What is "linear?"

MC
Posted By
Martin_Coleman
Feb 29, 2004
Views
311
Replies
7
Status
Closed
Can you help me understand what Linear means or tell me where to go please? Where to go to find out, that is!

OK, so I understand that linear means in a straight line so measuring an image in terms of resolution (ppi) is linear. After that things go a bit hazy. Why for instance are Curves and levels linear? What are: Linear Burn, Linear Dodge, linear gradient, Linear Light mode, linear sharpening? I know what dodge and burn do for instance and use the dodge/burn tool in my images. What makes it linear?

Are there too many questions there?

Thanks for you help.

Martin

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.

RW
Rene_Walling
Feb 29, 2004
OK, so I understand that linear means in a straight line so measuring an image in terms of resolution (ppi) is linear.

Actually, it’s not…

Linear is a mathematical term relating to functions meaning "directly proportional". In other words if the input increases by a certain amount, then the output increases proportionally.

A linear function curve you may be familiar with is the return of investing money for a set amount of time at a given interest rate (obviously, if you invest twice as much money, you will get twice as much interest and so on).

A non-linear function curve a lot of people may be familiar with is the increase in human population on this planet.
Y
YrbkMgr
Feb 29, 2004
Linear is a mathematical term relating to functions meaning "directly proportional".

Renee on the case! <golf clap>

To expand a bit further, without actually answering the question (cuz I can’t), directly proportional, or linear refers to, for every increase in one value, the other value increases by the same (proportional) amount.

So when photoshop applies an algorithm to an image to produce an effect, say, Color Burn, if you were to look at the pixel changes on a graph, they would be distributed as an applied curve (actually, linear is a curve, by definition). That means that some pixel characteristics are going to receive the effect more than others. BUT, it’s unequal in the amount it was appled, based solely on the characteristics of the pixel.

So if you want to apply the Color Burn equally to all pixel, you can apply a linear Color Burn, which affects the algorithm in such a way as to straighten the curve, thus that when applying the Color Burn algorithm, there is a 1 to 1 effect. For every X amount of say, brightness in a pixel, you receive X amount of Color Burn.

I could be lying though….

Peace,
Tony
P
pope
Mar 1, 2004
When as a kid I punched my sister she would give me a linear punch back. Then she got bigger and would give me non-linear punches. We now have a linear truce 🙂
DD
David_Dahlstrom
Mar 1, 2004
Linear is "of or relating to the Moon". Thus, a Linear Burn was what the Apollo astronauts used to insert their spacecraft into Linear orbit. A Linear Dodge, was the make of the LEM (Ford and GM lost the bid). A Linear Gradient is the slope of the Linear surface at the point of touchdown; Linear Light mode conserves energy by converting reflected light from the Linear surface into electricity; and Linear sharpening is the phenomenon of increased perceived visual clarity on the Linear surface resulting from its lack of an atmosphere.

Not sure what this has to do with Photoshop.

(hehehe)
JS
John_Slate
Mar 1, 2004
You’re a lineatic!
MC
Martin_Coleman
Mar 1, 2004
I thought that Lunar was "of the moon" or is that lunartic?

So linear only means in a straght line to 2 Dimensional people. Now, I am beginning to understand that it means if photoshop is doing something complicated after some kind of instruction from the user it will apply it algorithm and then mock you with a wierd result if you tell it to do the wrong thing.

So the challeng then with the linear functions is to put the correct "X" in to get the desired "Y" factor. I’m not sure if even I understood that but, back to the original post, if I understand what linear is will I be better at grappling with those linear functions?

Martin
Y
YrbkMgr
Mar 1, 2004
I thought that Lunar was "of the moon" or is that lunartic?

Actually, people who were crazy were thought to have gazed at the full moon too long, which is the origin of the word "lunatic".

if I understand what linear is will I be better at grappling with those linear functions?

If you’re a mathematician, possibly. Chris Cox, one of the Adobe Engineers/Designers/Gods, could probably do it. Remember the images in The Matrix? He sees stuff that way.

Outside of that, most folks I know, myself included use the old "hmm.. what’s this do?" technique.

<shrug>

Peace,
Tony

How to Improve Photoshop Performance

Learn how to optimize Photoshop for maximum speed, troubleshoot common issues, and keep your projects organized so that you can work faster than ever before!

Related Discussion Topics

Nice and short text about related topics in discussion sections