Metering Project Frequently Asked Questions

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


Jump to…

Please explain your categories.
What lens did you use for this?
If I adjust exposure compensation, my camera can meter in lower light levels, right?
Does vignetting affect the test results?
If I use a faster lens, I can meter in lower light, right?
If I use live view on my DSLR, I can meter in lower light, right?
Does metering mode matter?
Since you take photos with one-stop changes in light levels, how can you report metering failure with 1/10 stop precision?
Can I view your code? I want to understand your pipeline.

 

Please explain your categories.

Metering limit definition 1:
Metering failure occurs at the point where the camera compensates 2/3 stop for a 1 stop change in ambient brightness.

Metering limit definition 2:
Metering failure occurs when the image is 1 stop darker than the image taken at EV0. If the camera is already struggling at EV0, we report the light level that produces an image one stop darker than a photo of a well-lit white wall and consider the answer approximate.

Manufacturer claimed value:
What the spec sheet of the camera says about its metering capability. We have not attempted to translate this into ISO 100 f/2.8 units.

Moon phase equivalent to definition 1:
The illumination levels of definition 1 were converted to moon phase using the plot shown here. This should be viewed at approximate only, since the preferred exposure for moonlight conditions depends on the scene and user’s preference. Sean has a calculator for moonlit light levels on his website at http://sgphotos.com/blog/exptime.html, but this reports “expose to the right” exposure settings that aim to fill the camera’s histogram. The settings in that calculator are two stops offset from those of the plot.

Camera stops down lens to meter?
Some mirrorless cameras (Sonies) keep the lens stopped down to the user-specified settings even when not taking a picture. In other words, if you are using an f/1.4 lens and have the camera set to f/2.8, the lens sits at f/2.8 all the time. This reduces the ability of the camera to meter in low-light conditions and therefore is bad. “No” is the preferred answer to this category. There are two reasons for cameras to preemptively stop down the lens. First, it gives the user a real-time depth of field preview. Second, some lenses exhibit focus shifts when stopping down, so if the user focuses wide open and then stops down to take the picture, the picture will be out of focus. Spherical aberration causes this. The first reason can be mitigated by having a “depth of field preview” button, and the second issue can be solved with a lookup table of aperture-dependent focus shifts. It is lazy engineering to keep the lens stopped down and not give the user the option to meter with the lens wide open.

If DSLR: better in live view?
Can the camera meter in lower light when in live view? In most cases, the answer is yes. DSLRs normally split the light between the viewfinder and the AF/metering sensors. When the user switches to live view, all the light goes to the detector, and so it is all available for metering calculations.

If DSLR: benefits from <f/2.8 lenses?
I don’t entirely understand the mechanism of this, but some DSLRs do not improve their metering limits when moving to a lens that is faster than f/2.8. Metering improves from f/5.6 to f/4, and f/4 to f/2.8, but the metering at f/2.8 is the same as at f/2.0 or f/1.4. I suspect this is related to the fact that there are f/2.8 AF sensors and <f/2.8 sensors. The preferred answer in this category is “yes.”

Exposure compensation to put the histogram in the middle:
At EV0, what exposure compensation places the histogram spike in the middle of the plot? Different cameras have different ideas for “ideal” exposure, and this may be different from one camera to another even of the same model.

 

What lens did you use for this?

We used a Rokinon 50mm f/1.4 set to f/2.8. It is EF mount, which can be adapted to Sony E, Canon EF-M, Canon RF, Nikon Z, etc with a tube adapter (i.e. no loss of light). It has a mechanical aperture, so I can control the light level entering the camera. It cannot be adapted to Nikon DSLRs, unfortunately, so we used a Nikon 105mm f/2.8 Micro (also at f/2.8) for the D800E.

 

If I adjust exposure compensation, my camera can meter in lower light levels, right?

