Threshold activities

RH
Posted By
Ronald_Hirsch
Jul 24, 2004
Views
495
Replies
16
Status
Closed
Photoshop has a variety of paths to do "threshold" activities. And the new "Highights and Shadows" feature has sliders to adjust the boundaries between shadow, midtones, and highlights.

The layers palette has a "threshold" option for a layer.

But I’m still looking for a way to select a defined range of pixels by their brightness. In SELECT>COLOR RANGE, one can pick shadows, midtones, and shadows as the options. Photoshop roughly makes the boundaries each covering 1/3 of the 0-255 range.

There is a "Load" command in this window, but I’m not sure what can be saved and then loaded. Presumably only comething that was "selected" in the window can be saved and then reloaded.

Is there any way to select "midtones" for example, but to redefine what range that covers? With all the great things that PS can do, it would seem that this capability must be around somewhere.

Ron Hirsch
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MV
Mathias_Vejerslev
Jul 24, 2004
You can select midtones by selecting positives, and subtract a darkened negative copy.

For example, convert to Lab, copy the L channel into two alphas; a positive and a negative. Darken the negative a bit by raising the output level from 0 to 20.

Ctrl-click this Negative channel, then ctrl-alt click the positive alpha. Now you have midtones selected.

There are many ways to do this. Usually I just use Advanced Layer Blending to isolate midtones. See Phosphor "Haloless Sharpening – A Quick Tutorial" 2/20/04 11:03pm </cgi-bin/webx?50>

Mathias
PC
Pierre_Courtejoie
Jul 24, 2004
Nice workaround Mathias!
RH
Ronald_Hirsch
Jul 25, 2004
Mathias,

Thaks for the lead. I couldn’t find the message you noted – I assume that it’s on this forum. I looked via date/time, and searched via "phosphor" and "Haloless sharpening", but couldn’t find it.

Can you confirm the location?

But, I think from the info you noted, that I can get what I want. It also should make a handy action, with pauses for specific inputs.

Ron
DM
dave_milbut
Jul 25, 2004
here you go ron:

Phosphor "Haloless Sharpening – A Quick Tutorial" 2/20/04 11:03pm </cgi-bin/webx?50>
RH
Ronald_Hirsch
Jul 25, 2004
Hi Dave,

The info you noted is the same as provided by Mathias. I still cannot find anything resembling that on the Photoshop newsgroup on my mahcine.

I’ll go onto the Adobe site, and go to the forum there, and check again to see if it’s there. It’s definitely not in my NG threads. Possibly some of the messages have been deleted.

Ron
RH
Ronald_Hirsch
Jul 25, 2004
I found it on the Adobe Forum – thanks.

For some reason it’s not in my newsgroup listing.

I have used a similar approach in doing sharpening, but I guess I didn’t associate the steps involved with the different use I’m playing with, where I want better control of the boundaries between the three tonal areas.

Thanks again –

Ron
DM
dave_milbut
Jul 25, 2004
it’s in the PS lounge resource repository. I don’t know if that sub-forum shows up on the newsgroups. if it did, it’d be under

photoshop mac> photoshop lounge> resource repository.
RH
Ronald_Hirsch
Jul 25, 2004
I printed out your "haloless sharpening", and it’s now in my prized looseleaf collection of great things to use in Photoshop.

I’ve got a wide range of advanced sharpening techniques, ,ostly via actions. This one is superb. I’ve already committed it to an action.

Just curious – what values do you typically set in the unsharp mask window? I’ll typically be working with images that have been cropped out of a Kodak 14n (14 MP full), and will have a final image of 5 MP or so. I’m assuming that you deliberately oversharpen to start, as you noted in the tutorial.

I’d assume that the number of pixels in the image will impact the settings in the unsharp mask window.

Thanks again for the great info.

Ron Hirsch
MV
Mathias_Vejerslev
Jul 25, 2004
Hi Ron,

My favourite way of midtone sharpening is via a mask made with the negative positive trick. I then sharpen the midtones extreme – 240,0,5,2 for instance.

Mathias
RH
Ronald_Hirsch
Jul 26, 2004
Mathias,

Thanks for the info. Since there are only 3 adjustable settings there, can I assume that you meant 240 0.5 2? Or am I missing something?

Ron

My favourite way of midtone sharpening is via a mask made with the negative positive trick. I then sharpen the midtones extreme – 240,0,5,2 for instance.
MV
Mathias_Vejerslev
Jul 26, 2004
Yes, Ron. The confusion here is the European vs American decimal.

I have it all actionized, but my sharpening set is classified 🙂
MV
Mathias_Vejerslev
Jul 26, 2004
Here´s the rundown:

Convert to L*a*B

Duplicate L channel.

Invert duplicate (Ctrl-Alt-I).

On the inverted copy, Adjust Output Levels to 20>255.

Ctrl-click inverted, ctrl-Alt click L channel to get midtone selection.

You can now save the selection, or you can duplicate the Layer, select L channel, hit Ctrl-H to hide Marchine Ants, and apply USM; A:~450> R:0.3 – 1.0 T:0 – 4

I often oversharpen a tad, and adjust my new sharpening layer to taste. I finish off with a conservative conventional edge sharpening routine to add some haloing around contrasty edges.

This will sharpen only midtones, leave no haloes, and enhances micro detail of any photo, original or resampled.

Anyone interested: Roll your own action now. I’ve used this since I first read about it at <http://www.digital-ouback.com>, and people often commend the ‘crispness’ of my photos.

Mathias

PS: I didnt invent this. Search Google for ‘midtone sharpening’ for variations.
RH
Ronald_Hirsch
Jul 27, 2004
Thanks for the info. Looks very interesting

Is not the command to invert Ctrl-I? It wouldn’t invert, so I checked out the keystrokes, and believe you meant Ctrl-I.

The procedure does produce some great sharpening.

I’m finally going to shift into high gear on channels. That’s been an area that I’ ve never really concentrated on, and it seems like it has some awesome capabilities. I managed to locate someone who still has copies of "Channel Chops", and after reading the reports on it, even though it goes back to Photoshop 4, I ordered a copy. J&R is the only place I found that has any stock, as the book is out of print now

Thanks again

Ron
GS
Guy_Smiley
Aug 21, 2004
But I’m still looking for a way to select a defined range of pixels by their brightness.

Duplicate the layer your image is on. Apply the desired threshold to the duplicate layer. Create a "Reveal All" layer mask associated with the layer containing the original image. Copy the entire thresholded layer and paste it into the layer mask. Voila.
RH
Ronald_Hirsch
Aug 30, 2004
Thanks for suggestion. I was toying with something similar, but never got ir=t down to asuch a simple approach. Your suggestion makes it very simple and straightforward.

Ron Hirsch
GS
Guy_Smiley
Sep 1, 2004
Glad to hear it worked for you. I had never worked with masks before, so this took some fiddling around to figure out. I needed to perform this procedure on dozens of images, with the threshold set independently by eye for each image, so I put together an action to automate the other parts of the process.

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