C.A. in 18-55 kit lens

[dansellbuddy]

i went out shooting this last weekend, and shot a few trees with exposure times in the few second range with an ap. in the 8-11 range, iso 100 on a 20d. the pics seemed fine on cam, but i loaded them up last night on my laptop and saw some of the worst chromatic aberration i've ever seen. is CA dependant on shutter speed, aperature, focal length, or is it just poor lens engineering typical of a kit lens?

sorry, but don't have any pics here to upload right now.

[Jon]

At a guess you're referring to purple fringing around the dark leaves against the bright (in tyhe pic.) sky. Those are prime conditions for purple fringing, which is in large part a sensor issue (light spilling over the edges).

[Tee Why]

It's due to the optics and the sensor. If you don't like the CA, then you have to consider either getting rid of them digitally and/or consider a different lens with less CA.

[dansellbuddy]

thanks for the replies. i wasn't sure if it was purely lens, and hadn't even thought of the sensor, or if it were related to cam settings, which apparently isn't the case. thanks guys.

[Tsmith]

CA is really the biggest disadvantage of this Lens _ otherwise looking past the build quality its relatively a bargain.

[foxbat]

It's caused by dispersion in the elements. Even the most expensive lenses will do it if you try hard enough. The problem with the cheap lenses is that they do it rather too often in seemingly ordinary situations. Lens designers attempt to correct for it by using back-to-back lens elements (APO doublets) and/or glass made from exotic materials such as flourite. Problem is, they're expensive.

Chromatic aberration caused by lenses and how to correct it is a well documented topic. I've never heard of CA caused by a sensor and would like to see some scientific write-ups if anyone's got any. Or is this just hearsay?

[dansellbuddy]

a little off topic, but how is the 50mm 1.8 on CA?

[MichelleK]

will someone post a picture (and point out) what CA is??

michelle k

[MisterJP]

Some CA in a shot I took with my lens kit at Glacier Nat'l Park. Very noticable purple "glow" around the tree branches (blown up to show the CA better):

[MichelleK]

aaahhh...I see what it is now...Thanks

Michelle K

[Tee Why]

As for the 50mm f1.8, I use the lens once in a while and haven't seen much CA, then again, I don't do landscape shots that might show CA with the 50mm either.

As for decreasing CA, I thought if you stop up on the aperature from f8-16ish range rather than wide open or stopped all the way down, you can decrease the CA, but according to Bob Atkins article, it doesn't help.
here, take a look
http://bobatkins.com/photography/reviews/18-55d.html

[eljustino]

I took the 18-55 to France on holiday and used it heavily, before deciding to switch to the Sigma 17-50.

In the end though the 18-55 seems capable of better "critical focus" and it's very good in many ways. But it does definitely have this chromatic aberration issue for me as well.