Tag Archives: image

Nonlinear Curve Adjustments and Histograms

The last article on curves looked at linear adjustments and how those adjustments affect the image and the histogram. So now we’ll take a look at some nonlinear adjustments within the curves adjustment tool found in many photo editing software packages.

We’re basically building on our basic understanding of the histogram and our knowledge of linear curve adjustments to take the next step into nonlinear adjustments (the curvy curves).

NONLINEAR MANIPULATIONS

What I’m going to show here are some very basic curves at each extreme. The single bend and double bend curves are most commonly used during post-processing, but these are not the only options. Curves can have a large number of set points, bends, and inflections — it’s just not feasible to cover every possibility in an article like this.

SINGLE BEND CURVES

The simplest form of a nonlinear curve is accomplished by moving a mid-tone location toward the upper left or lower right corner, forming a basic arc with a single bend. Essentially, your black and white points remain fixed while your mid-tones become lighter or darker (aka: brightness). Also note that one end of your tones will take on more contrast while the other end will lose contrast due to the change in slope of the curve (remember: vertical = high contrast, horizontal = low contrast).

This can be used to brighten or darken the overall image if you want to maintain your highlights and shadows at their current values.

DOUBLE BEND CURVES

Also known as the “S-Curve”, this curve manipulation pushes one section of tones brighter and another section of tones darker (aka: contrast). Again, you can maintain your black and white points, but you also maintain some middle tone where the curve crosses the diagonal. On the note of contrast again, be aware that you will sacrifice contrast in one area to gain it in another.

This can be used to raise or lower the contrast of the overall image with a focus on the mid-tone areas. The bright/dark tone changes of the highlights/shadows are amplified by the mid-tone slope change — so it doesn’t take much to really change the contrast.

APPLYING NONLINEAR CURVES

The beauty of the curve adjustment is that you have such a wide range of possibilities — much more dynamic than a single slider adjustment. To apply curve adjustments, you simply click a location on the curve and drag it to the desired location. The curve will bend on its own based only on your set points. You can continue to add set points until you have the desired result.

Using the example image above (middle of series), here’s one possible curve that combines linear, single bend, and double bend curves. Keep in mind that I haven’t applied any basic adjustments and what you’re seeing is pure curves from an unprocessed raw file (except for the b/w conversion).

Notice that I used a double bend curve to increase contrast. Combine that with a single bend curve to increase brightness. And combine that with a linear adjustment to set my black and white points. I’ve also placed several extra points on the curve in order to bend it into the shape I wanted while maintaining a smooth transition.

As you work with curves, you’ll noticed that they sometimes have a mind of their own. Extra points will help shape the curve and provide you with the ability to make the adjustments you want. On that same note, too many set points can lead to choppy and lumpy curves. Non-smooth transitions generally begin to produce strange contrast artifacts that are easily seen in the image.

For you curves experts out there, what other tips and advice would you add to this discussion? How are you guys using curves to enhance your images?

How to Read Image Histograms

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

Top Photos From 43 Portfolios

On May 19, I announced that the Fine Art Photoblog was accepting portfolios to fill two new spots. In just two weeks, we had 43 outstanding portfolios come through: a few familiar names, and many new ones. This was a larger response than I had expected, and I have to admit that I’m wishing there were fewer portfolios to review!

Now the seven of us currently involved with the photoblog have the daunting task of selecting only two artists to potentially join us. We’ll be going through rounds of narrowing the field, defending our favorites, and coming to agreements. We take this task very seriously and it’s not something we’re prepared to rush in any way. So if you are one of the 43 who submitted a portfolio, please be patient while we work through this.

In the meantime, I wanted everybody to get some of the spotlight because I found this group of portfolios to be particularly inspiring. I’ve selected one photo (my own personal favorite) from each portfolio to be displayed as a sample. I hope you enjoy them as much as I do. The display order is based on the order that the portfolios were received.

The photos below are the sole property of the artist. They maintain fully copyright to their images, so please don’t use them without permission.

UPDATE: Aw crud… it turns out we had 44 portfolio entries. One from Dawn Armfield didn’t go through with the entry form. Sorry Dawn! We got you in there now.

