Untitled Document

Dan Margulis Applied Color Theory

Overlay Shadow/Highlight Examples

Overlay/Shadow Highlight Examples

Posted by: "John Arnold"

Thu May 10, 2007 9:23 am (PST)

Hi,

I have been reading PP5E and was a confused by something. In Dan's Bridge of Sighs example on page 421 I believe he says you should make a copy of the red channel, invert and blur it, then put it on it's own layer set to overlay. However, in a make ready column for Photoshop User magazine, he covered the same topic and he said to press Command-Option-1 (which I thought was the command to load the channel as a luminosity mask) to load the red channel as a mask. Then to save the selection as a new channel, invert it and use the apply image command on a duplicate layer.

I feel like a bit of a dunce here, but could use some clarification. Do these two approaches accomplish essentially the same thing? Also, if I choose the Command-Option-1 route, it seems to make a difference whether or not I invert before or after I deselect the selection. So which is correct? I seem to be getting different results so maybe I am doing something wrong.

Thaks for your help.

John Arnold

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Re: Overlay/Shadow Highlight Examples

Posted by: "John Bongiovanni"

Thu May 10, 2007 11:02 pm (PST)

Properly done, they're equivalent. There's some ambiguity in the invert step, and you left out blurring in your second description.

At an abstract level, what you want to do (in this example) is take the red channel, invert it, blur it, and use it overlay mode against the base layer.

At least two ways to do that (the two you referenced).

The easiest (in my view) is to create a duplicate layer. Set that layer's mode to Overlay. Then Apply Image using the (in this example) red channel from Background layer inverted. Then blur it appropriately (it should be obvious how much - you don't want halos). Then adjust opacity to taste.

The other path (a bit convoluted) is to create the inverted red channel first as a saved mask. You can create the non-inverted mask by command-option-1, then invert it by select->inverse, then save it. Or by saving it, selecting the saved channel, and Image->Adjustments->Inverse. I suspect that this is the source of your problem - two different ways to invert depending on where in the process you do it. At this point, you still have to create another layer, set it to overlay mode, and put the inverted red channel into it. So the first way is much simpler.

One other comment on your phrase "you should make a copy of the red channel ...". The red channel works fine for this image, but not for others. I recently shot a childrens birthday party outdoors in mid-day, and the green channel worked much better in this case. You have to figure out the right channel for the shot (which is why, I guess, that PS Shadow/Highlight isn't as good as Dan's technique).

You're looking for a channel where the stuff you want darkened is fairly light, and where the stuff you want lightened is fairly dark. For the shots I've done, not too hard to find.

I've also found in some occasions that you need to curve the second layer to set the "neutral point" for lighten/darken. It doesn't seem to make any difference whether you do that before or after the blur.

John Bongiovanni

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Re: Overlay/Shadow Highlight Examples

Posted by: "Rick Gordon"

Fri May 11, 2007 4:03 am (PST)

It's perhaps worth mentioning that the new Smart Filter feature of Photoshop CS3 can be very helpful in this situation and other ones where it may be handy to readjust the radius of the blur (or high pass, unsharp mask, or whatever) as you are also experimenting with the overlay mode variant and/or opacity.

Rick Gordon

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RICK GORDON

EMERALD VALLEY GRAPHICS AND CONSULTING

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WWW: http://www.shelterpub.com

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Re: Overlay/Shadow Highlight Examples

Posted by: "John Bongiovanni"

Fri May 11, 2007 4:03 am (PST)

One other thing I forgot to mention.

In some shots, it helps to do all of this in luminosity mode. That is, make two copies of the background layer. Do all of the above stuff on the top two layers. Then merge them and set the mode to luminosity.

In some shots, it doesn't make a difference. In others, it's quite noticeable.

Dan talks about this in PP5E.

John Bongiovanni

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Re: Overlay/Shadow Highlight Examples

Posted by: "George Machen"

Fri May 11, 2007 7:25 am (PST)

--- "John Bongiovanni" wrote:

... You have to figure out the right channel for the shot (which

is why, I guess, that PS Shadow/Highlight isn't as good as Dan's

technique). You're looking for a channel where the stuff you want

darkened is fairly light, and where the stuff you want lightened is

fairly dark. ...

Presumably the PS Shadow/Highlight command is using some "master channels" calculation for its equivalent of the blur-invert-overlay steps. Perhaps even a "3-6-1" grayscale. If so, then once again the inferiority of master channels manipulation rears its ugly head.

Also, don't forget that the shadow end of this kind of operation doesn't work so well in CMYK, due to the "ink police's" transference of shadow detail in CMY to K. Best to do it in RGB or LAB's L, or at most to the black plate in CMYK.

George Machen

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Re: Overlay/Shadow Highlight Examples

Posted by: "John Arnold"

Fri May 11, 2007 11:36 am (PST)

Thanks to everyone who responded to this. All of your comments are helpful and informative.

The easiest (in my view) is to create a duplicate layer. Set that

layer's mode to Overlay. Then Apply Image using the (in this example)

red channel from Background layer inverted. Then blur it appropriately

(it should be obvious how much - you don't want halos). Then adjust

opacity to taste.

If I use option number one as you describe above, and set the duplicate layer's blend mode to overlay, then what blend mode do I choose for the Apply Image command? I think in the MakeReady article, Dan used the overlay mode as the blend mode for the Apply Image command and then set the blend mode for the layer to lighten or darken depending upon whether or not he was addressing the highlights or shadows. Does that sound right?

