Photography News Issue 37

Photography News | Issue 37 | absolutephoto.com

Camera test 50

Performance: exposure latitude

-1EV

-2EV

Original image

+1EV

+2EV

A sunlit contrasty scene was photographed using a tripod- mounted sd Quattro fitted with a Sigma 24-105mm f/4 DG lens. The manually metered correct exposure at ISO 100 was 1/100sec at f/11. Shots were then taken by adjusting the shutter speed to give an exposure bracket of +/-4EV. SigmaX3Ffilesarenotcompatible with Camera Raw/Lightroom so the resulting Raws were imported in Sigma Photo Pro software, v6.4.0 and the files adjusted to correct for the under/overexposure. The software’s exposure slider is limited to +/-2EV, so the exposures beyond that range were not processed.

The sd Quattro coped well with two stops of underexposure and the converted file looked almost identical to the correctly exposed shot in terms of tone and contrast. If anything there was marginally more noise in the shadow areas but it wasn’t too distracting so it coped well with underexposure. With overexposure, the +1EV Raw looked the same as the correctly exposed shot but the +2EV shot was less impressive in the highlights where the maximum correction in Photo Pro was still not enough to give good details and what detail was present looked grey. The limit for overexposure is about +1.5EV.

Correct

Images In our tests of a sunlit contrasty scene the sd Quattro’s Raws showed itself quite tolerant to underexposure and recovery in software produced fine images. It was less amenable to overexposure and the upper limit for high-quality shots is +1.5EV. The software used was Sigma’s Photo Pro which is a free download, as there is limited third-party support for Sigma Raws.

Performance: Super-Fine Detail (SFD) mode

SFD image

For the ultimate image quality from the sd Quattro, you can choose SFD mode in the menu to give wide dynamic range, low-noise images. In this mode, seven bracketed exposures are taken so you need the camera on a tripod with the lens’s OS system turned off. And, of course, a static subject. Select SFD and key camera settings are fixed or limited. So, aperture-priority and manual are the only exposure modes possible, you only get Raw files (with the extension .X3I) and ISO is set to 100 only. Press the shutter button once and the camera takes a set of seven bracketed exposures and the write to card LED lamp glows for about 15secs. Obviously it depends on the shutter speeds used but for a sunlit scene where the correct exposure is 1/250sec at f/11 the bracketing sequence takes over 5secs, hence why you need a static subject. When you preview the images in thumbnail view you see the SFD7 icon and in single image view you can scroll through the seven bracketed images with a scale telling you which image you are viewing. If you delete an individual SFD image in-camera, all sevenwill be deleted. You do not get to see the final merged result in-camera. All you have done is captured a seven- image bracket that you can then import into the Photo Pro software to produce the finished result. In

software you can also extract the original X3F Raws so, for example, if for whatever reason the seven- image bracket didn’t work, you still have individual Raws to work with. We have seen Olympus and Pentax use their sensor-shift mechanisms to actually move the sensor for a series of exposures with the same camera settings to gather as much information as possible and we know it works. The sdQuattro’s sensor stays put and is exposure bracketing only. It is basically HDR with less midtone noise, so it’s good for interiors and even scenics – it can be used for any scene if there is no camera or subject movement. As you would expect, the SFD files are large – between 350-

400MB compared with around 50MB for a straight Raw file. Working with 50MB Raws in Photo Pro is slow so working with .X3I files isn’t fun and they do need more work. After importing into software my SFD shots lacked contrast, saturation and looked too cool compared with the X3F pictures taken at the same time. I produced similar looking results from both. Closeexaminationofcomparison shots showed that SFD does give cleaner images with less colour artefacting and noise while highlights looked better too. The benefits of SFD were clear but you do need stationary subjects otherwise you get some strange effects in areas of movement.

FromRaw

Original image