This post brings you a short color correction tutorial, which teaches you how to fix your night shots to remove the red color cast and make them look more natural.

Another opportunity for color correction…

Any question or comment on this article? Come over discuss it on our Editing, media [...]]]> Have you ever shot video at night, especially in cities, only to realize later on that your picture looks all red, orange, or yellow? This is due to the sodium vapor street lights, also known as broken spectrum lights.

This post brings you a short color correction tutorial, which teaches you how to fix your night shots to remove the red color cast and make them look more natural.

Another opportunity for color correction…

Any question or comment on this article? Come over discuss it on our Editing, media authoring, and color correction forum!

Best practices for shooting video at night

First off, there are some best practices that you need to know primarily, if you want to be able to shoot good video at night:

• Use manual focus. If you leave focus on automatic, focus hunting will occur because the insufficient light prevents the camcorder from locking on subjects.
• Use manual exposure and avoid too much gain. If you leave exposure on automatic, the camcorder will boost exposure by introducing gain, with 2 ghastly consequences: the night will not look black anymore but greyish; and the digital gain will be causing ugly noise in your picture. Gain is okay, even necessary, but not too much. For instance on the HDR-FX7 / HDR-FX7E, do not let gain exceed 9dB, or 12dB maximum maybe. On other camcorders the exact value may be different but the principles are the same.

Here is the original night shot. Although it was taken with an HDR-FX7E, this tutorial can apply to all camcorders.

Original video (before color correction)

So this picture does look fully red, and that is what we want to correct. Note however that there are 2 spots which have the right color: the grey cars, and the little shop’s white light. This occurs because there are multiple light sources in the scene:

1. Everything which is lit by street lights looks red, because the street lights are red. These are called broken spectrum lights because they produce only tiny bits of the whole light spectrum. Compared to daylight, the subjects you are shooting cannot reflect their true color because the light they receive is too narrow. In such situations, Manual White Balance is ordinarily useless because, even with a proper White Balance target (such as X-Rite’s ColorChecker White Balance Card), the camcorder is unable to establish white balance against broken spectrum street lights.
2. Those parts which are lit by car lights, or the little shop, have accurate colors because the car lights, or the shop’s lights, are strong enough to overcome the red street lights. This way they are able to provide the subjects with the wide spectrum necessary to reflect their true color.

This, we need to keep in mind, because we will need to fix the red color while preserving the correct parts.

First step: fixing the red color from the street lights

This first step is to apply Primary Color Correction, which means color correction that applies to the whole image. Here we’re going to steer the whole color away from red/orange, therefore applying a strong bias towards the complementary color (cyan). This screenshot was taken from EDIUS Pro, but there are similar features and you can obtain the same results with the 3-way color corrector included in any high-end editing software, such as Apple Final Cut Studio or Adobe Premiere Pro.

1st color correction: fixing the red cast

Here is the result: the red cast has effectively been removed. But those parts which were neutral (grey / white) have now turned cyan / green and this needs to be fixed in the final step.

Intermediate step (after 1st color correction)

Second step: recovering the grey & white areas

This second step is to apply Secondary Color Correction, which means color correction that applies only to parts of the whole image. Here we’re using an HSL key (Hue Saturation Luminance) to qualify only those parts of the picture which match the specific hue of green that we want to eliminate.

Then the simple trick is to desaturate those parts, that is remove all color from them so they turn grey / white again.

2nd color correction: restoring the white lights from the incorrect greenish hue

Here is the final result: from the initial horrendous red-looking footage, we have managed to produce much more acceptable video, which looks realistic enough to use in your final edited video without the audience screaming. As the best special effects are those which go unnoticed, here only the well-trained eyes will realize that the video was color-corrected.

Final video (after 2nd color correction)

Professionals would address such issue by color-balancing everything with 5500K-calibrated light sources, or setting some blue gel on the incandescent light source, or avoiding the situation altogether. That’s not practical for the casual [...]]]> There’s a dreaded situation regarding colors and lighting, which happens when you mix sunlight with other color temperatures. For example:

• Shooting outdoors with both direct sunlight and some shaded areas: the shade may appear slightly blue compared to the warm sun.
• Shooting indoors under incandescent lighting (using INDOOR White Balance) with some daylight flowing in at the same time through a window: daylight typically appears blue compared to artificial light.

Professionals would address such issue by color-balancing everything with 5500K-calibrated light sources, or setting some blue gel on the incandescent light source, or avoiding the situation altogether. That’s not practical for the casual videographer / hobbyist as you just can’t buy a whole set of lighting gear, let alone carry it around the world when travelling. Fortunately, there’s a work-around solution only a few clicks away if you have higher-end editing software such as Apple Final Cut Studio, EDIUS Pro, or Adobe Premiere Pro.

