CA with the Canon 10-22 lens (on a 7D Mark II)

[Colleen Cathers]

Brian,

I was recently shooting a snow scene with dark rocks, using the setup in the subject line.  I have CA on each and every edge of the snow.   The 10-22mm is rated pretty good for CA. 

Questions I have since I have used this lens for 4-5 years now and have not had as much of an issue as I did last weekend.

1.    Is CA strictly caused by the lens or can it also be the camera body and/or camera body+lens combo

2.    In the past I  was shooting with a T2I with AV F11 or so.   Now a 7D Mark II with F16-F22.     Does Aperture make a difference?

Any other suggestions to avoid as much CA as possible?

 

Thank you,

Colleen

 

 

[Brian]

4 hours ago, Colleen Cathers said:

1.    Is CA strictly caused by the lens or can it also be the camera body and/or camera body+lens combo?

It's 100% caused by the lens. CA happens when the lens is unable to focus the all different wavelengths of light on the image sensor at the same time. As the light enters the lens, it is bent slightly, and this phenomenon is known as dispersion. Lenses typically are designed to counteract this problem, with usually the more expensive lenses having better glass yielding the best results. That said, this is not a hard and fast rule. Even $2000 lenses can suffer from CA.

CA is mostly caused by high contrast-swing situations. Tree branches against a bright sky, dark rocks against white snow, etc. Where CA happens the most is towards the edges of the lens. So the center part of the lens will have less CA, compared to the outer rim. This means subject placement is key. If you frame your scene with your subject in one of the corners, and it's a high contrast situation, you might have CA issues around the subject. Or your subject could be dead-center and be fine, but the damn tree line in the upper left corner could have all sorts of purple fringes. 

[Brian]

6 hours ago, Colleen Cathers said:

2.    In the past I  was shooting with a T2I with AV F11 or so.   Now a 7D Mark II with F16-F22.     Does Aperture make a difference?

Stopping down and using apertures between f/16 - f/22 causes something called Diffraction. This is known as Circular Aperture Diffraction in the photography world, What this does to the image, is degrade overall image quality around the edges, almost like a smudging effect. Stopping down to f/22 can makes your image "fuzzy/less sharp," especially around the edges. Diffraction doesn't add to the CA problem.

[Brian]

Any suggestions to avoid as much CA as possible?

Avoid shooting high contrast swing areas. Purchase and use the BEST lenses you can afford.

For example, think using a 16-35 f/4 instead of a 10-22. But on a crop body, that won't be very wide. So the best thing I can tell you to do, is correct CA in ACR. There are sliders that will help minimize CA.

As for the camera body, it has nothing to do with CA. It just records what it's given by the lens. In really, it has to do with the sensor and the dynamic range that it has. The 7D Mark II is newer technology and has a better sensor which records the colors better.  That results you noticing it more now than with your older body.

The CA has always been there, it's just more obvious with the new camera body.

[Colleen Cathers]

Thank you Brian!