No. Look at any one of the plots, and consider what the X & Y axes actually mean. Adjusting exposure compensation would shift the curve up or down, not left or right. It would not affect at what EV the kink or drop occurs, and it would not affect our measurements for metering failure.

 

Does vignetting affect the test results?

Sort of. The lens transmission in the metered area affects the results, which is why we use a Rokinon 50mm f/1.4 at f/2.8 for all bodies for the standard test. This lens was chosen because it has a mechanical aperture that can be set by hand and stays stopped down, and also it can be adapted to many different mounts. Using one lens gives an even playing field to cameras from multiple brands. Returning to the original question, the metering of most cameras is weighted toward the center of the frame, so dark corners don’t have a big impact.

 

If I use a faster lens, I can meter in lower light, right?

Maybe. The metering of some DSLRs doesn’t improve when lenses become brighter/faster than f/2.8.

On the other hand, some mirrorless cameras (all Sonies, no Canon EF-Ms) stop down the lens in order to meter and autofocus. This is an extremely clumsy solution to the possibility that focus can shift with aperture, and is worthy of an extended blog post/rant. If you have a f/1.4 lens on a Sony but have it set to f/8, your metering is five stops worse than if the lens was set to f/1.4. So you only achieve better metering with a fast lens if you have it set to a fast aperture.

 

If I use live view on my DSLR, I can meter in lower light, right?

Probably. But your battery will die quickly.

 

Does metering mode matter?

Possibly. Most camera specs do not state the metering mode for the specified metering range. However, for example, the Nikon D800E claims EV 0 to EV 20 in matrix or center-weighted metering, but EV 2 to EV 20 for spot metering.

In case you’re wondering, our tests were all done with the camera in “evaluative” or “matrix” metering mode, and that is also what we use in real-world shooting conditions.

 

Since you take photos with one-stop changes in light levels, how can you report metering failure with 1/10 stop precision?

We interpolated between data points using a second-order spline fit. In most cases, this should be accurate to a tenth of a stop.

 

Can I view your code? I want to understand your pipeline.

Sure! The Arduino and Python codes for the project can be viewed at https://github.com/geekyrocketguy/laptop/tree/master/metering%20project. If you have further questions, Sean can be reached at sean@sgphotos.com.

 


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
(YOU ARE HERE)

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


 

Using An Integrating Sphere To Test Camera Metering In Low Light – Project Overview

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


What is the dimmest light level that a given camera can meter? For a nightscape photographer, and particularly for someone who films timelapse video with day/night transitions, this question is critical. Normally when I film a timelapse video that starts during the day and ends at night, I start with the camera in aperture priority mode, and the camera compensates as the sun sets.

However, as twilight fades into night, at some point the camera’s metering fails, and I have to switch the camera to manual mode and adjust the settings until night has fully fallen. Innumerable exposure errors have occurred because I didn’t switch to manual at the right moment, or irregularly changed settings in manual mode.

In recent years, some cameras have become able to meter at night, so switching to manual mode is unnecessary. Manufacturer metering specifications are completely wrong and useless. Therefore, while stuck in quarantine in 2020, Sean Goebel and I set out to build a standardized comparison of the low light metering abilities of different cameras.

To answer this question, we built an integrating sphere. An integrating sphere is a sphere that is painted white on the inside and has LEDs for internal illumination. The camera lens pokes into the sphere. Through the use of baffles, light from the LEDs has to bounce at minimum twice before entering the camera lens, and this causes the inside of the sphere to have almost perfectly even illumination.

In other words, it doesn’t matter where the camera is pointed inside the sphere–it’s all the same brightness. The sphere is carefully sealed so that light cannot leak inside from the outside.

 

 

Gray image showing what the camera sees

 

Here are the basics of the metering test: we use an Arduino (an open-source microcontroller) to control the LEDs inside the sphere and trigger the camera being tested. We calibrated the maximum light level of the sphere to be exactly 0 Exposure Value (EV0).

