Real world EXR comparisons
Fujifilm's EXR sensor and processing technology, as it is implemented in the X10 provides some quite clever and useful options for tuning the sensor's performance for either noise reduction or dynamic range. Yet we struggle to recall a more poorly documented feature from any manufacturer in recent memory. We've even had contradictory explanations of EXR's purpose and behavior from Fujifilm itself.
The Fujifilm X10 has three EXR modes - 'HR', high-resolution, in which the X10's full complement of 12MP is used to create images, 'DR', dynamic range, where you can capture images with a much greater dynamic range than would normality be possible, and 'SN' - signal to noise, designed to give cleaner, less noisy images at high ISO settings in poor light. Because of the way that they work (in effect by combining the signals from neighboring photosites) both DR and SN modes output 6MP images.
As well as EXR 'DR', the X10 also has a more conventional dynamic range expansion mode, which delivers expanded highlight dynamic range at full resolution at the expense of a reduced ISO sensitivity span. Confusingly, despite being completely different technologies, both EXR and conventional dynamic range expansion is described in the same way in the X10's menu system, as 'DR XXX%'...
Here, we'll take a look at what EXR means for everyday use; what you need to know to activate it and how to use it effectively in real world situations. For a more detailed examination of its peculiarities dpreview contributor Timur Born has written an interesting user impressions article.
EXR SN mode real world samples
The X10's EXR SN mode is pretty straightforward in both concept and operation. Instead of outputting a full 12MP file, the camera averages data from alternating pixels of the sensor. Because noise occurs randomly this averaging technique has the effect of reducing its appearance in the final image. In the samples below we photographed at three of the camera's highest ISO settings under a low-intensity warm household temperature light source. The warm light source accentuates red channel information, and by setting a custom white balance to correct for this, the camera must amplify the blue channel resulting in higher noise.
|6MP EXR SN mode ISO 800
f/2.5 1/15 sec.
|6MP EXR SN mode ISO 1600
f/2.5 1/30 sec.
|6MP EXR SN mode ISO 3200
f/2.5 1/60 sec.
With EXR SN enabled, the X10 produces impressively low levels of noise. The only penalty to be paid here is 6MP versus 12MP file resolution. Given that EXR SN mode behavior kicks in whenever the camera is set to 6MP mode, we thought it would be interesting to see how the noise levels shown above compare to a 12MP file at the default NR setting.
|ISO 3200 6MP (upsampled to 12MP) 100% crop||ISO 3200 12MP
|ISO 3200 6MP
|ISO 3200 12MP (resampled to 6MP)
For the comparison above, we've sought to level the playing as best we can by upsampling the 6MP file in the first set of images and then downsampling the 12MP file in the second. Both instances of resampling were done at Photoshop's Bicubic setting. The files are similar but the 6MP EXR file does maintain saturation noticeably more successfully than the 12MP file. The natively larger file is slightly crisper, as we'd expect, but not noticeably more detailed.
DR mode real world samples
The X10's DR (Dynamic range) mode has three distinct iterations. The first occurs when the camera is set to 12MP mode. In this mode you have access to DR 100, 200 and 400 settings via the shooting menu. DR 100 gives a normal exposure. Select DR 200, though and the camera cuts exposure time by 1/2 to prevent highlight clipping and then uses a tone curve to lift the midtones and shadows, providing a 'normally' exposed file. At DR 400, exposure time is reduced by 1/4, followed again by a tone curve adjustment. This is a pretty common method of extending dynamic range, and one that is featured in some form on many modern cameras - compact and DSLR.
|12MP DR 100%
Av mode, f/7.1 1/200 sec., ISO 100
|12MP DR 400%
Av mode, f/7.1 1/800 sec., ISO 400
|100% crop||100% crop|
|100% crop||100% crop|
In the samples above you can see that using a DR 400 setting, which raises the camera's base sensitivity to ISO 400, retains highlight detail that was clipped at DR 100. Of course, a downside to then having to lift the shadows (to produce a scene of equivalent luminance) is the potential for more visible noise. And as you might be able to see in the second set of crops, the DR 400 image is very slightly noisier by comparison, and some fine shadow detail is obscured. Yet the difference is fairly minor; one that we feel is certainly outweighed by the extra highlight range that the DR 400 setting provides.
