I've been putting together some tutorials for photographic retouching in GIMP, and have recently completed what I think might be useful to other GIMPers to know about: Luminosity Masks.
The basic premise is to use masks based on the luminosity of an image to restrict layer modifications to certain tonal values (only adjust light tones, or dark tones, or mid tones for instance).
Many people point to the Luminosity Masks tutorial by Tony Kuyper, so I put this together to show the same workflow for GIMP (there's also a short tutorial on using the masks for doing split toning in images).
I'm trying to get a better understanding of luminosity masks. Where can I find out just what operations Photoshop is performing when I control click on the rgb composite channel to make a selection (which I then save as an alpha channel)?
My assumption is that the brightest half of the image pixels are included in the selection and the rest are consigned to black. Is that even in the ballpark?
is there a way to view the RGB channels luminosity only? It seems I have to shut off two channels just to view one, and that one will be colored (red, green, or blue). How can I just view the channel in grayscale? Is this possible? Do I always have to shut two channels off to view one?
Also, I take it there are no adjustment layers in GIMP, correct?
I have a picture taken by a nasty camera : one side of the image is more luminous than the other. I need this image to be analyzed by another software that count cells, so it is very sensitive to color differences. I would like to normalize the light over the entire picture, so that the soft will effectively count cells. Is there a function in GIMP that allows to do that ?
I have a png file that has some letters, the letters are blurry after thescanning and I would like to enhance the tone of the letters, the lettersare black and the document is in many colours but black. How can I isolatethe black, thus the letters, from all the other colours and then enhance thecolour black so that the letters are thick and solid.
I usually try to see for myself but when I apply a layer mask, I don't think that there's any difference, so what do they change and what are they supposed to be used for?
I read tutorials all the time. They say to apply the mask, then erase the mask around where you want to keep, then delete the picture thats under the mask.
Why not just use an eraser and erase what you don't want?
You know how you can add a 'layer mask' to a layer and then apply various shades of grey to the mask to alter the transparency of the layer.
For some work I find this awkward as you cant see what your doing on the layer mask (or have a missed a trick here). Are there any alternatives? I would be nice if there was a blend mode to make one layer alter the transparency of the layer below.
Is there anything that can be done using an alpha channel, that can'tbe done using masks and layers, or vice versa? Context of question: I've worked extensively with masks and layers.I've never worked with alpha channels.For example:
Using an alpha channel:
1. Open two single layer images, A and B, neither one of which has analpha channel. 2. Drag the image B over to A and close B.3. Now image A has two layers, A and B. Put layer A on top, selectlayer A, set the blend mode to Normal, and add an alpha channel.4. Erase part of layer A, where-ever you want layer B to show through.At this point, layer A has an alpha channel with white where you wantlayer A to show, and black where you want layer B to show, but it doesnot have a mask.
OR
Using a layer mask:
1. Open two single layer images, A and B, neither one of which has analpha channel. 2. Drag image B over to A and close B.3. Now image A has two layers, A and B. Put layer A on top, selectlayer A, and set the blend mode to Normal (don't add an alphachannel). 4. Create a solid white mask for layer A. Paint black on the maskwhere you want layer B to show through.At this point, layer A has a mask with white where you want layer A toshow, and black where you want layer B to show., but it does not havean alpha channel.
In both cases, using a mask or using an alpha channel, the net resultis the same.So again, is there anything that can be done using an alpha channel,that can't be done using masks and layers, or vice versa?
Using Photoshop or Elements, it is possible to open up two image of the same subject (I.e. a building) taken taken at several minutes interval, then using the move tool you combine the two images, then add a layer mask, you can edit out any people or distractions, how is this possible in Gimp, I have both Photoshop and Elements (Both Legit), but I dont want to return to Windows.
