On Set with the Sekonic C-700: LED Color Consistency

Gaffers and DP’s already have enough to worry about on set without adding color consistency of the light fixtures to the mix. Unfortunately, as LEDs become increasingly popular color consistency has become too large an issue to simply be “fixed in post”.

In this video, Director of Photography Timur Civan discusses the challenges of using LED light fixtures on set and how the Sekonic C-700 Spectromaster helps him overcome them. He also highlights a few other features that have revolutionized the way he and his gaffers work.

Timur also recaps the crucial role the C-700 played in the 2017 LED Light Shoot Out. This epic gathering of 28 lights is the most comprehensive LED fixtures test ever undertaken!

Want to know how your favorite LEDs fared? Head over to No Film School and check out the results!

Posted in C-700/C-700R, cinematography, Color Meter, portrait photography, Professional Photographers on Light Metering, video   Leave a comment

Demystifying Flash Duration

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The Flash Duration for any strobe or flash is technically the length of time that the flash tube emits light for a single burst. As simple as that sounds, be aware that almost no flash or strobe company will tell you how long the actual flash duration lasts. Instead most companies quote what are known as the t0.5 or the t0.1 flash duration specifications, which I will define here in just a moment. These flash duration specifications are part of the standards for a “discharge duration” as defined by the International Organization for Standardization (ISO). Aside from these ISO standard specifications, the reason strobe companies don’t disclose the total flash duration is that the flash does not have a constant intensity over its entire duration. As in Figure 1 below, the flash intensity is brightest just after the flash is triggered and then generally decreases as shown in the curve below.

As you can see the t0.5 value is the period during which the flash intensity is above 50% of its maximum brightness. The t0.1 value is the period during which the flash intensity is above 10% of its maximum brightness. Hence, the t0.1 value is a much more accurate assessment of the actual flash duration.

As you can see the t0.5 value is the period during which the flash intensity is above 50% of its maximum brightness. The t0.1 value is the period during which the flash intensity is above 10% of its maximum brightness. Hence, the t0.1 value is a much more accurate assessment of the actual flash duration.

The t0.5 specification is the period during which the flash intensity exceeds 50% of its maximum brightness. What this means is that 50 % of the light is emitted after the t0.5 threshold is met. Hence, as you can see from the chart above, the actual flash duration can be significantly longer than the t0.5 specification. What this means for the photographer is that there is still a lot of light being emitted after the t0.5 threshold and thus there is the possibility for motion blur in the image. For sports photographers, or any photographers trying capturing fast moving subjects using flash, this is a major issue and the reason an in-depth understanding of flash durations is so important.

Because the meaning of the t0.5 specification is somewhat ambiguous, the ISO governing body set the t0.1 duration as the “total flash duration.” The t0.1 specification is the period during which the flash intensity exceeds 10% of its maximum brightness. As you can see in Figure 1 above, the t0.1 value is significantly more informative and much closer to the actual duration of the flash.

These two separate flash duration values allow us to compare the flash duration of various strobes fairly accurately. For the outdoor photographer that shoots adventure sports, or anything that moves quickly, selecting a strobe with a very short flash duration is a must. Most manufacturers offer strobe kits with extremely short flash durations that are marketed specifically to sports and action photographers. Some strobe companies even have flash cut-off technology built into their power packs, which reduces the flash duration significantly.

These two images show the effect of flash duration on a moving subject, which is this case was a bicycle wheel rotating with some serious speed. In the upper image, the t0.5 flash duration (as measured on the Sekonic L-858D-U) was 1/353 second, which is pretty slow as flash durations go. Because of the slow flash duration the bicycle wheel is blurred. In the lower image, the t0.5 flash duration was 1/5,350 second, which is a decently fast flash duration and hence, the wheel is frozen.

These two images show the effect of flash duration on a moving subject, which is this case was a bicycle wheel rotating with some serious speed. In the upper image, the t0.5 flash duration (as measured on the Sekonic L-858D-U) was 1/353 second, which is pretty slow as flash durations go. Because of the slow flash duration the bicycle wheel is blurred. In the lower image, the t0.5 flash duration was 1/5,350 second, which is a decently fast flash duration and hence, the wheel is frozen.

After going through all of these numbers and specifications, it can be a bit dizzying to figure out how fast a flash duration you actually need. In general, a t0.5 value of 1/2000th second or higher will be more than adequate for most photographers who need to freeze the motion of a moving subject. For faster moving subjects a faster flash duration will be needed.

