Photoshop :: Histograms: Luminosity Or Saturation?
Oct 11, 2008
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.
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.
For a couple months now I have experienced the "Building Histograms" dialog appearing on nearly every move or action; moving an object, adjusting a shape, zooming in & out, simply selecting an object.
The building of the histograms almost always takes up to 10+ seconds to complete.
I have followed other topics where there was no solid professional answer to the problem. The closest thing everyone was able to pin it on was the use of an extension or add-on. I have none of these.
In my opinion an update / fix should be applied for this. I won't be interested in further debugging or providing information. Simply stating that I am experiencing this for history sake.
I am working in Photoshop CS5 on a MacPro with Snow Leopard, 10.6.4. I have a file that is a little over a gigabyte open. Every time I make any changes to the file (i.e. select a different layers, grab the text tool, etc.) a menu pops up with a progress bar and says it is building the histgrams.
This process happens with EVERY move. As you can imagine, this has slowed my productivity down to a crawl. Can I do anything to make it stop rebuilding the histograms at every step?
Photoshop creates several preview images (more smaller than the original) for displaying the effects and creating histograms. So, I think that if I choose the cache level as 1 in the preference window, Photoshop does not create any smaller preview and it always displays information according to the original file.
But, this is not the case, as far as I can see. I set my cache level to 1 and it still displays histogram for cache level 3. So, my question is ... what is the secret behind the cache level?
The histograms on the library panel and on the develop panel are not same for most of the images, there is a tiny difference between them. What is the reason for this difference?
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'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?
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?
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.
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.
when trying to use luminosity selection keyboard shortcut and it dosent work . On pc i should be: ctrl alt ~ but nothing happens - no marching ants. Mine ~ key is positioned to the right on my keyboard just beside the return buttom. Could it be that im using the wrong key here or.... thanks for any surgestion. (Maybe there is another way to make the luminosity selection if it is my keyboard short cut that dosent work.)
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'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).
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.
If I'm using the color mask and i want to know the luminosity of an image can I use it for Luminosity mask?the reason is PP does not have something as Photoshop.
I have designed a brochure for a friend but the Printers say there is an issue with the saturation on the black.
The saturation I have done is apparently 400% but should be under 300%. I assume the brochures are being digitally printed as opposed to traditional methods.
My questions are:
How do I find out what the saturation of the black is ? ....and how do I change the black saturation without changing the saturartion on the rest of the colours ?
I go to use the Hue/Saturation Editor thing, Photoshop messes up on me. It goes to the eyedropper tool, the "X" in the top right corner goes faded, so that I can't click on it, but I can select colors on the picture (with the eyedropper) and on the little 2 color pallete thing in the bottom left corner, where it displays the foreground and background color. I can switch them, with the arrow, but nothing else, i can't switch layers, I can't select any other tools, or anything. Can someone help me with this? Also, this might help, I was following a tutorial that required me to change some sort of properties... a link to the tutorial is below; If you download the .PSD file, a warning box pops up on photoshop when you try and open it...
