In the previous article on the topic of Photo Editing with Histograms, I discussed the six basic adjustments found in Adobe’s raw processing engine and how those settings affect the image and the image histogram. Then I posted a poll asking your experience level with curves, which also offered up some basic concepts and links for further reading. I also posted a few videos having to do with curves adjustments. So if you’ve been following along, you should have a decent grasp of how the tool works.

In this article, I’ll be discussing how various curve adjustments affect the image and the image histogram — but only in the realm of linear curves. So… linear… curves? Yup, you can do straight lines in the curves adjustment and they have their applications. So let’s look at a few extremes, then I’ll show you how to apply the linear adjustment to an image in need. After this, we’ll dive into the curvy stuff. And after that… I’m sure I’ll have something else to ramble on about.

LINEAR MANIPULATIONS

Let’s just start with some basic straight-line adjustments. Wait… isn’t this supposed to be about curves? Have no fear, we’ll get there — but these basic concepts are essential for the advanced concepts. Keep in mind throughout these examples that the input scale is along the bottom of the curve dialog and the output scale is along the left side of the dialog.

Each of the following examples shows the curve dialog overlaid with the base histogram, the adjusted histogram, and the base image from bottom to top. The original image is shown in example 3.

What I’m showing above is a spectrum of linear manipulations within the curves dialog. We start at full contrast and work our way to zero contrast, followed by negative contrast. Let’s go through them one by one…

The first image shows what would happen if your curve was pushed vertical. What I’m doing is taking all the pixels with tones to the left of the line and forcing them to be black. I’m also forcing all pixels with a tonal value to the right of the line and forcing them to be white. Everything between the set black and white points is scaled according to the diagonal line, thus we see a higher contrast (remember what I said about slope a few days ago?).

The second image shows a high contrast linear curve. This is very similar to the previous example, but I’m allowing midtones to remain somewhere between black and white. I’m still forcing black and white pixels, but not to the extreme as with the vertical line adjustment.

This third image shows absolutely nothing — it’s what we started with. A perfect diagonal line from the upper right to the lower left corner represents a perfectly untouched input/output relationship.

The fourth image shows the opposite of the second image. Here, I’ve moved the black and white points along the edge of the box, but in the other direction. This tells the software to convert all perfect black pixels to some level of dark gray, and all perfect white pixels to some level of light gray. Everything between black and white is scaled accordingly, thus we see a lower contrast.

The fifth image shows a perfectly horizontal line — exactly opposite from the first image of absolute contrast. What I’ve done is mapped every single input tone to output a single tone value. All blacks, grays, and whites are now a single tone value.

And our final image shows the opposite of image three. I’ve turned the curve upside down, inverting all the tones. Blacks map to whites, whites map to blacks.

APPLYING LINEAR CURVE ADJUSTMENTS

Those of you acquainted with curves and levels will say “linear curves can be accomplished with levels!” True. I’m not disputing that fact, I’m just showing how to use curves in a linear fashion. For those using Lightroom or ACR, they don’t have access to levels within the raw processor interface.

At any rate, here’s how I would apply a curve adjustment to the base image/histogram.

So what did I do here? If you look close, you’ll see that I basically did a version of #2 shown above. I set my black and white points so that my histogram spans the entire tonal range. This gives me a true black and white tonal value in the image. Of course, it’s not perfect at this point, but it’s a hell of a lot better than it was!

This is the most used real-world application of the linear curve adjustment — setting your black and white points. There are other uses depending on your artistic vision, but you’ll have to explore those yourself.

So now that we’ve covered the linear adjustments, let’s move on to the non-linear stuff! Any questions on the linear adjustments?

photo credit: Travelin’ Librarian

I get a fair amount of questions on the post comments and direct contact. I should try to make a habit of highlighting some of those questions and responding to them because I’m sure others could benefit from that.

I dug back into the archives and pulled a few of the more general questions and answers. Hopefully these will help out some of you that may have the same questions. And if you have other questions, definitely ask in the post comments if it is specific to the article, or contact me directly if it’s something we haven’t covered yet. I’ll try to hang on to those from now on so I can share the answers with everybody.

So here we go, 10 Q&A bits from the archive.

Bill on “Quick Tip: Format Your Memory Card”

I have a memory card that we have already used. Now the computer is asking us to format the card. Is there a way to format the card without losing the photos on the card?

