Question about High Pass

[brucet]

Another silly question!!

When I open a new High Pass Adjustment layer it always opens at 100%. And produces a grey layer. Is this normal? I have to move the slider below 0 before I see any meaningful change. (I'm trying to replicate PSP's Clarity function). I'm getting what I want but the grey layer is bugging me.

regards

[photoken]

Yes, that's normal.

To get the "Clarity" effect, don't change the Intensity setting; instead, increase the Size until you just begin to see some detail in the gray. Click "OK" to close the dialog and then change the HP layer's blend mode to "Overlay".

The way the HP layer works in this case, is that it increases the contrast at edges in the image. You can see how it does that by increasing the Size to a large value -- the dark side of edges is progressively made darker as the edge is approached, and the light side of edges is progressively made lighter as the edge is approached.

For the "Clarity" effect, you'll find that using a Size value that just barely begins to show some details in the gray will give a subtle clarity effect. Increasing the Size value will give a clarity effect that becomes more and more noticeable until you're creating an image that's obviously been manipulated for an extreme effect.

[brucet]

Thanks Ken. I'll have a try tonight. 'Clarity' is always a bit subjective.

regards

[Hoogo]

Something about high pass:

You can find something like frequency in pictures similar to sound. Low frequencies create the rough picture, high frequencies add more and more details and edges.

There is a low pass filter, too: Gaussian blur. It removes more and more edges and details and only lets the low frequencies pass that make the rough picture. If you blur a black pixel on white background, the result is more or less light gray: All in all the area around that pixel had that nearly white color.

The high pass filter is just the difference between the original picture and the low pass filtered version. a black pixel on white background can have a difference of up to -255 compared to the blurred version, a bigger area of the same color will have a difference of 0, and a white pixel on black background can be up to +255 brighter. But as normal layers cannot store values between -255 and +255, that values are mapped to 0 to 255, with 128 being the neutral value.

That's why the high pass looks mostly gray: Lots of areas in pictures have soft gradients or little difference in color, so there's also only little difference between the original and the blurred picture.

'Clarity' is just one use case for the filter. We've had a nice thread about frequency separation lately, that shows that there's some more practical use for that filter, maybe it also gives a little more idea about high pass and low pass.

[photoken]

Excellent info, Hoogo. Thanks.

I think of the High Pass filter in terms of frequencies, and in image editing
Small Details = High Frequencies

So, the filter will "pass through" details whose size (frequency) is smaller than the size set in the filter. For a given image area, the more differences there are between adjacent pixels the more "details" (frequencies) there are and so the effect of the filter becomes stronger.

Your point about the other uses for a High Pass layer is important. It's a general-purpose tool that can be used for "Clarity", or Frequency Separations, and probably other things as well.

[brucet]

Ken I followed your suggestions. Seems a lot of clicking to get a result. And it's not possible to see a 'real time' preview as you change the settings. Yes it works. But it's a very hit and miss way of doing it. (Unless I'm missing something!!). Get it wrong and it's a lot of work to go back and retry.
Compared to PSP's Fill Light/Clarity functions it's very clunky. With PSP you can see what is happening as you move the sliders. Subtle changes are possible in PSP whereas in PL you need to flip back and forth to get the results.
Compare the number of clicks, in PL, to simply sending the layer to PSP via the External Program option.

regards

[photoken]

And it's not possible to see a 'real time' preview as you change the settings. Yes it works. But it's a very hit and miss way of doing it. (Unless I'm missing something!!).

Do you have the preview icon enabled?

HP dialog.jpg

Once you've established the Overlay blend mode for the HP layer, any changes you make in the dialog will be seen in the main editing window (as well as in the Before & After view in the dialog itself).

[brucet]

I follow what you are saying Ken. Once you do your settings and go back to Modifying the Layer then real time changes can be seen. But it would be helpful to see the changes as you do the first adjustments. So the first Adjustment HP layer is a bit of a hit and miss exercise. Experience makes it easier. But you do then have to take the next step of Overlay. Just seems the long way of doing it. I can do it a lot quicker by opening up PSP.

regards

[photoken]

brucet,

Don't forget what Hoogo and I mentioned earlier: the HP layer is not a dedicated "Clarity" filter, it's a general-purpose tool that can be used for other purposes as well. And, in addition, by implementing your "Clarity" as a layer, you can paint on the layer's mask to reduce its effect on specific image areas.

The HP layer method is not the only way of doing "Clarity", either. Search the PL Help for "Clarity", and you'll get to a page that has a description (brief) of using the Unsharp Mask adjustment or the Sharpen adjustment for a "Clarity" effect.

[Paul]

Hi,

I created an action to apply HP, then turn the adjustment layer into Overlay, and after that Modify the layer, with a pause. In that way, you get a realtime adjustment dialog, after the Overlay mode has been turned on.
You could try that.

- Paul

[chrischa]

Two thoughts about the workflow:

1. I prefer seeing the gray image first, so i can adjust the filter very exactly to the point, where the outlines of the objects become visible. Most of the time I don't have to adjust the result any further. (Sometimes I switch between Overlay and Soft Light afterwards, to see which one looks better.)

2. To build an action was my first thought, too. Now I downloaded yours, thanks Paul Finally, I deleted the last step, because my Adjustment Layer-Panel is always open. So I don't have to move and/or resize and finally close the High Pass-Window.

As I said, just two thoughts to show alternative ways for new users, no "that's the way"

[Paul]

OK, you can pauze the 'Create High Pass layer'-action by clicking once on the white square left of the name of the action. Then you will see the grey image first.

- Paul

[brucet]

Thanks folks. I understand HP. The only 'issue' I'm having is the round about way of using it for clarity in PL. My concern is about finding suitable solutions for clarity within PL not HP. I can't see how you can 'guess' what the results will be when you can't see the final result. Every photo is different so you need flexibility.

regards

[photoken]

1. I prefer seeing the gray image first, so i can adjust the filter very exactly to the point, where the outlines of the objects become visible. Most of the time I don't have to adjust the result any further.

I completely agree. Maybe this is something that only comes with experience, but I just "know" by looking at the gray image how far to push the Size adjustment.

[bkh]

My concern is about finding suitable solutions for clarity within PL not HP. I can't see how you can 'guess' what the results will be when you can't see the final result.

I don't quite understand your problem. Just create the adjustment layer and set the blending mode, then fine-tune the settings while viewing the result. Of cpurse, this doesn't work if you use the HP filter on a copy.

Cheers

Burkhard.