What is your opinion of this CA?

[moikle]

Below are two photo's, one a 100% crop of the area shown in the second photo. It was taken on my M8 with my Macro Elmar-M 90mm f4 fitted with a Leica UV/IR cut filter. I am taken aback by the extent of the CA which is also difficult to fix. Your comments welcomed.

Mike

[Jamie Roberts]

It's actually pretty easy to fix. Search the forum and you'll see a demonstration of shay Stephen's purple / green fringing action for photoshop.

Or you can get it here:

Color Fringe Reducer 5.0 - Shay Stephens Photography

[moikle]

Jamie,
I appreciate there are weapons in the arsenal that I can use. My thoughts are that this is a modern lens that really does not cut the mustard in the chromatic aberration area and I am quite disappointed with it.

Mike

[jacksparrow]

I think that's not a lens but a sensor issue, but please someone correct me if I am wrong.

[Jamie Roberts]

Understood, but it's a common digital flaw with fast lenses under certain high-contrast conditions; in my experience longer faster lenses are actually a little more prone to the problem (and I'm not just talking Leica).

Your raw processing (or lack thereof) will also make a difference.

EDIT: Jack--it's a combo of both. It's not just the lens, and it's not just the sensor. Case in point: a lot of Canon's very highest end glass does this on their highest-end digital cameras, where they didn't on the film cameras However, different designed lenses do NOT do the same thing. So I used to get green and purple CA / birefringence (is what Canon support called it) from my 85 1.2L v1 and 1ds2, which is why I bought the Shay Stephens stuff to begin with. When I'd swap a Leica 80R Lux--a different design, different glass, on the same Canon camera, wayyy less artifacts.

I've seen this very, very rarely on the M8, mostly when I've blown the highlights wayyyy out (on purpose).

[wlaidlaw]

My personal take on the situation is that C1 + DNG's seem to handle this situation very well. My Zeiss 21/2.8 Biogon seems to produce CA quite badly with the M8 and I would guess that this is due to the very contrast it has. If at any point I had light going through water, I had a problem. JPEG's were close to unusable but when I processed through C1 I saw a huge improvement. This was just as I was changing from ACR to C1 and I found C1 much better on this particular aspect.

Wilson

[jacksparrow]

Thanks Jamie, always nice to learn something new, specially when it's so clearly explained. :-)
I guess that in may points these systems (lens/sensors) are at the edge of the physical possibilities, so under certain conditions (high contrast as you say) those "flaws" come to light.

[etherfarm]

Keep in mind that CA is often addressed in post-sensor processing on many cameras, and as such CA in an image isn't always exclusively a property of the lens.

As Wilson points out, RAW converters deal with CA pretty effectively. If you're getting this image quality from a JPG, well, try RAW (you don't say what the original image format was, so just offering a suggestion). You're never going to get the best image quality from any lens/camera combination if you're shooting .jpg.

On the M8, I'd go so far as to say people who shoot .jpg can't really care too much about image quality--the significant difference in quality between RAW and JPG on the M8 is readily apparent. I find .jpgs out of the M8 horrendous, but I could say that of just about all cameras I've owned.

[volkerhopf]

Originally Posted by moikle

Below are two photo's, one a 100% crop of the area shown in the second photo. It was taken on my M8 with my Macro Elmar-M 90mm f4 fitted with a Leica UV/IR cut filter. I am taken aback by the extent of the CA which is also difficult to fix. Your comments welcomed.

Mike

Hi,
If you have access to Lightroom 1.1 then there is a real easy fix just enable under "Lens corrections" DEFRINGE= All and you are alright. I tried it with your photo.
Regards
Volker

[carstenw]

Mike, don't forget that it is not only the lens, which may contribute nothing to the CA here, not only the camera, which is certainly partly responsible, but also the raw engine. Try C1LE and see how it does. I am a Lightroom user, but this is not a strong point of LR or CS2/3.

Btw, CA should have two colours on opposite sides of the lines, if I understand correctly, ie. red and green on opposite sides of the wire. The purple fringing you see here is most likely a sensor-caused artifact, combined with raw engine problems.

[adan]

1) Actually, as CA goes indigital imaging, this is rather mild. If the insulators down at the bottom of the crop were showing it, that would be something else.

2) As I often repeat, there are at least 3 sources for CA in digital pictures: lens CA; microlens-induced CA; and 'blooming' of highlights. I guess a fourth might be prismatic affects from the glass covering the sensor, as well. The first two can be indistinguishable unless one also does a comparison shot on film, and all but the first are due to the sensor, rather than a lens fault. Which is why...

3) Most (all?) RAW developing programs have color fringing correction sliders - it can happen with any shot regardless of how good the main lens is. In addition, Photoshop itself (at least from CS2) has a lens correction filter under "Distortion filters" that will correct CA, as well as fix barrel distortion and keystoned verticals.

I use Camera RAW and have presets saved for all but two of my lenses to correct the CA they always produce. A click of the mouse for "15 C/V" or "90 'cron" or "28 ASPH" and it's gone.

Only my 21 pre-ASPH and 50 'cron are so close to perfect as regards CA that I can't find anything to correct.