No, formatting clears all the data from the card. Try downloading the photos from the camera to the computer with a usb cable (most cameras have this). If that doesn’t work, try a card reader (if you have access to one). You might even bring the card to a local computer or camera shop to see if they can access the images with a different card reader/computer.

Julia on “How To Create Photoshop Actions”

I’ve done a couple actions, but how on earth do I share them with friends? Can’t find the files on my computer… Do I have to save in some special way?

You have to save them out — you should see an options for loading and saving selected actions in the pull-down menu of the actions panel. This will allow you to save out a .atn file. Just make sure you have the action or group of actions highlighted before you save.

Jim on “Flickr Etiquette Basic Guidelines”

One thing I have noticed is that there seem to be many people who have no photos of their own, in fact they do not even have a buddy icon, and of course no real name given. These people tend to have amassed hundreds or thousands of favourites of women, some scantily dressed, some not. Many seem to be cross-dressers, perhaps looking for fashions to favourite. Most of these people never leave comments. Should I be concerned if photos of my wife are made favourites by these people? [...]

I know the type you speak of. I’ll usually block them just because they’re not trying to be part of the community and it’s really creepy when you look at their faves. Obviously, you can do whatever you wish with these followers, but I’m typically not a fan of the “super-creeper” gathering photos of my Wife.

Sangeeta Das on “13 Alternative Flower Photography Tips”

[...] I want to know how is the dew drop trick done… is it just a macro shot or some post processing?

The only way I know to do those dew drops is to use a macro or super-macro setup (with reversal rings and whatnot). Otherwise, you just can’t get close enough to get high quality images. http://www.wonderfulphotos.com/articles/macro/dewdrops/

Jim on “7 Reasons To Love Prime Lenses”

Are prime lenses really that much cheaper than zoom lenses? when I looked at canon 50mm f/1.8, which was probably the cheapest lens ever, it cost about $99. And the next one 50mm f/1.4 would cost as much as my Rebel XSi body. And neither one is the L series.

For the same quality, they are far cheaper. But they can be expensive too, especially when you want larger maximum apertures. With 50mm lenses, once you go larger than f/1.8, the price goes up exponentially. While the f/1.8 costs $99, the f/1.4 costs $400, and the f/1.2L costs $1600.

But now look at zooms in the 50mm range and you’ll see that you can’t get anything below f/2.8 or f/3.5. That’s a full 2 stops slower than what you can get with a prime, and the price is way higher than $99.

Adam on “60 Second Post-Processing Technique”

[...] if this is the first round of processing, wouldn’t further detailed processing potentially be done in something like photoshop? [...]

Photoshop would be one option to finish it off. I typically go back into Adobe Camera Raw (or Lightroom) to finish images with additional tweaks and adjustments. I’ll go into Photoshop if I need to do something extreme, utilize the LAB color mode, clone something more difficult than dust spots, etc.

Jeff W on “Making Fine Art Prints: Signing”

[...] If it’s “acceptable” to sign in ink or paint right on the image I would much rather do that in the future. I did try that with a white paint pen I got at Michael’s but even after drying overnight it smudged. Some of these just don’t adhere to photographic paper. Does anyone have a specific brand or type of pen they can recommend?

I’ve used two different pens, they both work great and dry fast.
http://www.sakuraofamerica.com/Marker-metallic-paint
http://www.marvy.com/product_details.aspx?ProductID=39

kevin on “7 Reasons To Love Prime Lenses”

Nice article, but what is the focal length we usually need? And what do you suggest for canon when price is not a problem? Is 50mm f/1.8 sharp enough? Or we need 1.2?

The focal length you need will of course depend on what you plan to photograph. Landscape photographers may opt for wide angle, portrait photographers for mid-range, sports photographers for telephoto, etc. If you use a zoom, take a look at your photos and see what focal length you typically shoot at — this should give you a good starting point. I can’t really comment on what to buy for Canon if price is not a problem, but I think the “L Series” lenses are the top quality pieces. As for the 50mm, f/1.8 will be fine for most people, and plenty sharp if you stop down one or two stops (as is the case with most lenses). The f/1.2 will give you more light, but I can’t comment on the sharpness gains over a f/1.8 or f/1.4.

