Interesting behavious/bug: Histogram/Level

VK
Posted By
Visu_Kaka
Oct 26, 2005
Views
190
Replies
3
Status
Closed
Can you explain following behaviour:

1. Create a new layer (transparent) – background layer. Ensure it is transparent (no fill)
2. Select black forgrund and white background color
3. Create new text layer, write some text in black
4. Rasterize the text layer
5. Use Gaussian blur to blur the text significantly.
6. Since text is blurred, you will see various shades of black including grey.

However, if you see the histogram, you will only see a single line in left most side indicating only concentration of black. This appears to be not correct.

Interestingly if your background layer was filled with some color, say white, you will see proper histogram with various shades.
Related Tags
bug histogram level

Master Retouching Hair

Learn how to rescue details, remove flyaways, add volume, and enhance the definition of hair in any photo. We break down every tool and technique in Photoshop to get picture-perfect hair, every time.

EZ
Earl_Zubkoff
Oct 26, 2005
There is only one color on the layer: black. What you think of as gray is really black at a lower opacity.

If instead of blurring you reduce the opacity of the layer using the slider in the Layers palette, you’ll see the same histogram.

By the way, a transparent layer can’t be a Background layer (although you can name it that); a true Background layer is locked at 100% fill and opacity.
VK
Visu_Kaka
Oct 26, 2005
I agree about background layer, what I meant was lowest layer.

However, what you said about opacity is not correct.

If it is only black color with different opacity, then why histogram shows various intensity level when lowest layer (the one below text layer) is filled with white.
R
RobertHJones
Oct 26, 2005
Visu,

"However, what you said about opacity does not seem to be right. Do you think opacity is maintained at pixel level, I guess not."

Actually, it is. Photoshop maintains two types of opacity — layer opacity, and pixel opacity.

Layer opacity affects all pixels in a layer equally. This is what is controlled by the opacity setting. If you place a solid black layer above a solid white layer and set the opacity to 50%, you’ll see a gray color. Hide the white layer and the info palette will confirm that all the pixels are 100% black.

Pixel opacity affects individual pixels. If you place a transparent layer above a solid white layer, set the foreground color to black, and then place a foreground to transparent gradient on the blank layer, you will see what looks like a grayscale. But, turn off the white layer and check the info palette and you’ll see the gradient layer is 100% black. This is pixel opacity.

Pixel opacity and layer opacity are independant. You can adjust the opacity of the gradient layer, for example.

Bob

How to Master Sharpening in Photoshop

Give your photos a professional finish with sharpening in Photoshop. Learn to enhance details, create contrast, and prepare your images for print, web, and social media.

Related Discussion Topics

Nice and short text about related topics in discussion sections