Rarely has a headline so technical been so genuinely exciting. In addition to the rumored addition of C-Log, a new report claims Canon will also significantly improve the crop factor for 4K video shot with the 5D Mark IV from 1.74x to just 1.27x, letting you take advantage of a lot more sensor.
The longer we wait, the more details come to light about Canon’s rumored firmware update for the 5D Mark IV. We already told you about C-Log, but according to a new report by Canon Rumors, the video capability of the full-frame camera will be improved even further with this update, especially where 4K shooting is concerned.
DCI 4K resolution will be increased to 5632 x 2970 or 1.27x crop factor.
UHD will go up to 5472 x 3078, or 1.29x.
1:1 4K sampling will remain an option for those who want to use the 1.74x crop
Canon will add full-sensor 3K capture at 60fps and HDR 24fps.
1080p will also use this same 3K mode, down-sampled to 1080 for improved perceived resolution.
Additionally, CR received more details about the rumor that you will need to send your camera into a service center for these updates. It sounds like, from this new report, you will not necessarily need to do this.
The new firmware will work on non-serviced cameras, but there’s a chance the camera will overheat. If you want to avoid this, you’ll be able to send your Canon 5D Mark IV in to be retrofitted with a better heat sink. All new models, meanwhile, will ship with the better heat sink already installed.
For now, none of this has been confirmed or officially released by Canon, so take it with the appropriate amount of repressed hopes. We’ll keep an eye out, and let you know as soon as any of this news becomes official.
Want to process your iPhone photos for Instagram on a laptop without having to transfer any files? In the future there may be a crazy new way you can do so. Apple has patented a new “accessory” that transforms a cell phone into a full-fledged laptop.
Filed in September 2016 and published on March 23, 2017, the patent is titled “Electronic Accessory Device.”
“The present application describes various embodiments of systems and methods for providing internal components for portable computing devices having a thin profile,” writes Apple product designer Brett W. Degner. “More particularly, the present application describes an electronic accessory device available to extend and expand usefulness of a portable computing device.”
So the basic idea is that the cell phone is a “portable computing device” that everyone now carries around with them, so why not allow it to transform into a laptop computer whenever the need arises? Then people will only need to buy one device (an iPhone) and an accessory (the laptop dock) instead of having to separately buy and manage a cell phone and a laptop.
For casual photographers who use their iPhone as a primary camera, this new invention would bundle the camera, cell phone, and laptop into a single system.
Here are two patent illustrations showing how an iPhone could be inserted into a dock space right where the giant touchpad on a MacBook ordinarily goes, turning the phone into the laptop’s touchpad (and presumably running the operating system and file system from the phone):
Perhaps the iPhone and accessory laptop combo would look something like this…
While the processor and data storage functions would be handled by the iPhone, the laptop dock could provide support in other areas — Apple suggests it could provide a graphical processor and other resources that “support the functions of the portable computing device.”
The patent also covers the same idea using an iPad, except the iPad plugs in as the screen rather than the touchpad.
You can read the patent filing for yourself on the USPTO website. As with all patent filings, there’s no guarantee that we’ll ever see this idea turn into a commercial product… but stay tuned.
Photographers using Cactus‘ new V6 II and V6 IIs wireless flash transceivers are about to get a huge update. Cactus is launching a series of brand-specific firmware upgrades that will allow you to mix and match camera and flash brands without losing TTL or HSS… and they’re free!
Cactus’ new transceivers already promise cross-brand High Speed Sync (HSS) with some of the biggest names in the industry. The so-called “X-TTL” updates will expand that capability even further, allowing you to maintain Through The Lens Metering (TTL) with Canon, Nikon, Olympus, and Panasonic flashes (or compatible third party flashes for these systems) when you use them with Sigma, Sony, Fujifilm, Canon, Nikon, Olympus, Panasonic or Pentax cameras.
In other words, you could use your Canon flash with your Fujifilm camera, and thanks to Cactus transceiver and this firmware update, you’d still be able to use TTL and HSS no problem. The tagline is “TTL without boundaries.”
According to the press release, the firmware updates will roll out in parts. The first rollout will go out to Sigma, Fujifilm, and Sony camera users, followed by “the remaining camera systems,” namely: Canon, Nikon, Olympus, Panasonic, and Pentax.