I am having trouble with using my layer masks. I can use the masks that are hidden (shown with black screen) and apply them with the white brush, but I cant get white or shown masks to be taken off with the black brush. Sometimes, not always I have trouble adjusting the opacity of white masks. I was playing around with actions I downloaded and after applying three actions to a photo, elements froze on me. I read about trashing preferences, I dont know what that does or means but I tried to hit cntrol alt shift when photoshop was opening and nothing happened. When it first opens it shows I can install the new inspiration browser ( i dont know what that is either) thinking it was a required update I tried to update and it gave me an error message, something about the installer has been mis-configured.
I just loaded Gimp 2.8 from 'ppa:otto-kesselgulasch/gimp' with the idea of using the 'all-in-one' new arrangement. I am using Mint 13 Maya and the new gimp interface is not yet in the repository.
That said, having opened the 'new' gimp I see the docks arrangement is a bit different. Whereas there used to be two docks one on either side of the drawing area, now the right hand dock is split screen.
The problem is that just for say the colour wheel it uses loads of screen space. I know I can toggle between 'all-in-one' and multi-mode but they both have a split screen for the docks on the right.
I don't see any obvious way to move the colour wheel dock back to where it has been under the toolbox and brushes docks.
Maybe this is a fixed arrangement in 2.8, if so I will have to go back to my Mint 13 native version.
What I need to do is, take an image, split it into strips about 1/4 inch wide but have them so I can put them back.the actual size of the slices can be varied but each slice has to be the same size across the whole image.
1. Is there a "show quick mask" feature for showing masks?
I know Gimp has a "*Show quick mask*" feature which shows what you have(and haven't) selected by displaying a red overlay over your image,allowing you to add to or subtract from a selection by using the paintbrush, but I haven't found a similar feature for showing masks.
Photoshop has this feature (it's called 'reveal mask' I think) and it basically just shows a red overlay of your mask on your image so that,similar to the quick mask feature in Gimp, you can see where you have and haven't masked through.
(I don't own Photoshop so I'm not sure if the red overlay shows the opacity with which you've masked through or whether or not you can edit the mask when it's being shown as a red overlay.)
2. Is there a command for showing the layer underneath the current layer I'm working on?
This is another feature that I've seen Photoshop has that is useful for blending multiple exposures (and lots of things, really).
Basically it's just a keyboard shortcut for showing the layer underneath your current when you hold down a certain keyboard command (it's not something you toggle since it's meant for quickly viewing what's on the layer underneath your current one).
I know I can press space bar to show or hide the layer I'm currently working on, but I can't do that unless I focus into the layers dialogue first. It'd be nice if I could activate that functionality from anywhere,regardless of whether I'm focused on the layers dialogue.
I made all my polygons with the same technique but somehow interactive polygon split tool does not split all polygons... I attached a file with which I have problem. Split tool just "disappears" after submitting changes...
We all know the invert function of Photoshop, easy and nice (well nor always but will fix this) to invert all colors.... The downside is than this trick will also invert luminosity... Light area become dark and dark area become light, this can ruin an image!
If you wish to invert an image and keep lighting intact the trick is really simple!
1) Open an image to be inverted 2) Duplicate you background layer (or the image layer), this layer will be used as a luminosity mask. 3) Select your original layer 4) Invert you original layer 5 (Optional) Link and Merge these layers
Done!
Trick : If you invert the luminosity(the copy of the original) rather the than original layer, you will inver the lighting of the image... Its also pretty cool!
I have always used the shortcut Ctrl+Alt+~ to get luminosity selection. It always worked in Photoshop CS3 and still does on my computer, but when I try it in CS4 nothing happens and it doesn't work. Do I have a preference or setting wrong?
1. Duplicate the image which is in RGB mode 2. Change the mode of the duplicated image to LAB color mode 3. Select "lightness" channel in the duplicated image 4. Move it into the RGB image as alpha channel 5. Copy this channel and invert the copied channel 6. Create two HSL adjustments with these two channels used as masks 7. Turn off completely the saturation sliders in the HSL adjustments for desaturating the image
Now, I can not get completely desaturated image after these steps..Is there a leakage between my luminosity masks?