For reference, EV0 is about the light level of a very dim restaurant or a landscape 20 minutes after sunset, and “correct” exposure settings for this are 1/8 s, ISO 6400, f2.8. The camera is set to aperture priority mode with an f/2.8 lens and takes a photo of the inside of the sphere.

The light level is dropped by half (to EV-1), and another photo is taken. Ideally, the camera detects the dimming of the light and compensates with a longer exposure time and/or higher ISO. The light level is dropped by one stop again (to EV-2), and this repeats until the ambient light level reaches EV-10. The correct settings for EV-10 are 30 sec, ISO 25,600, f/2.8, which are appropriate for a light level achieved under a cloudy moonless night without light pollution. Most manufacturers report that their bodies can meter to light levels of EV0 or EV1, but as our tests show, most bodies can meter well darker than this.

After collecting the 11 photos in Aperture Priority mode, each with half the light level of the previous photo, we use Python’s RawPy software library to calculate the average brightness of each raw file. We plot this against the EV that the photo was taken at. If a camera was perfect, the average brightness of the raw file would be constant, since the camera would double its exposure time or ISO with each new photo to compensate for the decrease in light. In practice, plots look like this:

For the first few dimmings, the camera effectively compensates, and the average brightness of the resulting image is constant. However, beyond some point (about EV-6 here), the camera only partially compensates for the decrease in light level–when the light drops by 1 stop, the camera only adjusts by 2/3 stop. Further along, the camera can no longer detect any change in brightness at all, and it does not adjust its settings at all.

Because cameras don’t abruptly change from perfect metering to completely nonfunctional metering, we define two criteria for metering failure.

First, we report at what light level the camera adjusts its settings only 2/3 of a stop for every 1 stop decrease in light. In other words, the first time it fails to compensate by at least 1/3 of a stop.

Second, we report at what light level the camera produces images that are half the brightness of (one whole stop dimmer than) its EV0 image.

Once you know this information about your specific camera, you can translate it to a specific ambient lighting condition (using this article here) that you can safely capture in Aperture Priority with your camera.

Say, for example, if your camera can meter correctly at EV-5, but fails at EV-6, that means your camera (with an f/2.8 lens) can correctly meter and expose a moonlit scene of ~50% illumination, but at ~25% illumination your camera will fail to meter correctly, and you should probably switch to manual exposure on such dark nights.


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
(YOU ARE HERE)

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


 

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)


 

How To Build an Integrating Sphere, Anyway?

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


An integrating sphere is used for measuring emission or detection of light. It is a sphere coated on the inside with diffuse white paint, and this scatters light uniformly and thereby eliminates directionality effects. To state simply, an integrating sphere has very even internal illumination, and in the case of this project, it doesn’t matter how a camera is pointed inside of it.

A vacuum-rated integrating sphere useful in cryogenic temperatures (which I used extensively in grad school for characterizing infrared detectors) costs tens of thousands of dollars. If you are alright with ambient temperature and normal air pressures, an integrating sphere can be 3D printed for a few hundred dollars. I could have done that, but part of the fun of this project was to do everything as cheaply as possible. I decided to papier mâché one.

I bought a beach ball at Walmart for $2 and collected the Penny Saver newsprint coupons that came in the mail for a few weeks. I read that flour and water papier mâché molds, so I used wood glue.

I did the first layer with white paper to make it easier to paint. The rest used newsprint.

After three couple-hour papier mâché sessions, separated by a day or two of drying, I had a newfound respect for just 3D printing these. Oh well.

Finally, I cut it in half and removed the beach ball. I cut a hole at one end for the lens.

I painted the inside with flat ultrawhite house paint and then sanded it to improve the smoothness. This image was after the first sanding but before the second coat.

Most integrating spheres use many LEDs for even illumination, but I only used two in order to achieve the dim lighting conditions.

I put a 1-stop neutral density and ¾ color temperature orange (CTO) gel over each LED to make it dimmer and warmer in color.