No word yet on when exactly the X-TTL updates will begin rolling out, but this website will keep you up to date. Once the free updates are live, all you’ll have to do is download the Cactus Firmware Updater and select your camera system to install the X-TTL firmware on your V6 II or V6 IIs.
If you use the Canon 5D Mark IV for shooting serious video projects, here’s some news that may be music to your ears: C-Log is coming to your camera.
C-Log is Canon’s Log Gamma curve that allows you to capture maximal dynamic range from the camera’s sensor in a limited bit-depth video file (as opposed to raw data). The resulting video looks flat, lacking contrast and saturation, but you’ll have much more flexibility to produce the exact look you’re aiming for when processing afterward.
Here’s a short 49-second video by DPReview that offers a quick look at using a log gamma curve:
Instead of a simple firmware update you can do yourself at home, this C-Log upgrade might be something that may require sending your camera to a Canon service center.
“There is no mention whether or not this will be a service you will have to pay for or not, or if future EOS 5D Mark IV cameras will ship with the feature,” Canon Rumors writes. “While we cannot confirm this information at present, we wouldn’t be surprised.”
Canon may make an official announcement for this C-Log upgrade at NAB 2017 in Las Vegas next month. No word yet on when the update will arrive or whether other Canon cameras such as the 1D X Mark II will receive similar upgrades.
Fujifilm has a history of releasing firmware updates so significant that you feel like you’re downloading a brand new camera. The company has just announced this type of upcoming update to the X-T2 and X-Pro2: the new firmware will bring a whopping 33 functional and operational improvements.
The updating will occur via two different firmware updates released in late March and late May. The improvements reflect “users’ requests for improving operability and adding new functions,” Fuji says.
There will be a brand new Voice Memo function that lets you record 30-second audio clips while in Playback mode, useful for saving some “notes” for photos to reference later.
There’s also going to be a new Copyright Info feature that lets you register the photographer and copyright holder’s name(s) in advance so that those details are automatically baked into the EXIF data of each photo.
Here’s a complete list of the big improvements headed your way if you own one of these two flagship X Series cameras:
March 2017 Update
1. Shooting RAW in Bracketing and Advanced Filters The update enables you to use the RAW format when shooting not only in AE Bracketing but also in other Bracketing modes (ISO, Dynamic Range, White Balance, Film Simulaitons) and also in Advanced Filter modes.
2. Extended ISO 125 and 160 selectable The update adds ISO125 and ISO160 to extended ISO levels available.
3. Programmable long exposure of up to 15 minutes Long exposure in the T mode currently goes only up to 30 seconds. The update will allow users to extend it up to 15 minutes.
4. ON/OFF for 1/3-step shutter speed adjustment (X-T2 only – already in X-Pro2) The update allows you to turn off the Command Dial’s function to adjust shutter speed by 1/3 steps in order to prevent unintended adjustments.
5. Full-range ISO adjustments with the Command Dial (X-T2 only) With the update, set the ISO “A” position to “Command” to adjust ISO sensitivity across the full range, including extended ISOs, with the Front Command Dial.
6. “AUTO” setting added for the minimum shutter speed in the ISO Auto setting The update adds an AUTO option for the minimum shutter speed in the ISO Auto setting, that allows the camera to automatically define the minimum shutter speed according to the focal length of the lens attached.
7. Faster “Face Detection AF” The update enables the use of Phase Detection AF for faster performance in Face Detection AF.
8. Improved in-focus indication in the AF-C mode The update reduces focus hunting in the AF-C mode, making it easier to track a subject.
9. Addition of a smaller Focus Point size in Single Point AF The update adds a smaller Focus Point size in Single Point AF, bringing the total number of available sizes to six. The new smallest size facilitates pin-point focusing.
10. Addition of “AF Point Display” (X-Pro2 only – already on X-T2) With the update, you can choose to have AF Points constantly displayed in Zone AF and Wide / Tracking AF, making it easier to track a subject.
11. Addition of “AF-C Custom Setting” (X-Pro2 only – already on X-T2) The update adds “AF-C Custom Setting” for specifying focus-tracking characteristics. Choose from five presets according to your subject’s type of movements.
12. Addition of “Portrait / Landscape AF Mode Switching” (X-T2 only) The update allows you to specify separate AF mode and AF point settings for portrait orientation and landscape orientation.