C B on “Cross Processing Tips and Suggestions”

[...] I have some Ektachrome that I plan to cross process. I was wondering if shooting it through a red filter would make it so the green wasn’t so extreme? [...]

I’m not sure what would happen if you shot with a color filter… it might work, but it might also take some experimentation to get the filter strength and color correct.

C B on “Cross Processing Tips and Suggestions”

[...] Will E-1 or E-2 film cross-process with C-41 chemistry? Or should I just sell it to someone who’s a collector and buy E-6? I don’t want to pay the big bucks to have it processed E-2.

I really don’t know about E-2 stuff. I did find a discussion about it at photo.net: http://photo.net/film-and-processing-forum/00DzKU

So next time you have a question on a given topic, feel free to ask in the comments. I usually try to answer right there within a day or two, but I might also bring it back up in another post like this in the future. And if anybody else out there has something to add to the questions above, chime in right here or on the original posts!

More great stuff from the Epic Edits Flickr Pool! This selection of photos is from those entered in the pool between 01/10/2010 and 01/24/2010.

• 1,521 Members (24 New)
• 27,720 Photos (606 New) [Slideshow]
• 50 Discussions (0 New)
• 27 Selections

Photography is just like every other skill — it requires three things: 1) a basic understanding of the fundamentals, 2) lots of practice, and 3) some raw talent (and maybe a little luck). Books won’t help you much with the last two, but they’re perfect for the first one.

Photo Nuts and Bolts: Know Your Camera and Take Better Photos is a book that focuses on the fundamental theories and mechanics of the camera. So this goes way back to the very nature of light and the tools we use to capture it.

Aimed at the beginner to intermediate dSLR user, the book steps through the foundations of modern photography. Understanding your camera and the light it captures is the basis of solid photography and is essential to more advanced topics.

You can purchase Photo Nuts and Bolts from digital Photography School. Links in this post are affiliate links to the product — It doesn’t cost you anything extra, but I get a cut of the sale.

ABOUT THE BOOK

Photo Nuts and Bolts is a 64 page downloadable eBook containing 10 lessons in the fundamental theories and mechanics of photography. The three column layout and minimalistic formatting make this book easy on the eyes and a pleasure to read. Supporting photos and diagrams are scattered throughout as needed, but are not overbearing in their presence. Each lesson is approximately three to four pages long, making them a moderately quick read.

The 10 lessons in this book are very concise and to the point (I’m particularly impressed because I’m a rambler). The material is presented as introductory reading for the given topic. While it does go into details, it will leave the reader with a basic understanding and a thirst for more. The last page of each lesson helps quench that thirst with homework challenges, additional resources to various websites and web articles, and questions/answers and comments from fellow photographers on the given topic.

The flow of the book is fairly important, and I would suggest reading the lessons in order since they build on each other. We start off with a few lessons in light and optics, followed by exposure controls, and finishing up with additional camera controls. The end of the book also has a glossary of the basic terms used throughout the book.

As a bonus for the launch of the book (1 week only), you’ll receive a one page pocket guide intended to print out, fold up, and… stick in your pocket. This little guide gives you some general camera settings that may be useful for 10 different situations (outdoor sunshine, outdoor dusk, indoor action, indoor low-light, etc.).

ABOUT THE AUTHOR

Neil Creek is a fellow photography enthusiast that decided to take a shot at the professional side of things a few years ago. He’s been doing well photographing, teaching courses, and writing for the digital Photography School. I’ve known Neil for some years now, and his enthusiasm for the art of photography has only grown each day. The writing in this eBook reflects his high level of understanding in the technical and mechanical/optical aspects of photography.

MY FINAL THOUGHTS

This is a good solid book that teaches the foundations of photography in a concise and meaningful fashion. And even if you’re somewhat familiar with the topics, there are a lot of background and theory details presented that you don’t typically see outside of textbooks.

Readers of the digital Photography School blog will notice that many of the lessons in the book have been published in the past months. So why buy the book? A lot of stuff has been reworked and touched up in these articles. Plus, the last two chapters are completely new. It’s also handy to have everything in consecutive order and in one package so you can quickly reference the topics at any time.

I would suggest this book for beginner/intermediate photographers wanting to gain a better understanding of their equipment (the dSLR in particular). If you’re struggling with concepts like exposure controls, lens controls, light metering, white balance, and other fundamentals, this book should straighten you out.

