Inspiring

Question

Luminosity

Forum|Forum|7 years ago
July 25, 2018
8 replies
2859 views

Hi folks.

I've done the usual Google and YouTube search, but can't find a good tutorial on Photoshop Luminosity that isn't a platform for selling another piece of software.

Can anyone recommend a good tutorial, even on Adobe site?

[Moderator edited title to fix typo.]

This topic has been closed for replies.

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BigDingusAuthor

Inspiring

When I first posted here, it was to learn about Luminosity. I knew absolutely nothing. However your discussions between you are revealing loads for me to soak up like a sponge. Excellent.

Ussnorway7605025

Legend

in my book the best use for them is turning summer photos into winter

here is one that covers the basics but the trick is as old as Photoshop itself and there are many fine-tune options so look around

Summer To Winter - Snow Photoshop Tutorial - YouTube

Stephen Marsh

Community Expert

I would suggest that Luminosity (RGB) and Lightness (L of Lab) are indeed different, however in practice they are similar in how they are used.

D Fosse

Community Expert

Stephen_A_Marsh wrote
I would suggest that Luminosity (RGB) and Lightness (L of Lab) are indeed different, however in practice they are similar in how they are used.

It should be easy enough to test. In my own limited testing I have found them to be identical. And it would be the logical way to do it, since the Lab version is always present in the background. Those data are easily pulled up.

Note, however, that if you display a luminosity mask as a single-channel grayscale image, it will be displayed according to your working gray. Your working gray is assigned.

So you need to keep gamma identical. In practice that means you must test with Adobe RGB and Gray Gamma 2.2 as working gray. All other combinations will change the tone response curve in the mask representation on screen.

Stephen Marsh

Community Expert

OK. I'm travelling with only a laptop right now, no Photoshop, so I'll have to look into it later.

Question: What does the RGB composite curve actually represent? Answer: RGB Luminosity.

RGB luminosity is often “disguised and hidden” in Photoshop, here is a solid fill of 128r128g128b in sRGB. The Lab L value is 54. The RGB composite curve is value is 128…

How about with a bright colour that does not have equal channel values? A lime green sRGB of 151r255g0b has a Lab L value of 91, however the RGB composite curve has a marker of 196. Notice that in Lab, the L value on the curve precisely lines up with the histogram value. In the RGB version, the RGB histogram value is at 151 (median value) and not 196 (luminosity value).

Norman Sanders

Legend

If your objective is altering and controlling luminosity (discrete from color), consider switching to Lab Color Mode where the L channel (luminosity) is separate from the magenta/green and yellow/blue channels that build the image. An excellent book devoted to Lab Color is "Photoshop LAB Color" by Dan Margulis. For starters I recommend the 2006 edition.

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BigDingusAuthor

Inspiring

Thanks for that Norman

D Fosse

Community Expert

Photoshop Luminosity is identical to the Lab L channel. You don't need to switch to Lab mode just for that.

Lab is always at work in the background in Photoshop. Color management in Photoshop uses Lab as Profile Connection Space, so Lab values are always readily available. This is what Luminosity blends and selections are based on. When you load a luminosity selection, you get Lab L, and not a desaturated RGB version, which is different.

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BigDingusAuthor

Inspiring

Axel, been looking at your links. You found better ones than I did. Thanks

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BigDingusAuthor

Inspiring

Thanks Axel. I too found loads on YouTube but they then go into how to use their own addons etc.

Trevor if I was wanting to use their sofetware I would deffinately reward them. However, all I want is the knowledge to do it myself and not have someone use an underhand method of selling their software by pretending to help.

Trevor.Dennis

Community Expert

BigDingus wrote
Hi folks.
I've done the usual Google and YouTube search, but can't find a good tutorial on Photoshop Luminosity that isn't a platform for selling another piece of software.
Can anyone recommend a good tutorial, even on Adobe site?

Can you give us some context?

Are you asking what it is, or how to use it?

Are you thinking of masks, or blend modes?

If you don't feel that the work people put into developing useful software is worth rewarding, then Sven Stork's Luminosity Mask extension is free unless you want to make a small donation.

https://svenstork.com/interactive-luminosity-masks/

https://www.adobeexchange.com/creativecloud.details.12307.html

AxelMatt

Community Expert

I've searched with Google and Youtube and found tons of tutorials.

A Simple But Effective Way to Create Luminosity Masks in Photoshop - YouTube

How To Create Luminosity Masks In Photoshop - YouTube

Creating luminosity masks in Photoshop | Photo Tools Weekly | lynda.com - YouTube

Understanding Luminosity Selections and Luminosity Masks Basics - YouTube

My System: Intel i7-8700K - 64GB RAM - NVidia Geforce RTX 3060 - Windows 11 Pro 25H2 -- LR-Classic 15 - Photoshop 27 - Nik Collection 8 - PureRAW 6 - Topaz Photo AI

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