Dan Margulis Applied Color Theory - Black Ink In Shadows

From: Grant Waddell, INTERNET:mylo@direct.ca
To: Dan Margulis, 76270,1033
Date: Sun, Feb 11, 2001, 11:48 AM
RE: [colortheory] Shadow Creation

I need some advice. I have been trying everything to master the creation of shadows in the CMYK environment. Through reading an trial and error I have arrived at the following.

Create shadows on the black plate only to avoid color shift on press. I create a selection, feather it, fill it with a black to transparent gradient. I then adjust the transparency of the layer until I get the right density. Then add noise [gaussian-mono] to alleviate banding, typically 4%-6%.(photoshop5.5).

The shadows on screen look great. The banding isn't a huge issue. It's the hard edge that I get 8 out of 10 times where the shadow grades down to paper white. On screen it's perfect. But on press, it comes down to 5-4-3-2% and then paper white.

I always thought it was because the pressman is pushing the black ink on press. Somebody then said that I need to "protect the white". Meaning that the dot wasn't holding on press at the upper end.

Am I doing everything that I can to create the best shadows possible.

Grant Waddell


From: Dan Margulis, INTERNET:76270.1033@compuserve.com
Date: Sun, Feb 11, 2001, 2:17 PM
RE: [colortheory] Shadow Creation

Grant writes,

>>Create shadows on the black plate only to avoid color shift on press. I create a selection, feather it, fill it with a black to transparent gradient. I then adjust the transparency of the layer until I get the right density. Then add noise [gaussian-mono] to alleviate banding, typically 4%-6%.(photoshop5.5).>>

Everything is OK except the first sentence. Everything in moderation. Drinking a glass or two of red wine a day to prevent heart disease is a great idea. Drinking nothing but red wine is not so smart.

Similarly, using black ink to prevent color shifts in a shadow is a smart move; using *nothing* but black ink isn't a good idea.

>>The shadows on screen look great. The banding isn't a huge issue. It's the hard edge that I get 8 out of 10 times where the shadow grades down to paper white. On screen it's perfect. But on press, it comes down to 5-4-3-2% and then paper white.>>

This is one of the two major problems caused by all-black shadows. The other is that often the shadow needs to be trapped to the object, because they don't share common inks.

>>I always thought it was because the pressman is pushing the black ink on press. Somebody then said that I need to "protect the white". Meaning that the dot wasn't holding on press at the upper end.>>

It could be the pressman, but it's much more likely that the smaller dots are being lost during any contacting or platemaking step. If it were a press problem you'd probably see some scum at the edges of the shadows.

One way or another, the solution is to add CMY to the shadow. You don't want an all-CMY shadow any more than you want an all-black one. To find out the appropriate value,

1) Change your CMYK Setup (PS 5.x) or Color Settings/CMYK/Custom CMYK (PS 6) to Heavy GCR.

2) Go into the Photoshop color picker, and type in the darkest black you think the shadow might need, e.g. 0c0m0y0k.

3) Read the LAB value above it. In my case, it now reads 64L0a0b. Type the top number again, right over itself. This forces Photoshop to recalculate the CMYK value.

4) Read the new CMYK numbers (in my case, 29c20m22y27k) and use them to create your shadow. With this much black, there's no chance of a color shift, but you won't have those ugly edges or a trapping problem.

5) Restore your original CMYK Setup so that you won't get Heavy GCR on your next sep.

Dan Margulis


From: Terry Wyse, INTERNET:terry@mail.allsystems.com
Date: Sun, Feb 11, 2001, 5:54 PM
RE: Re: [colortheory] Shadow Creation

on 2/11/01 2:14 PM, Dan Margulis wrote:

> 1) Change your CMYK Setup (PS 5.x) or Color Settings/CMYK/Custom CMYK (PS
> 6) to Heavy GCR.
>
> 2) Go into the Photoshop color picker, and type in the darkest black you
> think the shadow might need, e.g. 0c0m0y0k.
>
> 3) Read the LAB value above it. In my case, it now reads 64L0a0b. Type the
> top number again, right over itself. This forces Photoshop to recalculate
> the CMYK value.
>
> 4) Read the new CMYK numbers (in my case, 29c20m22y27k) and use them to
> create your shadow. With this much black, there's no chance of a color
> shift, but you won't have those ugly edges or a trapping problem.
>
> 5) Restore your original CMYK Setup so that you won't get Heavy GCR on your
> next sep.
>
> Dan Margulis

Finally someone with the "guts" to say you CAN use a 4c drop shadow. I'd been preaching this for several years during my past life as a RAMpage trainer (the RAMpage RIP has a cool "trapping" feature called "Smart Shadows" that allows you to *automatically* overprint a contone drop shadow on any object, raster or vector, in a page layout - it's very cool and useful if you're doing a lot of drop shadows). Like Dan said, just use a fairly high amount of GCR and you won't have color shift/gray balance problems. Printers/pressman freak at the sight of a 4c build in a shadow but it works.

