LR Brush Mask: Some Cool Advise

https://www.youtube.co​m/watch?v=LypUUCT7XFQ
I wouldn't have thought of this alone, huge brush and no feather, but it can work great.

Also:
http://forum.luminous-landscape.com/index.ph​p?topic=99076.0

Oops.Make that advice.

Ive been doing that for ages, works amazingly well for getting all of the branches of a tree against a contrasting sky

Thanks for sharing.

Very cool idea. Thanks Elie.

Is this is the Lightroom sticky?, if not can it please be added

awesome! I'll be trying this tonight!

This is agonizingly frustrating to watch, considering that the blue channel of this image would give you an even better mask with no effort. Or a luminosity mask. Hey, whatever floats your boat! You suffer for your art.

kirk

A useful technique but would be easier if he used the zoom, especially on that second small tree. I was shouting at the screen every time he undid/redid.

kirkt wrote in post #17498071
This is agonizingly frustrating to watch, considering that the blue channel of this image would give you an even better mask with no effort. Or a luminosity mask.

kirk

Please post an image of the blue channel. That would be interesting to see.

I can't post someone else's images, but if you google "Aspen Grove" and use an image that is similar to the one in the video, you can inspect the R, G and B channels. "B" will give you dark foliage and grass and light trunks - that is, it will isolate the trunks for whatever method you choose to boost their exposure. You can add a curves adjustment to increase the contrast of the mask if you desire. The dark knots on the trunks will also be dark, so the adjustment to which you apply the B channel as a mask will not affect the dark knots.

The G channel will have light foliage, so that is not the best choice for isolating the trunks, which will be light in all channels. The R channel may be an OK candidate as well, depending on what you are trying to accomplish. However, green leaves and grass usually have a lot of yellow in them, so these features will be darker in the B channel than the R channel, typically (Blue is the opposite of Yellow).

Also, the B channel mask does not simply select the trunks, the intensity of the mask is based on the original luminance of the B channel - so brighter areas of the trunk let more adjustment through, while darker areas of the trunk let less adjustment through - that is, the contrast of the original tones is preserved through the adjustment. I do not know if the LR mask is this nuanced, or simply a uniform selection based on color/tone (all pixels in the selected area get affected equally by the adjustment).

Here is an image I found by Googling it on the Bing:

http://images.summitpo​st.org/original/252326​.jpg

open it in PS and Assign it sRGB.

In PS you would create your adjustment layer (for example, a curves layer) with a blank mask. Select the mask, use "Apply Image..." and use the Blue channel of the background layer in Normal blend mode to apply the Blue channel of the original image to the mask. Takes a few seconds.

kirk

kirkt wrote in post #17498071
This is agonizingly frustrating to watch, considering that the blue channel of this image would give you an even better mask with no effort. Or a luminosity mask. Hey, whatever floats your boat! You suffer for your art.

kirk

I know that it is much easier to do complex selections in PS, but then you do lose the ability to apply them directly to the RAW file that LR (or ACR) allows. I know that several other RAW processing programs now have similar capabilities to the Local brush in LR/ACR, but I'm guessing that again they only have limited selection capability, as they are working with RAW data, not RGB. Of course it would I suppose be possible to generate an RGB separation to use as the basis of a mask, but that is usually outside the capabilities of most of the RAW processing programs that I am aware of.

As to your other question, the local brush is mostly of fixed density, although you can vary the density of the brush to paint in various areas. The brushes also have a feather effect. The real problem is that you have very little control over it. A single slider from 0 to 100. LR/ACR also offers a gradient filter effect, with the same tools as the local brushes. Unfortunately though you cannot mix the application of a gradient filter and brush. This could be very useful in that you could use the brush to deselect areas from the gradient filter, to allow for uneven backgrounds etc. I hope that this will become a feature in LR/ACR in the future. At the moment I have to go to PS in order to add a gradient filter to a sky, which is then masked around the aircraft in the middle of the shot. Very handy for the often drab plain skies we get here in the UK.

Alan

BigAl007 wrote in post #17499383
Unfortunately though you cannot mix the application of a gradient filter and brush. This could be very useful in that you could use the brush to deselect areas from the gradient filter, to allow for uneven backgrounds etc. I hope that this will become a feature in LR/ACR in the future. At the moment I have to go to PS in order to add a gradient filter to a sky, which is then masked around the aircraft in the middle of the shot. Very handy for the often drab plain skies we get here in the UK.

Alan

This is possible in ACR in PSCC. I assume this will be added to the LR gradient adjustment in LR6.

I do not know how LR makes auto mask decisions on the image data - I would think that it works on RGB data in LR's internal working space, not raw linear digital numbers.

kirk

If anyone is interested - this video is being discussed with the author (Wayne Fox) over at LuLa:

http://forum.luminous-landscape.com …topic=99076.msg​811071#new

Jeff Schewe made some additional comments about working with the Auto-mask brush in the thread that might also be useful to folks that use LR for making local adjustments.

kirk

Thanks for that link, I'm pretty good with the adjustment brush but can always use new pointers.

[edit] Some pretty cool tips in there.

It might even work for flyaway hairs against a backdrop, like he's doing for leaves against a sky.

I do already use the Auto Mask in Erase mode for refining an adjustment.