13. Change of focus frame position while enlarging it The update allows you to move the position of focus frame while enlarging it in Single Point in the AF-S mode or in the Manual Focus
14. Activation of the Eye Sensor in video recording (X-T2 only) The update allows you to use the Eye Sensor during video recording to automatically switch between EVF and LCD.
15. Change of ISO sensitivity during video recording (X-T2 only) The update allows you to change ISO setting during video recording.
16. Re-autofocusing in video recording With the update, half-press the Shutter Release button or press the button assigned to “AF-ON” function during video recording to re-do autofocusing.
17. Display live histogram during video recording (X-T2 only) The update allows you to display a live histogram during video recording.
18. Optimization of external microphone’s input level (X-T2 only) The update optimizes external microphone’s input level (lower limit revised from -12dB to 20dB) to reduce white noise when an external microphone with preamp is connected.
19. Addition of “Eye Sensor + LCD Image Display” in the View Mode The update gives the “Eye Sensor + LCD Image Display” option in the View Mode that allows you to shoot through the viewfinder and check images on the LCD, just as you would with an SLR.
20. Shorter EVF display time-lag (X-Pro2 only – already in X-T2) The update shortens EVF’s display time-lag in the AF-C mode so that you will not miss a photo opportunity.
21. Constant “Dual” mode display (X-T2 only) With the update, the small window in the Dual mode stays on even when you half-press the shutter release button.
22. Automatic vertical GUI for LCD (X-T2 only) With the update, when you hold the camera in the portrait orientation, the camera will automatically display the GUI on the LCD in the same orientation.
23. Name Custom Settings The update allows you to assign a specific name to Custom Settings 1 – 7.
24. Copyright information in EXIF data The update allows you to register the photographer’s name and the copyright holder’s name in advance so that the camera automatically adds the information to EXIF data for each image.
25. Voice Memo function The update enable you to record 30-second “Voice Memo” clips in the Playback mode.
26. Extended AE Bracketing The update extends AE Bracketing from the current 3 frames +/-2EV to up to 9 frames +/-3EV.
27. Addition of “Shoot Without Card” mode With the update, you can have the “Shoot Without Card” mode turned OFF so that the camera can not shoot when there is no SD card inserted.
May 2017 Update
28. Support for computer tethering via Wi-Fi (X-T2 only) The update adds support for computer tethering via Wi-Fi.
29. Addition of “All” AF mode (X-T2 only) With the update, select “All” in the AF mode so that you can select the AF mode and Focus Area size by only using the Command Dial.
30. Function extension for “Shutter AF” and “Shutter AE” (X-T2 only) With the update, you can specify different settings for AF-S and AF-C in “Shutter AF” and for AF-S / MF and AF-C in “Shutter AE.”
31. Addition of “-6” and “-7” to EVF’s brightness setting Additional options of “-6” and “-7” to the “EVF Brightness” setting so that, even in an extremely low-light condition, the brightness of the EVF does not distract you from shooting.
32. Switchover of the main and sub displays in the Dual Display mode (X-T2 only) The update allows you to switch between the main and sub displays in the Dual Display mode.
33. Function assignment to the Rear Command Dial With the update, you can assign a specific function to be activated when the Rear Command Dial is pressed.
ISO is one of the three major exposure settings in the exposure triangle of a digital camera — shutter time, f/number, and ISO. Of the three, it is ISO that is probably most misunderstood. Even more so than f/number. In fact, it is a common misconception that higher ISO settings will cause images to be noisier. In fact, the opposite is often true. Wait, what?
That’s right, higher ISO settings alone do not increase image noise and higher ISOs can even be beneficial to low-light photography. In this post, I talk about the craziness surrounding ISO settings, how ISO actually affects exposure, and how to find the optimal ISO setting on your camera for astrophotography.
Learning how to optimize exposure settings is one of the most helpful skills when attempting astrophotography. “What exposure settings should I use?” is probably the most common question I get. For beginners who are new at trying astrophotography with their regular digital camera and lens, I usually recommend starting with my Milky Way Exposure Calculator. That calculator will provide an excellent starting point when making your first attempts at shooting the night sky.
