index separation tutorial.
this tutorial is for intermediate to expert level photoshop users, as well as
for those who are familiar with using channels for spot color separations.
here's
an explanation by another website on the advantages of index over halftones
wrecks 'n effects let's begin! (image on top. explanation below image)
never resize index seps in RGB mode. everything will become 'dirty'.
ideally, create index separations at print size. you can however resize
index seps in index mode without significiant quality loss
Onward!
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1. Resize to 200 DPI at print size. - 200 DPI is not a concrete setting.
I've gone as low as 160 dpi on a detailed image and had relatively undistinguishable
results. It seems DPI from 160-200 yield the best results, but that is using
our specific meshes and inks. There are too many variables to give a concrete
number here.
2. Saturate if necessary. Images that are low contrast and low saturation....
makes Jack a dull separation. Low constrast and low saturation makes Jack a
dull separation. Low constrast and low saturation makes Jack a dull separation.
Low constrast and low saturation makes Jack a dull separation. Low constrast
and low saturation makes Jack a dull separation.
It will yield a bevy of gray or whatever middle tone color swatch you may have
chosen.
3. Sharpen if necessary - Sharpening essentially helps to crispy the
contrast and saturation. Otherwise see #2 and Jack.
4. Swatch palettes are wonderful, you will see... Most swatch palettes
start with a default set of 30+ colors. You will want to reduce the swatches
to none before you begin to add your own color swatches. To empty the palette,
hold ALT and mouse over the colors, a pair of scissors will appear, click to
manually cut the extra colors out of the palette. It would be handy to save
your empty palette for future use. BTW, in Photoshop, you can cut extra brushes
out of your brushes palette with the same method. (Works for most other palettes)
Adding colors to the swatch palette is easy. While mousing over the RGB image
with your brush or paint bucket tool, hold ALT, which will allow you to color
pick. Now mouse over your swatch palette and click to drop the color into the
palette.
HOW TO CHOOSE COLORS.
1. Choose dominate colors.
2. Choose vivid primary colors.
Sometimes, if there are enough print heads/screens available, I will choose
an extra color for an object in the tee that takes up a majority of the design
space. Most Nascar tees have a car that take up more than 40% of the design,
so I will choose an extra swatch of color so that the car looks good. For a
car, I usually choose the basics, white, black, main color of car, and one light
or dark analogous to the main color of the car depending on highlights and shadows.
If it has a alot of shadows, I will choose an additional dark main color, or
vice versa if the highlights on the car is extrememly hot. That way, the car
is being separated with 4 colors.
5. Save the swatch palette you just created.
** random tip: There may be times where you may opt to use halftone separations
along with index, since gradients are handled better by halftones. drop shadows/glows
are better handled and printed with halftones. Or logos that call for a specific
PMS color need to be cleanly separated by manual method as indexing will sometimes
yield mixed dots even if you specify specific colors.
2. Select all, copy, undo three steps - essentially copies the index mode image
into the clipboard so you can paste back into the original RGB mode.
You probably want to label the layers. never can be too safe these days, with
all the gangs, diseases, and Avian flu. I usually have the layers labeled: index,
flat RGB, clean yellow mask, etc. Make sure you have a copy of the flattened
RGB (if you have the image built in layers). Leave the index mode image on the
top layer.
1. Sometimes you cannot tell if one hue or another is too dominating until
you have them dropped into channels, but it is a good idea to take a look at
the index separations. If you have text or logos that require a specific color,
undoubtedly they will be speckled with colors you know do not belong, so for
text or other objects that are solid colors, it is best to separate manually.
** gray is your enemy, if you didnt choose gray in your swatch, it has dressed
itself in another color and is trying to fool you. it will be most likely be
the most midtone color there is.
heres why. you take a picture thats 16.8 million colors and drop it down to
8-12. when PS calculates who becomes what color, it takes the midtone colors
and curses them to be gray, the dullest of a non partying colors... they dont
drink or smoke, they are really uncool like Mark H, so theres going to be alot
of it. thats why we saturate the image at the beginning...
now.... what you've just read, is just based on an assumption and may not be
true, but it sure did sound like it would work. its like if you read a book
on brain surgery. you would have a basic understanding, and would be able to
talk about it over coffee, but put yourself in the operating room, you would
probably just cause permanent neurologic deficiencies in the patient, and maybe
then some.
let's look at how to create channels.
how to create channels.
1. open channels palette. press new channel button to make a buncho new empty
WHITE channels.
2. leave an Alpha channel right below the BLUE channel. this will allow for
easy toggling back to RGB. when you click on the layers palette, PS for some
reason will select all channels excluding Alpha channels. since we will be changing
most of the channels to spot colors, they will be chosen as well, which is frustrating.
so when you do choose on the layers palette, since the Alpha channel left under
2 will not be chosen, you can use the shortcut apple-4 followed by apple-~ to
just show RGB! this works because when you choose an unchosen channel, it turns
off all other channels, then by choosing RGB by using apple-~, it then just
shows RGB!!! YEAH... workaround for an annoyance!
3. double click on another Alpha Channel.
4. which will bring up 'Channel options' menu
5. select spot color
6. click in the color swatch area
7. which will bring you to 'Color Picker' menu
8. go to your swatches palette and begin from the first swatch. the color will
change in the 'Color Picker' menu.
9. press 'Custom' which will bring up the PMS color swatches. it will automatically
choose a PMS color closest to your swatch. press OK from the PMS color picker.
