You probably don't know what ISO means – and that's a problem
Whatever camera or phone you have, it’ll report the ISO value it used to take its photos. Despite its ubiquity, ‘ISO’ probably doesn’t mean what you think it does. Worse still, it may be holding your camera back, both in terms of the images it takes and in the tools it provides you. This means it's potentially holding your photography back, too. Part of the problem stems from the fact that ISO sounds like something you were already familiar with.
At first glance, ISO settings look just like the sensitivity ratings used for film (to the extent that there are some people who still refer to ASA: the US standard incorporated into the ISO standard for film). But ISO in digital isn’t the same as film. it’s essentially a metaphor for the way film sensitivity worked, if you got it processed in a minilab machine. This is a problem.
It causes confusion
The apparent familiarity and simplicity of ISO setting leads to a number of common misunderstandings. Despite what you may have heard or read, changing the ISO of your camera does not change its sensitivity.
ISO changes the lightness of the final image but it doesn’t change the fundamental sensitivity of your sensor. Nor is it an indicator of amplification being applied: although many cameras do increase their amplification as you increase the ISO setting, this isn’t always the case.
This may sound like semantic nit-picking, but it causes a lot of misunderstandings. It’s widely thought that the additional noise in high ISO image comes from the ‘background hiss and hum’ of the sensor’s amplifiers. This feels right: we’ve all heard more noise if we turn up the volume on an audio amplifier. Unfortunately it’s simply not true: most noise actually comes from the light you’re capturing, so it primarily depends on your shutter speed and aperture.
The ISO standard doesn't specify that amplification needs to be used, nor does it specify what happens in the Raw file
The ISO standard doesn't specify that amplification needs to be used, nor does it specify what happens in the Raw file. All it does is relate initial exposure to output JPEG lightness, however that is achieved. The only thing you can be sure of, at the Raw level, from an increase in ISO is that if it prompts a reduction in exposure, you'll collect less light and therefore see more noise for each tone from the scene.
There's an ISO standard that's slightly more pertinent to Raw files, which looks at when the sensor becomes completely saturated, but this doesn’t correspond to the standard used by your camera. So next time you see a graph comparing ‘Manufacturer’ and ‘Measured’ ISO, what you’re actually looking at is the ‘JPEG ISO’ vs ‘Saturation ISO.’ Any differences between the two mainly tell you how many stops above middle grey the manufacturer's JPEG tone curve is designed to deliver.
It encourages poor exposure
As well as giving a false sense of simplicity, ISO’s increasingly tenuous attempt to mimic film ratings can mean making poor use of sensor response.
Film (particularly negative film) has a very distinctive response curve that gives lots of latitude for recovering highlights. Digital is very different: it offers a much more linear response but with a hard, unrecoverable clipping point in the highlights. And no, your favorite software doesn't really recover completely clipped highlights from your Raw file*.
|This graph shows the signal-to-noise ratio (essentially the noisiness) at different brightness levels of film and digital. The film response peaks and then gradually declines, with plenty of scope for recovering highlights from the right-hand side of the curve. The digital response rises to much higher levels than the film, then cuts-off abruptly. So why would you expose these two media in the same way?
Illustration based on DxO's analysis
And yet, despite these differences, the digital ISO standard is based around ‘correctly’ exposing JPEG midtones**. A 2006 update to the standard gave manufacturers some flexibility in terms of how many stops of highlights they wanted in their JPEGs above middle grey***, but it still encourages exposure based on midtones, with a pre-set number of stops above this for highlights.
That’s not the best way to expose digital. The best results are achieved by giving as much exposure as possible without clipping the brightest tones you care about: a process called ‘exposing to the right.’ This maximizes the amount of light, and hence signal which, in turn, optimizes the signal-to-noise ratio (essentially ‘noisiness’).
And yet, by worrying about the JPEG middle grey, cameras end up giving every image the same number of stops for highlights, even though this is wasted in low DR scenes (that highlight space isn’t used and exposure is lower than optimal) or insufficient in high DR situations: the lovely colors of the sunset you’re shooting are lost, unrecoverably, to clipping.
This problem isn’t easily solved: there are times that exposing-to-the-right will result in noisier midtones than you want. In these situations, you have to let the highlights go. However, fixating on JPEG midtones isn't helpful.
It warps camera development
This brings us to the biggest problem with using a clumsy metaphor for film sensitivity as the way of setting image brightness in digital: it means we aren’t given the tools to optimally expose our sensors.
ISO ends up conflating the effects of amplification and of tone curve, meaning you have to do your own research to find out what your camera’s doing behind the scenes, and what the best way to expose it is.
We aren’t given the most basic tools: Raw histograms or Raw clipping warnings that would help optimize exposure
The preview image your camera gives, the histograms it draws and the exposure meters and guides it offers are all based on JPEG output and their midtones, because ISO says that’s what matters. This means we aren’t given the most basic tools we need: Raw histograms or Raw clipping warnings that would help optimize exposure. It means no development has been done to create more sophisticated tools that would help you judge the quality implications of exposing to the right, and when to let the highlights go.
In short, ISO is an increasingly shaky metaphor that promotes misunderstanding, obscures what your camera is doing and robs us of the tools we need to get the most out of our cameras. Isn’t it time for something better?
