Photoshop :: Histogram Luminosity Values Changed
Jan 5, 2013
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. ?
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Jan 9, 2009
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?
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Feb 9, 2012
I am fairly new to Gimp, but love it. I am a marine biologist and I would like to use this program for my research. I do need to export the histogram values as I need to do some calculations (pixel count and value). Is there any way I can do this?
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Nov 13, 2013
definitive function and use of the X/Y split colour numbers in the LR soft proofing histogram?
It's the only function inside of Lightroom that I can't figure out - is it a point sample between original and proof, or an area sample?
And whatever it is, what are you supposed to do with the info; you can't "lock" a sample point a la Photoshop can you.
There must be some prescribed method of usage for the info, otherwise why is it there?
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Mar 15, 2013
I'm trying to show, using the eyedropper tool, the actual values of pixels in an 8-bit grayscale image (Mode command confirms that's what's there). In the Info panel, the eyedropper tool displays percentages for every type of color information (K, CMYK), while the "8-bit" field remains blank.
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Nov 16, 2002
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!
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Nov 16, 2008
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?
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Sep 6, 2013
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?
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Jan 31, 2013
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?
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May 12, 2006
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?
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Jul 30, 2009
Hican i do a color luminosity mask ?for example for a range of colors or for yellow? may somebody help me?
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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.
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Jan 12, 2007
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
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Feb 4, 2012
I'm trying to replace a colour in PE9 (Enhance > Adjust Color > Replace Color) but it's only replacing the luminosity, not the colour.
For example, I'm trying to replace a pasty white with full red (255,0,0) and it just comes out grey....
I can't find any switches for 'color/luminosity/hue' etc
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Oct 21, 2012
New action set?
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Sep 20, 2005
Is there a way to assign this to a shortcut key?
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Apr 14, 2008
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.
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Jul 18, 2013
I have an attribute blocks and this att block has two tag values , is there a simple code for to change 1st tag values automaticly according to 2nd values ?
for example :
1st tag (50x50) - 2nd tag ( 100 ) ==> 50x50-100
if i enter 201 valuse to 2nd tag then 1 st tag has to change as 100x100
if i enter 501 valuse to 2nd tag then 1 st tag has to change as 150x510
I attached a jpg file for explain much better
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May 23, 2012
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.
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Dec 8, 2007
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.
I m using Photoshop 7.0
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Jun 25, 2006
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.)
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Apr 18, 2013
Is there a way to have no layer value set for the description keys. I set all the layers, and now I realize I'd rather set this to no layers (boxes are all unchecked). I'd rather see no value under the layer column, but there doesn't seem like a way to set this.
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Apr 11, 2008
Does anybody knows wich was the first PS version to include this window? silly question but I cant find it in version 7, I think the one with the eye in it´s logo.
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Jul 10, 2006
I sometimes see a razor
thin line on the right edge.
Is that clipping?
I mean it very clear when I see the mountain slamming up to the right, but many times I see a normal mountain rise and fall, and then seem to see this razor thin blue green or red line on the right edge.
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Sep 28, 2012
What happened to CMD Option ~, for select luminosity? I am looking to bring back detail to the Wii controller.
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May 22, 2012
about cs6 , why the histogram is always set to colors? i mean is a bug like cs5 it should be set by default to rgb
every photo i load it's always set to colors and i guess there is not option to save and have rgb by default.
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Feb 25, 2009
Other than using the PrtScrn procedure,
way to save/copy the histogram of an image?
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Dec 21, 2012
Can AUTOCAD sum values that are entered as text values? Attached is a table text whose right final values should be all sumed up? Is this possible inside AUTOCAD?
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Mar 22, 2012
I am using the histogram function in PS CS4 for Windows. I am using the magic wand tool to choose numerous "green" elements (for example). As I choose more and more elements, the pixel amount goes up in the histogram table. For some weird reason, when I choose enough elements to hit around 50000 pixels, the amount reverts to 12000 and goes to "cache level 2". I need to be able to have a total of all my elements for the project I'm working on. Is this a memory issue? How can I increase the cache?
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Oct 19, 2011
Why the histogram for a gradient is not flat, as I guess it should be? Or, how to make a gradient that results in a flat histogram (that is, with the same number of pixels for each level)? The screen capture annexed should clarify the subject.
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Jun 15, 2011
For a research project, I am calculating the area of the cytosol of a cell by finding the total cell area and subtracting the total nuclear area. I have been using the lasso tool to select the boundaries and then the histogram to measure the total pixels in that selection area. Proportionately, the nuclear pixel area should always be smaller than the total cell area since the nucleus is inside that cell. Most of my measurements have been accurate, but I started to run into the problem in which occasionally the nuclear pixel area is larger the total cell area. This does not make sense, which means that Pixel # that the histogram records must not actually be counting every pixel. I have tried to do some reading online and it sounds like the histogram is made based on different color intensities. If that were the case, that histogram pixel count is not the total area of the selection but rather only the pixel count that is being used to calculate the histogram.
I have tried changing the Channels from grayscale to RGB, etc. to see if that might use more of the pixels but there is no difference. What is the difference in these measurements and how can I make sure that the histogram counts every pixel?
Also, once I have that issue figured out, to convert my pixel count to a cell area, do I use the equation
A=P/s^2?
A=real cell area
P=pixel count
S=linear pixel/cm.
I have a bar scale from the microscope on the bottom of each image, thus I can accurately find this variable. I would have to square it since I need the area. Does that look correct?
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