This is when all colors don't come to focus in exactly the same place. It has nothing to do with color rendition, purity or saturation, which are related to color transmission and contrast. When you have chromatic aberration you lose sharpness and may see various colors fringes on bright edges.
See a great article by Zeiss explaining the different ways different lens design tackle this here. These explanations are about the different ways one corrects color fringing, which is completely different from color rendition (transmission)
Chromatic aberration is classified by which colors are affected (primary or secondary) and in what direction (axial or lateral). Thus you talk about a kind of chromatic aberration by combining the two terms, for instance,"secondary lateral chromatic aberration."
Lateral Chromatic Aberrations are colored fringes seen on sharp, contrasty edges in the sides and corners of pictures. It's something you'll see if you enjoy photographing white lawn furniture against dark backgrounds.
This happens because lens' magnifications can vary very slightly with different colors. This means the image can be very slightly different sizes at different colors. When this happens, the colors don't line up perfectly and you'll see colored fringes towards the sides.
This is the aberration most often seen today.
It doesn't vary with aperture, although a lack of sharpness will hide it.
Axial or Longitudinal Chromatic Aberration means colors focus nearer or farther away. The problem is they come to focus at different places along the lens axis. You see this manifested as different colors coming in and out of focus at different places. This was last seen in photography with fast telephoto lenses and was cured with Nikon's ED glass.
Primary Chromatic Aberration is where the far ends of the spectrum, red and blue, focus differently. Modern lenses have this completely corrected. This is when light is spread out exactly as a prism does. Photographic lenses are corrected so the red and blue ends of the spectrum focus in the same place. That's the easier part.
Secondary Chromatic Aberration is what's left when primary chromatic aberration is corrected. Now the middle of the spectrum, green, is doing different things than the two ends, red and blue. This has never been completely corrected, with the exception of true apochromatic lenses. The lenses sold to photographers for less than a month's salary aren't really apochromatic. Nikon's ED glass likewise was invented to minimize this. Secondary chromatic aberration manifests itself as green/magenta artifacts.
The only chromatic aberration seen commonly today is secondary lateral chromatic aberration. Lay people call this "purple fringing" for the green/magenta artifacts seen at the corners of images on bright, contrasty things.
And here is a very good article on how to test lens for various issue, and how to migitate it.
However, it should be noted that this CA is a natural beheavior of light , because different color of light has different wavelengths and hence they will arrive at different location on the sensor. It is more significant for long lens... but this 135L prime lens should not have very serious CA....
btw, I am curious to know how you test the 135L in the shop ?
I normally would just concerntrate on the resolution, contrast and color when I test the lens at wide and tele end and also at widest aperature and f8.
According to expert lens picker Naka, here's the steps:
1. Put the lens box with one sharper edge pointing towards u. Shoot the tiny lines of wordings in different languages. This is to check for sharpness.
2. Shoot a black object. Then zoom in to check for dust.
3rd step I add one:
3. Shoot at the black wordings on white background of the lens box. For example, I took a few pics of the words: 85mm F1.8 EF Lens. Can see purple fringing around the edges of the black wordings.
I didn't try the 3 batteries test for focusing etc cos got CA I sian half liao...
Please correct me if the methods used are wrong or share your methods.
1. for dust, you most likely cannot see... even if you see some dust, the dust could be from the sensor instead of from the lens itself. The best way to check for dust inside a lens is to use your naked eye and see thru the lens into a bright light.
2. You are right, CA does happened mostly with a high contrast... but I am not sure if this is the correct way to test this piece of lens for CA. Perhaps, you should borrow Naka's lens to see if this purple fringing is occuring on his lens also.
Usually when i shoot, i put the camera and lens on the table and use timer to shoot at words for no.1. Make sure no vibration. This also determines whether got back/front focusing problem.
My 135L no CA that I can notice leh, later i test, sekali got