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05-18-2012, 03:46 AM   #1
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Post Processing

Hello Folks,

Yesterday I downloaded GIMP from GNU. There is no documentation other than the online help. I've never done any sort of post processing before, and really don't know what to do.

What are two or three things I should learn to do, and how do I do them? If I can get started, I'll pick it up.

Thanks, Tom

05-18-2012, 04:06 AM   #2
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Let me google that for you

05-18-2012, 04:18 AM   #3
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There are books available too if you prefer:

GIMP - Books about GIMP

Another option is to search on "Gimp tutorial" or "Gimp tips" on Youtube
05-18-2012, 05:09 AM   #4
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QuoteOriginally posted by Tatume Quote
Hello Folks,

Yesterday I downloaded GIMP from GNU. There is no documentation other than the online help. I've never done any sort of post processing before, and really don't know what to do.

What are two or three things I should learn to do, and how do I do them? If I can get started, I'll pick it up.

Thanks, Tom
Oh I just realised you are new to post processing all together.
I am not sure of its full compatibility with PEF/DNG files but you get a bit of extra head room with these formats over JPG (IE white balance is better, more detail can be recovered from shadows and highlights)
Some of the basic things you will want to learn how to do. (methods can be found in google as I don't use gimp)
  • White Balance (this corrects for different types of lighting)
  • Tone
    • Exposure
    • Recovery (for detail in bright sections of photo)
    • Fill light (for lighter shadows)
    • Blacks (for the darkest parts of the photo)
  • Brightness
  • Contrast
  • Clarity
  • Vibrancy
  • Saturation
  • Sharpening
  • Noise reduction


05-18-2012, 06:02 AM   #5
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There are Gimp video tutorials also...

05-18-2012, 07:54 AM   #6
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You shoudl read this article by a senior PF member:

Post-Processing Workflow in GIMP - Introduction - PentaxForums.com

It may help you to answer some basic questions.
05-18-2012, 07:55 AM   #7
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QuoteOriginally posted by Tatume Quote
What are two or three things I should learn to do, and how do I do them?
There are numerous books on the subject as well as DVD's and online tutorials. It isn't something you just sit down and do, the learning curve is extremely steep to do it right, at least for me. I have been using Lightroom and GIMP for over a year and still feel like a complete novice. My point is just that PP is an ongoing thing, technology improves, your skills improve.

Chaos_Realm gave you an excellent primer, about what I was going to say but he beat to me to it. It is important to develop a workflow and follow those steps. Some things need to be done first, like white balance, some absolutely last, like noise reduction and sharpening.
05-18-2012, 10:44 AM   #8
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Frankly, if you are new to PP, and you're wondering what two or three things to try first, number on that listed would be, download a simpler program. GIMP is a pretty big and complex program more suitable to experts than for newcomers to PP. Among free programs to get started with, I'd consider something like Picasa first. I'm sure there are others too. Then, if you eventually find your needs become more exotic and you run into limitations in the somewhat more basic functionality provided by the other more user-friendly programs, then I'd turn back to the GIMP. But doing simple things should be simple, and other programs are much better suited to that.

05-18-2012, 11:18 AM   #9
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QuoteOriginally posted by Marc Sabatella Quote
Frankly, if you are new to PP, and you're wondering what two or three things to try first, number on that listed would be, download a simpler program. GIMP is a pretty big and complex program more suitable to experts than for newcomers to PP. Among free programs to get started with, I'd consider something like Picasa first.

COOL! And it works so easy.

Last edited by Tatume; 05-18-2012 at 01:40 PM.
05-18-2012, 02:24 PM   #10
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Tatume,

There are at least three things you will most likely want to do with any photo:

Sharpen for counteracting the anti-aliasing (AA) filter
Select black, midtone, and white points.
Crop

I'm using GIMP 2.6.11 so menu selections might have moved around if you installed 2.8. And since I don't know what tools you have docked I will refer to menu driven commands.

If your photo is a .jpg the first thing you should do is load your photo and immediately save it as a .tiff. This will allow you to save the photo as you work on it without degrading it every time you save it as a .jpg.

Then you should do an unsharp mask on the photo to deconvolute the effects of the AA filter.
Found in the menu at: Filters >> Enhance >> Unsharp Mask.
Successful settings depend on your camera, but I find that a radius of 0.6, amount of 1.0, and a threshold of 0 works well for this. This will not be a radical sharpening but it is noticeable.

Then you should select your black, midtone, and white points. GIMP has an auto white balance menu command which does this and is found here: Colors >> Auto >> White Balance.
Over time though I have preferred using the Levels tool available at: Colors >> Levels.

The Levels tool shows a histogram of the pixel values in your photo. By default all color channels are shown, but this should be confirmed by the drop down box labeled "Channel" having the word "Value" in it. The other options are the red, green, and blue channels along with the alpha channel.

Under the histogram are three sliders you can move to define your level of black, midtone, and white in your photo. Or you can use the eyedropper (right below the sliders) to capture a pixel value from your photo to define the black and white points, but not midtone.

This tool takes time to master and when one really gets serious you can define each color channel as a curve through this window, but for now appreciate the changes you can make with the black, midtone, and white point selection under the histogram.

To crop the photo access the menu item: Tools >> Selection Tools >> Rectangle Select, and select the area you want to keep in the photo. Then select the menu item: Image >> Crop to Selection.

This is just the bare beginnings of GIMP, or any photo post-processing, but hopefully it will get you started.
05-18-2012, 04:24 PM   #11
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Thank you GHL,

These three things are the basis for the beginning of my education. I'll also try them in Picasa.

Sincerely, Tom
05-19-2012, 06:49 AM   #12
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Hello Folks,

I've been busy learning PP, and I have to say, it's been an eye-opener. On some photos even the little I know makes a tremendous difference. This is a subject I now know I must pursue in earnest. Thank you.

Take care, Tom
05-19-2012, 07:28 AM   #13
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QuoteOriginally posted by Tatume Quote
What are two or three things I should learn to do, and how do I do them? If I can get started, I'll pick it up.

Thanks, Tom
Figure out how to:

1. Rotate image to make the horizon level.
2. Change exposure.
3. Change contrast.
4. Remove dust spots.
5. Crop.

I don't use GIMP or Picassa, so I can't tell you how...
05-20-2012, 07:27 AM   #14
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I upgraded(?) to gimp 2.8 when it first came out. It's not a trivial update from 2.6, so much so that I went back to 2.6. Besides seeming much less intuitive to me (and surprisingly incompatible with 2.6), at least as of last week 2.8 hadn't been well integrated with ufraw (for the various OS platforms.) Once the integration issues are well ironed out, I guess I'll have to take the plunge and learn various new ways of doing the same old things, but I'd definitely recommend starting with 2.6.

Paul
05-20-2012, 08:28 AM   #15
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QuoteOriginally posted by tibbitts Quote
I upgraded(?) to gimp 2.8 when it first came out. It's not a trivial update from 2.6, so much so that I went back to 2.6. Besides seeming much less intuitive to me (and surprisingly incompatible with 2.6), at least as of last week 2.8 hadn't been well integrated with ufraw (for the various OS platforms.) Once the integration issues are well ironed out, I guess I'll have to take the plunge and learn various new ways of doing the same old things, but I'd definitely recommend starting with 2.6.
Paul - thanks for the summary. I've downloaded 2.8, but haven't run the upgrade yet and may now hold off from doing so. I tend to use it more for image manipulation than photo processing, but I'm not in the mood for new learning curves at the moment. I have enough of those with my K5 and various lenses.
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