The center ring bounces the LED light back, thereby forcing at least two reflections before entering the lens. I later put a sheet of paper over this in order to dim it further.

The initial fit test, before additional painting, and work to make it light-tight.

 

Integrating sphere in use.

Here’s the Arduino (lower) and my interface board (on top). The Arduino is the Duemilanove I originally bought for my timelapse motion project a decade ago. The knurled knob in the top center of the photo is a variable resistor which controls the voltage to the LEDs. This enabled me to adjust the max brightness level to 0 EV, and then I glued it to avoid further brightness changes. The dual-pin female plug at right is where the LED connects. The 2.5mm connector at bottom connects to the wire for triggering the camera, and the two integrated circuits alongside it are optocouplers for triggering focus and exposure (equivalent to a half-press and full-press of the shutter button). The pushbutton on the left enables me to interrupt the code if I want to go faster. The Arduino provides a USB interface to the user, and the code it runs can be viewed here.

Project price list:

Beach ball $2
3 bottles wood glue $12
Flat ultrawhite paint – sample size $3
Black spray paint $4
Opaque black fabric $4
Arduino Duemilanove $20 if bought new
Paper folder (thin plastic for baffles) $2
LEDs $5 for 30, used 2
Optocouplers $5 for 50, used 2
Variable resistor $4 for 3, used 1
Total $61

 


 

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?
(YOU ARE HERE)

Timelapse Methods Compared: Aperture Priority VS Holy Grail Method


 

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

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


Exposure Values (EVs) are units that photographers use to measure the brightness of a subject or environment. In the days before electronic cameras, photographers used hand-held light meters that reported the light level in EVs and equivalent camera settings. Eventually, light meters shrank enough to fit inside cameras, and this made automatic exposure possible. EVs are usually quoted for ISO 100 images–if the ISO is not specified, this can be assumed. The formal definition of EV is:

where N is the f-number, t is the exposure time, and S is the ISO. EV0 corresponds to a 1-second exposure with a f/1.0 lens at ISO 100. A change in EV of 1 indicates that the light has doubled or halved.

You may notice that this definition of EV does not include any information about the scene. Some assumptions must be made about how a scene of a given brightness should be mapped to the film’s or detector’s dynamic range. The next step is

where L (denoted Lv in many physics texts) is the luminance of the scene in units of cd/m2, and K is the reflected-light meter calibration constant. 1 cd (candela) = 1 lm/sr (lumen per steradian) = 1 lx m2 / sr (lux square meter per steradian). Canon, Nikon, and Sekonic use K = 12.5 cd ISO / m2 for their metering systems, so my calculations do too. Therefore 0 EVISO100 corresponds to a luminance of L = 0.125 cd/m2. However, there is no wavelength information in these units. Luminance is the total spectrum of the subject’s light multiplied against the human eye’s response. Mathematically,

where L is the luminance of the earlier equation, is a dimensionless luminosity function described shortly, and Le,Ω(λ) is radiance and has units of W / (sr m2 nm), and λ is wavelength. The luminosity function gives the normalized response of human vision to light of different wavelengths. As shown in the plot below, is 0 below 400 nm and above 700 nm, and it peaks at 1.0 at 555 nm.

In other words, we can’t see light outside the 400-700 nm range, and our peak sensitivity is to 555 nm (yellow-green) light. I used the Judd/Voss 1978 luminosity function because it seems to be fairly standard, though I could not find any reference to it in the light meter literature I reviewed.

I borrowed a spectrophotometer and pointed it into my illuminated integrating sphere. I commanded the Arduino to power the LEDs at maximum brightness. The resulting spectrum is plotted in red above and is the Le,Ω(λ) in the third equation above.

