Tech Talk — Anti-Aliasing artwork for best possible Ka-Blam reproductionon October 12, 2008 at 4:04 pm
Ka-Blam offers top-flight print-on-demand services for comics and trade paperbacks. I am pleased with their print quality on my Lore trade paperbacks — great contrast with rich black ink on bright white paper, good cover stock, vibrant color printing, and great binding.
The perceived resolution also looks much, much higher than the true 300dpi of the images. At a reading distance, each page looks like a 600 or 1200dpi print, even though the images are only 300dpi.
This higher perceived resolution is made possible by two things: antialiasing and Ka-Blam’s ability to print insanely fine grayscale tones.
I’ll explain the easier one first. Page 4 of the Ka-Blam sampler (a sample page from Sara Turner’s The Search for Lennox) and the very first “puzzle piece” page of Lore, Vol. 1 demonstrate Ka-Blam’s supremely fine grayscale tones. Ka-Blam may request 300dpi originals, but they use a machine capable of far higher resolutions than 300dpi, and they lavish this high resolution on the grayscale tones.
In short, each pixel element on a 300dpi image is made up of even finer dots when printed through Ka-Blam.
So, an artist can get greater perceived resolution out of a Ka-Blam print if he uses antialiasing, a technique normally reserved for graphics displayed on low-resolution displays like televisions and computer screens:
The Sphinx on the left uses no antialiasing. Only black and white pixels define the image. The “staircase” look of the diagonal lines is called “aliasing.” The Sphinx on the right uses antialiasing. Black, white, and 254 levels of gray pixels inbetween define this image. The gray pixels smooth the appearance of the image.
Normally, high-resolution aliased images are used in print. This is because the printer uses only black ink on white paper, so images are best defined with only black and white pixels. A gray pixel would get translated into black-and-white pixels, and at high resolutions, the printer normally runs out of pixels. This risks making a high-resolution antialiased image look “fuzzy” when printed.
However, Ka-Blam’s printers work at resolutions so much higher than 300dpi that, contrary to conventional printing wisdom, an antialiased image can look better. When confronted with a gray pixel on a 300dpi image, a Ka-Blam machine does not run out of resolution to define the gray pixel. The resulting tone will look fuzzy when examined closely with a magnifying glass, but it will still look smoother than a 300dpi image that uses only black and white pixels.
So…an antialiased image can work best for Ka-Blam reproduction. At SPX last weekend, most people could tell the difference between an aliased and antialiased 300dpi image on a Ka-Blam printer. Some could not. For those who want to create antialiased images of their work, though, the following tutorial is for you.
STEP 1: Start with a high-resolution original.
I’m not going to discuss scanning techniques here. That’s a whole tutorial in and of itself. Just start with a 600dpi or 1200dpi original that prints perfectly on a 600dpi or 1200dpi laser printer.
STEP 2: Convert the image to “Grayscale” in an image editor
An antialiased image needs grayscale pixels. If you start with a 1-bit “Bitmap” image that’s defined only with black and white pixels, some image editing programs will not be able to antialias the image when they reduce the size. If the image is already in “Grayscale” or “RGB” mode, this step is not necessary.
This step is also not necessary if you use the Irfanview freeware program to resize your images to 300dpi. IrfanView converts bitmap images to grayscale and resamples the image while scaling in one step. An image editor like Photoshop, however, requires that the user first convert a bitmap image to grayscale for antialiasing while scaling. In Adobe Photoshop, you’ll find it under “Image->Mode->Grayscale.”
STEP 3: Resize the image
Again — if you’re using IrfanView, skip step 2.
- In IrfanView, go to “Image->Resize/Resample.”
- Activate “Preserve aspect ratio” and set the DPI to 300.
- Under “Size method,” choose “Resample (better quality)” and leave it at its default “Lanczos” filter.
- Then define the size. If you’re starting from a 600dpi image, set the new size to 50%. If you’re starting from a 1200dpi image, set the new size to 25%. You’ll find the size definition under “Set new size as percentage of original.”
- In the upper-left hand corner, confirm that the “New size” is smaller than the “Current size.” If not, you might have to enter the percentage value again.
- Then hit “OK” to create a 300dpi, antialiased version of your original image.
- Go to “File->Save As” to save this image out under a different filename. That way, you can return to your higher-resolution original in case anything goes wrong.
In Photoshop, follow Step 2 and convert your image to “Grayscale” mode. Then…
- Open up “Image->Image Size”
- Make sure “Resample Image” is activated, and leave it at its default of “Bicubic.”
- In the “Resolution” box, type in “300.”
- Click “OK” to create a 300dpi antialiased version of the high-resolution original.
- Use “File->Save As” to save out this 300dpi version under a different filename from the original.
Both Photoshop and Irfanview give you a choice of antialiasing filters. In Photoshop, the “Bicubic” filter works fine for antialiasing comics art. In Irfanview, I have not seen much difference between the filters when reducing the size of black-and-white artwork, so I leave it at its default of “Lanczos.” Now that you know the above steps, consider experimenting to see what filters you like best.
NOTE for Manga Studio users
Folks using Manga Studio for their comics don’t need the above steps to generate antialiased 300dpi images for Ka-Blam. If they’re drawing at 600 or 1200dpi in Manga Studio, all they need to do is export the results at 300dpi in “RGB” mode for antialiased 300dpi images of their work. Lore, Vol. 1 was exported at 300dpi in “RGB” mode out of a 1200dpi Manga Studio EX 3.0 project.