Chromatic aberration at the wide angle end of zoom lenses.

[mxbuck]

I have a Fuji S9500 which has a fixed zoom lens on it: 6.2mm to 66.7mm physical f.l., equivalent to 28mm-300mm on a regular 135 format cam. It has a macro capability and a super macro setting at the 6.2mm f.l.

So far I've been happy with this cam and its lens capability. Until I got on Yaketti and started getting more rejections due to chromatic aberration. This was so bad that I couldn't fix it with at least 3 different software solutions, including my own channel registration scripts. Finally I looked at the Fujicolor User Forum and lo and behold my worst fears were substantiated. That is that the Fuji's all purpose zoom did indeed suffer from bad chromatic aberration at the wide angle range. The article also said that this was a common problem in these kind of all purpose lenses. From a design perspective, I can understand that its nigh impossible to make a lens perfect at all of its range - there's bound to be compromises.

 You'll often see the effect - a strong blue aura - around very sharp edges that are backlit. Typically if the edge contrast is very strong you'll get the blue cast. It doesn't seem to be a channel mis-registration otherwise software solutions would have worked. It may be an edge diffraction problem because its most predominant at strong contrasting edges.


Which all means... I need to upgrade if I want to stay in this.  Either that or shoot more carefully at -1,-2 EV lower to suppress edge blooming.

Any ideas for a cheap fix or do I trade my cam in for something better?

[JamesC]

Max, as discussed in the macro thread the only solution I came up with was the replace colour command in Elements. You use an eyedropper tool to pick the offending colour and use a 'fuzziness' slider to widen or narrow the tolerance of the selection. Three other sliders appear - hue, saturation and lightness. Depending on the image you can adjust these to either just desaturate the colour, change its hue to blend in with the rest of the image or darken/lighten it. It made a couple of unuseable shots useable. CS must have something similar but I don't own it so can't say.

[hardingbr]

Hi Max,
Any lens is capable of chromatic aberration.  I even get it sometimes with my best prime lenses.  But I believe it is much more pronounced on zoom lenses and even more so on the small lenses on P&S cameras.  My understanding is that one of the factors in the high priced lenses is that they employ exotic crystaline filters to minimise the CA effect. It is much more difficult to position these on a zoom lens.  I am not familiar with your camera but lens hoods (even home-made hoods) can decrease the CA effect as part of the problem that causes CA is light coming in at all kinds of angles from the sides striking the front glass of the lens.  With my old Kodak P&S camera I could screw in length multiplying lenses to the front of the built in lens (i.e. 1.4X, 1.7X, 2X and 3X).  The bigger the multiplication factor the worse the CA became. I could not take a photo of a swan or an egret. Using a lens hood helped a lot, but eventually the Kodak had to go.  Software fixes such as the Photoshop plug-in filter by Darla can darken the blues and magentas to a certain degree, but a better lens and careful attention to the direction of the light source is the best way to go. Hope that helps.

[mxbuck]

Yes it does. I'll try and heed that advice. As for software solutions, they only work if the problem is limited to a small number of visible areas. In some of my tree shots, every little twig exhibited the effect, so a manual fix would be impossibly tedious.

The lens hood on my cam is inadequate, I'll have to get another one.

Thanks

[hardingbr]

Yes Max,
I completely forgot about the smaller sensor size in these cameras, which also partly answers some of my questions.  I believe it was Syman that referred to more pixels on the same physical size sensor = more noise.  The XT is an 8mp and the Xsi is a 12mp.  The 5D is also a 12mp but the sensor is physically larger. 
About P&S cameras.  I recommend that one carries a P&S in their pockets to catch the candid shots that one would miss wit the bigger cameras.  I have posted a number of photos taken with my Panasonic Lumix 7mp P&S on various sites and have been accepted with no problems.  The biggest obstacle to P&S cameras is that they don't give me the RAW option.  So, if the JPG image is not exposed perfectly, there is not much I can do to recover the image.