[byRo]

If you take a look at the threads concerning sharpening / blurring / high-pass filter you will quickly discover two things:
1) The radius is very important;
2) Nobody tells you just how to get it right.

Hope this will help out.
[details]

They say the best way to learn is to teach - had to rewrite this three times because I kept on finding better ways to do it.

Have fun,

byRo

[Ed_L]

Please don't add another tutorial for a few days. Although I'm sure this is explained very well, it's going to take a couple of days to sink in. When it does, I'll be looking for another one from you. These are great! Thank you for putting in the work so we can all understand it better.

Ed

[DannyRaphael]

Ditto, "Thank you for putting in the work so we can all understand it better."

An awesome package of knowledge.

[byRo]

As Danny pointed out to me - the "How to use the Graphics Eq." part could use some (a lot) more detail.
Tonight I'll edit the tutorial, but in the meanwhile.....

The green band-pass layers are all initially turned off with blending set to "Normal".
Starting from the bottom:
- turn the layer on;
- take a look at the information and decide:

1) This is something that will help;
2) This is something that is working against you;
3) Neither one or the other.

In the first case change the blending from Normal to Overlay. If the effect is too much change to Soft Light, or if you want more change to Hard or Linear Light.
In the second case invert the layer <ctrl><I> and proceed as above.
In the third case just turn it off and go to the next above.

Note: the initial "Normal" blending is only to help visualize the content of each band, if you are going to use it change the mode to Overlay etc..
If anything else isn't clear - PLEASE ASK.

byRo

[SWEngineer]

Rô, excellent work here! Sadly (for me), I only have Elements, so I can't play with your action file. (If you can coax Richard Lynch into helping make this compatible with his HPA3 work, I'd be deeply indebted to you both.)

Am I correctly understanding that these are true band pass filters? e.g. the 10 - 20 layer (filter) would be (using the invert / linear light subtraction trick) Highpass(20) - Highpass(10) or equivalently GaussBlur(10) - GaussBlur(20)?

This opens up an entire new dimension for selectively modifying images. In addition to tone & color, its obvious now that one can work with "frequency" with near equal ease. The example you posted and your suggestions for using your graphic equalizer barely scratch the surface of what can be done with this tool / idea. At least from my perspective as an artistically challenged, but mathematically inclined person, this may be the most valuable tutorial I've ever read. Thanks so much for sharing this. You are awesome Rô.

-Mark

[byRo]

Hi there, Mark,

Originally Posted by SWEngineer

Am I correctly understanding that these are true band pass filters? e.g. the 10 - 20 layer (filter) would be (using the invert / linear light subtraction trick) Highpass(20) - Highpass(10) or equivalently GaussBlur(10) - GaussBlur(20)?

Well, as true as Photoshop will get you*. A more practical way to generate the band is to do the high-pass filter at the higher radius limit (e.g. 20) and then G.Blur the layer at the lower limit (e.g. 10)

Originally Posted by SWEngineer

Sadly (for me), I only have Elements, so I can't play with your action file.

The action file is just a quick way of making up a whole load of bands. With a bit of practice you can estimate a good band and do the High-pass / GBlur trick above.

Originally Posted by SWEngineer

This opens up an entire new dimension for selectively modifying images. In addition to tone & color, its obvious now that one can work with "frequency" with near equal ease.

Exactly

Originally Posted by SWEngineer

...but mathematically inclined person...

*Then you're going to just love the FFT (Fast Fourier Transform) stuff!

Rô

[JustChecking]

thanks for an extremely interesting article

reminds me a bit of my first lectures in image processing, when i've been trying to figure out how to do USM in image domain w/o having to convert to spectral domain (FFT)... how trivial it is! and yet it took me few hours

[delic]

This has a lot of applications.. Awesome stuff especially masking related..

[venivedi]

Wow, cool. I'm so impressed by a layer named 'clipping'

[byRo]

Originally Posted by venivedi

Wow, cool. I'm so impressed by a layer named 'clipping'

Glad you liked it.
As I remember there is an action for setting up the layer in the ten-minute tool box - then you can use it anywhere.

Rô

[palms1]

Thank you
yet again another must read tutorial, I have just had a go with unclipping and need to practice that before i have a go with something else, but there again my fingers are starting to itch ! ! ! ! ! !

[venivedi]

Thank you again, byRo. Sometimes I don't see any clipped area because of lighting circumstance, monitor setting and etc. So I really appreciated your effort.

[hpycmpr]

Thanks, byRo. Great tutorial. You mentioned "Next up: Sharpening: The true story". Is there an accompanying sharpening tutorial?

[byRo]

Originally Posted by hpycmpr

...Sharpening: The true story". Is there an accompanying sharpening tutorial?

Thanks for the nudge, hpycmpr. I knew I had written it, but I couldn't find it posted either!

Then I remembered that it was on my "to do" list when my computer got nicked. Luckily I have found an e-mail with a draft prevew that I sent to a highly-respected fellow member, so I should have it up soon.

Rô

[hpycmpr]

There are plenty of sharpening tutorials floating around, but I look forward to yours. Judging from your other tutorials, I'm sure you will something fresh and insightful.