Luminosity masks

[Simon Wantling]

Hi, I often see people referring to Luminosity masks 30% or something similar,. Can someone explain them to me or point me to some useful I don how to use them and why,

thanks

[shane shacaluga]

Good question

i would like to know this too.

[Diane Miller]

I'm on the road with just an iPhone until later this


Check the ETL forum, the recent thread Great Spotted Woodpecker, Rachel Hollander's answer.

[Diane Miller]

Sorry, trying to type on an iPhone while riding in a bouncy pickup. And can't edit a post -- I hit send by mistake for the second time today.

Rachel summarizes the very particular use that is so commonly cited here. The reference to Tony Kuiper will give you a more complete overview.

She mentions the very important fact that once you have an image in PS you have any blown whites and blocked blacks glued in and can't recover them. It is better to go back to the raw file for the kind of darkening that is done by that method. It's very easy with some some slider adjustments.

To put these luminosity adjustments in perspective, they go back to the days of film scans when we had limited control of tonal contrast. What we can do now in a good raw converter (ACR / LR are excellent and surpass Canon DPP in tonal control; I can't speak for any others) makes the basic lightness (and the inverse darkness mask, which I've never seen mentioned here) of limited use. The higher order masks Kuipers mentions are often of more use as they allow isolation of narrower tonal rangers which is more difficult in raw conversion.

Hope this makes sense as a continuation to my truncated post above.

[Rachel Hollander]

Hi Guys and thanks Diane. For convenience I've copied my post from the thread Diane mentions above but without the posted image:

You can Google "Tony Kupyer luminosity mask" to get some tutorials but here's a simple version of instructions.

In PS click on the "Channels" palette.

Once the Channels are showing click on the top RGB Channel (which is actually all 3) while also pressing the "Ctrl" key. This will select the highlights.

Make a duplicate layer and then in the "Layers" palette make a mask of the selected highlights.

Still in the layers palette, go to the drop down menu which should say "normal." Select "multiply" in the drop down menu and then adjust the opacity of the layer to taste.

I think what Diane is referring to as the inverse darkness mask is what I know of as a luminosity screen mask and is used to lighten some of the darker areas of an image. Follow the first 2 instructions above.

Once the highlights are selected, under the "Select" drop down menu, choose "inverse." Now instead of the highlights being selected the darker areas of the image are selected.

Make a duplicate layer and then in the "Layers" palette make a mask of the selection.

Still in the Layers palette, go to the drop down menu and choose "screen" and adjust the opacity to taste.

As Diane says, it would be better to recover the detail in the RAW prior to conversion and then to use a luminosity mask or multiple luminosity masks if necessary to just refine it.

Shout if you have any questions,
Rachel

[Diane Miller]

Thanks, Rachel -- good idea to copy it here, and to expand on how to use it to lighten dark areas. I mostly see it mentioned here as some "standard" way to darken light areas.

It isn't difficult to re-tweak a raw file, if you use ACR or LR. It has been possible for several versions of PS / LR to open a RAW file as a Smart Object, which lets you go back at any time and re-adjust the raw conversion parameters on the actual raw file. Of course, any pixel layers you have added on top of the raw file, such as a cloning layer, will no longer match, and adjustment layers may need re-tweaking, but that isn't a big deal when you want the best possible image.

[Don Nelson]

Rachel
You can select any of the channels, not just RGB, to use this method. R, G, or B, might provide a more useful mask than just RGB. And you can further modify the mask using many of the usual techniques.
see also links at
http://www.earthboundlight.com/phototips/photoshop-luminosity-masking.html
A good one here on using the technique to blend an HDR with a normal image http://www.digitalcameraworld.com/2012/11/27/luminosity-masks-why-raw-hdr-is-the-best-hdr/

[Rachel Hollander]

Don - I'm aware that you can use each individual channel. This wasn't meant to be a full tutorial on luminosity masks but was something I had posted for suggestions on improving a particular image posted in ETL.

Rachel

[Don Nelson]

Rachel
since this appears to be moved, it no longer is obvious that you are replying to a specific image. I saw this in the Digital Photography Workflow section. I'll have to go see if I can find the original image thread, thanks

[Diane Miller]

Here it is:

http://www.birdphotographers.net/forums/showthread.php/114992-Great-Spotted-Woodpecker