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Thread: Luminance Masks

  1. #41
    ajohnw's Avatar
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    Re: Luminance Masks

    Footloose. I don't use PS but yes that sounds like it should do it. It's worth understanding all of the selection options. For instance it's possible to form a union of 2 and subtract another. Some basic GIMP tutorials always go through this area. PS tutorials seem to focus more on bells and whistles rather than making use of the basics that the bells and whistles use. Personally I have great difficulty just using things without knowing how they work.

    One other aspect I would also bear in mind is the thresholds method as I call it which from the video can also be done with levels in PS. This gives manual control of where the black and white clipping points are - that is what a mask is, some black and some white with nothing in between *. It's also worth remembering the other GIMP technique I linked to. In that one the various luminosity ranges finish up in layers. Each layer is a copy of the original with a mask applied to limit it's luminosity range. The rest is effectively transparent. Those masks can be obtained with thresholds or channel based masks formed using the selection options etc.

    Actually from memory Lightroom has a simple thresholds based luminosity mask - a slider that limits adjustments to selectable brighter parts of an image. Just something noticed in a video and I may be mixed up. What it seemed to lack is a slider to adjust the brighter end so that specific tones could be adjusted.

    * Apart from blend widths of course but often gaussian blurs may be a better option when selections are being added and subtracted etc.

    John
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    Last edited by ajohnw; 14th January 2015 at 10:49 AM.

  2. #42
    ajohnw's Avatar
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    Re: Luminance Masks

    Going back to the original image it shows a common problem with masks. There is a halo on the edge of the block of ice / snow on the bottom edge. They are a pain in the neck because they seldom reduce as people would like when the size is reduced. This may be down to the level of blur used in the preset used or the accuracy of the mask.

    I would probably do something like this with the shot to try and get visually representative mid tone colouring. The black is clipped so I couldn't get any shape into those really. Halo removed poorly with a clone brush. It's best to do this on full sized images if it's needed. Blur brushes are sometimes easier. Or healing.

    Luminance Masks

    Don't know really. I need to walk away from shots for an hour and look again before I decide I have what I wanted.

    John
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  3. #43

    Re: Luminance Masks

    It's really fruitless to try to do anything meaningful with images posted to this forum that are not originals.

  4. #44
    Thlayle's Avatar
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    Randy Butters

    Re: Luminance Masks

    Quote Originally Posted by Richard Lundberg View Post
    It's really fruitless to try to do anything meaningful with images posted to this forum that are not originals.
    Richard, I'm thinking you mean THE original, in this case a RAW file (?).

    John, thanks for the additional feedback. It helps me to hear what you are seeing. The problems with masks & haloing is something I find very difficult to manage at times, whether using luminance masks or other selections. That said, I will add that I chose this image not as an exemplar per se, but just as a visual to go along with my question about using this technique. So all feedback helps.

  5. #45
    ajohnw's Avatar
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    Re: Luminance Masks

    Quote Originally Posted by Richard Lundberg View Post
    It's really fruitless to try to do anything meaningful with images posted to this forum that are not originals.
    Much depends on the jpg and they often need a different type of initial workflow. This one for instance is limited at the black end due to clipping but if your monitor is any good you will see that I have introduced a slight amount of shape to it. The highlights are clipped to but only over a small area.

    Halos are often caused by gaussian blur being applied to masks at some default level. A pain on some GIMP plugins because they could have added a slider to adjust it. Some have some haven't. This is why it's worth knowing how to do things from scratch.

    Inverting a selection is often a bad idea while it has feathering. Growing or shrinking them by 1 pixel before inverting can help sometimes. Feathering can also cause the effect all on it's own most often if for some reason it has spread out over and area that should be left alone.

    John
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  6. #46

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    Nigel

    Re: Luminance Masks

    I realise this is an old thread but it is a subject that has recently caused me to become more interested in it. Many years ago I watched Pradip Chowdhury (Photoshopper27) do some luminosity mask tutorials which I found interesting but the Lee Varis ones I found really excellent. I've watched about 3 hours worth today.

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