By inserting the measured spectrum and Judd/Voss luminosity function the third equation, I calculated the luminance L. This was then inserted into the second equation to calculate the brightness of the sphere in EVs. Finally, I adjusted the current to the LEDs using a variable resistor and collected new spectra until the sphere was EV0. At that point, I glued the variable resistor so it couldn’t be bumped.

At this point, the maximum brightness of the sphere was EV0. Next, I pulsed the LEDs at 240 Hz with various duty cycles to achieve dimmer lighting conditions. EV-1 was achieved by turning on for 1/480 of a second and then off for 1/480 of a second (i.e. a 50% duty cycle). EV-2 was achieved by turning on the LED for 1/960 of a second and off for 3/960 of a second (i.e. a 25% duty cycle). And so on, until EV-10 was 4 microseconds on followed by 4163 microseconds off (0.1% duty cycle). This technique is called pulse width modulation (PWM).

The Arduino struggles with microsecond-precision timings, so some adjustments to the above scheme were made. Finally, to check that the PWM response was as commanded, I put a camera in the integrating sphere and doubled the sensitivity (ISO and/or shutter speed) with every 1 stop decrease in light. The result was this plot:

In an ideal world, the result would be perfectly flat. In reality, this is a 9% peak-to-valley nonlinearity. The quasi–EV-10 lighting level is log21.0949 = 0.13 stops brighter than it should be. Since camera meters have 0.33-stop increments, and most cameras have no metering sensitivity at EV-10 anyway, I consider this nonlinearity acceptable.

In summary, light is a function of many quantities: wavelength, flux, directionality, polarization, phase, coherence, and so on. A photographic light meter simplifies these parameterizations of light into a single number: EVs (or, equivalently, ISO, shutter speed, and aperture). I measured the internal radiance of the integrating sphere using a spectrophotometer and adjusted its LEDs to achieve EV0. The conversion from radiance (i.e. actual physics units) to EVs (photographer units) involved three assumptions in the math: 1) the metering calibration constant of K=12.5, which is the value used by Canon, Nikon, and Seikonic; 2) the Judd/Voss 1978 luminosity function for the human eye’s response to color; and 3) the radiance reported by the spectrophotometer. The spectrophotometer had been calibrated in the previous year, and these assumptions are reasonable, but any change in them would affect the calibration from LED output to EVs of ambient brightness. Finally, I confirmed that the pulse width modulation of the LEDs creates lighting conditions as expected.


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
(YOU ARE HERE)

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

Timelapse Methods Compared: Aperture Priority VS Holy Grail Method


 

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


 

The New Champion Of Astro-Landscape Lenses | Sigma 14-24mm f/2.8 DN for Sony FE Mirrorless

Sigma 14-24mm f/2.8 DG DN FE Art, Sony A7III | Photo by Sean Goebel, sgphotos.com

Ladies and gentlemen, we have more witchcraft at 14mm. And also at 24mm. The Sigma 14-24mm f/2.8 DN Art (FE; this is NOT the same optic as the previous DSLR version) …is basically flawless.

OK, we’ll wait to call it “flawless” until we can put it on a ridiculously high-res sensor like the 61-megapixel Sony A7R IV, but for now, let’s just leave it at this: It disproves at least two “impossibilities” that have been assumed about zooms…

Not only does it defeat one of the existing 14mm prime lens champions, the Sigma 14mm f/1.8 Art, it also performs astonishingly well at both ends of its focal range. In fact, it actually matches the current 24mm champion, the Sony 24mm f/1.4 GM.

Achieving just one of these feats is extremely rare, but achieving both at once is quite unprecedented. The “conventional wisdom” is absolutely that primes are always sharper than zooms, and that zooms are always noticeably softer at one end of the range or the other, or in the middle.

Of course, this isn’t an in-depth, extensive review. We’ll wait for Roger Cicala at LensRentals.com to put 10 copies of this lens on OLAF, and see how that goes. And, of course, more actual nightscape adventures with 40-60 megapixel cameras would be great, too.

