The Color Modes: Bitmap

This is the first in a series of posts discussing the color modes in Adobe Photoshop. My previous post, ‘256 Shades of Gray: A Ribald Tale of Bit Depth’ covered the color modes available in Photoshop when starting a new document. This series of postings will go into each one of those modes in a little more depth plus cover the other secondary color modes.

The Bitmap Color Mode in Adobe Photoshop

So when would using the Bitmap color mode be useful, or even necessary, in Photoshop?
What I’ve frequently used the Bitmap mode for is for a persons signature or a one color graphic or logo that needs to be included in a layout. Also when I haven’t had a high res digital file of a one color graphic, but I do have a clear and sharp print which I can scan and bring into Photoshop. And when I say “one color”, I mean one “solid” color, as a Bitmap cannot include multiple percentages.

When creating a Bitmap file you have the option of selecting a custom DPI. For Bitmaps you should not select anything lower than 1200 dpi at 100% print size. So when you place a Bitmap in an Illustrator or InDesign document it should be at 100%. If you need to scale the graphic up or in the layout, you should resize the file in Photoshop so that it resets to 100% in the layout program. You should be able to scale down without any negative effects.

And remember that anything that appears white in the Bitmap Photoshop file will appear and print transparent in the layout program.

Once in the layout program you can apply any color to the Bitmap file. If for any reason you do want to add a gradient or other effect to the Bitmap graphic you can do that in the layout program using an Opacity Mask or Effects Filters in Illustrator and Effects Filters in InDesign.

Bitmap files are pretty simple but pretty handy too...and not too limited if you consider the effects you can apply in Illustrator and InDesign.

    

Swatch Names in Illustrator and Their Connection to Photoshop Spot Channels

If you like to keep your swatch names in Illustrator organized (as you should), remember that when you place a Photoshop file that contains spot channels in an Illustrator document, the spot channel colors are added to the Illustrator Swatch panel. And the names appear exactly as they are written in the Photoshop channel.

So if you have a swatch created in Illustrator that is supposed to print the same color as the color in the Photoshop file, it should be written the exact same way. If it’s not, when the Photoshop file is placed in Illustrator, a new swatch will be added in addition to the swatch in Illustrator.

You can quickly fix this conflict by first clicking on the swatch color name in the Swatch panel that comes from the Photoshop file, then hold your Command key (Control key on PC) and click on the similar (but different) name of the swatch created in Illustrator. Then, with both swatches highlighted, select ‘Merge Swatches’ from Swatch panel option menu. This will combine the swatches into one to ensure that they separate to the same printing plate. This will also match the coloring of any vector graphic in the file to that of the spot color in the Photoshop file.

If you try to merge the name of the swatch from the Illustrator file to that of the Photoshop file…it won’t work. The swatch name from the Photoshop file is essentially locked into the Illustrator file. That’s because you can’t make changes to a Photoshop file using Illustrator. Makes sense.

If you prefer the swatch name format from the Illustrator file, just open the Photoshop file and change the name of the spot channel to match that of the Illustrator file. After you’ve saved the file and refreshed the Illustrator document, the swatch will combine with the Illustrator swatch. But the old Photoshop swatch name will probably still exist. You can get rid of it by selecting ‘Select All Unused’ and click on the trash icon in the swatch panel. If that doesn’t work, you should save the document, close it and reopen it. That will free up any unused swatches to be deleted.

CUSTOM SPOT COLORS

If you’ve created a custom spot color in both the Illustrator & Photoshop documents, but they are of different hues/tints, the hue/tint that exists in the Illustrator document will be adapted to the color from the Photoshop file. This is not a bad thing. It will ensure that your colors are common throughout all files associated with the primary Illustrator file. The hue and tint in the Photoshop file will stay the same. It will just appear different in Illustrator to ensure a match color.

If this isn’t to your liking you can adjust the swatch color in Illustrator to match that of the Photoshop file. This is probably the better approach anyway. It keeps things clean and organized.

Smaller PDFs with Presentable Quality Using Custom Settings

In the process of distributing art as PDFs via email for review and approval you sometimes end up with some pretty beefy-sized PDFs. Although the PDF format is great for it’s compression, you can still face the challenge of a PDF that is too large for emailing. But if you compress a file too much, you may end up with images and graphics that are of poor quality. There are ways of avoiding these problems by adjusting PDF creation settings.

First of all, the old ‘best’ way of making a PDF was by creating a postscript file, then running it through Acrobat Distiller, with adjusted settings, to get good quality and good compression. Distiller still exists, it just runs behind the scenes within the built-in PDF saving features in Adobe Illustrator, InDesign and Photoshop. The setting adjustments are all done within the “Save Adobe PDF” dialog box. You get to this dialog box, under the File menu, in Illustrator by choosing ‘Save As…’ or ‘Save a Copy…’, in InDesign by choosing ‘Export’ and in Photoshop by choosing ‘Save As…’. Then just choose PDF for the format.

By choosing any of the menu options noted above, you will arrive at the dialog box shown here.

‘Save Adobe PDF’ dialog box in Adobe Illustrator.

The resulting PDF saved with the default preset, in Illustrator, will give you good quality for viewing and printing. But you will be left with a file size that may be too big for emailing. The example below, using the Illustrator Default preset, generated a 22.5 MB file.

Zoomed in, you can see that the quality is very good.

The major contributor to a large file size for a PDF is usually a bitmap, or photographic image, as shown above. So that means you’ll want to adjust the settings under the ‘Compression’ tab, as shown below. What I’ve found that works the best for reduced file size with good quality images is downsampling to 250ppi for images above 299ppi. Since most high res images are 300ppi, you want to make sure to type in 299. This setting reduced the same 22.5 MB file to a 1.9 MB file. The quality of this PDF is great for on-screen viewing and printing. If you are just concerned about on-screen viewing or placing in PowerPoint or Keynote, 150ppi instead of 250ppi will work just fine.

Other settings to consider, within the ‘General’ screen, are unchecking ‘Preserve [Illustrator or Photoshop] Editing Capabilities’ and selecting the latest version of Acrobat under the ‘Compatibility’ drop down menu. You can also experiment with different settings within each tab of the dialog box to see the results.

‘Compression’ screen with options to downsample bitmap images.

If you are happy with the results of a particular group of settings you should save the settings as an Adobe PDF Preset. To do this, click on ‘Save Preset’ in the lower left corner of the ‘Save Adobe PDF’ dialog box. You will be presented with a field to type in a custom name (see below). Type in the name a click ‘OK’. This preset will now always be in your ‘Adobe PDF Preset’ drop down menu. Even if you were in Illustrator when you created the preset, it will also be an available preset when using Photoshop or InDesign…and visa versa.

If others in your workgroup like the results of your PDF settings, you can pass the preset file along to them. To do this, in your Finder, navigate to /Users/your user name/Library/Application Support/Adobe/Adobe PDF/Settings. In there you will see custom presets with a ‘.joboptions’ extension. For example, I have a preset called, ‘Hi-Quality, Low File Size.joboptions’. You can grab a copy of your ‘joboptions’ file and pass it along to somebody else who would then drop it in the same location on their computer.

Saving a group of settings as a preset.

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