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Saturday, February 03, 2007

Demythologizing Photoshopping—Six Insights

by Ctein

1. THIS IS MOST IMPORTANT: Data is (are?) not the same as information. Data are bit values. Information is what the photograph tells you visually. You may lose data and not lose information. In fact you may gain information. Untouched data is often not higher-quality information. What you care about is information. A trivial example: when you white balance an image file, the color-corrected photo that you save has sacrificed some of your original data, because some RGB value ranges were compressed with others were expanded. But it gains you useful information on the colors of objects in the photograph and you don't lose any other information.

2. Less editing is better than more because editing can lose information. That's not the same as will. We teach students to do as little editing as possible to minimize the chances they'll degrade their information, and because really excessive fiddling will cause visible information loss. But it's just a good workflow principle, especially for newbies, not a rule of nature (or even art). Plus...

3. Tonal editing done in 16-bit mode almost never loses data or information, no matter how extreme. (Spatial editing is another matter.) I recommend people with enough computer muscle always work in 16-bit mode, even if their starting point is an 8-bit file. Makes for less worrying about such losses.

4. Layers do not change the nature of the data and information manipulations you've done. They preserve the original file unchanged, but in terms of the output result (on screen or printer), the same adjustment applied directly to a file and applied in a layer has precisely the same effect on the photo. (By the way, you do not need to flatten a layered file [or convert from 16-bit to 8] before printing. Photoshop flattens and converts the data as it renders it for printing.)

5. Doing all your editing in a single session in Photoshop does not produce better data or information. So long as you save as TIFF or PSD, it doesn't matter whether you do your editing in one session or twenty before printing.

6. Low-compression ratio JPEG's won't cost you any visible spatial detail, but JPEG doesn't support 16-bit color. Avoid saving your files as JPEG unless you don't care about losing your 16-bit data.

Posted by: CTEIN


Blogger Spike said...

Lack of 16-bit editing in ALL operations was why I jumped off the Photoshop bandwagon a couple of years ago. Ridiculous to pay so much money for a crippled program. I guess PS finally went 16-bit a few years ago, but by then I'd moved on.

9:33 AM  
Blogger Mike Johnston said...

"but by then I'd moved on"

To what?


12:51 PM  
Blogger Michael Seltzer said...

Nice piece. Especially the reminder about the difference between data and information. Data are always discrete bits, facts, points on a graph.... Information is relational, that is, it is what we think the relationship between the data is, or suggests. (It is also relational in that our relationship to the data and/or to the object/reality/experience the data attempts to describe affects how we see the data). As such, information is interpretive, it is meaning, and is supplied by us in reaction to the data (or sometimes in reaction to previous meanings we've already learned), and is, usually, not inherent in the object (or the data) itself. But we are meaning makers, it's where we live, it's what we do. Unless you are a mystic, in which case you are trying to get rid of interpretation, to peel away the layers of meaning we apply to the world, so that you can get to some fundamental, some essential experience of unmediated nature, of the mystous, the divine. Of course, if you accomplish this, probably at that point you begin building up another, different, set of meanings, though the better mystics might resist that. In any case, as photographers what we are trying to create is information, not data.

2:37 PM  
Blogger Spike said...

Picture Window Pro. It's been 16-bit throughout for a long time, perhaps since inception. I realize Photoshop is the monster program that can do everything, but for my purposes, PWP has been an excellent fit.

2:47 PM  
Blogger Jeff Kott said...

OK, here's the dumb question of the day, but it's bugging me:

How do you pronounce "Ctein"?


3:42 PM  
Blogger Mike Johnston said...

Ctein is pronounced "kuh-TINE."

And it's really legally his only name. Which sometimes leads to problems...for instance, on one site he has to be none Ctein," because not having a first name is not an he answered "Name: First_______" with, of course, "none."


4:09 PM  
Blogger soboyle said...

So converting 8 bit jpgs shot in a point and shoot into 16 bit tif or psd files will buy you what? Your not creating more useful data when you make the conversion, what is the advantage? Less chance of posterizing if you are doing heavy editing?

7:32 AM  
Blogger beulmann said...

You can bring it down to one point:
Do whatever you want with your photos, but always keep the originals.

3:12 PM  
Blogger Unknown said...


Pretty much. It is loosely analogous to only being able to work in integers and then being allowed to use fractions. So you can move half a step between two 8 bit points. These small errors can build up if you do much editing, particularly in areas of constant tonality.

16 bit editing doesn't change the end points of the scale, but provides a lot more steps in between to land upon, which helps a lot if you are editing beyond very basic adjustments.

10:48 AM  
Blogger Dave New said...

And so I ask, "What could be more 'Ctein'?"

And the answer is, "'none'. 'none' is more 'Ctein'."

(Sorry, couldn't resist -- and apologies to "Spinal Tap")

12:27 PM