Photoshop command CALCULATIONS. Removing backgrounds. Links and text instructions

Here’s some places to check to help learn to use the Photoshop command CALCULATIONS.

This is arguably the most difficult of Photoshop techniques. It is not useable for all backgrounds on pictures and artwork, and, different instructions by various sources use a different approach so the method can be confusing.  Even the Adobe people use the method differently than other so called “recognized” authorities (Authorata!).  🙂

My experience is; this is the best method for clearing backgrounds and other areas, however there is usually some additional clean-up to really finish the work professionally. Think of it this way; Calculations uses the mathematics of Photoshop on each pixel to identify a path, rather than you using your hand-eye coordination to draw a path.

     Here’s a Tip from me, Jimmy J.J. James.  If you have a complex background, cut out the majority of it with some tool like eraser or lasso etc. Then you can try these Calculations techniques on the portion remaining.

Also, a very good practice session before you dive into using Calculations is the first site in the list.

  The pic with the eagle can be moved into your Photoshop and if you have the screen space reduce the instructions to fit the side of your screen and follow the list of tasks in your actual program

The following list includes some explanations with text only.

This works for early editions of PS with slight changes, mostly by searching the menus for the commands that have been moved in newer versions.

Start here:

Best for background removes:

Text and screenshots:

Complex masking made easy with channels and calculations. Posted by: Andrei Oprinca August 21, 2010:

“This tutorial will show you how to mask complex objects on single color backgrounds using alpha channels and image calculations and remove color cast. This technique can be applied to subtract objects from complex backgrounds too. You will not even need the brush tool.
This is a technique that I’ve seen on a DVD but it was applied on portrait retouching and the purpose was different.
On more complex backgrounds you will need to use this technique using additional tools like the brush tool and other selection techniques like Color Range.
Although it looks like it’s a long tutorial, once you practice this, you can do all these actions in less than a minute.
This is the result that you will get using the channels masking technique.”

1.) Removing objects with Calculations

2.) (*Important technique) Removing the color cast in Photoshop. Important method of deleting color edges of selections taken from single color backgrounds. The CALCULATIONS command can leave in the selection, a rim (slight edge) of color around an object, or a color cast, usually “reflected” background color.

Watch these in the proper order:

Techniques for removing backgrounds.


Photoshop Top 40 #33 – Calculations


Photoshop Top 40 #32 – The Pen Tool


Photoshop Top 40 #31 – The Brush Tool


How to Cut Out Hair in Photoshop. Very good site for various masking and “cutting-out”. Also and nice list of links for other processes in thotoshop.  The short list is here:

The list above is linked.   This is the HOME page. Don’t let “employment” in the title stop you, it has a LOT of other information (long with tips about getting a design job).

Select the picture to get to the site.






text and example:
How to use calculations in Photoshop to help mask from channels
Posted on June 19, 2009
When using channels to mask an object from a fairly simple background but one that is too complex for the wand or color range tools there is a technique that can be used to cut down the amount of time you spend brushing into the areas you want to mask and the calculations command is the key to this, here’s how it works.
Text explanation of calculations:
Explanation of Apply Image:


  • Darken through Darker Color — These are the additive modes that will add an image to the layers below.
  • Lighten through Lighter Color — These are subtractive modes that lighten the layers below using the current layer.
  • Overlay through Hard Mix — These are lighting modes.
  • Difference through Divide — These are negative effects.
  • Hue through Luminosity — These are color modes.

Photoshop /

Extract an object from its background.

free tutorials.

Good information for Pre and Post CS5 adobe programs.

***Free Book pdf that is very useful for ALL versions of Creative Suite/Photoshop etc. etc. (including MOST everything in CS6).  CHECK THE INDEX for a nice chapter or three about calculations and related retouching tasks. The CALCULATIONS COMMAND information starts about page 370, however, there is a lot of material regarding various masking technique and deleting parts of a picture on the pages before and after. You can check within the index for this book right in this blogs embeded pdf or the download address for the complete volume is at end of this section.

Masking with the Calculations Command for Adobe Photoshop CS5 One-On-One

DOWNLOAD LINK for FULL PdF. To the address line below add to the beginning of it      http://www.

adobe text only instructions.

  • Blend channels with the Calculations command
  • Blending layers and channels
  • Blend channels with the Apply Image command
  • Add and Subtract blending modes


Several good methods, especially if you don’t want the “basic vanilla one click” Black and White built in looks . Nice stuff for unique B/W treatments


Short explanation FROM ADOBE WEB PAGE:

The calculation commands perform mathematical operations on the corresponding pixels of two channels (the pixels with identical locations in the image) and then combine the results in a single channel. Two concepts are fundamental to understanding how the calculation commands work.

  • Each pixel in a channel has a brightness value. The Calculations and Apply Image commands manipulate these values to produce the resulting composite pixels.
  • These commands overlay the pixels in two or more channels. Thus, the images used for calculations must have the same pixel dimensions


–Apparently WordPress has decided to put some advertising in the middle of my posts. Sorry.  If I had a way, I would delete all advertising on the Internet, and, recommend readers not click on it.– J.J.J.J.


About Jimmy J.J. James Washington DC Research is donation only. There are no fees, no charges, no hourly rates, none. Free help finding information in DC from Government, Museums etc. family research. Findings are from physical facilities, offices and sites in the DC area. Original sources, writings and unusual facets of a subject or person or location are lost, changed, inaccessible, or simply passed by as computer searches become new electronic repositories. There are however still brick and mortar archives, museums, libraries, monuments and Government locations that contain a fantastic amount of non-electronic surprises. Embassies, Trade Missions, Diplomatic offices are wealth of International information you will not find online. Why am I doing this? I am a retired writer and photographer, a longtime DC resident interested in DC culture and history, and in the knowledge contained in museums, archives, government offices, facilities and other sources of free information that Washington DC has to offer. Not everyone has the opportunity or ability to work in the District of Columbia. Hopefully I can pass on some of this accessible knowledge to you. My research, time and experience are free. If you can afford to, please help keep the site working, donate. Some of the things I do: I can send you original non-copyright photographs of locations, specific places and graphite rubbing of names chiseled into monuments. I can send you interior photos of Art Galleries, building design and anywhere and that allows pictures. I can't tell you your business etc. but I'll try to get you within one degree of the original detail you are looking for. Also, I won't write your school term paper, but if you know of something here you need I'll try to locate it for you.
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