* Highlight recovery sliders usually rely on only one of the color channels having truly clipped, and try to guess the value of the clipped channels, based on the remaining, unclipped one, so tend to be limited in their effectiveness. [Return to text]
** We put the word "correctly" in inverted commas because the more you think about it, the harder it becomes to pin down what 'correct' exposure might be. If you're certain that you know what 'correct' exposure means, then you should probably check through the assumptions that underpin it. [Return to text]
*** This change is why the JPEG ISO ratings used by manufacturers don’t need to coincide with clipping-based Raw ISO numbers. We’ve previously written an article about how it works. [Return to text]
|Mycorrhizal Fungi. by SpartanWarrior|
from Wild Mushrooms
|Idehan Ubari, Lybia by HQ|
|Djoko5 by Cutka|
from UNposed... UNexpected... YOUR BEST Street Shot
|Falls in the fog by Jill Hancock|
from Not so long
MIOPS has announced Flex, a new smart camera gadget designed to make it easy and simple to capture lightning strikes, action images, holy grail timelapse videos and much more.
This year, despite the disruption, plenty of amazing cameras, lenses, accessories and other products came through our doors. Now, as the year winds down, we're highlighting some of our standout products of the year. Check out the winners of the 2020 DPReview Awards!
Fujifilm's 3.00 firmware update adds a new Pixel Shift Mult-Shot mode to its GFX 100 camera that works alongside a new Pixel Shift Combiner program to output 400MP Raw images made up from 16 individual still images.
You don't need to spend a fortune to buy a camera that's designed for videography. We took a look at the field and selected the Panasonic S1H and GH5 as the best cameras for serious videographers.
Fujifilm has announced a special version of its 100MP GFX 100 for infrared imaging. The new camera will be available for special order in early 2021.
The event, which will show off a new 'DN' lens for mirrorless camera systems, is set to take place at 7am ET (4am PT) on December 1.
The 'One Shot' documentary highlights the incredible amount of preparation and work involved in photographers capturing iconic moments in Olympic history. It also features nearly 150 wonderful images from past Olympics games.
The adapter will bring full autofocus, aperture control and EXIF data transfer capabilities to Pentax K-mount lenses when used on select Sony E-mount camera systems. No price is given at this time, but the adapter is set to be available by the end of the year.
In a year when social distancing became a way of life overnight, Senior Editor Barney Britton maintained a small sense of connection via the Fujifilm X100V.
We've rounded up a collection of the best deals currently active on cameras, lenses, software and accessories. This will be a living article that gets updated throughout this holiday week, so be sure to check back to keep up with the latest offers.
With new iPhone models comes new iFixit teardowns. iFixit has taken apart the iPhone 12 Pro Max and found some interesting details and gotten a look at the iPhone 12 Pro Max's internals, including its new camera technology.
Canon's RF 85mm F2 Macro IS offers EOS R-series shooters an affordable, stabilized and fast-ish portrait prime. Take a look at what it can do.
Oceanographic Magazine recently announced the winners of its 2020 Ocean Photographer of the Year awards.
For many of us, photography is a welcome retreat from the raging storm that is 2020. If you happen to be shopping for a photographer this season, we've got some gift ideas that we think will help enable and enrich this pursuit.
Finnish company VALOI has launched a new Kickstarter campaign for the VALOI 360 film digitizing system. By combining the VALOI 360 with a digital camera and light source, you can easily digitize your rolls of 35mm and 120 film.
Smartphones capture amazing video, but to kick production value up a notch consider adding a compact gimbal to your kit. This week, we test three leading smartphone gimbals: The DJI OM 4, the Moza Mini MX and the Zhiyun Smooth XS.
Don McCullin's illustrious career is set to arrive on the silver screen in a new film adapted from McCullin's autobiography. Tom Hardy is set to star as McCullin with Angelina Jolie directing.
In addition to the 23mm and 33mm F1.4 lenses it announced for Fujifilm cameras, Tokina has also unveiled a 17–35mm F4 lens for Canon EF and Nikon F mount camera systems.
Nikon has released an updated version of its visual lens roadmap, showing off three new silhouettes for its forthcoming 'Micro 50mm' prime, 400mm S-Line super-telephoto and 600mm S-Line super-telephoto lenses.
From funky film stocks, to home developing and digitizing solutions, we think these are the best film photography gifts in 2020.
The new 23mm and 33mm F1.4 offer 35mm and 50mm full-frame equivalent focal lengths, respectively. The 23mm and 33mm F1.4 lenses will be available for $479 and $429, respectively, starting December 11.
Chroma Cameras has announced the 679 camera system. It is a modular medium format camera system allowing photographers to easily, and affordably, build a versatile 120 film camera for multiple lens systems and film backs.
Halide Co-founder and Designer, Sebastiaan de With, has shared an incredibly detailed analysis of the iPhone 12 Pro Max's camera tech and explains why the changes, compared to the iPhone 12 Pro, are far more impressive than initial reviews suggested.
Camera battery design has been relatively unchanged for years, but new Kickstarter campaign for the X-tra battery hopes to upend convention and give photographers a more powerful, quicker and better camera battery.
Canon has released firmware updates for four of its mirrorless cameras, its flagship 1D X Mark III DSLR and its RF 50mm F1.2 L USM lens. The updates mainly address minor bugs and brings support for newer lenses to Canon's mirrorless cameras.
Vaporware no more: the much-speculated-about Zeiss ZX1 has arrived. Combining a 37MP full-frame sensor, minimalist controls and Lightroom Mobile built in, it's a refreshing – if a bit quirky – take on the smartphone-meets-camera concept.
Nikon unveiled the Z6 II last month, adding some more processing power and a few other modest upgrades to its 'multimedia' full-frame mirrorless offering. We got our hands on one and have some preliminary samples to share – take a look.
The Nik Collection 3 by DxO has been updated to version 3.3, adding 25 new presets to celebrate the company's 25th anniversary.
The Voigtlander 29mm F0.8 Aspherical lens for Micro Four Thirds (MFT) systems will become the fastest commercially-available lens on the market when orders start in December.