Episode 032: Fade to Gray – Monochrome conversion (1)

LeafDownload the Video!
Download the companion file! (…if there is one…. ;-) )

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

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13 thoughts on “Episode 032: Fade to Gray – Monochrome conversion (1)

  1. This is going to be an interesting series. Now that you mentioned Ansel Adams here, I begin to wonder if you figured out some kind of zone mapping for the picture of the leaf at 23HQ.com.

    Very nice show, Serge

  2. No, zone mapping has to start with the exposure – and I shot this with my point&shoot by simply pointing and shooting. ;-)

    The Zone System is in part translatable to the digital world – Chris Marquardt has done something about that at Tips from the Top Floor..

  3. I like to mention something remarkable.
    Have you ever tried to convert a chroom object into monochrome? I have.
    And only the background turned into monchrome. The chroom object already was monochrome. Isn’t that remarkable? I never thought about it.

  4. these are the formulas how the grey value is calculated with the various desaturate methods (from the gimp doc)
    Average Brightness = (R + G + B) / 3
    Luminosity = 0.21 * R + 0.71 * G + 0.07 * B
    Lightness = ½ * (max(R,G,B) + min(R,G,B))

    the average method is the simplest method to create a greyscale image… it just treats each color channel equal. this is more a technical way

    the luminosity is adapted to the human eye. it reflects the sensitivity of the eye to the different colors

    well i don’t know where the lightness method comes from

    near the end of the video you showed those small differences in the rgb values (i tried to reproduce this… but somehow i could not find pixels with different rgb values).
    but i do not think that these are rounding errors.
    this can be a method to virtually increase the number of grey values
    it also uses the fact that the sensitivity of red green and blue of the eye is different
    for example
    0,0,0 <- base color
    0,1,0 <- this is a little brighter for the human eye
    1,1,1 <- this would be next real grey value
    the color fault is so small that it is not visible
    if you e.g. draw a gradient from one color to another then this method is also used

  5. Yes, there are countless ways to come to the same result. ;-) An other way is to grab the green channel (least noise) and try to work from there. But channel mixing is even better. See next episode…

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  7. Great to find that collection of Ansel Adams photographs which you can use on your web site! I’m a fan of this guy and will be happy to feature some examples of his work on my site, /Link removed by Rolf – commercial site for selling posters./

  8. As you may have noticed this is a project about digital image manipulation. We do it with the light on here. ;-)

    Why not use the technology that is available? And why do you use such modern stuff like industrial plastic film instead of making your own emulsion on glass plates? That is the real stuff! (I did that once – was fun but not to be repeated.)

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Anything to add from your side of the computer?