Digital Light & Color

Was doing some comparisons of resizing methods and while doing so, discovered one of my images has noticeable C.A. so have gone off on a tangent to fix this problem. I read the help menu details of how to operate the C.A. transform and, for the most part, it is understandable. However, a couple questions:

The help menu describes a marker that is placed over the centre of the input image, and then suggests to get the best C.A. correction, that this marker be positioned at the point in the image in line with the optical axis of the lens. It then talks about clicking and dragging to position the marker.

My questions are:

Isn't the centre of the input image also the optical axis of the lens? And if it is not, how do you find that axis by moving the marker around? What indicators are available to determine this spot?

Or is this manipulation only necessary if the image is cropped prior to doing the C.A. correction? And if so, again how does one determine the location of the marker?

I could not find any tutorial or other document (other than the help menu) that provides an in-depth description on this part of the operation.

Thanks,

Marv

Normally the optical axis is aligned with the center of the frame so you can just ignore the center marker. There is no easy way to figure out exactly where the optical axis intersects the image plane anyway so as you point out this feature is not very useful. By all means remove CA before cropping.

Thanks Jonathan for the info, and very quick reply.

Happy Holidays to you and all DL-C staff.

Marv