[UPDATE: Read my full review of the Sigma 14-24mm f/2.8 DN Art HERE on SLR Lounge! Verdict: Even at 42-61 megapixels, it stands as the sharpest 14-24mm lens ever made.]

TLDR: if you’re an astro-landscape or nightscape etc. photographer of any kind, this is the lens to buy! In fact, it’s even a reason to switch to Sony completely, which is a third rarity for any lens. (Although, there are already adapters to use Sony FE mount lenses on Nikon Z mirrorless.)

Either way, it’s a good time to be a nightscape photographer! But, enough talk. Here’s the proof: (NOTE: these test images were made on a 24-megapixel Sony A7 III)

24mm Test (Sigma 14-24mm f/2.8 DG DN FE Art | Sigma 14mm f/1.8 Art | Click the image to view it full size!

24mm Test (Sigma 14-24mm f/2.8 DG DN FE Art | Sony 24mm f/1.4 GM | Click the image to view it full size!

That is unprecedented, indeed. The only question left might be, “how does it compare against the DSLR version, the Sigma 14-24mm f/2.8 DG HSM Art?” Well, we weren’t able to perform a direct comparison, however, based on all the tests I have seen, (and I’m really good at guessing coma performance from other people’s truly terrible sample images!) …I think it is indeed safe to say that although the DSLR Sigma 14-24mm is really good, this new Sigma 14-24mm is better.

Just about the only way in which that massive chunk of glass offers a bit more is its vignetting; the mirrorless 14-24mm, as a much smaller optic, does have a faint bit more extreme corner darkening. Of course if, as a nightscape photographer, low vignetting is EXTREMELY important to you, the Sigma 14mm f/1.8 will have the brightest f/2.8 corners of any lens ever to reach 14mm, simply because it’s stopped down more than a stop at that point.

So, if you don’t care about weight, and you do care a ton about vignetting, (and less about coma) …you could stick with either of the older Sigma DSLR lenses that hit 14mm. However, as a wilderness backpacker, this new mirrorless 14-24mm is the new champion.


These test images and the beautiful sample nightscape photo were provided by Sean Goebel. To see more of Sean’s work, visit sgphotos.com or follow him on Flickr.

Happy 7th birthday, Canon 6D. You’re still one of the best values in astrophotography!

Today, in 2012, the Canon 6D was announced. It only had a single SD card slot and Canon Rebel-style focus point layout, (so I didn’t count it as a top choice for my day job as a wedding photographer) …but its sensor was, and still is, a huge milestone in high ISO image quality. So, happy birthday, Canon 6D! (Also known as the 6D mk1 or 6D classic, now)

Canon 6D – Astrophotography Legend

The 6D sensor was shockingly good in its day. It forfeited just two megapixels compared to its bigger brother, the Canon 5D mk3, but it was actually significantly better than its predecessor at high ISO image quality, particularly 3200-6400 where many nightscape photographers will likely spend a lot of time.

Smart photographers who needed incredible image quality more than they needed the flagship AF and dual card slots that the 5D3 offered, opted for the 6D as soon as its image quality was extensively tested and nightscape, landscape, and adventure photographers, in general, realized that not only did it have great image quality at high ISOs, it had better dynamic range at its base ISO than all previous Canons ever, including all flagships.

Though, admittedly, that base ISO dynamic range was still 2-3 stops behind Nikon and Sony, so if you also do a ton of shooting at ISO 100, then I must stop praising the 6D for a second and suggest that you consider the similarly priced (used) Nikon D750, which recently had its 5th birthday, I  might add. The D750’s high ISO image quality is not as good as the 6D’s, (though it’s close!) but its dynamic range at ISO 100 is still considered “insane” *1 by today’s standards. (Just like the D600 and D610, BTW.)

*1 “insane” is a scientific measurement that means “way better than most photographers will ever need. In fact, you’re more likely to see a bigger difference in image quality by just making sure you use perfect technique, than switching from this camera to anything better.”

