Color Haze?

[Ceberus001]

Can anybody tell me why there's always a colorful outline of objects when I take pictures using my Canon XTi? It is pretty annoying. Sometimes it's more noticeable than others, but it's always present.

[another view]

Can you post an example? Are you using any filters (UV or other)? Is this happening with only one lens, or more than one? Are your lenses clean? How do you clean your lenses?

Sorry for the Spanish Inquisition - an example will help a lot, but answers to the questions will help along with it.

[A.M.D.A.]

Sounds like "chromatic aberration" to me. This colored fringes occur more often with poorer-quality lenses - and in certain lighting situations.

I find that filters do increase CA, especially "close-ups", "tele" and "wide".

And, I also ask to please post an example photo if possible. This will help determine your problem exactly, and confirm if it is indeed CA.

[freygr]

Can anybody tell me why there's always a colorful outline of objects when I take pictures using my Canon XTi? It is pretty annoying. Sometimes it's more noticeable than others, but it's always present.

If you are using a Canon lens take it back, you got a defective lens. If you do not have a "Canon" band lens you where sold a cheap lens for you camera, go spend some money and get a good lens for you camera.

You should post a sample as it could be something other than a poor lens.

[Wild Wassa]

Canon acknowledge that their lenses have problematic performance issues when zoom lenses are used at wide angles.

Strong red/green fringing is visible even at low magnifications and that changing aperture has little to no effect. At longer focal lengths this is less of a problem.

This type of chromatic aberration can be corrected in software and most efficiently, if you are shooting RAW.

Canon state that using a standard converter 'Adobe Camera RAW' , processing with -30 Red/Cyan and +30 Blue/Yellow will effectively eliminate chromatic aberration.

Using Canon's 'Digital Photo Pro' software, hopefully which came with your camera, Canon have added lens aberration correction support. This allows RAW shooters (in particular) to elliminate chromatic aberration, correct unwanted fall off (peripheral illumination) correct geometric distortions (like barrel distortion) and fix colour blur (axial chromatic aberration).

DDP's aberration corrections use specific profiles for the different lenses. It is relatively simple, and takes little effort or skill to tweak the functions.

I notice that many digital photographers are turning their images into a square format nowadays ... because a camera lens can out-perform the camera's sensor? ... or they haven't read their manuals?

Warren.

[Frog]

I don't see it in your gallery photos.

[Wild Wassa]

Frog if you look at Ceberus' image titled 'Jones_Lake_RAW_079', you can see the magenta fringing on the tree trunk on the far left.

Chromatic aberration is most noticable at the periphery of an image or anywhere within an image when the lateral brightness contrast between objects is high.

In the worst case scenario, when exposures that display various chromatic aberrations are tone mapped, the aberrations themselves are enhanced to going right off the dial, as in the first example below.

The first image displays bad chromatic aberration made worse after tone mapping. The 2nd and 3rd images are enlarged areas from image 1. The final image has had the majority of aberrations corrected. I don't have a corrected version of image 1. The same lens and focal lengths were used in both the shots.





.. ..





Warren.

[Wild Wassa]

"I tried adjusting the chromatic aberration using just lightroom (my usual editor) and I noticed it helped. It didn't fix the problem completely but I figure a lot of it was just because I did a lot of editing on the selected image." - Cerberus

One last question. The fringe is still there, but is for the most part colorless. Is there any good way to get rid of the fringe?" - Cerberus.

Cerberus, If you look at the RH stanchion of the boat hoist, in the bottom image, there is still the 'magenta/green separation' (which is Canon's term), which is only one pixel wide. Canon state, that the software correction fixes the majority of the fringing.

If the magenta/green separation is still noticeable after correction then I'll manually cut it back if the image is important ... but reduced to only one pixel wide, if adequately hidden, I find acceptable.

I'll do a test in a few days, most likely next Monday (Sunday US), using a a Tamron LD Zoom (very affordable) and a Canon EFS zoom (somewhat affordable) and a Canon L series zoom (which is not at all affordable) and look at the magenta/green separation issues between the lenses. It is something I've been meaning to do for a while.

I'll post the results on this thread.

Warren.

[Wild Wassa]

I've done the lens tests but I'm going to re shoot it. I didn't photograph enough detail and contrast at the periphery of the images, where problems will be most evident and I didn't cover a broad enough range of f-stops to show the brightness fall off. Doing a simple lens test wasn't as simple as I thought.

Warren.

[Kajuah]

If you are using a Canon lens take it back, you got a defective lens. If you do not have a "Canon" band lens you where sold a cheap lens for you camera, go spend some money and get a good lens for you camera.

All lenses have CA, whether it noticeable or not, even the 70-200 2.8 L has CA wide open. It isn't a defective problem and you shouldn't take your lens back because of it, there's lots and lots of remedies to CA, some specifically designed and some crude. Sometimes it's user error - shooting into the sun or towards a heavy, orange light source causes very prominent CA.

You would need a lens like the 400 mm 2.8 L stopped down to 5.6 not to see CA even a little bit.

I strongly advise investing in photoshop for their sponge tool to eliminate CA - thats what I do, and it works brilliantly !

To me the photos don't look very CA'd, it's barely noticeable and in areas nobody would be looking necessarily, anyway, I wouldn't have been able to see it if the zooms weren't available