Special Exposure Modes
Handheld Twilight mode
Handheld Twilight mode isn't a new function, but it is one which we have found useful in several recent Sony cameras. In this mode, accessible through the 'Scene' position on the virtual mode dial, the camera takes several exposures at its highest framerate, then blends them together in-camera to reduce the impact of high ISO noise. Although pixel-level sharpness isn't perfect, handheld twilight mode is a quick, easy and (usually) effective way of grabbing a smooth and colorful shot in conditions where normally you'd need to use either a high ISO sensitivity setting or a tripod.
|1/60s F4 ISO1600, Handheld Twilight||1/50sec F4.5 ISO 1600, A mode|
100% crops (noise)
100% crops (fine detail)
This example shows the advantage of Handheld Twilight mode in this kind of situation. With similar exposures, the HHT version is noticeably less noisy in areas of continuous tone compared to the same shot taken in A mode. Pixel-level sharpness is slightly compromised, because it's compositing multiple exposures, but the impact is remarkably low, and with so many pixels to play with there's still plenty of detail in the file.
Like other recent Sonys, the NEX-7 also has an 'Anti Motion Blur' mode that works in a similar way (although it has its own position on the virtual exposure mode dial). The main difference between the two is that Anti-Motion Blur is designed for use with subjects that move, and is therefore biased towards using higher shutter speeds and correspondingly increased ISO sensitivities.
(3D) Sweep Panorama
The NEX-7 includes an automatic sweep panorama mode that allows you to create large, high-resolution panoramas in-camera. As with other recent Sonys this comes in 2 flavours. In Sweep Panorama the camera simply records a single JPEG file, but in 3D sweep panorama it also constructs a stereoscopic image in the standard MPO format, which you can then play back on a 3D TV.
You can select the sweep direction before you start using the rear or left dials, and set exposure compensation with the right dial. The electronic levels display is particularly useful in this mode, as it helps you avoid tilting the camera as you sweep.
|Sony's Sweep Panorama mode works impressively well - even in this highly detailed scene you'll struggle to find any obvious stitching errors|
|This example was shot in 3D Sweep Panorama mode - click here to download the 3D MPO file|
|Composition is necessarily somewhat imprecise - here the camera has cropped just a fraction too too tightly at the top of the frame (despite the panorama being deliberately framed 'loose'), while leaving a blank grey area at the right. You'll usually need multiple attempts to get the results you want.|
|The camera will go to great lengths to continue stitching even if you don't sweep it completely straight.|
In common with our experience of this mode in other recent Sony cameras, Sweep Panorama works pretty well, and creates usefully high-resolution files compared to the same function in Sony's Cyber-shot compacts. However don't expect to manage anything resembling precise composition - the camera will crop the final image unpredictably at the end, particularly vertically, so it's always best to frame a little 'loose,' and take multiple attempts at a given scene until you get the results you want. You can also get occasional stitching errors with close subjects or anything that's moving, but on the whole the results are impressive.
Dynamic Range Extension
DRO and HDR
Dynamic range optimization (DRO) is a means of creating a single image that covers a large brightness range in a way that looks natural to the human eye. DRO applies a series of tone curves to each area of similar local brightness within a single image, in an attempt to balance details in the shadows while maintaining local contrast. For a more in-depth explanation of how the system works please take a look at our 2009 article about the technology behind DRO.
Auto HDR works by combining multiple exposures (one normally exposed, one over exposed and one under exposed), using automatic exposure bracketing up to 6EV. This allows for a larger dynamic range to be recorded than the sensor is capable of capturing in a single shot, but is only available in JPEG mode. The camera saves the processed HDR image alongside the normally exposed image.
|DRO Off||100% crop|
|DRO - Level 5||100% crop|
|HDR - 6.0 EV||100% crop|
These samples give some idea of the effects and limitations of DRO and HDR (although it's not a subject that really needs this treatment). DRO goes a good job of lifting the shadows, and because it's a single-shot process there's no effect on detail. In contrast, HDR results in a slightly soft image at the pixel level, with visible degradation of fine detail. This is presumably a result of the inevitable slight camera movement between frames, which could be eliminated if only you could trigger AutoHDR using the IR remote release (with the camera on a tripod) - but the camera won't let you do this.
What these shadow-region crops don't tell you, though, is that HDR can do a fine job of retrieving blown highlights, which DRO can't do much about. This is illustrated below (although again it's not the perfect subject) - the HDR shot picks up some additional detail in the windows.
|DRO - Level 5||HDR - 6.0EV|
We'd be tempted to leave DRO on Auto, at least when shooting at low ISOs - it does a good job of retrieving shadow detail and presenting it naturally, without a huge penalty in terms of shadow noise. We're more equivocal about HDR, especially as you have to turn RAW off to access it (with the concomitant risk of forgetting to turn it on again). It can be genuinely useful in extreme conditions, such as when shooting into the low winter sun as below, however the output can still look a little 'flat'.
|Conventionally-processed version||HDR-Auto version|
A note on Autobracketing
Features such as DRO and AutoHDR are without doubt useful, but the kind of enthusiast photographer most likely to be attracted by the NEX-7 will probably be more interested in generating their own HDR images after the event from carefully-bracketed RAW files. However the NEX-7 doesn't do well here: autobracketing is only available as 3 shots at 0.3 or 0.7 EV increments, which isn't really enough for serious HDR work.
Equally annoying is the fact that, while each trio of bracketed shots is captured from a single press of the shutter button, autobracketing can't be combined with the IR remote release to eliminate camera movement between frames. Instead both functions are considered separate drive modes and accessed from the same screen.
What this means is that, for the serious HDR shooter, the NEX-7's autobracketing facility isn't very useful. What is doubly annoying is that the AutoHDR mode would provide an excellent option, if only it recorded RAW files and could be used with the remote release. Instead, for this specific purpose, Sony has snatched defeat from the jaws of victory.