Timelapse Photography: “Holy Grail” Method Versus Aperture Priority

(This article is a supporting part of our ongoing testing of low-light camera metering reliability)


One of the most challenging genres of modern digital photography is nightscape photography, and one of the most difficult ways to capture this subject is with a day-to-night (or night-to-day) timelapse.

As an example, from bright sunlight to a moonless, starry night, a camera’s exposure will need to change by a whopping TWENTY stops or so.

Simply put, no camera can capture that range without adjustment, and this is unlikely to change. And, no matter what, the best image quality will always come from a correct exposure. Therefore, it becomes necessary to adjust your exposure during any timelapse in which the light changes significantly.

Before we continue, let’s make one thing clear: for most nightscape (also known as landscape-astrophotography or astro-landscape) photographers, if you are only capturing still images of a scene then you will do well to only ever use manual exposure, and to completely ignore your camera’s light meter. Instead, your histogram alone should be trusted.

How To Adjust Your Exposure During A Timelapse

There are multiple ways to tackle these challenging conditions, such as sitting by your camera for two hours, carefully checking and adjusting the exposure every minute, and then attempting to correct the stepped” exposure brightness in post-production.

Or, you could try letting your camera meter do its job, and hope that it knows how to correctly meter a night sky and not just give you pure black photos.

The Holy Grail Timelapse Method

The “Holy Grail Method” of timelapse photography is, in a nutshell, sitting next to your camera and manually adjusting the exposure. Between every single shot, you check your histogram, and bump up (or down) the exposure by 1/3 of a stop if it’s needed.

If you’re doing a full day-to-night timelapse and you’re going from bright daylight to a moonless, starry sky, that means you could be adjusting your exposure (and bumping your camera’s pointing?) 60 different times!

Unless your tripod is a boat anchor and you have a very gentle touch, this is very likely to create highly visible shaking in your final timelapse. You can try using a Bluetooth/WiFi-paired cell phone (most camera brands’ mobile apps allow you to control your camera’s exposure), but you’ll still create a very noticeable brightness “jitter” that has to be corrected very carefully in post-production with specialized software. (See the video above for a full demonstration!)

NOTE: the above video was made using a Nikon D800, which failed to meter correctly almost immediately after sunset, which is why back then I was still a fan of the Holy Grail Method. In our standardized test, the D800E fails to meter at about EV0, which is one of our worst scores.

Today, however, many cameras (especially mirrorless cameras that use their main image sensor for metering) can meter well below EV0. Depending on the ambient light of your nightscape, (moonlight, nearby light pollution, or Low-Level Landscape Lighting), you might be able to get…

The Benefits Of Aperture Priority (And Auto-ISO) For A Day-To-Night Timelapse

First and foremost, if you use Aperture Priority and auto ISO, you won’t have to touch your camera nearly as much. You might have to dial in some positive exposure compensation right after sunset or just before sunrise, but that’s about it.

Second, there is an added bonus that many people don’t realize! More and more (though not all) cameras have an additional perk of auto-ISO: they actually use extremely small exposure increments, much smaller than 1/3 stop, resulting in a perfectly smooth transition from day to night.

Nikon’s latest cameras (D850 and newer) have a built-in interval timer which is capable of exposure smoothing, and it works very well! Sony, Canon, and other cameras may or may not have this feature; the best way is to just go out and test your particular camera!

Speaking of testing: in the past, there has been a fundamental problem with this timelapse method: many cameras’ light meters would just completely fail and you would get a timelapse that rapidly transitioned to nothing but black frames.

HOWEVER, lately, more camera have been able to meter very well in extremely dim light, such as the light of a full or even crescent moon, and a select few cameras, shockingly, can meter a pitch-dark, moonless starry night sky with impressive accuracy.

That is why we created THIS TEST CHART, so that you can know what types of lighting conditions you can trust your specific camera to give a good exposure in.

Conclusion | The Best Day-To-Night Timelapse Transition Method

The combination of not having to touch your camera dozens of times during blue hour and having quite smooth output makes the second choice seem very tempting: use the “Holy Grail Method” if you must; however, you could get perfectly smooth exposure transitions by using auto ISO and Aperture Priority, thus saving significant work in post-production and likely producing a higher quality final result.


Integrating Sphere & Camera Metering Test Project

Main Project Page – Test Results

Project Overview – What Is An Integrating Sphere, and How We Used One to Measure Cameras’ Low-Light Metering Capability

Frequently Asked Questions / FAQ

What are EVs, and What do They Mean for Different Cameras? (Non-Technical Explanation)

The Technical Explanation of EVs, and Calibration of the Integrating Sphere

So, How Did You Build an Integrating Sphere, Anyway?

Timelapse Methods Compared: Aperture Priority VS Holy Grail Method

(YOU ARE HERE)


 

What Are EVs In Photography, And What They Mean For Different Cameras (Non-Technical Explanation)

(This article is a supporting part of our ongoing testing of low-light camera metering reliability)


Exposure Values (EVs) have two common usages. First, they can be used to quantify the brightness of a scene. Higher EV numbers indicate a brighter scene. Second, they can describe differences in exposure settings (for example exposure compensation).  In both definitions, a change in EV of 1 indicates that the light level has doubled or halved. Below are the approximate EV ratings of an assortment of scenes:

Chart credit: Brent L. Ander

Photographic light meters typically meter a scene and report its EV plus the exposure settings appropriate to capture it. The table below shows what settings correspond to different EV situations.

Chart credit: Brent L. Ander

To use the above chart, suppose you want to know what shutter speed properly exposes a 5 EV scene at f/4 and ISO 400. Look down the ISO 400 column to the row with “5”, then follow that row right to the f/4 column. The appropriate shutter speed is ⅛ second. If this is still unclear, the link gives several more examples.

Below is a graph of the ambient brightness in Exposure Values for moonlit landscape conditions. You can also use this moonlight exposure calculator to check exposure for a specific aperture and ISO and moon phase.

Chart created by Sean Goebel

EVs and Your Camera’s Histogram: Different Dynamic Ranges Result In Different Histograms For The Same Light

Due to cameras having different dynamic ranges, however, that lone histogram spike will fall in a different place for one camera versus another.

To demonstrate this, I set a Canon M5 and Sony A7m3 to the “correct” EV0 settings of ISO 100, f/2.8, 8 seconds, then inserted them into the sphere with it set to EV0. The same 50mm lens at 2.8 was mounted via an adapter to both.

As you can see, the Sony (left) reports that the scene is ⅓ stop underexposed, but its histogram is perfectly centered. The Canon (right) reports that the scene is 1 stop overexposed, but its histogram is slightly left of center. EV0 is about where it should be (middle of histogram), but the two cameras have different ideas of where in their dynamic range it should go. Canon and Sony have programmed their metering differently.

In summary, the exposure value of a scene describes its brightness, and it can be converted into camera settings that can capture the scene. However, because different models of cameras have different dynamic ranges, not all cameras will place the histogram bump in the same place, even with the same settings and lens.


Integrating Sphere & Camera Metering Test Project

Main Project Page – Test Results

Project Overview – What Is An Integrating Sphere, and How We Used One to Measure Cameras’ Low-Light Metering Capability

Frequently Asked Questions / FAQ

What are EVs, and What do They Mean for Different Cameras? (Non-Technical Explanation)
(YOU ARE HERE)

The Technical Explanation of EVs, and Calibration of the Integrating Sphere

So, How Did You Build an Integrating Sphere, Anyway?

Timelapse Methods Compared: Aperture Priority VS Holy Grail Method