Kept Light Photography

Photography and Writing by A. Cemal Ekin

After further studying the behavior of the exposure and brightness sliders and discovering how strong upward exposure adjustments can cause serious color shift, I am modifying my workflow as shown below. Instead of relying mostly on exposure adjustment I am beginning to think that brightness adjustment is a more stable tool. On a photograph +2 exposure or +150 brightness produce almost identical results the latter being slightly more restrained. Ideally, this much adjustment should not be necessary, but in a pinch try the brightness first. Now I understand better why Lightroom “Auto” tonal adjustment almost always uses the brightness slider.

I have been using Lightroom since its original public beta before version 1 was released. It has become an indispensable tool in my workflow like many other photographers. It offers a very good set of tools for photographers in a very usable interface. Those of you who go back that far may remember another product before Lightroom was even announced, Raw Shooter Essentials and Professional. The Essential was free and the Professional was worth every penny I paid for it. Adobe thought likewise and purchased the company and its technology along with it. Several tools in Lightroom, later in Photoshop are descendent of Raw Shooter series. The most notable ones that are visible outside are Recovery, Fill Light, Vibrance, and Clarity sliders. Along with these, I would not be a bit surprised if the entire “Basic” group descends from RSE including brightness, blacks, and exposure. Interestingly, I have found the information on the “basic” group the most spotty and “soft” in presentation and explanation. Generally, explanations go like this “brightness is kind of exposure control but leaves the endpoints alone”, “it is a kinder and gentler exposure slider”, and so on. There are many discussions on a variety of forums and you will read a variant of these explanations peppered on the Internet. Even Martin Evening in his quite encyclopedic volume on Lightroom does not provide a fully satisfying explanation of how the Exposure slider adjustment differs from the Brightness slider adjustment.

Gray Scale Ramp 16-stepsTo better understand the behavior of these sliders, which seem to do very similar but not identical things, I decided to study their behavior on an artificial gray-scale ramp. In Photoshop, I created a 1200×1200 blank image and filled it from left to right with a gradient map going from black to white. To make reading values more consistent, I posterized the gradient fill with 16 steps. After importing the PSD file into Lightroom, I took RGB readings from each strip and recorded them on each strip in Photoshop. The resulting file had the steps all identified as Lightroom saw the RGB values. Since they were all identical, I did not repeat the numbers for R, G, and B channels.

I created an Excel spreadsheet with the original measurements as the baseline. Then proceeded to increase the Brightness adjustment in three large steps of 50, 100, and 150. After each adjustment, I measured the value of brightness (RGB values) on each step and recorded along the baseline measurements. Then I went in the negative direction, -50, -100, and -150 and recorded the brightness values. The intention here was to measure the change affected by each step of adjustment on different values of grays.

Brightness Adjustment ResultsExposure Adjustment ResultsNext, I zeroed the Brightness slider and changed the Exposure slider in +1, +2, +3 and -1, -2, and -3 settings while measuring and recording the resulting values in each step of the gray-scale ramp. I charted the observed differences in tonality in the following graphs, one for Brightness adjustments and one for the Exposure adjustments.

Now, let us take a look at the charts and see what we can observe. Clearly, the overall behavior of both sliders seems to be similar. However, some important points to note are:

  1. None of the settings produce a linear response, the effect starts low, peaking at some point, and then diminishing again
  2. When increased, Exposure seems to affect the shadows more than Brightness
  3. When decreased, Brightness appears to impact the highlights more than Exposure
  4. Since the endpoints are black and white they do not register any change
  5. Reducing Brightness seems to be a better way to tame the highlights and high values
  6. Increasing Exposure seems to be a better way to deal with opening the shadows and low values
  7. The effects mentioned in 5 and 6 are most pronounced with extreme adjustments, probably not used often
  8. Some settings produce nearly identical results, see Exposure = – 1 and Brightness = -50 graph

In practice, neither adjustment will likely be used alone. When used in combination with Blacks, Fill Light, and Contrast the results can vary significantly depending on the choice of tools. Real images bring their own problems that may stem from using one adjustment over the other. So, a generalized statement on which tool to use is difficult to make. However, the shape of the histogram will likely give clues as to the best starting point. The Lightroom’s built-in “intelligence” seems to favor using Brightness more than Exposure when the “Auto” option is used, and I have not yet seen only one slider adjustment being sufficient.