You can purchase Photo Nuts and Bolts for $19.97 just for this first week for an undetermined time period, after which point it will return to the regular price of $29. Plus, the pocket guide is only available for the first week purchases, so grab it soon!

Since a lot of the regular Epic Edits readers utilize the RSS feed, I think it would be handy to give a shout out to the sponsors each month and say “thank you” for partnering with us. These folks provide the funds to keep the site running, and they provide services and products that are useful to photographers. So here’s the line-up this month:

Proud Photography

Proud Photography hosts an online photography school, currently with two offered courses: Interactive Online Photography Course and The Expert Wedding Photographer. You can also read my brief review of Proud Photography here.

Also… stay tuned for an announcement in the next few days that should help fill out the remaining ad spots — but I’m going to need some help on this one.

Reading histograms is an important skill to acquire in the world of digital photography. Most images from digital cameras will require some amount of post processing, particularly if you shoot raw format. And most of the processing can be done by viewing the aesthetics of the image as you go, but having the ability to read and manipulate a histogram will increase your productivity and output quality.

So what exactly is a histogram? And how the heck do you “read” one? Take this, for example:

At a glance, it doesn’t tell you much. But there are certain things that you can take from the histogram. No, it doesn’t tell you that it belongs to a photo of a deserted trailer half buried in the middle of the desert. It doesn’t tell you if the image is in focus or if your composition is good. It only tells you the tonal values of the pixels contained in the image — blacks on the left, whites on the right.

For this article, I’ll be looking at a black and white image and histogram in order to simplify things. Color histograms work on the same concepts, but with 3 channels rather than one.

MID CONTRAST AND BRIGHTNESS

This is pretty much a straight b/w conversion with no contrast or brightness adjustments. It doesn’t look too bad, but it isn’t terribly dynamic either. And if you look at the histogram, you’ll see that the pixels fall into a centered group with a little breathing room on the shadows and highlights. We’ll use this one as our baseline to compare against. The other histograms will show this in a transparent green.

LOW CONTRAST

You can visually recognize the lower contrast in this image, and that correlates to a change in the histogram distribution. The pixels near the black and white points have moved in toward a neutral gray, which gives the appearance of lower contrast. The whole thing has basically been squeezed to the center.

HIGH CONTRAST

Again, you can visually recognize the higher contrast in this image, and the histogram changed too. The pixels near center have basically migrated outward toward the blacks and whites, thus giving us more contrast. This time we’re squashing pixels from the middle outward.

LOW BRIGHTNESS

Lower brightness is just a shift of tones toward the black region. You can see that the entire histogram has been pushed to the left. Also notice that the tonal range has been decreased, as shown by a narrower histogram.

HIGH BRIGHTNESS

Higher brightness is a shift in tones toward the white region. Here you can see that the entire histogram has been pushed to the right. Also notice that the tonal range has been increased, as shown by a wider histogram.

THE FINAL IMAGE

You can see that I went with a high contrast, high brightness image for my final path. The histogram shows this with the wide tonal range and a heavy concentration of pixels in the highlights.

CAN YOU SEE IT NOW?

This chart shows a combination of contrast and brightness adjustments on the example photo. As you move from left to right (low brightness to high brightness), you can see the histograms shift to the right. As you move from bottom to top (low contrast to high contrast), you can see the histograms widen.

Click the image for a larger version

The reason I’ve posted this article is because I want to get into the topic of manipulating the histogram during post processing — using it to guide you in what adjustments to apply. So the next article will look at how some of the basic adjustments affect the histogram and the image. We’ve already covered contrast and brightness adjustments here, but there are a few others we’ll need to utilize.

In the meantime, here’s some additional reading on the topic of histograms:

Working With Image Histograms
Photoshop Tip: Understanding Histograms
Camera Histograms: Tones and Contrast
A Practical Guide to Interpreting RGB Histograms

Here is a series of videos given at Google campus covering many subjects in Digital Photography and Imaging – the class series is called PhotoTechEDU – online at YouTube – in the Google Tech Talk topical section.

This series of engineering grade lectures covers in depth many aspects of digital imaging, image processing/ editing and photography.

Naturally, you need a broadband Internet access

You have thousands of photos and want to earn some money for buying a new gear? When your photos are realy good, you have chances to improve your bank account. Some of these tips looking crazy or at least strange, but… why not?