Once you’re comfortable making your first exposures, the next thing I recommend learning about exposure is how to optimize your ISO setting. That’s what this article is all about. To begin, here are a couple of glossary items that will hopefully help:
In digital photography, ISO is a standard (specifically ISO 12232:2006) for exposure brightness developed by the International Standards Organization (ISO). Different camera sensor models have different sensitivities so we need some way to correlate them so like exposures yield like brightnesses. Some people pronounce each letter (aɪ-es-o) but I think it’s easier to just say it like a word (aɪso).
Signal is the part of the photograph that we want. Light is signal. Signal is the image. Without the signal (without light), we can have no image. The more light that we can gather, the more signal we have. In general, the more signal, the higher the quality of the photo.
Noise is the part of the photograph that we do not want. Noise is interference appearing as speckled grain that obscures the signal and thus the details of the photograph. Noise is usually generated by heat or imperfections in the behavior of the electronics of our digital cameras. Some noise is random with every shot (shot noise) and some noise is produced consistently by the camera’s sensor (upstream read noise) or produced by the electronics after the sensor’s signal has been amplified (downstream read noise). In general, the more noise, the lower the quality of the photo.
Signal-to-Noise Ratio (SNR)
The ratio of signal to noise in an image. The higher the signal-to-noise ratio, the higher the quality of the image. More light = more signal = good. More noise = bad. Collecting more light is the best way to increase signal-to-noise ratio.
The full range of light of a scene, from the darkest darks to the brightest brights. A high dynamic range scene has extremely bright highlights (such as the sun) and extremely dark darks (such as a fully shadowed black rock). A low dynamic range scene has relatively uniform light across the scene where the brightest parts of the image are not much brighter than the darkest parts of the image. Cameras only capture a limited dynamic range of light. If the dynamic range of a scene is high enough, anything outside the range of the camera’s sensor will either be blown out to pure white (in the case of very bright areas) or crushed to pure black (in the case of very dark areas). In general, a camera sensor capable of capturing a higher dynamic range of light is more desirable.
A disclaimer: I’m an engineer, but I’m formally and primarily trained in mechanical engineering. I have some relevant experience, but electrical and computer engineering isn’t my main mode of expertise. My intention with this article is to simplify these concepts in a way that hopefully makes sense to a larger, non-technical audience. If you’re familiar with this topic and you see any glaring mistakes in this article, please feel free to let me know.
Also, all of the points made in this article apply to RAW image files. It’s very important to shoot astrophotos in RAW format to preserve the best data collected by the sensor. Don’t start complaining when you try any of the tests in this article on your JPEGs. Also, much of the benefit of optimizing ISO selection applies primarily to low-light shooting (like astrophotography) where we have a relatively small amount of signal competing with the various noise sources that encroach upon our photographs.
ISO is Amplification or Gain
It’s a (very) common misconception that increasing ISO increases the sensitivity of a camera sensor. ISO doesn’t change sensitivity. Increasing ISO simply increases the brightness of a photo by amplifying the sensor signal. In the electronics world, amplification is sometimes called “gain.” Like we can “gain” weight if we increase our eating, we can “gain” brightness if we increase our ISO.
ISO in no way affects how much signal (light) the camera can collect. If we actually want more sensitivity with a camera, we need to either increase shutter time or aperture size (lower the f/number).
Higher ISOs Don’t Increase Noise
OK, to the main point: Higher ISOs won’t increase the visible noise in a photo.
Read that again, realize that it contradicts what you probably think you know about ISO and then let me elaborate:
All other things being equal, a higher ISO will do the following:
A higher ISO will increase the brightness of an image
A higher ISO will decrease the total dynamic range of the image
And, in many cases (like astrophotography), a higher ISO will actually decrease the visible noise
OK, I know what you’re thinking: “How come when I use a higher ISO, I get more noise?!” Here’s why:
For most imaging situations, photographers will usually use P (Program), A/Av (Aperture Priority/Aperture Variable), or S/Tv (Shutter Priority/Time Variable) modes on their camera. In these exposure modes, using a higher ISO setting will result in an image with more relative noise. What most people don’t realize is that the increase in noise is not because of the increase in ISO.