I am trying to calibrate my screen using gretagmacbeth eye one. Everything works o.k. apart from my colour temprature and luminosoity. The colour temprature is way down approx 10% and so is the luminosit, it is no where near the rcommnded levels. To the extents I have now got a red tint on my screen due to the colour temprature.
So how can i overcome this, can i buy a special lightbulb or kit for the room i work? Or what do I do?
In the histogram palette menu there are red, green and blue histograms to give the saturation of those colors, and a luminosity histogram to give the overall ( greyscale) brightness. There is also an RGB option, presumably to give a composite version of the red, green and blue saturation.
In Levels, however we have the same thing, except there is no luminosity option, only RGB. But RGB in this case cannot be a composite of the three color channels, as we use it to adjust brightness and contrast; in other words it is presumably the same as Luminosity in the histogram palette. Despite this, when I do adjustments to an image the RGB histogram in Levels looks identical to the RGB histogram in the histogram palette. I'm using PS 3 Extended.
Colorizing a photo can be fairly simple using Adjustment layers and Hue/Saturation, what I've never been able to do though, was convert black to white within a photo. The other way around, white to black, is fairly easy to pull with decent and satisfactory results. Black to white on the other hand, seems to give a lot of trouble in maintaining proper and believable luminosity. If I have a black plastic object, for example, that I'm attempting to turn white... through all random experimentation I have done the object either becomes another 'material'... ie. metallic, or the object becomes too washed out (loses detail) to even make the eye believe the change is real and the material is still the original. I do know, though, that people are capable of creating the illusion of all sorts of material and surface through photoshop. So, if someone has an idea on how to 'colorize' and image while maintaining the original and proper reflection of light on the surface of the object,
Attempting to lighten plastic center plate using levels, loses correct material luminosity and becomes metallic
Attempting to lighten plastic center plate, using Lightness/Saturation, loses vast amount of surface detail, becomes 'flat' and washed out
I'm currently recording the median luminosity and standard deviation of luminosity values in various photographs. This has been an ongoing project so I've been working on it for probably the last 4 months. Today I resumed my work and had to go back and check a previous photo that I had already recorded luminosity values for and noticed that the luminosity values that I had originally recorded were different than the values I'm seeing today in the histogram.
The attached picture shows the histogram I'm using (and have been using since I started this project). It is showing a median luminosity and standard deviation of luminosity for a photo that originally gave me this median luminosity value: 75 and this standard deviation: 27.87
I accidentally changed some setting in photoshop that affected the luminosity readings, or if the luminosity values of a photo are estimated by photoshop and thus aren't always the same etc. ?
I know what the documentation says that they do, but it doesn't appear to be the truth. For example, if I take my image and overlay it with a 50% gray layer set to Luminosity mode, I would expect to see the hue and saturation of my image, with the luminosity of every pixel set to 50%, but that isn't what actually happens.
I'm on Win 7, 64 bit, and CS6 (released). I've got the Spot Healing brush active and I Shift + Right-click to bring up the Blending options. I cannot change to Luminosity. It will change in the drop down box on the tool bar however.
When I first noticed, it was Lighten that it wouldn't change to. I've rebooted the PC a couple of times and now it seems to be the Luminosity mode.
How to create a luminosity mask in Photo paint?I know there was a macro but the site is in Russian and I'm not so good in that to read the instructions.
Recently I noticed the histogram in PS4 displaying color channels instead of luminosity. And all three RGB colors seem to spike off the top of the window. Is there a way to only display the luminosity histogram curve? Also, how often would be considered normal to have to re-set preferences?
I have a diamond image, which obviously has different shades in it, it actually has dark, like dark brown shades, which i want to change to lighter smth like light yellow, i tried replace color, hue/sat//light but the effect is not realistic like an actual diamond looks, it is loosing its luminosity. i even tried with magic wand tool, by selecting each darker part and changing color, but it does'nt look realistic either.