When you set the X10 to 6MP mode you trigger a different set of behavior at the DR 200 and DR 400 settings. This time, the camera exposes half of the sensor's photosites at the nominal exposure (to capture shadow detail) and the other half for a shorter duration (to preserve highlight data). The two 'separate exposures' are then merged into a single 6MP file that delivers greater dynamic range than a normal exposure, as shown in the examples below.
|6 MP DR 100%
Av mode, f/6.4 1/170 sec., ISO 100
|6MP DR 400%
Av mode, f/6.4 1/180 sec., ISO 100
|100% crop||100% crop|
As you can see above, highlights that were completely clipped in the DR 100 shot are rendered with impressive detail at DR 400, but the base ISO sensitivity setting remains unchanged, at ISO 100. It's important to note that you can trigger this 6MP DR behavior either by setting the camera to 6MP mode and then selecting the DR option or you can set the X10's mode dial to EXR and select its DR-Priority option. The sole difference being that the former method allows you to save in RAW+JPEG mode, while the latter is JPEG only. In both instances, the you are able to reap the benefits of DR 400 without increasing ISO sensitivity.
The question then is whether to use the 12MP or 6MP implementation of Fujifilm's DR technology. In the examples below we photographed the same scene at both resolutions. Again, remember that shooting in EXR mode allows you to retain additional highlight detail at base ISO, while shooting in 12MP mode at anything other than DR 100 requires raising the ISO sensitivity.
To level the playing field, the first set of crops shows the 12MP file downsampled to 6MP (via Photoshop's Bicubic mode). In the final set of crops we upsampled the 6MP EXR mode file to 12MP.
|12MP DR 400%
Av mode, f/4.5 1/1700 sec., ISO 400
|6MP DR 400%
EXR mode, f/4 1/500 sec., ISO 100
|12MP downsampled to 6MP 100% crop||Native 6MP 100% crop|
|Native 12MP 100% crop||6MP upsampled to 12MP 100% crop|
As you can see, there is not a whole lot separating the 12MP and 6MP versions. Even when downsampling the 12MP file, image noise is still a touch more prominent compared to the 6MP EXR version. And the upsampled EXR file doesn't lack for any significant fine detail compared to the 12MP version, suggesting that the benefits of shooting at a 2 stop EV lower ISO setting outweighs the additional pixels you get in 12MP mode.
EXR 800 and 1600
Switching the mode dial to EXR and choosing the DR-Priority option gives you access to DR 800 and DR 1600 modes which in theory, give even greater degrees of highlight retention. This triggers a 'hybrid' method of dynamic range expansion in which each half of the EXR sensor is exposed differently and a post-capture tone curve adjustment takes place.
There is a price to be paid for this extra headroom, however. As you can see in the samples below, image quality does drop at these two highest settings, with noise becoming more visible in midtone and shadow areas. Shooting at DR 800 requires an ISO 200 minimum and shooting at DR 1600 can only take place when base ISO is restricted to 400. Fortunately, in our time spent shooting with the X10, we've only rarely encountered real-world scenes in which DR 800 or higher actually retained meaningful highlight detail compared to DR 400.
6 MP DR 100%
|6MP DR 400%
Av mode, f/4.5 1/450 sec., ISO 100
|6 MP DR 800%
EXR mode, f/4.5 1/850 sec., ISO 200
|6 MP DR 1600%
EXR mode, f/6.4 1/850 sec., ISO 400
How should I use EXR mode?
If you're an auto-everything point-and-shooter, EXR Auto mode is definitely worth playing with. In this mode, the X10 will just select the appropriate EXR setting for the situation, usually quite sensibly. Your card will fill up with a mixture of 12MP and 6MP shots depending on the environment that you're in. And as we've seen in the examples on this page, the 6MP images can compare quite favorably against the full resolution captures.
If you're interested in taking full control over exposure, however, using EXR becomes a little more complicated. You could be forgiven for thinking that EXR is an exclusively JPEG-only, automatic exposure mode, but in fact, as we've mentioned elsewhere on this page, it is possible to shoot 'DR' EXR mode and maintain full exposure control and even be able to shoot Raw files. You just have to manually select medium resolution (6MP) capture first (and RAW+JPEG mode if you want to shoot raw files), at which point you can extend dynamic range by up to 2EV (from 100% to 400%).
Note that using either Silkypix or Adobe Camera Raw you are able to take advantage of the EXR data in the resulting Raw files. But its not at all obvious. At default exposure settings a DR 400 image will not show significantly more highlight detail than the same scene captured at DR 100. Yet, by setting the exposure slider to a negative value - commonly as much as -2 stops EV - you can access the expanded highlight range while maintaining color accuracy.
Some photographers may balk at voluntarily reducing the X10's output resolution from 12MP to 6MP but in our opinion it's worth it because 'DR' mode is very useful, and arguably the most valuable of the three EXR settings. As you can see from the examples on this page, and previously-published samples, setting the X10 to its DR EXR mode delivers significant benefits in expanded dynamic range, effectively making clipped highlights a thing of the past in all but the most extreme scenes.
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