I hadn't thought of Dan's K=? to Lab, retype Lab value, Lab = CMYK trick. Very cool.

As to the "harsh edge" or drop-off issue, as a test have them output the film (or plate) with ALL LINEARIZATION AND/OR DOT GAIN CURVES REMOVED. Although the dot percent will be off, this may point to calibration/reduced gray levels as the problem. Just a thought.

Switching to a different screening algorithm can also help as well.

My (adjusted for inflation) $.03 worth,

Terry
_____________________________
Terence (Terry) Wyse
PrePress Specialist
All Systems Integration, Inc.
781.935.3322 voice
781.935.6622 fax
http://www.allsystems.com
terry@allsystems.com
_____________________________


From: INTERNET:pbeck@abcschoolsupply.com, INTERNET:pbeck@abcschoolsupply.com
Date: Mon, Feb 12, 2001, 10:10 AM
RE: [colortheory] Re: shadow creation

There are two kinds of shadows. Cast and Drop. If you are making drop shadows I suggest you stick with the photoshop dropshadow found in layer effects. If you are making cast from a studio shot on a background try this:

1. Make path around subject and save
2. Pick best channel for shadow generation (channel with most contrast between
shadow and background)
3. Duplicate that channel and make that channel active
4. Gaussian blur channel appropriate amount (10 works well for 300 dpi images)
5. Make path active selection
6. contract path by one point
7. Delete inside selection and deselect
8. Using curves, delete or deaccentuate all non shadow tone
9. use eraser and airbrush to paint out all extra (non shadow) tone
10. Select product(with path), contract 1 point and inverse selection
11. copy (you're copying the shadow)
12. Goto composite view
13. Select prod.(with path), inverse selection, delete background
14. Goto black channel, Paste shadow
15. Goto composite channel. Check for gaps between prod and shadow. If you find gaps you may need to refine your path. conversely if your paths are super accurate you may be able to delete the contracting the selection 1 point step throughout.

If you are making a cast shadow totally from scratch...Well, Good Luck! but try this:

1. make path around subject and save.
2. Make path active selection
3. copy subject and paste on new layer
4. create new layer, and fill selection with black on new layer
5. turn background layer off and make new layer. Fill all white
6. Deselect
7. Gaussian blur on layer 2 (10 again)
8. using edit/transform/distort, squish, stretch, pull to one side and other wise mangle your layer 2 till it looks like a shadow might look
9. Layer 2. make curves adjustment layer and pull curves to the right tonal range. Assuming CMYK Pull CMY to 0 in shadows and pull the black to whatever density to want your shadow to have. You may have to adjust the layer order but you should have the subject on top. the shadow next and the white layer last and on the bottom the original background turned off. You don't really need the white layer. It's just so you can see the effect you're creating.

The key to all this is creating shadows that live on the black plate only and feather to 1 before disapearing. I think your mistake was creating selections and feathering rather than blurring non selected blocks. Also your add noise will add a tone value on 4 channels so if you add to the shadow you're essentially getting a minimum of 1,1,1,1 for a total of 4 points of density as opposed to my shadows that feather to ,0,0,0,1 before dropping off.

Hope this helps,

Paul Beck
ABC School Supply


From: INTERNET:sdelvecchio@ambrosi.com, INTERNET:sdelvecchio@ambrosi.com
Date: Tue, Feb 13, 2001, 9:11 AM
RE: Re: [colortheory] Re: shadow creation

The Way I make black only drop shadows is:

1) I outline the merch with a path, convert this to a selection and *J to copy past to another layer.

2)I then return to the background layer and convert it to Black only by going to: Adjust Hue/Saturation /colorize /Desaturate.

That makes the background layer gray scale with all the set down shadows and fall offs of the original.

If I need to lighted it or delete part of it I can use all my normal tools with out worrying about the merch. If the fall off needs to be softened I make a loose selection and feather it a lot /inverse the selection and fill with white or delete.

Adobe Photoshop training classes are taught in the US by Sterling Ledet & Associates, Inc.