Is this chromatic aberration?

[montreal]

Hello everyone,

I thought chromatic aberration was "supposed" to be purple or cyan. In this case (see picture and crop) it looks more red. That's due to the lense and not the sensor right? It was taken with the kit lense.

Here is the exif:
Tv( Shutter Speed )
1/400
Av( Aperture Value )
13
Metering Mode
Evaluative
Exposure Compensation
0
ISO Speed
200
Lens
18.0 - 55.0 mm
Focal Length
18.0 mm

PS: I do realize that I cropped a tiny area of the pic and that I shouldn't expect the image to be perfect at that level. I just want to know what causes the situation.

[VanceW]

Yes, that's CA.

And yes, from my understanding, it's the lens that causes it.

[DavidW]

The first attempt to cancel (lateral or, as it's called by some, longitudinal) chromatic aberration in a lens should remove almost the entirety of the red/blue focus error. That leaves a secondary chromatic aberration, which is because the error left by the primary correction is green on one side, and red + blue = magenta on the other. This secondary chromatic aberration is what's often called "purple fringing". Correcting secondary chromatic aberration is difficult - it needs expensive elements made of things like UD glass and fluorite to stand the best chance.

In this case, I doubt that even the kit lens is behaving so badly as to show significant primary CA. More than likely, it's secondary CA, but with so little blue light around that that the magenta fringe you're expecting is red. Checking in Photoshop, the surrounding pixels all seem to have B less than half the value of R.



David

[montreal]

Thank you for your answers. David, that's the best description of the problem I read so far!
:)