CA (chromatic aberations)

If I get CAs, does it mean I am using poor quality lenses, have over-exposed highlights, or is it just somethig I have to learn to live with when it comes to digitial photography?

I recently bought an *istDl, and have noticed thepurple haze around some highlights. I downloaded some filters to help the problem in Photoshop, but I was wondering about avoiding them in the first place. (lens I am using is a rikenon 50mm, f1.4, and only notice the problem in bright, outdoor photos.)

CA is a factor in cheap lenses. Even pro lenses can exhibit some, but it sounds like the lens you're using is a dog. Borrow a decent K mount lens and try agin!

I beileve rikenon was an inexpensive richoh kit lens. They may have been rebadged coca-cola bottles...I'm not sure... find a good sales clerk that'll let you slap on a better lens and fire some shots out the store window and see if that solves your problem.
Also a hoya, tiffin, or b+w multicoated circular polarizer may help you out to a fair degree.

From my experience, there are two types of CA.

1) Where the lens shifts some colours more than others. Try taking a photo of newsprint and examine in Photoshop at 200%. You may see red or purple fringing.

2) Highlight CA. Some of this is perhaps unavoidable. Two of my most expensive Pentax lenses exhibit this under very bright highlight conditions (SMC-F 100mm/f2.8 macro and the new SMC-DA 12-24mm/f4) The amount of CA varies with the quality of the lens. With the two lenses I mentioned, it's probably not visible in a print - just when you blow up to 200% in PS.

Type (1) can be fairly easily removed. Photoshop CS2 has a CA removal feature in both RAW conversion and lens correction filters. I have just started using PTLens (which is very reasonably priced) and can remove much of the CA, as well as barrel/pincushion distortion and vignetting. Definitely worth a try

Yet I have found that nothing except some colour adjustment action, or manual removal will get rid of type (2) CA (which can still remain after removing type 1). But definitely get rid of type 1 first... then do the second.

Failing that... convert the image to B&W

Matt

Moving slightly off topic (and I already mentioned this in relation to sharpness), has the move to digital increased our awareness of things like CA and the sharpness/softness? I think that now we have the ability to examine our photographs in much greater detail than most of us (amateurs anyway) wouldn't have managed by looking at a 7 x 5 print. Are we less tolerant of something that was there all along, but that we weren't able to do much about until the age of digital?

With the advent of digital photography, some problems have reduced and others have increased in importance. For example, the need to spot prints to remove blemishes has now gone (thank goodness for that) but Chromatic Abberation has taken on a more important status.

CA is basically where the colours projected by the lens onto the sensor do not all focus at the same point, caausing fringing. This wasn't much of a problem with film until longer telephotos were used, hence the introduction of low dispersion glasses. With CCDs we get CA even with ultrawides, and this may be due to the design limitations set by the sensor. It needs parallel rays of light ideally and this is called telecentric design when applied to lenses.

I have seen CA in practically all lenses some of the time, not always, but the more expensive lenses are really pretty good. The 16-45 is excellent in this respect, but not totally free from the phenomenon.

The cure? Software can re-align the colours and CS2 has the means to do this. You can also shift the position of individual channels in PS7 to reduce the effect.

Or you can clone out along edges. Sue does this sometimes, and totally removes CA, but her patience is much greater than mine.

To return to the original post, Ricoh (Rikenon) lenses are pretty good and a 50mm F1.4 is well worth hanging on to.
I do hope that metafiction isn't too disheartened by the above replies and I'm sure that he can get some excellent results from that lens - careful use of a lens hood and choice of aperture should help in bright conditions

Kimbo, you're right, I hope my attempt at humor didn't offend. They aren't really rebadged coke bottles. but there was also an attempt to add some (hopefully) useful info there too.

I thought it was funny

I had a Rikenon 35-70 (F4 I think), back in my ME Super days and was never disappointed with it. The camera came with the M50mm F2 and the Rikenon was my first zoom lens, perhaps not great but it was ok!

I was hoping someone would come to the defence of this lens. I am quite pleased with the lens in the majority of situations. Some the natural light portraits I have done are excellent. I did the above mentioned test with the newspaper, an the kit lens under those conditions (18-55) has no CA, and the Rikonen has the slightest amount. I was a little disappointed, but the prints of the portraits I have done are awesome, so I think it's a keeper. Besides, it only cost me $40 usd.