The increase in relative noise when using a higher ISO in an automatic exposure mode (like P, A/Av or S/Tv) is actually due to the reciprocal decrease in shutter time or the decrease in aperture size as a result of using an automatic exposure mode. Most people are misattributing the increase in noise to the ISO when it’s actually caused by lower signal-to-noise ratio due to the shutter or aperture.
When setting a higher ISO on one of these autoexposure modes, the camera tries to achieve a neutral exposure and compensates for the increase in ISO by decreasing the amount of light entering camera. This reduction in light is done automatically by the camera by either decreasing the time the shutter is open (when in A/Av mode) or by using a higher f/number and thus decreasing size of the lens aperture diaphragm and letting in less light at a time (when in S/Tv mode), or by a combination of both (when in P mode).
So a reduction of light by the shutter or the aperture is the reason that the image appears noisier. It’s not noisier because of the higher ISO. This reduction of light is a reduction of signal and a reduction of signal yields an overall lower signal-to-noise ratio and thus a noisier photo.
How Do Shutter, Aperture and ISO Affect Noise?
A simple comparison test can show that relative noise levels are primarily affected by shutter and aperture and not affected nearly as much by ISO. In these tests, all settings are kept identical except the one that we wish to test which is adjusted by two stops. Then, in post processing, the images are equalized in brightness and compared.
Here’s what one of my complete test image looks like. It’s a RAW shot of Orion from a city suburb, made on a Sony a7S with the Zeiss 55mm/1.8 lens:
How Shutter Time Affects Noise
8s, f/2.8, ISO 3200
4s, f/2.8, ISO 3200 (+1 stop in post)
2s, f/2.8, ISO 3200 (+2 stops in post)
Conclusion: Shorter shutter time = less signal-to-noise ratio = noisier photo
How Aperture (f/number) Affects Noise
8s, f/2.8, ISO 3200
8s, f/4.0, ISO 3200 (+1 stop in post)
8s, f/5.6, ISO 3200 (+2 stops in post)
Conclusion: Higher f/number = less signal-to-noise ratio = noisier photo
How ISO Affects Noise
8s, f/2.8, ISO 3200
8s, f/2.8, ISO 6400 (-1 stop in post)
8s, f/2.8, ISO 12800 (-2 stops in post)
Conclusion: Higher ISO ≠ more relative noise
So of the three tests on my Sony a7S, shutter speed and aperture very obviously directly affect the apparent levels of noise in the photograph while ISO has nearly no effect. This is completely contrary to what many people would expect when they think about higher ISO.
In low-light photography, there is one aspect of ISO that can greatly affect the amount of perceived noise for any given ISO setting: downstream electronic noise. Let’s see how different types of cameras can be affected by downstream electronic noise.
ISO-Invariance and Downstream Electronic Noise
There are variations from sensor to sensor and camera model to camera model in how ISO affects low-light images. Understanding how your camera sensor behaves can help you find the optimal ISO setting for astrophotography. There are two fairly common configurations that we see in most modern digital cameras so we can split most cameras into one of two camps, ISO-variant and ISO-invariant.
Cameras use varied levels of analog amplification to adjust ISO. In a simplification of this case, the amplifier boosts the electronic voltage readout from the sensor by 2x for each ISO: 100, 200, 400, 800, 1600 and so on. Higher ISO means more amplification of the sensor output data.
After the sensor data is amplified by the ISO, it’s sent through some (downstream) electronics (such as an analog to digital convertor) to ultimately change our data from voltages into a digital file of numbers that’s readable by a computer. One of the distinct characteristics with ISO-variant cameras is higher contribution of noise from these downstream electronics.
If there is relatively little signal to begin with (e.g. in low-light situations), the lower ISO settings might not apply enough amplification for the voltages of the sensor data to overcome the contribution of electronic noise made by the downstream electronics. That means that in low-light situations like astrophotography, ISO-variant cameras will actually show more noise at low ISO settings and less noise at higher ISO settings. The Canon EOS 6D, still one of my favorite choices for a DSLR for astrophotography, is highly ISO-variant and actually shows its best low-light noise performance at ISO 6400 and higher!
Most Canon DSLRs are highly ISO-variant. There are a few exceptions to the Canon lineup that are not as ISO-variant including the new Canon EOS 5D Mark IV and the Canon EOS 80D.
