Maze artifacts

Category : Photography March 13, 2012

maze patterns d40Not as cool as it sounds. I found this problem with a set of RAW images I took with a Nikon D40 during a recent studio portrait shoot. There was a nasty herringbone/moire pattern effect displaying on the screen of the camera as I was shooting, also present in the RAW images when I brought them into Aperture 3.2.2, and on closer inspection there was a maze-like pattern in the pixels. The problem was being caused by an error in the way the RAW data was being demosaiced – can’t currently be fixed in Aperture, Lightroom, or Adobe Camera RAW. However I used the excellent open source app Cornerfix and followed these instructions to adjust the BayerGreenSplit value and batch save the images as DNG files. The results look fine in ACR, but the images are still broken in Aperture – I’m presuming it overrides or ignores the BayerGreenSplit value in the EXIF data. The only Aperture-friendly option I’ve found at this point is to fully process the DNGs using ACR, export as TIFs, then import into Aperture. Sadly this means no RAW control over the images in Aperture but at least I can re-process them in ACR if I need to. Massive thanks to Sandy McGuffog at Chromasoft.

HDRI photography – stained glass window

Category : Photography November 15, 2011

Bacon's College stained glass window (photo composite)I needed to photograph an image of this stained glass installation which was to be used for a Christmas card. The three panels are backlit by three vertical fluorescent tubes and covered by a protective plastic screen. I found I couldn’t get a decent shot of it despite trying a range of lenses and settings. The fluorescent tubes were prominently visible in the shots, and the more richly coloured segments let through far less light than the brighter ones, and looked dull.

To compensate, I mounted a Nikon D5000 with a Nikkor 50mm 1.8 on a tripod, and took three RAW shots bracketed 1EV apart. I combined the images in Photoshop CS5 using Automate > Merge to HDR Pro and spent some time tweaking the plugin’s settings to create an image which gave a more equal prominence to the colours, while reducing the highlighting caused by the flouro tubes. I used Photoshop’s Lens Correction filter to remove some slight barreling at the edges, and Curves to tweak the overall contrast.

Bacon's College stained glass window (original photos)