In contradiction to the above paragraph, the latest Hi-Sync and HS technologies allow for using shutter speeds above the maximum flash sync speeds of most DSLRs. This means we can stop the action, and still sync with a strobe, using a high shutter speed like 1/8,000th second, to stop the motion of an athlete instead of using a fast flash duration. HS technology requires a slow flash duration, typically less than 1/800th second, to work properly, which can be quite confusing. Nevertheless, regardless of what technique and technology is being used, knowing the actual flash duration is always an important factor when working with a moving subject.

The Sekonic L-858D-U, as shown here, can measure the flash duration of any strobe or flash. It can also be set to measure the t0.5 or the t0.1 flash duration. And of course it can also measure ambient exposures, flash exposures and also HSS flash exposures—all of which makes it the most powerful and versatile light meter on the market.

The Sekonic L-858D-U, as shown here, can measure the flash duration of any strobe or flash. It can also be set to measure the t0.5 or the t0.1 flash duration. And of course it can also measure ambient exposures, flash exposures and also HSS flash exposures—all of which makes it the most powerful and versatile light meter on the market.

Sadly, most flash manufacturers don’t tell you the flash duration for each power setting, though some have this information in the manual that comes with the flash. A few manufacturers display the actual flash duration for that exact power setting on the flashes LCD readout, which is very handy. But these numbers aren’t always accurate and the actual real-world flash durations can vary widely from flash to flash. Because of this, using a light meter like the Sekonic L-858D-U, which can very accurately measure the flash duration, as well as the light output, is quite helpful. Using a light meter like the Sekonic L-858D-U will help to reign in control of the actual the flash duration.

– Michael Clark, guest blogger

Posted in Flash Duration, L-858D-U, Sekonic   Leave a comment

Accurate Exposure is Key to Getting the Best Possible Color in Camera

A large number of photographers remain horribly confused by color management. However, it’s a fairly simple process that ensures our images maintain a consistent appearance when viewed in print or elsewhere. Very few photographers are aware that accurate exposure plays a key role in extracting the best possible color and making post production more efficient.

White Balance

To obtain accurate color, we first need to set the White Balance correctly which can be done by photographing a neutral target to set a custom White Balance. This sets the base color temperature for the scene, so greys lose any color bias, while whites remain clean – without hints of magenta or blue, for example.

Sekonic Grey Card

It doesn’t matter if the target image is upside-down or even blurred with camera shake, but it must be evenly illuminated and accurately exposed, otherwise the White Balance is likely to be incorrect. This is just one example of how exposure plays a part in color management.

Don’t Rely on the Camera’s Histogram for Judging Correct Exposure

There is a common misconception among photographers that you can rely on the camera’s histogram to judge the correct exposure, but this is a major error if you are shooting RAW files. The problem with camera histograms is that they display information based on the output of sRGB JPEGs, which offer nowhere near the potential range of tones found in Raw mode.

Digital sensors are linear devices, which means the biggest chunk of data is stored in the brightest part of the exposure, followed by a subsequent drop with each successive reduction in luminance. In practice, camera histograms start flashing highlight warnings long before necessary for RAW files with huge potential losses in dynamic range.

Depending on your camera, up to 50% of the potential dynamic range could be lost if you rely on the camera’s histogram, so if your camera is capable of reproducing a scene with 10 stops of dynamic range, 5 stops could be lost instantly with no means of recovery. That one small error is likely impacting every image you shoot; leading to flatter images with reduced shadow & highlight information unless you use a handheld meter to set an accurate exposure.

Use a Light Meter to Cut Down Post-Production Time

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My personal choice is the Sekonic L-758D (also marketed as the L-758DR and L-758 Cine) that allows for exposure profiling based on the exact characteristics of the camera’s sensor and includes precise feedback about exposure latitude in any given situation. Using a handheld meter is actually the lazy man’s solution to cut down on post production work, while being no slower in practice than studying a histogram and estimating adjustments.

Photographers shooting JPEG need to be especially careful to set an accurate exposure and White Balance, since changes made in post production are highly destructive and likely to produce histogram combing, which represents missing data. The visual impact of this is will be rendered as abrupt tonal transitions that are particularly noticeable in areas of the sky, for example. See the below before and after histogram results of a JPEG file in Photoshop following a very minor tonal edit.

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Histogram Prior to Edit

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Histogram Post Edit

The simple fact is that if you set an accurate camera exposure and White Balance the rest of your color managed workflow should be remarkably straightforward; allowing you to exploit the full potential of your camera, while cutting down dramatically on time spent in post production. All of this and much more is discussed extensively in my new book Colour Management Pro.

– Ashley Karyl, guest blogger

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Posted in Color Management, L-758D   1 Comment