Canon EOS 650D/Rebel T4i In-Depth Review
Handheld Night Scene
The EOS 650D gains two automated multi-exposure scene options on the mode dial. The Handheld Night Scene mode was first seen on the Canon PowerShot SD4500 IS. This mode is designed to enable low light image captures without the use of a tripod. It does this by enabling a faster shutter speed and then capturing four successive exposures which are then combined to reduce image noise. In this scene mode the only parameters you can adjust are the 'ambience' setting and drive mode along with the ability to enable/disable flash output. You are also limited to JPEG-only output. Users who desire more control over exposure and shooting settings may also want to consider the 650D's MultiShot NR mode which we examine on the image quality tests page of this review.
In the examples below we compare Handheld Night Scene output with a manually exposed capture set at an identical aperture with sharpening and noise reduction at their defaults. The images were shot handheld, maintaining the same camera position as much as possible.
As you can see, in Handheld Night scene mode the image is cropped, presumably to allow for the automated image alignment that takes place during processing. Helpfully, this crop is previewed in live view, so that you can accurately frame the final composition. Once the individual frames have been merged and aligned, the image is then upsampled slightly to match the 650D's native resolution of 5184 x 3456. All of this work is very processor intensive. After each press of the shutter button you must wait for about nine seconds or so before taking another picture, though you can still access the camera's menus.
|Handheld Night Scene mode:
ISO 12800, 1/10 @f/3.2
ISO 6400, 1/5 @f/3.2
When pointed at the same scene, Handheld Night Scene mode opts for a higher ISO (12800 vs. 6400) to attain a faster shutter speed, which can minimize camera shake between its four exposures. Of course, using a higher ISO sensitivity also increases the potential for visible noise. We would expect then that Canon's engineers have tailored a combination of noise suppression and sharpening settings to minimize noise. And as you can see in the samples above, 'handheld' mode indeed provides a cleaner image than the normally-processed JPEG. It's equally as clear, however, that the end result is a somewhat softer image.
We must give Canon credit though for an impressive balance of noise suppression and image detail. At such high ISO settings, there is precious little, if any, penalty to be paid in terms of fine detail for these reduced noise levels. As a quick and easily accessible mode for the point-and-shoot oriented user, Handheld Night Scene mode provides cleaner looking images with minimal detail loss.
What more seasoned users give up though, is the ability to simultaneously capture a Raw file, which could easily be processed to taste in their preferred raw converter software. Below we show a comparison between the same Handheld Night Scene capture and a Raw file with which we've taken just a few moments in ACR to adjust sharpness and noise reduction settings.
|Handheld Night Scene mode
ISO 12800, 100% crop
|ACR 7.1 with custom NR and sharpening
ISO 6400, 100% crop
|100% crop||100% crop|
With minimal effort in ACR, you can achieve equivalent chroma noise reduction and opt for slightly greater luminance noise in order to produce a more crisp image. Keep in mind though, that we are looking at 100% crops and that to reap any practical benefits of these ACR settings you would need to be making a very large print.
HDR Backlight Control
The 650D's second multi-exposure scene mode is labeled HDR Backlight Control and aims to expand the dynamic range to include more information in both highlight and shadow regions. With this shooting mode enabled, three consecutive images are captured - each at different exposure - with the files then merged into a single composite image. As with 'handheld' mode, the image is cropped - again presumably to accommodate the automated image alignment - and then upsampled to the 650D's standard resolution. This a JPEG-only mode. And the image settings you can adjust are limited to drive mode and JPEG size/quality. You cannot specify the bracketing range of the three exposures. Nor can they be accessed as individual files. In the samples below, we compare HDR Backlight Control with a traditional exposure using an identical aperture.
|HDR Backlight Scene mode: ISO 100, f/3.5||Av mode: ISO 100, f/3.5|
As you can see, HDR Backlight Control is able to preserve color information in the highlights that had been clipped in the single-shot exposure. The shadows appear ever so slightly more open in this mode, but clearly the emphasis is on maintaining highlight detail. As mentioned earlier, bracketing among the three exposures is fully automated; you can't specify an EV range, for example. In our time spent using this mode, we've seen 'HDR' retain between 1 and 1 1/2 stops of color-accurate highlight data. You can gain a full 2 stops EV of highlight data by using the camera's auto exposure bracketing feature, but HDR mode of course saves you the extra effort of aligning and blending the separate images to form the composite.
As with any shooting mode in which multiple images are blended together, HDR Backlight Control works best with static subjects. Any movement during the three exposures can lead to ghosting, where an object partially appears in multiple locations, as shown in the example below.
Overall, HDR Backlight Control works as advertised and gives beginning users an easy way to extend dynamic range for greater highlight detail, moving subjects notwithstanding. Our biggest complaint though is with image softness of the final result. In side by side comparisons, both handheld and on a tripod, we've seen softer results from 'HDR' mode than from shooting in the PASM modes, as you can see below.
HDR Backlight Scene mode: ISO 100, f/4
Av mode: ISO 100, f/4
While we also saw slightly softer results from the 'handheld' scene mode, the comparison above stands in sharper relief because - as with the situations in which you'd actually use 'HDR' - we're shooting at a low ISO, in which there's greater potential for rendering fine detail. To be fair, while more experienced users may prefer to get sharper results through manually blending images, we suspect many first-time DSLR owners will be satisfied with these results, particularly given the point-and-shoot nature of its implementation.
Bear in mind that if you opt to use these (or any other) scene modes, live view operation offers a distinct advantage. It is only in live view that you can manually set the AF point along a wide portion of the scene. In through-the-viewfinder shooting, the camera automatically selects among its 9 central AF points, with no way for the user to manually choose a specific AF point as is possible in the PASM modes.
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