February 26th, 2008 by Rolf
In this last episode (for now…) about monochrome con- version I show you a way to get full control over the process of making a monochrome image.
I “decompose” the RGB image into three layers, each containing one of the three colour channels.
By adjusting the opacity of the three layers I mix the channels as with the channel mixer. But I have the full image as “preview area” and can change the values as long and often as I want.
Each of the layers can be further modified with the curves tool, other tools or partially masked off. Don’t forget to make a safety copy of the layer.
The image on the top of this page was done in this way. It’s an enhanced version of the one I showed in the video. I have added a masked red layer for the background and a bit red layer for all of the image. This version is in the files for downloading – just two layers more than in the video.
The challenge
You can use this technique in the current challenge. Do a monochrome conversion with GIMP, post the image in the meetthegimp.org photogroup at 23 and be sure to use the tag “mtg-monochrome”. The challenge ends March 31 1600GMT and I’ll draw a winner by random choice.
The TOC
00:34 Introduction
02:50 The leaf picture again
03:26 The colour channels
04:40 Decompose
06:26 The colour layers
08:00 Mixing the layers
09:20 Understanding the layer mixing numbers
10:15 Examining the layers
11:57 Adjusting the layers
13:00 – Curves on the blue layer
15:00 – And a layer mask
16:50 Summary
18:50 The Black and White Challenge
19:30 – Slide show
22:36 The web-site
24:49 The End
TOC made by paynekj
Contact me!
You can leave your comments on this blog or write me a mail.
This work is licensed under a
Creative Commons Attribution-Share Alike 2.0 Germany License.
Tags: b&w, layers, monochrome
Posted in Gimp, Gimp video tutorial | 14 Comments »
February 19th, 2008 by Rolf
I promised a better way to convert coloured images to monochrome. And here is the Channel Mixer. It allows you to mix the amount of the red, green and blue channel of an RGB image and change the appearance dramatically. The image to the left is an example that I stole from a terrific website Cambridge in Colour. You see the original (in colour) and some outputs of the channel mixer.
Then I tackle the “double face” from episode 31 again. I convert the new passport image with the channel mixer and get a better skin tone. Adding the same colour tint to both halves of the image and getting rid of the grain by blurring give a better result than before.
But the channel mixer is not the final stop on the road to the “perfect” monochrome image. Next week I’ll use layers and the curves tool to get an even better result. And then there are duotones and sepia….
Finally I start a new challenge for you. Do a monochrome conversion with GIMP, post the image in the meetthegimp.org photogroup at 23 and be sure to use the tag “mtg-monochrome”. The challenge ends March 31 1600GMT and I’ll draw a winner by random choice. No interview partner as a random generator- I’ll go high tech this time. 
Some links from the video
The TOC
00:34 Site statistics and plugging
04:12 Parrot example image
05:06 The problem with simple desaturation
06:00 Cambridge in Colour tutorials
09:56 Channel Mixer
11:20 – Average settings
11:47 – Preserve luminosity
14:32 Double face re-visited
15:00 – Convert to monochrome using the channel mixer
17:57 – Colour matching
19:00 – Curves adjustment
20:01 – Blur the grain
21:52 The Gimp web-site
23:10 Next episode – a better way
23:44 The Black and White Challenge
26:59 The End
TOC made by paynekj
Contact me!
You can leave your comments on this blog or write me a mail.
This work is licensed under a
Creative Commons Attribution-Share Alike 2.0 Germany License.
Tags: b&w, channel mixer, monochrome
Posted in Gimp, Gimp video tutorial | 17 Comments »
February 12th, 2008 by Rolf
Today I’ll start a series about mono- chrome or black and white conversion of digital images. It’s a new topic for me – so I start with a bit of background, some images from the Masters and a bit about the easy ways to make a quick conversion by desaturation and tweaking the curves a bit.
The image here shows the output of the three options of the desaturation dialogue without further manipulation. From top left to bottom right: lightness, luminosity and average. Which is best? Depends on the image.
In the next episode I’ll show you a better but more complicated way to do this with the channel mixer.
You can find the files used here on the Download Page.
Some links
If you really want to know what’s behind the three options in the desaturate dialogue, go to the GIMP documentation. It’s math.
The images shown in the beginning of the podcast are from Wikimedia. They have a glorious collection of copyright free images from Ansel Adams and others.
A gold mine is the “American Memory” collection of the US Library of Congress, especially the images made for the Farm Security Administration. A must to check out – don’t let the site design put you off.
You find the Focus Ring feed and the new Focus Ring at the Photocast Network. Check out the other podcasts as well, but stay subscribed to this one.
The TOC
00:34 Introductions
02:34 Example image 1 – Breadfruit
03:44 Example image 2 – Leaves
05:25 Example image 3 – Mountains
05:59 Example image 4 – Grand Canyon
07:20 Example image 5 – Yellowstone lake
07:26 Black and White photography advice
09:00 The original image
09:50 Method 1 – Mode to greyscale
10:30 – Curves adjustment
12:43 Method 2 – Desaturate
14:38 – Comparing desaturation methods
16:13 Colour Channels in brief
19:59 The End
TOC made by paynekj
Contact me!
You can leave your comments on this blog or write me a mail.
This work is licensed under a
Creative Commons Attribution-Share Alike 2.0 Germany License.
Tags: b&w, desaturate, monochrome
Posted in Gimp, Gimp video tutorial | 12 Comments »
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