10. under the 'Channel Options', it should automatically change the name of
the Channel.
Now repeat steps 3-10 until you have named the other Alpha channels with the
rest of swatch colors.
On colored shirts, create spot color channel named 'Tee', fill with 100% black,
and give it a spot color of the shirt color.
The order of the channels is top down. The top is what would be printed first,
thus the 'Tee' color channel is first follwed by the base white if used. Usually
gray/middle tones will go near the top, and black and highlight white will go
on the bottom. Visually, on screen, it shows from the bottom up. You may have
to move some colors around to get the image to show proper, but it will hardly
ever look 100% like the original RGB. Move colors that are dominant/important
in the image to the bottom of the channels. If you have highlight white, it
will not show properly. No worries.
I usually put black on the bottom and duplicate it. Visually this shows what
black will turn out on the shirt with some dot gain. If you havent compensated
and lightened the shadows before indexing, you will be able to tell where black
will eat everything.
Ive started to set the color of the base white to NOT WHITE. Depending on the
color of the shirt, say if it is a blue shirt, I set the spot color option on
the base white as a midtone blue... as base white on a blue shirt, yields....
midtone blue. Makes sense eh? Visually in the channels, its a better representation.
Next section - how to drop index selections into channels.
1. Have the index mode image showing. Make sure only the RGB channels are showing
in the channels palette.
2. Select > Color Range
3. Fuzziness = 0.
4. Choose color from swatch palette starting from left. Press OK in Color Range.
5. Result will be a selection only around color of the chosen swatch.
6. (not shown) Choose the appropirate channel you created earlier, and fill
with BLACK.
7. (not shown) Deselect All
8. Repeat steps 1-7 until you have done all the colors you had chosen in your
swatch palette.
Keyboard Shortcut Tip: Apple-D to deselect, Apple-~ to toggle back to RGB mode.
If you are manipulating channels with the use of the layers, use Apple-D, Apple-4,
Apple-~.
After dropping the first round of index mode separations into channels, I found
that gray dots were mingling in the Talladega logo. I re-indexed to clean up
the original index separation.
Compare this image the text in this separation compared to the first index
separation shown a few images before. See how there are no more grays dirtying
up the text?
So above, the image was re-indexed with red, yellow, orange, white and black.
Violin! You Reak Ugh! No more gray in the text. But now everywhere else, the
separations are incorrect. It is easily fixed, by creating a mask and deleting
outside the mask. I usually label re-indexed sections as 'CLEAN' etc etc. that
way Iknow to leave them above all other layers, since from then on, they will
always retain their index information and separate accordingly for further re-indexing.
For most index separations, I will re-index sections of the image with limited
palettes, and then combine all of them for one final separation.
heres another example of separating in sections for clarifacation.
the image above was sent to me as a 5x7, 200DPI jpeg to be upsampled and printed
at 15.5x18 with 10 colors. it was reduced to 160 DPI and the print came out
pretty well.
the black with yellow outlines image is an example of how i separated the image
into color sections. each section is separated with the minimum needed colors,
so they will not be dirtied up by the other colors. this can be tedious, but
if you knock out the paths/masks you'll save yourself alot of frustration cleaning
up the separations. (example... section 2 was only separated with blue, light
blue, and white, nothing else. section 6 was separated with black, white, yellow,
and gray)
so make sure to separate (as in layers, not index separate) your image into
sections, whether it be during creation or afterwards with paths so it will
be easier to indexs separate later.
observe the image above. saturating the image is necessary to make sure that
gray or a midtone color will not dominate the majority of the index dots. it
is a learned skill as far as knowing how much to saturate. in the meanwhile,
one can take the flattened rgb and convert to index and investigate. if the
index pattern seems to be dominated by one color, you could just as easily undo
and index again. most of the time i will index an image, drop everything into
channels to see where the problem areas are. once you get the hang of it, it
shouldnt take much time.
lets skip to the point where we have indexed the image and dropped the colors
into the channels.
heres an example of what happened to the gray plate.
the left image is the gray index channel. the right is the manipulated one.
i took an airbrush and manually cleaned up the plate. whats cool on a dark shirt,
which would have a base white, is that the base white will take place of where
the gray ink should be.
another reason i knew where to take the gray index out is i had all the colors
laid out in the channels. i usually place the gray plate near the top of the
channels palette which means it will be printed early on. with all the colors
turned on in the channels except RGB, if you toggle the trouble plate on and
off, you can see where it is needed and where it is not. turned back on, i took
an airbrush and erased the pixels where i did not think the gray index dots
were unneeded.
above is the black plate. left is original. right is manipulated. black has
a tendency to heavy up, so just as the gray plate, i erased some of the pixels
anticipating the dot gain. in the red 1 area, the black ended up fine. in the
blue 2 section however, after printing, there was no contrast between the shadow
underneath the car and the valance. it all turned black. in hindsight, the pixels
should have been reduced approximately 70% more.
lets make base white.
to make base white, take the original non-index mode rgb layer, and use Image
> Adjsutments > Selective Color > and take the Black out of the Red,
Yellow, Orange... any colors that would need a base white. Royal blue, and red
need to be reduced down quite a bit, as when one desaturates an image, they
do not desaturate as much as other colors. see how much black i took out of
the rgb layer on right.
after adjusting the black, desaturate, inverse, and use levels to make sure
the middletone is leveled out to make sure ink will not be in the shirt area.
this is also the same method to create highlight white except you will use adjustments
to darken areas like red, yellow, etc.
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