ISO-Invariant cameras have lower downstream read noise such that in low-light shooting conditions, the signal to noise ratio stays more constant as ISO settings change. In a simplification of this case, the sensor data is already amplified above the minimal contribution of downstream read noise sources before being converted to a digital signal. The result is a camera with low ISOs that tend to have less shadow noise and less of a variation between ISO settings. Most of these types of cameras are considered relatively ISOless or ISO-invariant. One camera that shows a great example of ISO-invariance is the Fujifilm X-T1. An example of the X-T1’s ISO-invariance test is available at the end of the article.
Notes and Exceptions
Okay, it’s not all black and white: many ISO-variant cameras eventually act like an ISO-invariant camera above a certain high ISO setting. Above some threshold ISO, these cameras fully overcome their noisy downstream electronics and show minimal difference in signal-to-noise ratio with higher ISOs. Most Canon cameras act this way above about ISO 1600. Knowing what that threshold ISO setting is can help us achieve the best low-light performance.
Similarly, many ISO-invariant cameras may have one or two distinct jumps in gain that will affect the overall read noise contribution to the image. In this case, there may still be a threshold ISO above which it is beneficial to shoot in low-light conditions. The Sony a7S acts this way with changes from approximately ISO 100 to 200 and 1600 to 3200. The Sony a7S’s best low-light performance is actually around ISO 3200 and above. Otherwise, the differences between ISO settings in low-light conditions on the a7S is relatively minimal.
Ultimately, both configurations achieve the same goal of brightening the photo to correspond with the particular ISO setting but the end result can be quite different, especially when shooting in low-light scenarios. ISO-invariance is a distinct enough trait in the behavior of a camera that DPReview has added an ISO-invariance test to most of their latest camera reviews. I personally think it’s very helpful to know how a camera acts in order to find out where it will perform best in low-light photography.
ISO vs. Dynamic Range
One of the distinct negative aspects of using too high of an ISO is reduced dynamic range. The more that we amplify the data that makes up a digital image, the more that we risk brightening it so much that it blows out the brightest parts of the image to pure white and loses detail in those parts of the image.
In the dynamic range test below, I made exposures of the star Antares at the highest ISO settings of my Sony a7S using the same exposure settings and varying only the ISO. As the ISO increases, the star appears to get larger because it’s being gradually more and more overexposed with each higher ISO. In practice, with the Sony a7S, the reduction in dynamic range doesn’t become too much of an issue until about ISO 51200 and higher but the difference in each stop is still apparent.
As a side-note, notice how similar most of the ISO settings between 1600 and 204800 look to each other in terms of noise, especially relative to the Canon EOS 6D sample above. The Sony a7S is a fairly, although not completely, ISO-invariant camera.
In my experience, except for the brightest stars, blowing out any part of an astrophoto to the point where we’re losing a lot of data is very, very rare. The bigger risk of using too high of an ISO in landscape astrophotography occurs when there is a larger, brighter (usually artificial) light source in view of the shot such as a street lamp, light pollution from a nearby town or your buddy’s headlamp.
Since we lose a little bit of highlight data with each higher ISO, choosing the optimal ISO for astrophotography is a little bit of balancing act between using a higher ISO for better noise performance (especially in the case of an ISO-variant sensor) or a lower ISO for better dynamic range.
Finding the Optimal ISO for Astrophotography: The ISO-Invariance Test
Stand back, we’re going to try science! In order to find the best ISO to use for astrophotography, I recommend doing an ISO-invariance test. Most of the samples shown in this article up to this point were made with an ISO-invariance test. It’s a super easy test to run: all we need to do is to take about 7-10 RAW photographs, one at each whole-stop ISO and then we match the exposure brightnesses in post processing. This test is easier to perform in a low-light scenario so I recommend doing this test outdoors at night or in a dimly lit room. Maybe make it an astrophotography trip.
If you’re performing this test while shooting the dark night sky, use my Milky Exposure Calculator to determine the shutter time and aperture setting. If doing the test in a dimly lit room, first use your camera’s (P) Program exposure mode at ISO 3200 to determine your shutter time and f/number.
Shoot in dark conditions: a dimly lit room or outdoors at night
Shoot in RAW file format!
Use (M) manual exposure mode
Set “daylight” white balance (just so it doesn’t drift)
Disable all forms of noise reduction (Long Exposure NR, High ISO NR)
Shoot one exposure at each whole stop ISO (100, 200, 400, 800, etc.)
