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David Kilpatrick | all galleries >> Sony Alpha 900 > roxburgheaisle17-35f11-17mmDRO+3.jpg
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roxburgheaisle17-35f11-17mmDRO+3.jpg
20-SEP-2008

roxburgheaisle17-35f11-17mmDRO+3.jpg

This is a DRO+3 JPEG straight out of the camera (but converted to sRGB, it was actually an aRGB shot). The next image uploaded shows a before and after, to give you an idea just how extreme the DRO processing can be. I use this subject as I have used it before, and it shows up DRO effects perfectly.

You will notice some severe posterizing in the top right corner. DRO+ is not only using an underexposed raw file (it has to in order to recover the fully lit outside scene) it is using one produced with a 17-35mm (D) Konica Minolta lens fitted. The Alpha 900 has applied sensor-shading gain (a shading map) corresponding to a 17mm focal length, which means that although the centre of the shot may be at ISO 200, the corners will be at ISO 800. Without this shading-map, all similar shots would show extreme vignetting, microlenses or not, newly designed lenses (16-35mm CZ) or not. It's a fact with all DSLRs.

When DRO+3 gets to the corners, which are still dark from remaining 'allowed' vignetting and the deep shade of the conditions, it is boosting to maybe ISO 3200 by a digital process and that results in some pretty horrible artefacts. But there's no other way, it happens in all similar re-lighting processes when encountering an extreme.

The 17-35mm lens acquits itself very well indeed on the Alpha 900. The geometry, here uncorrected, needs only a very small adjustment if any and the extent of colour fringes (again, uncorrected) small enough to be considered very good.

Sony Alpha DSLR A-900 ,17-35mm Konica Minolta f2.8-4 (D)
1/125s f/11.0 at 17.0mm iso200 with DRO Manual +3 full exif

other sizes: small medium large original
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