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[marko]

One of the absolute bestest feature additions to MC14 is the image preview window. It offers to display 'histograms', which is great, if I knew how to interpret them!!

What are they used for?
What can they tell you about an image that you can't tell by looking at the image itself?
MC histograms are multi-coloured. What do the different colours represent?

I've worked out that darker images have more histogram activity to left, and brighter images have more activity to the right, but I can see that just from looking at the image itself ?

Anyone?

-marko.

[joh]

Marco,
here is an article: http://www.kenrockwell.com/tech/histograms.htm
/OLle

[glynor]

Marko -

This book is my photo editing bible:

Real World Adobe Photoshop (there's also a newer CS4 Version, but Bruce Fraser is no longer listed as an author so it might be different) (UK Link to CS4 Version)

It is certainly Adobe Photoshop focused, but that's not an issue if you're serious about learning the real techniques.  Still, the authors are fantastic and go deep into the details of the "why" and "what for" in addition to the "how" and it can really help you understand color-accurate workflows and a wide variety of medium-to-high-end imaging techniques.  I think there are 2 full chapters on using and understanding histograms alone.

(Please Note: I have the original Photoshop CS version of this book, but I've looked at the CS3 version and it is very similar to mine but updated.  It looks like it may have changed to become more photography-focused and less print-production focused in the latest CS4 edition.  Bruce Fraser is a well-known Print Production guru.  He now has a few of his own CS4-focused books.  That said, I'd guess the CS4 version would still be VERY good, and might be even more in-line with things you'd be interested in as an amateur photographer and photo-editor.)

[DarkPenguin]

Marko -

This book is my photo editing bible:

Real World Adobe Photoshop (there's also a newer CS4 Version, but Bruce Fraser is no longer listed as an author so it might be different) (UK Link to CS4 Version)

It is certainly Adobe Photoshop focused, but that's not an issue if you're serious about learning the real techniques.  Still, the authors are fantastic and go deep into the details of the "why" and "what for" in addition to the "how" and it can really help you understand color-accurate workflows and a wide variety of medium-to-high-end imaging techniques.  I think there are 2 full chapters on using and understanding histograms alone.

(Please Note: I have the original Photoshop CS version of this book, but I've looked at the CS3 version and it is very similar to mine but updated.  It looks like it may have changed to become more photography-focused and less print-production focused in the latest CS4 edition.  Bruce Fraser is a well-known Print Production guru.  He now has a few of his own CS4-focused books.  That said, I'd guess the CS4 version would still be VERY good, and might be even more in-line with things you'd be interested in as an amateur photographer and photo-editor.)

The late Bruce Fraser was a well known print production guru.  He has been dead for two and a half years.  One of his business partners, Jeff Schewe, has produced a number of books that might otherwise have been produced Bruce Fraser.  Jeff is a well known commercial photographer out of Chicago which might explain the photography focus.

[DarkPenguin]

I finally remembered this guys name ....

http://www.ronbigelow.com/articles/histograms-1/histograms-1.htm
http://www.ronbigelow.com/articles/histograms-2/histograms-2.htm

He has a lot of good articles...

http://www.ronbigelow.com/articles/articles.htm

[glynor]

The late Bruce Fraser was a well known print production guru.  He has been dead for two and a half years.  One of his business partners, Jeff Schewe, has produced a number of books that might otherwise have been produced Bruce Fraser.  Jeff is a well known commercial photographer out of Chicago which might explain the photography focus.

Wow.  That's really sad.  It does explain why they removed him as an author on that book, though obviously.  Now that you mention it, I do think I vaguely remember that Bruce had died, but I had certainly forgotten.  I guess this book (which is actually listed as a first edition) was mostly written by Jeff, though they probably started the project together.

[DarkPenguin]

Yep.  I have that one.  Never met the guy but he was clearly a giant in the digital photography world.

[marko]

I finally remembered this guys name ....

http://www.ronbigelow.com/articles/histograms-1/histograms-1.htm
http://www.ronbigelow.com/articles/histograms-2/histograms-2.htm

He has a lot of good articles...

http://www.ronbigelow.com/articles/articles.htm

Those two pages were most informative, though, when talking about channel histograms, he used curves instead of levels in order to protect the red channel, which left me wondering how he knew the red channel would be protected, and, is the knowing when to use curves and when to use levels just a 'level of photoshop experience' thing... I shall think about buying a book...

Thanks for the helpful links and replies.

-marko.

[Daydream]

is the knowing when to use curves and when to use levels just a 'level of photoshop experience' thing...

On short yes. Certain things can be done in Photoshop in more than one way. You eventually develop your own 'digital workflow'.
The longer explanation has to do with the fact that Curves provide a better overall control, since you can set many control points inside the grid, altering brightness and contrast, as opposed to Levels where you have only the sliders for Black (dark, left) and White (highlights, right).

[glynor]

Those two pages were most informative, though, when talking about channel histograms, he used curves instead of levels in order to protect the red channel, which left me wondering how he knew the red channel would be protected, and, is the knowing when to use curves and when to use levels just a 'level of photoshop experience' thing... I shall think about buying a book...

Easy answer - ALWAYS USE CURVES.

The Levels tool is just a "dumbed-down" UI for the Curves tool.  Photoshop does almost all color-channel manipulations through Curves internally, and using that tool gives you access to the "bare metal" as it were.  That book I mentioned has a whole section on why you shouldn't use the Levels tool.  It comes down to that the Levels tool can throw data away much too easily.

Generally, the only exception to the general "always use curves" rule is for grayscale images.  In that case, the Curves and Levels tools work identically.  This is a pretty good rule-of-thumb, once you learn how to use the curves tool well.  However, for general photo editing where you just want to tweak some brightness levels and add a bit of fill lighting and maybe correct a color cast a bit, the Shadows/Highlights tool is a godsend.  It is a specialized Curves interface that makes many common adjustments much more visual and simple-to-use.

So, a simple way to do many easy adjustments is this:
1. Layers -> Duplicate Layer
2. Image -> Adjustments -> Shadows/Highlights

If you need to get fancy, do:
1. Layers -> New Adjustment Layer -> Curves

EDIT:  By the way, Marko... http://forums.creativecow.net/ and http://library.creativecow.net/tutorials/adobephotoshop

[glynor]

Yep.  I have that one.  Never met the guy but he was clearly a giant in the digital photography world.

I took a seminar he taught at either NAB Show or something that NAPP put on a long while back (probably 5 years ago now), I don't remember which.  He was intense but an amazing teacher.  He could make the most dense subjects seem simple.