Here is my workflow for tonal adjustments: (Modified after the follow-up analysis of how these adjustments affect color shift)

  1. Set the “appropriate” white balance (I am avoiding “correct” since the WB depends on context and sensibility of the photographer)
  2. Set the “White” point, the highlight end using Exposure Brightness; remember not every photograph has a “White” point in Zone 9, don’t push it
  3. Set the Black point using the “Blacks” slider; these two adjustments will likely provide the necessary contrast
  4. If necessary, adjust the mid-tones with the “Brightness” Tone Curve, Exposure, even brightness
  5. If there are blown highlights, gently introduce “Recovery”
  6. If there are blocked shadows that need a hint of detail, use the “Fill Light” slider
  7. For finer tuning, use the Tone Curve adjustment either in parametric or point curve mode
  8. Use the HSL panel, starting with the Luminosity group and fine tune the brightness of each channel as well as saturation as necessary (easy, a little goes a long way!)

Here are some more graphs each showing a pair of Exposure-Brightness adjustment results for easier comparison. Of course, some of you may be wondering why I chose 50 unit increments for Brightness and 1 stop increments for Exposure. I have no scientific reasoning behind it other than I wanted to divide the Brightness and Exposure ranges into 6 and these numbers seemed “reasonable”. Also, look at the sample photographs resulting from different adjustments. You will be hard-pressed to tell the difference in some instances (well, most instances) except the “Auto” setting which I left without further tweaking. As you see, at least depending on the image, it is possible to create virtually identical results with significantly different adjustments.

Although this post has not reached a definitive conclusion on the behavior of these two adjustments, it at least has provided you with carefully measured results and how they compare. I am sure you can develop your own conclusions that will work for your workflow.

 

 

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Comments

  1. Nice article. Found your site through the lightroom page on facebook. keep up the great work. I for one appreciate it.

  2. I appreciated your article on brightness vs exposure – useful info. I also checked out your HDR explanation & understand the difference between an image that uses HDR as an enhancement vs one that is obviously not the original shot(s).
    I’m a heretic in the sense that I prefer Bridge over LR. Bridge is a versatile tool that I use to organize all my files including my photos. I do have LR3 but by the time I bought it I was accustomed to Bridge & it’s workflow process.
    When I bracket I use a .5 to 1 stop change rather then 2 full stops each way. Even one full stop increments is pushing it – I can end up with way too many blown highlights.
    I use full manual unless I’m in a fast movement situation. I’ve been using CS5’s PS HDR adjustments with decent results. Like you I want to enhance the image not create something that is ‘fake.’ I tend to take the bracketed images & work with them in camera raw before combining to HDR. I use luminance & saturation to work with the colors until I’m satisfied & then combine. I’ve also been using individual images in PS’s HDR adjustments. I’ve watched video that created their own pre-sets & copied the positions as a base for establishing more of my own pre-sets.
    I guess my point is there’s more then one way to ‘skin a cat.’ If you have more links or insight to HDR techniques & presets please post. I haven’t been able to afford photomatix & rely on the new CS5 HDR tool.
    Jon

    • You are correct Jon, in the world of digital photography there are many roads that will take the user to a destination. There is “the best way,” “the right way,” and “my way”! Obviously I am sharing my way of doing things with, I hope, sufficient explanation of why I do it the way I do. In fact, I recently wrote “On Photography” and expressed my displeasure at PSA’s condoning tools-based photography where the tool seems to be important. Here is the result of a search for HDR on my site:
      http://www.keptlight.com/index.php?s=hdr

      I do appreciate your comments and sharing your workflow with me and others. For HDR Photoshop has come a long way in CS5 making it easier to use with its set of benefits. Take care, and thank you for your comments.

  3. Excellent article. Now I have a logical flow to start making adjustments. Before it was always “well lets try this”.

    Thanks.

    • I’m very glad that you, and others, have found the article useful. There is still some mystery behind these adjustments, I wish Adobe or one of their evangelists would clearly articulate the core benefits of using each of these adjustments. As you see, indistinguishable results can be obtained using significantly different adjustments. We’ll keep trying to understand the mystery.

  4. Nice analysis, and great tips for adjusting an image. I do like how you can use a wide range of settings to get similar images, much like you can achieve identical exposures with different combinations of aperture, ISO, and shutter speed. It lets you recover and compensate when experimenting without having to start over.