Although the Canon 6D lacks a lot of pro features, it wins big in one way- that “magnify” button can be programmed to offer 1-click 100% zooming, unlike the Nikon D600 and D610. It even plays back the zoomed-in image if the LCD is off!

Indeed, when shopping used, you can easily find a good condition 6D for $700-800, making it one of the best values on the market today for anyone who needs a hard-working full-frame sensor in a very affordable package.

Why buy a Canon 6D instead of a newer camera?

By the way, if you’re curious: why wouldn’t you buy a newer camera instead, let alone a camera for a newer, more future-proof mount? There’s the 6D mk2 and the 5D mk4 for Canon’s EF DSLR mount, both which are old enough to be found for decently good deals on the used market. Plus, there’s the Canon EOS RP which is the newest mirrorless camera body in their RF lineup, yet it debuted at a mere $1300 and can be found for under $1000 used, if you’re patient…

Glen Canyon, Utah | Canon EOS RP, Irix 15mm f/2.4

The answer is, yes, all these newer cameras are good, great even. BUT, they’re all not as “clean” at ISO 3200+ as the 6D sensor, as per photonstophotos.net. Shocking, but true.

Oh, and what about the Sony A7-series cameras that are also starting to get old, the 1st-gen and 2nd-gen A7, A7S, and A7R series cameras? You can definitely find them for under $1K, that’s for sure! But, this is because as underwhelming as the 6D’s other specs are, (autofocus, card slots, etc.) …the early Sonys are worse. Also, most of their oldest sensors are far worse at high ISO image quality.

The only old Sony A7-series cameras that have equal or better high ISO performance versus the Canon 6D are the A7R2, A7S, and A7S2. (As well as the A7R3, if you count it among the now-replaced cameras since the mk4 is here, but the R3 is still a $2500 camera, and remember, we’re shopping for a ~$700 full-frame body.)

So, if you’re just breaking into astrophotography now, if you’re on an extreme budget, and especially if you’re at all familiar with Canon cameras already, then the 6D is still your best value, despite being 7 years old. Whether or not it’s actually the right choice for you depends on your total budget for both lenses and bodies, and of course the other features you are likely looking for beyond image quality. Last, but the polar opposite of least, remember: it’s not about the gear, it’s about getting out there and shooting.

Search for a used Canon 6D on B&H (Latest price check: $689.95-$879.95, depending on the condition)

2020 Astro-Landscapes Photo Calendar Available Now!

The 2020 Astro-Landscapes calendar is finally here!

It took me two years, but I’ve finally captured enough photos to create the next calendar I had dreamed of making: A panoramic landscape adventure photography calendar.

This is no ordinary landscape photo calendar, though. I had another ambitious goal for my next photo calendar: I’ve annotated the calendar days themselves with a few of my favorite types of landscape photography opportunities, such as a moonrise at sunset or moonset at sunrise, or nights when photographing the Milky Way could be optimal during a new or low crescent moon.

Now, each month you’ll not only be able to enjoy another photo from somewhere in the beautiful American West, but you’ll also be able to quickly glance at a few great shooting opportunities every week!

The 2020 calendar will be 7×12″, and is NOW SHIPPING! There will only be 200 printed, and only the first 100 will be signed and numbered.

Local pick-up is available, however, calendars cannot be reserved without entering into the system, so please order your calendar using the second link below, and you will be contacted for a chance to meet up around Orange County, CA.

Thank you in advance for your support, and here’s to 2020 being full of beautiful adventures!


Order Now! (limited supply remaining, discounted price) $14.99 + shipping






My Passion For Panoramic Photography

I’ve loved panoramic photography ever since I first picked up a camera about 20 years ago. I’ve always enjoyed creating “extreme” panoramic images, however, when I decided that I wanted my next photo calendar to be a panoramic calendar, I realized that most of my existing panoramic images simply would not work well in the desired format.

