Secrets of Digital Photography
iCrAb Filter +



Good just got better!

The iNovaFX iCrAb Filters change the size of Red and Blue color channels to reduce chromatic aberrations.

Roll your mouse over this detail to see the iCrAb990/24+ Filter at work.
This is the extreme corner of a 24-inch wide print if viewed at full size.

Two new ones now do that job better than before. Introducing the iCrAb990/24+ and iCrAb990/ZW+ iNovaFX Photoshop Action Filters.

iCrAb990/24+ is to be used on both of Nikon's own wide angle converters, the WC-E24 and WC-E63.

The iCrAb990/ZW+ is used for the slight chromatic aberration of the zoom lens when shots are made at full wide zoom.

Best when used on the 990 camera, these filters treat the process in a new way and reduce the Dread Red Spread which is an algorithmic phenomenon of the red channel.

If you wish to also eliminate the barrel distortion of the image, run this filter first before running the iBC24@W.990 or iBC63@W.990. Those filters must be run on a horizontal full size image only. You may have to rotate and enlarge the Photoshop Canvas size to 2048x1536 pixels before running the iBC filters.

That procedure step by step looks like this:

  • Use a Full Size 2048x1536 image only.
  • Rotate the shot to horizontal format if it is vertical to start with.
  • Enlarge the Photoshop Canvas of a 3:2 image to 2048x1536 pixels if starting with a 3:2 shot.
  • Run the new iCrAb iNovaFX Filter.
  • Run the appropriate iBC24@W.990 or iBC63@W.990 barrel reduction filter.
  • Crop to eliminate canvas borders and any color fringe from 3:2 originals only. (Not needed for 2048 wide originals.)
  • Rotate the shot back vertical if necessary.

950 shots:

To use the filter with a 950 camera image, blow the shot up to 2048x1536 pixels first by enlarging it by 128% exactly. Don't worry about the slightly softer detail. We'll fix that in a moment.

Do the above bullet list of things to your shot.

Notice that you don't use the iBC filters for the 950 since you are working with a larger shot at this stage.

Reduce the image to exactly 78.125% of its current size. Your image will "tighten up" and detail will become better looking by quite a bit.

When compared to the original, even though chromatic aberration and barrel distortion operations have been performed on it, the shot should look extremely close to the original in sharpness and detail. A tiny drop of Unsharp Mask may help. Radius: 0.3 pixel. Influence: 70.

The crop from the iCrAb and trim from the iBC filters will produce a smaller shot, but not by much. No need to worry about those steps for the 3:2 mode, either, so the 3rd and 6th steps won't concern you.


While the effect is most dramatic with the iCrAb990/24+ filter, both use a technique in which the red channel's radial spread of brightness is reduced. This may irritate certain shots but the general effect is a more controlled red channel with less fringing inside and outside of bright areas. If other artifacts increase, you will have to judge which version to keep. Before or After.


These filters are presented to the eBook owners only. They represent an incremental improvement over the iCrAb filters that come on the CD. Keep both, just in case the first group work better with certain images.

eBook owners have the code book in their hands to download these files. If you don't have the eBook, you can get it here.

Get out your secret decoder eBook and get ready to insert the secret password. The Download Page awaits you.