Niels Henriksen

Niels Henriksen

Joel Witmeyer

Joel Witmeyer

Daniel Hellerman

Daniel Hellerman

Cesar Tardaguila

Cesar Tardaguila

William Fawcett

William Fawcett

Chica

Chica

Stuart Murdoch

Stuart Murdoch

Martin Joergensen

Martin Joergensen

Boris Taratutin

Boris Taratutin

John P Sercel

John P Sercel

Gilbert Maker

Gilbert Maker

Broderick Smylie

Broderick Smylie

Mathias Pastwa

Mathias Pastwa

Bob

Bob

Mike Pearce

Mike Pearce

Scott Ward

Scott Ward

Sebastien Noir

Sebastien Noir

Ed Zawadzki

Ed Zawadzki

Damien Franco

Damien Franco

Alexander Artemenko

Alexander Artemenko

Ariel Diacovetzky

Ariel Diacovetzky

Gunjan Karun

Gunjan Karun

Steve Berk

Steve Berk

Scott Anderson

Scott Anderson

Kevin Flint

Kevin Flint

Amanda Loomis

Amanda Loomis

Allison Jacobsen

Allison Jacobsen

Craig Bell

Craig Bell

Javiy

Javiy

Kelly Garnett

Kelly Garnett

Aaron Boot

Aaron Boot

Dawn LeBlanc

Dawn LeBlanc

Christian James

Christian James

Ryan Pennington

Ryan Pennington

Blake J. Nolan

Blake J Nolan

William Rugen

William Rugen

Karola Riegler

Karola Riegler

Melissa Beach

Melissa Beach

Jeremy Brooks

Jeremy Brooks

Gregor Winter

Gregor Winter

W. D. Naismith

W D Naismith

Zachary Cobb

Zachary Cobb

Vahid

Vahid

Dawn Armfield

Dawn Armfield

I hope you all enjoy taking a look at these photos and I encourage you to browse through the portfolios.

Simply Religious

Simply Religious

Brian Auer | 02/09/2008 | La Jolla, CA | 75mm * f/2.0 * 1/8000s * ISO100
[Print Pricing] [Contact for Signed Prints] [See it at Flickr]

This church in La Jolla, California caught my eye for its stunning white simplicity. The clear blue sky also helped to compliment the building and its elegance. I was on a photowalk, and we had just started down the road toward the beach and everybody was excited to get shooting. And so, I framed the building to include mostly sky while leaving a good portion of the church (and its surroundings) left to the imagination. I took two shots with different compositions of this church top, and this one turned out best.

Simply Religious Post-Processing

  1. Unprocessed RAW
    This one turned out a little overexposed. I shot it at f/2 with my 50mm lens and it pushed my shutter speed up to 1/8000, maxing it out. I probably should have set the f-number to at least f/2.8.
  2. Processed RAW
    Mainly I just recovered the highlights and darkened the overall image, getting it ready for Photoshop.
  3. LAB Saturation
    I saw that the blues were a little muddy, so I ran it through my LAB Saturation Photoshop Action and brought out the color while adding a bit of contrast.
  4. Clone & Sharpen
    Somehow I sort of forgot to deal with the little bit of brickwork on the bottom edge, so I took that out with the patch tool. Then I sharpened it up a bit.
  5. Curves Adjustment
    I wasn’t totally happy with the tones and colors, so I added a curves adjustment to bring up the highlights and push the shadows down. I left the blending mode to “Normal” so the blues would get a little punch too.

Enjoy!

Radially

Radially

Brian Auer | 03/08/2008 | Venice Beach, CA | 75mm * f/4.0 * 1/60s * ISO100
[Print Pricing] [Contact for Signed Prints] [See it at Flickr]

This was shot using all natural light (it was in the shade on a very sunny day) and the camera was handheld with a 50mm lens. This plant caught my attention as I walked the canals of Venice, California — it was along the sidewalk behind the houses. The pattern was so very strong, and the colors so deep that I couldn’t pass it up. The water droplets on the plant were just icing on the cake.

