March 24, 2011 4 Comments
Zoom lenses covering large zoom ranges often compromise image quality in various ways – but almost all show some degree of chromatic aberration. Especially zoom lenses going ultra wide have a tendency to show lots of chromatic aberration in the wide end of the zoom range.
The Lens Tool in Capture One Pro 6 can automatically fix chromatic aberration in any RAW file by analyzing the content of the image. This ensures the best possible correction customized for your images compared to corrections based on a few lenses in a lab.
With tool presets for the Lens Tool, you can create presets for your own lenses. Lens Tool presets work very well even if your capture conditions are not 100% identical.
The two pictures above show a 200 % zoom of the left side of a picture which has been shot with a prosumer zoom lens at its widest zoom range. The left image shows a severe amount of chromatic aberration with lots of magenta and green colors along all vertical structures in the image. This level of chromatic aberration is quite disturbing and should be fixed. To the right, you see the same area after it has been fixed in the Lens Tool in Capture One Pro 6. All the false colors have been removed and the image looks natural.
Create your own presets to deal with chromatic aberration
To fix a problem with chromatic aberration, open the Lens Correction Tool found in the Lens Tool tab. Under the drop down menu for chromatic aberration select analyze. After a few seconds, a correction based on the result from the analysis will be applied. If you have zoomed into an area of the image with severe chromatic aberration, you will immediately see the fantastic effect of the tool.
When photographing landscapes with wide primes, I usually shoot at f5.6-f10. With the lenses I use, I find that the amount of chromatic aberration is practically constant in that f-stop range which means that you can make presets that works perfectly.
When using zoom lenses, the amount of chromatic aberration is highly dependent on the zoom rate (focal length) which makes it more difficult to use presets. Nevertheless, I find them quite useful. For my carry-around zoom lens, I find that I only need to fix chromatic aberration for the widest end. I have made three presets: one for 17mm, one for 20mm and one for 23mm.
The benefit of using a well-made preset is that you can correct a series of shoots very fast by copying and pasting the correction from the preset to a selection of images. Remember that the Search and Filters functionality in Capture One Pro 6 can help you find all shots made with a specific lens and focal length.
When selecting an image for making a preset, you should select an image which has been shot at your typical shooting f stop and focus distance. It is also important that your target image contains structures all the way from the center to the edges of the image. If you plan to shoot an image for making a good preset, consider turning your camera to insure good coverage from corner to corner like in the image below.
Often you will see that zoom lenses with large zoom ranges also suffer from barrel distortion and some sharpness fall-off. When making your presets, you can off cause add these types of corrections to your preset.