaces, as and when required. However, there is also a "Health Warning" that needs to be considered – "Photoshop does not keep track of any colour space conversions undertaken by P-to-P", which means that the user could potentially save an image with the wrong colour space profile (tag) embedded within it (remember, that unless you specify otherwise the profile saved with an image will be that of your current Photoshop work space).

 

Image

 

The "From" pop-up is where we select the "Source" colour space and the "To" pop-up the "Target" colour space.

It is also generally recommended that in Profile-to-Profile mode you specify the specific "To" and "From" colour spaces (e.g. From: LS2000Scanner - To: Adobe RGB (98) rather than From: LS2000Scanner - To: RGB), even if Adobe RGB (98) is the colour space you have chosen in the RGB setup dialog as your normal workspace.

Note: It is normally best to keep "Black Point Compensation" Unchecked when converting from scanner profiles.

  • For a more comprehensive explanation on scanning workflow see Bruce Fraser's Article at:-

http://macworld.zdnet.com/1999/09/create/fraser.html

  • For a comprehensive explanation on what each of the colour management "Engines" and render "Intents" actually do, please refer to Andrew Rodney’s Tips page at:-
http://www.digitaldog.net/tips.html

Profile-to-Profile has three main functions:

  • As a time saver, whereby we find, that having opened a file without colour space conversion we realise that we should have done so. By using P-to-P we can avoid closing the file, shutting down and restarting Photoshop.
  • We can also use it to convert between the native colour space of our input devices (e.g. scanners) and our current workspace. I mentioned earlier that some scanner manufacturers (e.g. Nikon LS2000 and LS 30 film scanners) allow you to scan images in the devices native and usually very wide colour space. The problem is that Photoshop has no idea what colour space the image is in because there is no embedded profile, and worse still no equivalent to "Profile Mismatch" or "Missing Profile" for images imported via Acquire mode (i.e. "Twain" or "Plug-in" modules). So in this situation we must force the colour space conversion ourselves.
  • You should also note that quite often a P-to-P using the devices "Native" or even "Customised" profiles could result in quite dramatic shifts in colour, hue and saturation. This usually occurs if you have made colour and gamma adjustments within the scanner software. Remember, if you propose to use device profiles within your scanning workflow then you must never make colour adjustments within the scanner software. Remember also that, what you see in the scanner Preview window is based on your "monitor space" and bears no resemblance to the actual colours, etc seen by the scanner. So if you carry out your colour adjustments within the scanner software I recommend you use your monitor profile in the "From" pop-up window of the P-to-P dialog and not the scanner profile, be warned!

Note:  The one rider to my previous statement regarding the need to use P-to-P when scanning into Photoshop is if you use software such as LaserSoft's SilverFast, or on your scanner software is designed specifically to integrate with the Photoshop CMS, which is unfortunately still a very rare occurrence, NikonScan 2.5x being an exception. When configured correctly such software will allow wysiwyg previews.

  • The final use of P-to-P mode is for preparation of print files for output the RGB printers or film recorders whose drivers do not contain any form of colour management or were we chose to switch it off deliberately. A typical example of the latter would be when using "Customised" printer profiles.

6. Colour Wheel and Colour Correction

Again, whilst not strictly speaking part of colour management I have decided to include some basic information on the subject of colour correction techniques. These are not unique to Photoshop; in fact much of my colour theory has been gleaned over a period of twenty years printing Cibachrome prints in a conventional darkroom.

During those years it has never ceased to amaze me, how some supposedly intelligent individuals just came apart (mentally) at the thought of even trying to identify and correct a colourcast. So before I begin here’s what I consider to be one of the best presentations of the RGB/CMYK colour wheel that I have yet to come across. This diagram has been copied from a book (classified by me as a must have book) entitled Photoshop 5 Artistry, by Barry Haynes and Wendy Crumpler. I know it’s a breach of copyright, but just think of the free advert I’ve just given them .

 

RGB to CMYK Colour Relationships

 

Remember the significance of both colour spaces; RGB is what we see on our monitor and CMYK are the inks used to create the various colours in print.

Before we look at the diagram in use let’s deal with another issue that seems to cause confusion – the term "complements". As the diagram shows:-

  • Red is the complement of Cyan, so Cyan filters out Red Light;

  • Green is the complement of Magenta, so Magenta filters out Green Light; and

  • Blue is the complement of Yellow, so Yellow filters out  Blue Light

What does this mean?, simple; by reducing "red" we’re actually adding "cyan". By increasing "magenta" we’re reducing "green", and so on.

So what makes the above version of the colour wheel so good? Well just look at the relationships between RGB and CMY and how they are specified.

Most of us (me included) appear to have some difficulty in specifying a cast in one of the CMY colours but virtually none when it comes to specifying a cast if it’s "red", "green" or "blue" biased. So in this context I will let you decide how to interpret the diagram yourself, but remember we all make mistakes, and its only through finding the appropriate correction through trial and error that we will ever learn the true art of colour correction. One "Tip" though, it is always preferable to make colour adjustments that effect one colour rather than two, think about it!

At least with this diagram there’s a better chance that we can quickly establish the most appropriate correction. I hope it makes the task of determining the bias of a colourcast all the more easier for you in the future, so please feel free to Print the diagram and pin it to your workroom wall for reference.

When it comes to actual colour correction inside Photoshop I think most novices find the "Variations" or "Color Balance" dialogs to be the easiest to get to grips with. However, they don’t really provide you the level of control required to make accurate colour adjustments. On many occasions you will find that the colour cast in say the shadow region is one colour and the cast in the highlight another colour. The best option for colour correction in that situation is to use the "Curves" tool, I know it’s a complicated tool to use, but the sooner you learn to use it, the sooner you will produce top flight colour corrected images. You may also find some benefits to be in using the "Selective Color" controls. I have found two books of particular benefit when trying to perfect the art of colour correction; i.e.;

    • Real world Photoshop 5, by David Blatner and Bruce Fraser, and
    • Photoshop 5 Artistry, by Barry Haynes and Wendy Crumpler
Both books offer a wide range of advice on all things Photoshop and should form a good foundation upon which you can further develop your knowledge in its use.

 

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