Lightroom: Clipping & the Histogram

Posted by CWade in Lightroom, Tutorials | Tagged | 5 Comments

Just a quick post to talk about photographic clipping and some ways to deal with it in Lightroom.

If you’re not really familiar with the idea of clipped highlights (sometimes referred to as “blown” highlights) or crushed blacks, Wikipedia does a satisfactory job of explaining the concept:

“In digital photography and digital video, clipping is a result of capturing or processing an image where the intensity in a certain area falls outside the minimum and maximum intensity which can be represented…The clipped area of the image will typically appear as a uniform area of the minimum or maximum brightness, losing any image detail.”

Fun stuff- now onto the Lightroom portion of the tour!

Understanding clipping goes a long way toward conceptualizing the way histograms represent an image. In the Develop Module, make sure you have the Histogram Panel maximized.

The screenshot below shows an image with its color histogram on the upper right:

I’ve chosen this photo because, straight-out-of-camera, it has some clipping-specific exposure problems.

A closer inspection shows us that there are runaway peaks at both ends of the histogram:

The vertical axis represents the number of pixels in each tone range; horizontally, left to right, you read dark/blackpixels –> light/white pixels.So, the strong peak at the far left is telling us that the image suffers from too many black pixels and possible loss of data- crushed blacks. The peak continues all the way to the top of the histogram, indicating there is some data loss. The peak on the right of the histogram is both narrower and shorter, indicating that the clipping is not as extreme, but that there still may be some blown highlights.

What you’re shooting for in a histogram is a gradual curve in the center-ish, with no peaks at either end- more or less similar to this one:

which belongs to this photo:

Here’s a purloined, and slightly generalized, graphic to help:


Diagram borrowed from The Digital Story blog.


(Incidentally, The Digital Story has a good podcast on understanding exposure via histograms.
)

Histograms are a great way to check for clipping in-camera (and in software like LR). In fact, you should always check your histogram while you’re shooting. Many photos appear correctly exposed on the camera’s LCD, but in reality can be far off from the intended* exposure . This has happened to me often enough, and photographers pay for mistakes like this with extra post-processing time.

*I’m a non-believer in “proper” or objectively “correct” exposure.

(I realize this is a )

In Lightroom, there’s an efficient and wonderful way to check for clipping in an image. In the top corners of the Histogram Panel are little triangle switches!

On your keyboard, simply press J to activate them! This action causes:

red squares are my mark-up

…this [awesome] nonsense to happen. The red coloring indicates blown highlights, while the blue indicates crushed blacks. So now you know exactly where in your image clipping is occurring, and can make decisions as to whether or not that clipping is appropriate/ acceptable to you.

You can leave the triangle switches ‘on’ while you adjust any exposure parameters of your photo, an extremely useful feature of Lightroom.

(Jacts as a toggle, so pressing it again will turn the color overlays ‘off.’)

Alternatively, you can choose to activate only one switch at a time, either by hovering over it- just for a quick reference- or by clicking it. In this black and white image I wanted to check on the highlights:

You can see there is very little clipping. The clipping here is acceptable to me because this photo is the epitome of a ‘high-contrast situation,’ as it’s a silhouette. Silhouettes are one of the few image types in which dramatic clipping on both ends of the histogram is not only acceptable, but expected.

Most clipping in silhouette photos will occur in your blacks, however:

That’s a lot of missing data! (Which is perfectly fine here because we just want to show the form and outline of the tree and its branches.)

What if you encounter unwanted clipping?

To a very high-degree, Lightroom will allow to you to fix the situation, excepting the most extreme under- and over-exposures.

To fix a peak in the left of the histogram and bring up the blacks, you can try upping the exposure, fill light (use a light hand here!), and brightness. There are sliders for all of these parameters. Most importantly though, is correcting the lows in the Tone Curve Panel:

You can try bringing the ‘darks’ and ‘shadows’ up which should create a curve similar to the one I’ve drawn (dark red line). Don’t overdo it, or you’ll introduce a particularly nasty type of digital noise known as banding noise. Banding noise is my personal nemesis, and it should be yours too!

As always, the switch in the top left of the panel will toggle any changes ‘on’ and ‘off.’

Hot Tip: pressing Alt on your keyboard will bring up the words ‘Reset Region’ in the Tone Curve Panel. Clicking the words while Alt is still pressed will reset anything you did to the curves! (If you do this by mistake you can always go back in the History Panel and click the previous state.)

What about clipped highlights?

Pre Post-processing Tip:
Data in the blacks is easier to recover than data in highlights, so if you’re faced with a high-contrast situation that’s not a silhouette, it’s wise to underexpose by a stopor two.

/Tip

To correct clipped highlights and recover whatever data is recoverable, use the [surprise!] Recovery Slider, located in the Basic Panel:

Notice that the histogram responds to the slider’s movement by lightening the area that recovery will affect (circled).

Even though I’ve recovered highs to +95/100, the histogram tells me they’re still clipped; you can see how the dandelion is still mostly a white blob, auniform area of the maximum brightness.” Some photos just can’t be salvaged entirely.

And that’s why histograms should be checked on your LCD while you’re shooting!

I hope this guide has been helpful, but not too unwieldy- I wanted to be thorough!

Happy shooting.

5 Responses to Lightroom: Clipping & the Histogram

  1. eddyizm says:

    excellent post!

  2. photograph background removal says:

    Great stuff!
    Keep posting.
    Thanks for sharing.

    Regards,
    clipping path

  3. Tyler Wainright says:

    Great write up – I use Lightroom 3 and it's always good to learn some tips on how to manage the workflow better. Thanks for sharing

  4. Anonymous says:

    helpful.

  5. Anonymous says:

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