Radially Post-Processing

  1. Unprocessed RAW
    Straight out of the camera — untouched.
  2. Processed RAW
    I did a few basic adjustments to get the white balance correct and to bring up the contrast and saturation. Nothing very extreme though.
  3. Dodge & Burn
    Here, I used non-destructive dodging and burning techniques to really make the contrast stand out where I wanted it.
  4. LAB Saturation
    Using the technique I outlined previously for boosting saturation via LAB color mode, I strengthened the greens that are so inherently present.
  5. High Pass Sharpen
    I used a very subtle sharpening by running the high pass filter and setting the blend to overlay at 50% opacity.

As you can see, lots of little changes really add up from start to finish.

Abused and Ignored

Abused and Ignored

Brian Auer | 03/08/2008 | Venice Beach, CA | 75mm * f/2.5 * 1/8000s * ISO200
[Print Pricing] [Contact for Signed Prints] [See it at Flickr]

I found this beautiful lady in Venice Beach. She didn’t say much, but I think she was into me. Don’t let her distant stare fool you, she had quite the personality. Underneath of her “I’m sexy and I know it” facade, she’s screaming for attention. Because she is, after all… abused and ignored.

Abused and Ignored Post-Processing

  1. Unprocessed RAW
    There you have it, straight out of the camera.
  2. Processed RAW
    Minimal processing for white balance and exposure (using the “Auto” setting in ACR).
  3. Color Curves
    I used the technique from my “Redscale Process” described some weeks ago. After adjusting the curves, the blend mode was set to “color”.
  4. Color Fill
    Again, from the mentioned Photoshop technique. Opacity set to 20% and blend mode to “color”.
  5. Luminosity Curves
    Added some contrast to make it a little more punchy. Blend mode was set to “luminosity” to preserve previous color adjustments.

Now if I could figure out how to create the same effect in ACR I’d be pretty clever.

Wide Open

Wide Open

Brian Auer | 02/23/2008 | San Diego, CA | 15mm * f/6.3 * 1/1000s * ISO100
[Print Pricing] [Contact for Signed Prints] [See it at Flickr]

When the wind is just right, the skies above Black’s Beach team with para gliders and hang gliders. This particular shot was taken at a 10mm focal length (15mm full-frame equivalent) as I stood very near the edge of a 300 foot sand cliff above the Pacific Ocean. The gliders ride the updrafts as the wind comes off the ocean and shoots straight up along the face of the cliff. These thrill seekers can ride these winds for extended periods of time and never lose altitude. The Gliderport is located on the Torrey Pines State Reserve, nestled between the beach towns of La Jolla and Del Mar. La Jolla can be seen in the background of this photo as it extends out into the ocean to form a point. And those little dots on the sand below… those are people.

Wide Open Post-Processing

All of the following post-processing steps were done with Adobe Camera Raw — no Photoshop was used on this photo.

  1. Untouched RAW Image
    This is what the image looked like straight out of the camera. Not too shabby, but it needed some work on a few areas. I decided to keep the color on this one because of the sky in the upper portion of the image.
  2. Basic Adjustments
    I set the white balance to a temperature of 5500 and a tint of +8. Then I brought the exposure to -.5, set the recovery to 100, no fill light, blacks at 13, brightness at +14, contrast at +35, clarity at 35, vibrance at +17, and saturation at +7. Do note that a lot of these settings weren’t made in this order — there’s a lot of back-and-forth between these settings and the settings on the other two panels I used.
  3. Tone Curve Adjustment
    I set a “strong contrast” on the point curve, and added some extra contrast on the parametric curve with highlights set to -28, lights at +26, darks at -13, and shadows at -4.
  4. Vignette and Sharpen
    In the detail panel, I set the sharpening to an amount of 50 and a radius of 1.5. In the lens corrections panel, I added some positive vignette. So instead of darkening the corners, I lightened them to even out the image and brighten the foreground. At 10mm, my lens tends to produce a slight amount of vignette, so I punched up the value in ACR to +50 with a midpoint of 0. I lost some contrast in the clouds (which I over-contrasted just for this reason), but I gained a whole lot of brightness in the lower left corner.