Keep all other settings the same, change only ISO
Match exposures in post processing and compare
For my test on the T5i, here’s what the complete images looked like with the crop of the test area highlighted. I cropped the results of the test to a small area that included some midtones and some shadows.
Straight out of the camera, the crops of the RAWs looked like this:
In terms of noise, this comparison is deceiving because the brightnesses don’t match between exposures. In order to level the playing field, we need to match the brightnesses. To do so, I used Exposure adjustment slider in Adobe Lightroom to match all of the exposure brightnesses to the ISO 3200 exposure. The ISO 100 image was pushed all the way to the max +5EV setting on the Exposure slider, the ISO 200 +4EV, the ISO400, +3EV and so on…
Here’s the complete summary of how we match all the exposure brightnesses in Adobe Lightroom.
ISO 100 gets pushed +5EV
ISO 200 gets pushed +4EV
ISO 400 gets pushed +3EV
ISO 800 gets pushed +2EV
ISO 1600 gets pushed +1EV slider
ISO 3200 has no adjustments made
ISO 6400 gets pulled -1EV
Another way to do this in Adobe Lightroom is to select all of the exposures, then highlight the ISO 3200 exposure and select Photo > Develop Settings > Match Total Exposures or press Command+Option+Shift+M (Ctrl+Alt+Shift+M).
Once equalized, here’s what the exposures look like:
Upon comparison of the exposures, it’s immediately apparent that the Canon EOS 700D/T5i is not completely ISO-invariant. It appears as if that the camera reaches its best low-light performance at ISO 1600 and higher. ISO 1600, 3200 and 6400 look almost identical meaning that the 700D might be ISO-invariant from ISO 1600 upwards. Below ISO 1600 is a different story: As the ISO lowers, image quality degrades until the point of being nearly unusable at ISO 100. In order to preserve some dynamic range, but still get the best low-light performance on the 700D, it’s clear from the results of the test that ISO 1600 is the optimal setting.
Example: Fujifilm X-T1
Just for comparison, I ran a separate ISO-invariance test on my Fujifilm X-T1, this time at 30 seconds and an aperture of f/2.8. The results are distinctly different from the Canon.
The difference is that there is no difference… between the ISO 200 setting (the lowest it goes on the X-T1) and the ISO 6400 setting, noise levels are identical. This means that the Fujifilm X-T1 is completely ISO-invariant. The noise levels across the ISO range don’t change in the slightest. This means that it doesn’t really matter which ISO you use on the Fujifilm X-T1 and the optimal setting might even be ISO 200 in order to preserve dynamic range.
That said, there’s also a little bit of impracticality if attempting to shoot astrophoto at ISO 200 as the image preview on the back of the camera would be very dark and evaluation of other important factors like focus and composition would be difficult at ISO 200. Luckily, we’re usually not risking too much dynamic range by bumping ISO up to a moderately high level, assuming there are no bright artificial light sources in the photo. So using ISO a slightly higher ISO might be the more practical choice, keeping in mind our tolerance for reduced dynamic range.
Contrary to popular belief, higher ISOs don’t create more noise and using a higher ISO can actually be beneficial when shooting in low-light scenarios, especially on cameras with ISO-variant sensors. Run an ISO-invariance test on your camera to determine the best ISO setting to use when shooting astrophotography. ISO behavior varies from camera model to camera model and testing out each ISO setting can help determine the best ISO to use for the best noise performance in your astrophotography.
It’s important to understand that ISO-variance or invariance doesn’t necessarily make a camera better or worse at low-light, it’s just different. Knowing how a camera behaves is an important step to achieving the best image quality.
More and more cameras manufacturers tend to be making their cameras more and more ISO-invariant, as they develop sensor technology with reduced downstream read noise and improved dynamic range at low ISO settings.
Do you know which ISO on your camera gives the best low-light performance? Do a test to find out!
About the author: Ian Norman is the co-founder and creator of The Photon Collective and Lonely Speck. Ian is a full-time traveler, photographer and entrepreneur. In February 2013, he called it quits on his 9-to-5 to pursue a lifestyle of photography. Follow Ian’s photography adventures on Instagram. This article was also published here.