What are these purple spots

broah · 04-09-2012, 09:03 PM

The lens I used for this shot was a tamron 70-300mm which I used on my K-r all the time. Are these purple spots the lens or the camera, and it's on a lot of my photos now? And why does this happen on the K-5 but i've never seen this happen to me in 2 years using the k-r?

Last edited by broah; 06-20-2013 at 02:06 PM.

stevebrot · 04-09-2012, 09:20 PM

Those are specular highlights. See the outline of the iris diaphragm blades on the one to the left? The purple color might be longitudinal chromatic aberration (LoCA) or it may be what is called Purple Fringing (PF). PF is a semi-mythical phenomenon that seems to be the result of an interaction between certain lenses and some digital sensors. It was very prevalent in the early days of digital to the extent that every good camera review included a section on resistance to PF. Film will show CA, but PF is completely absent. Either way, the best way to deal with it is in PP. Many tools include features to minimize fringing or remove CA.

Steve

broah · 04-09-2012, 09:25 PM

Thanks for the very fast reply. It just seems strange to me that this never showed up k-r. Oh and a slight correction...I only had my k-r for 1 year not 2!

Philoslothical · 04-09-2012, 09:38 PM

That Tamron has a reputation for having horrible CA problems, so it's not surprising at all that it shows up in a shot like this. It's more surprising that you haven't noticed it sooner. If you review some of your older shots and look for high contrast areas that are slightly out of focus (tree branches bring the issue out especially easily), you'll likely find some signs of it.

It's not too hard to fix in post processing. There are a few ways to go about it, a quick search will turn up all you need.

04-09-2012, 09:03 PM	#1
broah Forum Member Join Date: Feb 2011 Posts: 66	What are these purple spots The lens I used for this shot was a tamron 70-300mm which I used on my K-r all the time. Are these purple spots the lens or the camera, and it's on a lot of my photos now? And why does this happen on the K-5 but i've never seen this happen to me in 2 years using the k-r? Last edited by broah; 06-20-2013 at 02:06 PM.

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04-09-2012, 09:20 PM	#2
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Those are specular highlights. See the outline of the iris diaphragm blades on the one to the left? The purple color might be longitudinal chromatic aberration (LoCA) or it may be what is called Purple Fringing (PF). PF is a semi-mythical phenomenon that seems to be the result of an interaction between certain lenses and some digital sensors. It was very prevalent in the early days of digital to the extent that every good camera review included a section on resistance to PF. Film will show CA, but PF is completely absent. Either way, the best way to deal with it is in PP. Many tools include features to minimize fringing or remove CA. Steve

04-09-2012, 09:25 PM	#3
broah Forum Member Join Date: Feb 2011 Posts: 66 Original Poster	Thanks for the very fast reply. It just seems strange to me that this never showed up k-r. Oh and a slight correction...I only had my k-r for 1 year not 2!

04-09-2012, 09:38 PM	#4
Philoslothical Veteran Member Join Date: May 2011 Posts: 1,889	That Tamron has a reputation for having horrible CA problems, so it's not surprising at all that it shows up in a shot like this. It's more surprising that you haven't noticed it sooner. If you review some of your older shots and look for high contrast areas that are slightly out of focus (tree branches bring the issue out especially easily), you'll likely find some signs of it. It's not too hard to fix in post processing. There are a few ways to go about it, a quick search will turn up all you need.