The other path (a bit convoluted) is to create the inverted red

channel first as a saved mask. You can create the non-inverted mask by

command-option-1, then invert it by select->inverse, then save it.

If you go this route and use command-option-1, then should you save the selection first, unselect and then invert? If I invert while the marching ants are still visible, I seem to get a different result.

One other comment on your phrase "you should make a copy of the red

channel ...". The red channel works fine for this image, but not for

others. I recently shot a childrens birthday party outdoors in

mid-day, and the green channel worked much better in this case. You

have to figure out the right channel for the shot (which is why, I

guess, that PS Shadow/Highlight isn't as good as Dan's technique).

You're looking for a channel where the stuff you want darkened is

fairly light, and where the stuff you want lightened is fairly dark.

Thats' a great way to simplify the thought process.

I've also found in some occasions that you need to curve the second

layer to set the "neutral point" for lighten/darken.

I am not so sure what you mean by setting the "neutral point" for lighten/darken?

Once again, thanks for the great insights.

John Arnold

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Re: Overlay/Shadow Highlight Examples

Posted by: Stephen Marsh

Fri May 11, 2007 7:27 pm (PST)

While on this topic, in the FILES section of the Yahoo ACT site one can find an action titled "Margulis PSU ON2004.atn" that was created by Herb Ripka to illustrate "How to re-create the Shadow/Highlight effect of Photoshop CS as described by Dan Margulis in the Oct/Nov issue of Photoshop User titled "Making Two Ends Meet", pg. 44-47."

Regards,

Stephen Marsh.

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Re: Overlay/Shadow Highlight Examples

Posted by: "John Bongiovanni"

Sat May 12, 2007 5:30 am (PST)

If I use option number one as you describe above, and set the

duplicate layer's blend mode to overlay, then what blend mode do I

choose for the Apply Image command?

Normal mode.

If you go this route and use command-option-1, then should you save

the selection first, unselect and then invert? If I invert while the

marching ants are still visible, I seem to get a different result.

I think your problem is that you invert differently for a selection and for a saved channel. For a selection, you use Selection->Inverse. After you've saved the channel, you need to select that channel in the Channels tab, then use Image->Adjustments->Inverse. Either method should give you the same result.

I am not so sure what you mean by setting the "neutral point" for

lighten/darken?

In overlay mode, anything over 50% grey is lightened, anything less is darkened (progressively so). The neutral point is the lightness which is neither lightened nor darkened. Basically, you use a master curve (the overlay channel being the same in all channels at this point), grab a point that you think is OK (neither to be lightened nor darkened), and moe it up or down). You'll see the effect, and move it to a point that pleases. It may be that you could do some curving ahead of this to obviate this move - I don't know. But it seems to me that a control over the neutral point is useful.

Re: Overlay/Shadow Highlight Examples

Posted by: "ChrisBroadhurst

Mon Jun 4, 2007 9:32 am (PST)

Hi,

I enclose the action steps in text form for you, but you can download the action from the site

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Set: Margulis PSU ON2004

Action: S/H-Red Channel

Set Selection

To: red channel

Duplicate Selection

Select channel "Alpha 1"

Set Selection

To: none

Invert

Set Selection

To: none

Select channel "Alpha 1"

Gaussian Blur

Select RGB channel

Duplicate current layer

Set current layer

To: layer

Name: "Darken"

Apply Image

With: calculation

Source: channel "Alpha 1"

Calculation: overlay

Set current layer

To: layer

Mode: darken

Set current layer

To: layer

Opacity: 50%

Duplicate Background

Set current layer

To: layer

Name: "Lighten"

Apply Image

With: calculation

Source: channel "Alpha 1"

Calculation: overlay

Set current layer

To: layer

Mode: lighten

Action: S/H-Green Channel

Set Selection

To: green channel

Duplicate Selection

Select channel "Alpha 1"

Set Selection

To: none

Invert

Set Selection

To: none

Select channel "Alpha 1"

Gaussian Blur

Select RGB channel

Duplicate current layer

Set current layer

To: layer

Name: "Darken"

Apply Image

With: calculation

Source: channel "Alpha 1"

Calculation: overlay

Set current layer

To: layer

Mode: darken

Set current layer

To: layer

Opacity: 50%

Duplicate Background

Set current layer

To: layer

Name: "Lighten"

Apply Image

With: calculation

Source: channel "Alpha 1"

Calculation: overlay

Set current layer

To: layer

Mode: lighten

Action: S/H-Blue Channel

Set Selection

To: blue channel

Duplicate Selection

Select channel "Alpha 1"

Set Selection

To: none

Invert

Set Selection

To: none

Select channel "Alpha 1"

Gaussian Blur

Select RGB channel

Duplicate current layer

Set current layer

To: layer

Name: "Darken"

Apply Image

With: calculation

Source: channel "Alpha 1"

Calculation: overlay

Set current layer

To: layer

Mode: darken

Set current layer

To: layer

Opacity: 50%

Duplicate Background

Set current layer

To: layer

Name: "Lighten"

Apply Image

With: calculation

Source: channel "Alpha 1"

Calculation: overlay

Set current layer

To: layer

Mode: lighten

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Regards

Chris

Web Site: http://www.broadhurst-family.co.uk/lefteye/