Selecting fuzzy edge by color?

D
Posted By
davsf
Feb 21, 2011
Views
984
Replies
2
Status
Closed
I am very new at photoshop and I am trying to learn how to select an object that has fuzzy edges against a background whose color varies but is distinguishable from the object. Think of a fern bush (mostly green and brown stems) against a background that is a reddish wall of a barn. Some of my more experienced photoshop friends tell me to just carefully trace out each leaf and stalk, which is way too time consuming. I can test the colors of the pixels near the edges and I see that the red compononent makes a marked jump from the object to the background, and, I believe their must be some algorithmic method whereby I could designate a matrix of colors that constitute the background (or inversely, the object), and then I should be able to move a small circle around the visible edges and let the program figure out which pixels fall either within the object or within the background based on the color limits I specify.

I want to believe photoshop already has this feature available, but, the learning curve is immense, so, if anyone can jumpstart me please advise.
J
Joe
Feb 21, 2011
surface9 wrote:

I am very new at photoshop and I am trying to learn how to select an object that has fuzzy edges against a background whose color varies but is distinguishable from the object. Think of a fern bush (mostly green and brown stems) against a background that is a reddish wall of a barn. Some of my more experienced photoshop friends tell me to just carefully trace out each leaf and stalk, which is way too time consuming. I can test the colors of the pixels near the edges and I see that the red compononent makes a marked jump from the object to the background, and, I believe their must be some algorithmic method whereby I could designate a matrix of colors that constitute the background (or inversely, the object), and then I should be able to move a small circle around the visible edges and let the program figure out which pixels fall either within the object or within the background based on the color limits I specify.

I want to believe photoshop already has this feature available, but, the learning curve is immense, so, if anyone can jumpstart me please advise.

Try not to believe thinh not believable. Graphic is made by number of pixels hugging each other. If the photo is hi-rez and you don’t zoom in too close then you may be able to see up to 100-300% without (or very little fuzzy edges). If it’s a low-rez then you may see of of them, and none graphic program can do anything about it.

The only type of graphic you can zoom in hundreds/thousands of time is vector type (not Bitmap type)

What you need to learn is.

– The limitation of what Photoshop can do. So becareful with the original, and make sure the original is hi-rez and top quality

– To get around the limitation you need to use Photoshop technique(s) to blend, smooth, increasing number of pixel (like enlarge and 16-32 bit mode etc.).

Years ago when hi-rez DSLR camera wasn’t available I tried to use FEATHER but since I have been using higher resolution (more pixel) and top lens etc. I haven’t used the Feather option for many years now.
R
Ragnar
Feb 22, 2011
"surface9" wrote in message
I am very new at photoshop and I am trying to learn how to select an object that has fuzzy edges against a background whose color varies but is distinguishable from the object. Think of a fern bush (mostly green and brown stems) against a background that is a reddish wall of a barn. Some of my more experienced photoshop friends tell me to just carefully trace out each leaf and stalk, which is way too time consuming. I can test the colors of the pixels near the edges and I see that the red compononent makes a marked jump from the object to the background, and, I believe their must be some algorithmic method whereby I could designate a matrix of colors that constitute the background (or inversely, the object), and then I should be able to move a small circle around the visible edges and let the program figure out which pixels fall either within the object or within the background based on the color limits I specify.

I want to believe photoshop already has this feature available, but, the learning curve is immense, so, if anyone can jumpstart me please advise.

You have already spotted that the red channel shows better contrast at the edge than the other channels. SO . . . copy the red channel into a new alpha channel and edit its Threshold until the edges of the object show up clearly. Tidy up the rest of the now black-and-white image and CTRL-click the channel to create the selection you need. You may need to have several go’s at it to get the result you want.
Hope this works. Undoubtedly others will suggest a less ‘quick-and-dirty’ way of doing what you want.
R.

Related Discussion Topics

Nice and short text about related topics in discussion sections