Bokeh Artifacts After RAW Convers

ddjchemist · 03-11-2012, 04:51 PM

I was taking some pictures with my new K-5 and 135mm f/2.5 SMC lens (one with 6 elements) and I noticed some wierd bokeh artifacts in some of my images. These artifacts are not present in the RAW (PEF) image. They come up after converting the images from PEF to JPEG using Lightroom 3.6 (64-bit). Does anyone have an idea what is going on? I am sure that I might just need to change some setting in Lightroom. Any help will be highly appreciated.
Below is an example.

Attached Images

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Last edited by ddjchemist; 03-11-2012 at 04:57 PM.

jezza323 · 03-11-2012, 05:16 PM

which bit is the artifact?

ddjchemist · 03-11-2012, 05:27 PM

Can you notice wave-like lines in the background?

tim60 · 03-11-2012, 05:39 PM

There is also a sharp halo around the chair in the background. Try using much less compression (i.e. the biggest file size jpg) that the processor can make. Do not post the image, but let us know the result by describing it.

I suspect that this is a compression artefact caused by converting a large RAW image to such a small file, and is inherent in the mathematics of jpg compression. The RAW image is a sampled image of the 2D space - and represents it according to well understood rules, such as the Nyquist sampling criterion (most commonly impactingthe sampling rate in audio applications, but theoretically of general applicability to sampling any analog information.) Then there is a second sampling like process of the jpg compression of the RAW.

Personally, I do not like jpg. As a compressed file format it is very sensitive to any corruption of the file, whereas a lossless format makes a bit error only affect one pixel, not the whole image. Sometime I might share some horrendous jpg artefacts arising from a p&s camera which was native jpg and must have got corrupted with transfers of files between discs.

I like to use my 50" TV as a picture frame (inflicts my pictures on my visitors, but without the painful connotations of the old 35mm slide night). It frustrates me that the only file format supported by my TV is jpg, why not TIFF or BMP or some other pixel by pixel format?

ddjchemist · 03-11-2012, 06:01 PM

Hi Tim,

I think I found where the problem is. I processed the images with Lightroom 3.6 (64-bit), but used another 32-bit software to view and resize my images. Now, if I view my images with a 64-bit software, I don't see the artifacts.

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03-11-2012, 05:16 PM	#2
jezza323 Veteran Member Join Date: Jan 2009 Location: Brisbane Photos: Gallery Posts: 1,421	which bit is the artifact?

03-11-2012, 05:27 PM	#3
ddjchemist Senior Member Join Date: Jul 2008 Location: Boulder, CO Posts: 156 Original Poster	Can you notice wave-like lines in the background?

03-11-2012, 05:39 PM	#4
tim60 Pentaxian Join Date: Apr 2011 Photos: Albums Posts: 8,756	There is also a sharp halo around the chair in the background. Try using much less compression (i.e. the biggest file size jpg) that the processor can make. Do not post the image, but let us know the result by describing it. I suspect that this is a compression artefact caused by converting a large RAW image to such a small file, and is inherent in the mathematics of jpg compression. The RAW image is a sampled image of the 2D space - and represents it according to well understood rules, such as the Nyquist sampling criterion (most commonly impactingthe sampling rate in audio applications, but theoretically of general applicability to sampling any analog information.) Then there is a second sampling like process of the jpg compression of the RAW. Personally, I do not like jpg. As a compressed file format it is very sensitive to any corruption of the file, whereas a lossless format makes a bit error only affect one pixel, not the whole image. Sometime I might share some horrendous jpg artefacts arising from a p&s camera which was native jpg and must have got corrupted with transfers of files between discs. I like to use my 50" TV as a picture frame (inflicts my pictures on my visitors, but without the painful connotations of the old 35mm slide night). It frustrates me that the only file format supported by my TV is jpg, why not TIFF or BMP or some other pixel by pixel format?

03-11-2012, 06:01 PM	#5
ddjchemist Senior Member Join Date: Jul 2008 Location: Boulder, CO Posts: 156 Original Poster	Hi Tim, I think I found where the problem is. I processed the images with Lightroom 3.6 (64-bit), but used another 32-bit software to view and resize my images. Now, if I view my images with a 64-bit software, I don't see the artifacts.