    I haven’t actually tested this yet, but I’ve always worked with the theory/assumption that a RAW file held more exposure information than a JPG – and therefore Lightroom would have more to work with (i.e. when recovering blown highlights). I have always gone to the Exposure tool first to tweak the strongest aspect of my image (fix exposure for either highlights or shadows) and then recovered the rest using the other tools.

    Could it be that you would find different results between these two formats, or would they be essentially the same because both brightness and exposure settings would have the same range of extra data to work with in RAW? Interesting thought..

    • Karl, you are correct that RAW has FAR more information than the JPEG format can carry. It is particularly information-rich at the high end of the spectrum; that’s why you will see recommendations that your histogram should be to the right. You can extract plenty of highlight detail from a RAW file that may be totally obscured in JPEG. The other major difference is that JPEG format is an 8-bit format that uses 255 shades to define each of the Red, Green, and Blue channels. Today, most digital cameras, at least the DSLRs, will record 12-14 bit information giving you 4096-16384 shades in each of the RGB channels. You can see the richness in information. Due to the linear nature of digital exposure, about half that spectrum is used by the highest tones, half of the remaining, the next highest tone and so forth. That’s the reason for the high end being richer in information. There is some discussion of bit-depth and information we can carry in the following post. You need to view the presentation slides for the detailed information. Thanks for stopping.

      http://www.keptlight.com/2009/02/dont-bruise-the-pixels/

  5. Good work but I wonder what the effect of the Recovery slider would be for recovering highlights instead of reducing Brightness and how they might compare.

    • Jon, the recovery slider works in a much narrower range in the highlights and has little effect on the shadows. If I were trying to salvage an overexposed photograph I would probably start with the exposure slider first and see how much it extracts from the highlights. Then I will likely use the recovery slider, finally, and possibly moving to the brightness slider. Some of these adjustments can, and probably should be augmented and complemented by adjustment curves.

  6. I think your article is very useful for confused users.
    But there is one thing that is omitted in most cases (in discussions, articles)- how adjusting these setting affect colors (and there is a difference)- maybe you can take a look at this ;)

    • Jan, that is an excellent idea, I was wondering about the effects of these on color you gave me more reason to study that too. In Photoshop, extreme adjustments with curves will certainly add unwanted color shifts. Because of that I separate the luminosity adjustments from color adjustments in Photoshop in two or more curves layers. In Lightroom there is no such facility and one must be careful not to disturb the colors. More work for me!

  7. Thank you for an interesting article! There is however more difference between the two sliders to discover. For example, try an image with blown highlights. The exposure slider can recover much detail from the blown highlight while the brightness slider seems worthless for this task, even though the brightness slider when lowered decreases the highlights more than the exposure slider according to you research.

    • Fredrick, for extracting highlight detail the recovery slider is very good, you are right. So, all the usage depends on the needs; as I said it is difficult to make a generalized statement on when to use what. At least for me it is.

  8. I also discovered you through the Lightroom page on Facebook.
    Really enjoyed the article.
    Bravo. G.

  9. Great article. I appreciate the time and effort that went into putting this together. I tweeted this article under Warnerwoodphoto.

    Thanks

    John

  10. Nice article, I’m very interested in workflows of various people to learn more on lightroom, this surely was helpful

  12. very nice article, thanks for doing the research !

    whats your position on the +50 default of brightness ?

    i put it on 0 and use exposure and brightness to dial it back in.

    or should i leave it athe default and start from there. still confusing :)

    whats your position on not using the basic sliders in LR and just send the converted raw file in 16bit to PS curve tool (because of the 14bit levels in my raw file) ? and do the black, white, brightness and contrast work there ? on seperate channels in RGB if necessary ?

    with my new camera 5dmark II my brightness and contrast work is a lot less than with the older camera with cheaper lenses ;)

    • Glad you enjoyed it Eric. Now that I am using LR 4, some of these adjustments make more sense although I have some other issues with LR4 as you can read on several other posts. That said, consider LR3 brightness a gamma-corrected, kinder, gentler adjustment. Exposure seems to be a stronger “lever” to pull and moves rapidly. If you do not mind working with a different clarity slider and some printing issues, you may consider upgrading to LR4. I say this with some reservation because of my misgivings in the clarity and printing areas.