Enjoy!

The Place To Be

The Place To Be

Brian Auer | 02/09/2008 | La Jolla, CA | 19mm * f/4.5 * 1/400s * ISO100
[Print Pricing] [Contact for Signed Prints] [See it at Flickr]

This shot was taken during the La Jolla photowalk in early February. At the time, I found the scene to be very interesting — the hut, the birds, the people, and the ocean in the background really seemed to work together in this candid shot. I kept things fairly well centered because of the strong symmetry already present in the hut. The Birds and the people served to break up that symmetry in isolated areas, so I didn’t feel I needed to break it up even more. Lucky for me, I also left some extra room at the top of the frame, which served as a nice backdrop for some heavy vignette.

The Place To Be Post-Processing

All of the following post-processing steps were done with Adobe Camera Raw — no Photoshop was used on this photo.

  1. Untouched RAW Image
    This is what the image looked like straight out of the camera. It could probably work as a color image too, but I wanted to go colorless.
  2. Black & White Conversion
    Before doing anything, I switched to grayscale. I pushed the red, orange, yellow, green, and aqua to negative compensation while the blues, purples and magentas were pushed in the positive direction.
  3. Basic Adjustments
    I left the white balance set at a temperature of 5800 and a tint of +3. I left the exposure, recovery, and clarity set to zero, while I boosted the fill light to 46, bumped the blacks up to 36, dropped the brightness to 16, and pushed up the contrast to 52.
  4. Tone Curve Adjustment
    Using the parametric tone curve, I set the highlights to +41, lights to +39, darks to -44, and shadows to -76. This gave me the strong contrast I was after, and I actually pushed a bunch of the highlights and shadows off the histogram.
  5. Vignette and Sharpen
    In the lens correction menu, I set the vignette to an amount of -76 with a midpoint of 19 — and this gave me the strong frame around the hut while filling in some of that sky. As a last step, I set the sharpening under the detail menu to an amount of 50 with a radius of 1.5 pixels.

Enjoy!

The Fine Art Photoblog is Officially Here!

Remember way back when I posed the question “Want to Sell Your Art?“, then the overwhelming response from 30 great photographers, and finally we narrowed it down to six outstanding individuals?

Well, the last you guys heard from me on this was early January. We didn’t forget about the project or drop it — not even close. We’ve been working out the kinks, improving the site, and getting the business end of this thing in order. These guys I’m working with have been staying up until 2, 3, 4AM almost every night pouring their time and energy into it. After all the hard work we’ve done, I’m very happy to announce that we’re off and running.

VISIT THE FINE ART PHOTOBLOG

SUBSCRIBE TO THE FEED

Seriously, check it out. All seven of us have different styles and backgrounds, and the photos presented are fairly diverse. We’re displaying images at (or near) 800 pixels, so they’re a treat to look at. And if you think they look good at 800 pixels on your computer screen, you ought to purchase a print — pixels do these images no justice in comparison to a high quality print job.

We’re offering up prints at two different levels: those that are affordable, and those that are collectible. The affordable prints are still very high quality, but they won’t be signed or sold as a limited edition. The collectible prints are signed by the artist and limited in number if that particular artist chooses to do so. For more info on the site, check out the press release.

Even if you’re not in the market for a print right at the moment, the site is worth a browse. So head over there, check it out, and tell your friends!

Drag ‘n Drop Into Photoshop

Drag N Drop Cursor

There are several ways to open an image with Photoshop. One easy way is to grab the image file, drag it into Photoshop, and drop it into your workspace. This way you can skip the whole dialog box or the right click menu from within the OS. I know this works with Windows, but I’m unsure about this functionality with Mac users. The one hook to using this method is that you need to have Photoshop already up and running.

Another perk of this method is that you can place a new image into another image as a new layer. You just need to have one image already open in Photoshop, and you then drop it on the image rather than the Photoshop background. This is handy if you’re working on textured photos, composites, or graphics.

In addition to that, you can grab images from your web browser by clicking, dragging, and releasing into Photoshop. Then you don’t have to save the file to your computer before opening it.