So, I made some compromises on my goals for the perfect aspect ratio, (7×12″) and I set off on many wilderness adventures to capture more images. Many of my adventures were centered around a singular photographic goal, and yet the images which found their way into this calendar turned out to be almost entirely the unexpected moments of serendipity and breathtaking light which simply cannot be predicted a year in advance.

For this reason, I decided to add not just helpful information about photo opportunities, but also a brief story behind each photo to help set the scene and give a brief glimpse into the moment itself. I am currently writing a book containing many more of these adventure stories, which showcase such authentic moments in the wilderness, and hopefully encourage other photographers to seek out the beautiful opportunities that nature has to offer.

My Passion For Astro-Landscape photography

I first began calling my imagery “astro-landscapes” when I became interested in nightscape photography, and for a period of time, it was the only subject I pursued. After a few years of nightscape photography “dedicated” adventures, however, I realized something- On all of the trips I took, many of the truly memorable moments, and indeed most of the best photographs, were not nightscapes, but images depicting whichever moments were simply the most breathtaking in terms of unique weather, seasonal phenomena, or serendipitous alignments of the sun or moon with earthly subjects.

During this process of discovery, not only did I realize that Astro-Landscapes was about so much more than just nightscape photography, but also, my desire to simply be outdoors as often as possible grew. Inevitably, also, my desire to sit at a computer and post-produce the images dwindled. I came to the following conclusion: I’d rather be outdoors capturing real moments of nature, instead of “fabricating” them later on a computer.

This has been my driving force ever since, and each of the images in this set of 13 represents very basic photographic techniques: Many are single exposures with nothing more than color-correction and cropping to a 7×12 aspect ratio, and others are very simple panoramic stitches, or basic noise reduction layers. In other words, these moments unfolded with the exact timing, scale, and juxtaposition that you see in each image.


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Moonset at Sunrise in the Alabama Hills | Eastern Sierra, California, August 2018 Nikon D750, 70-200mm f/2.8, 200mm, f/8, ISO 100, 1/100 sec

I wish I could say this moment was perfectly planned months in advance, but the truth is, it snuck up on me completely un-planned. I was car-camping in the Alabama Hills during a solo road trip, and had only planned to do a little nightscape photography before getting back on the road.

As per the usual for most of my road trips, I was too exhausted from driving and hiking all day, so a 40-minute nap at 1 AM turned into a 4-hour nap. When I awoke, the moon was still well above the distant, jagged peaks of the eastern Sierra.

At first, I didn’t think anything of it; I was more concerned about getting on the road as soon as possible. Thankfully, the fading stars and pink-blue light of astronomical dawn lured me into telling myself, “just a couple quick shots, then I’ll get going.” Another 30 minutes later, as the last few stars were disappearing and the moon was getting awfully close to the horizon, it finally hit me- I was about to witness one of the holy grails of mountain landscape photography: a perfect moonset at sunrise.

Except, it wouldn’t be perfect; I was in the wrong spot. After snapping two “safety shots” at 200mm of the first kiss of purple alpenglow on Mt Whitney, I threw my gear in my car and raced “backwards” away from the scene to a slightly more distant vantage point. That few hundred yards was exactly what was needed to allow me to start a timelapse in which the moon nestled perfectly into the visual notch to the right of Mt Whitney, as the sun’s first rays washed over the majestic Eastern Sierra.

This image was processed in Capture One Pro 11. I found that Capture One did the best job of representing such bright, warm colors and tonality without appearing artificially saturated, nor excessively “preserved” as some bright highlight tones can appear in other raw conversion software.

Thank you again for your support!


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Crowds, Chaos, & The Death Of Solitude

I did not grow up with “Nature-Deficit Disorder”, as Richard Louv puts it. Thankfully, I grew up exploring the outdoors, climbing trees and rocks, going camping, and eventually going on more arduous adventures to extremely remote places. Continue reading