Enters Secondary Color Correction. Secondary CC is color correction that you apply only on some part of the picture, based on some criteria.

Any question or comment on this article? Come over discuss it on our Editing, media authoring, and color correction forum!

Removing the blue tint in shadows

For example in the following before/after comparison, the cars under the shadow have a slight blue cast which is effectively removed with secondary CC.

All that was needed was to qualify the incorrect parts of the picture with a HSL key (Hue Saturation Luminance) targeted at that specific blue hue, then desaturate the color away from blue.

Removing the blue color from outdoors daylight

Here is another example: daylight casts a strong blue color on the white walls around the paintings, because the camcorder’s white balance was aligned to INDOOR (i.e. tungsten) temperature. Here the picture was a bit trickier to correct and two distinct corrections were needed: one for the blue cast on the upper half, one for the slightly purple cast on the bottom part.

There’s still maybe a slight cyan tint on the upper right part, but this is as far as we can go without altering the paintings themselves and it is already a considerable improvement on the initial image.

Read Steve Hullfish’s book

You get the idea now… If you would like to further explore the techniques of color correction, read the splendid book by Steve Hullfish: The Art and Technique of Digital Color Correction.

This opens up a whole range of possibilities for the hobbyist or the apprentice videographer alike.

The first obvious observation about RED is the complexity and cost – RED requires considerable (maybe unanticipated?) expertise and effort to establish a workflow. This all drills [...]]]> I have been following with much interest the ongoing efforts by expert RED users in learning how to use this camera and let it live to its promise of digital-film-for-the-indies. Most unexpectedly however, it also triggered in my mind some lateral thoughts about ordinary videographing – how can we shoot video towards a more rewarding and fulfilling picture experience.

This opens up a whole range of possibilities for the hobbyist or the apprentice videographer alike.

The first obvious observation about RED is the complexity and cost – RED requires considerable (maybe unanticipated?) expertise and effort to establish a workflow. This all drills down to the second obvious observation that – contrary to video cameras – RED does not produce ready-to-use images. By purposeful design instead, the DSLR-like sensor outputs raw data which requires specific out-of-cam software to execute tasks that are ordinarily in-cam, such as white balancing or handling highlights (knee). For further reference, read these posts:

• PVC – Camera Log: RED? Or Cyan?
• ProLost: Digital Cinema Dynamic Range
• ProLost: Exposing to the Left vs. Exposing to the Right
  (although this one is more about photography than video, but should apply equally well…)

But then, with some lateral thinking, is it really a valid assumption that video cameras should output ready-to-use images? After all, in the film industry color grading has long been a natural part of the production process and, in a way, RED is only extending similar requirements into the digital world. Once past the initial learning curve, maybe people will get used to the postproduction constraints of RED and find that a familiar, natural step.

Similarly and by extension, check out Kevin Shaw’s informative website about colors, especially the PDF addressing the key question of When to Color. These paragraphs particularly caught my attention – quote:

“There is a myth that shooting video to begin with removes the necessity for color correction; scene matching and style are still needed. It is true that electronic capture has an inherent dynamic range that’s closer to video, but the downside is that this dynamic range is insufficient to capture exteriors and many available light situations. As a result the colorist must optimize clipped whites (or at least diminished white detail), crushed blacks and the flatter linear contrast of video originated material. [...]
The color style and effect very often requires a collaborative effort between the DP and colorist. Some projects are shot straight and the decision on color is left for later, but often a DP will expose and light with color correction in mind. This entails good planning and communication, but almost always produces better results. […]
In conclusion, color correction – like editing – could be done in camera, but it takes a lot of time and effort and still produces an inferior result. Ideally, it is refined continuously throughout post-production, with the finer and more elaborate tweaks happening after everything else.”

Well, that is thoughtful insight! Okay, RED is not film and it is not an ordinary video camera either. But here is my point: how about “ordinary” camcorders, e.g. HDR-FX7? Should we shoot video “for the editor”, i.e. with the intent to minimize postproduction work down to the simplest edit – at the expense of overblown highlights for instance if the scenery has too much contrast? Use Auto White Balance, betting that colors will be right on?

Or should we shoot video “for the colorist”, i.e. focus right from the start on the final intended look and choose that color / gamma correction are an integral part of the video workflow? This includes underexposing if necessary (only as much as needed to optimize highlights), and use fixed or preset white balance even if colors look wrong right out of the camcorder (fixed WB is easier to correct in post with a proper color target).

I guess this depends on how much effort you are willing or allowed to put in postproduction. With my experience as a hobbyist with no budget or constraints, I vote for the latter option (shoot for the colorist), and will post supporting examples or tutorials when time allows.