extreme color aberration

[Coast]

I recently completed 2 albums, both are the Muir Woods Redwoods, truly an enchanted forest. Each album photographed on a separate day. I only use the a6000, the 1st day I used my Rokinon 12mm f.2. I really like the lens, super sharp, lite weight - compact, very reasonable price. It's all manual so I set the a6000 on manual and adjusted accordingly each photo. It was a sunny day.

 

The 2nd day I used my Zeiss 16-70mm f.4 only. I don't care much for it. Being mostly a night shooter I bought a fast Rok 21mm f:1.4 for nights. This was a cloudy, foggy as usual day.

 

I was shocked by the amount of purple ca each shoot had and not just at the edges but in the dead center. It seemed that when branches were against blue sky the camera couldn't differentiate either on the cloudy day or the sunny day.

 

So I'm asking if anyone knows what happened, that I got the same result, under such different circumstances and if you have any shooting tips you use that could help w the color aberrations. I would like to control it during the photographing

 

You can go to my whole album by clicking on my name Coast below

 

This is a photo w the Rokinon

Muir Woods National Monument, on a sunny day, wide angle by Coast, on Flickr

 

 

This photo is w my Zeiss on the cloudy day

Cathedral Grove, Muir Woods National Monument; San Francisco Bay Area by Coast, on Flickr

 

thanks for any help and tips

[Guest all8]

Its a very difficult shot because of the dynamic range.

 

Try a smaller aperture and underexpose by a stop or two.

[Coast]

Hi thanks; the zeiss was set on intelligent which is full auto 

on the Rok I just went w what looked best in the view finder. It was really hard because looking up into the sun the setting was too bright for the sun or too dark for the  shaded, there didn't seem to be a middle ground . But I will keep a smaller aperture in mind next time and see if that is better

thanks a lot for the advice

[Gilgenberg]

like timde said, you can control the purple fringing with the aperture

 

use the magnifier in the highest setting to choose the right aperture on the points where the dynamic range is very high 

 

and you can also correct this problem in post with lightroom for example

[Guest all8]

This is a similar shot, taken with a Loxia 21mm at f4, which is 1 stop smaller than a wide open aperture, so not that much smaller, and you can see I also had a bit of trouble with the exposure. In the end I decided it looked OK as a so called "high key" image, and even at that large aperture there was no purple fringing (or at least no much).

 

https://500px.com/photo/158486755/fagus-sylvatica-beech-triplet-by-tim-rule

 

It might be a case that the Loxia 21 is corrected for fringing with certain lens elements, I know that my 50mm Loxia can cause purple and green fringing when used with larger apertures, but its a classical design, and that is part of the charm ...

[Golem]

I suspect it's just the nature of sensors or
maybe their filter packs ... maybe both.
 
This is the center of a much larger image.  

It's "only" a kit lens, but it's the short end,

it's the center, and it's 2 stops down from

wide open, so lens IQ, especially central,

would not be an issue at those settings.

 

It's from an a6000 which is a known high

performance APSC imaging machine. To

me, this is normal to digital photography.

I'm open to hearing otherwise and seeing

any samples, especially of high contrast

subject edges as included below.

  

  

Here's a 3.5mm wide area near the center

of the sensor. Focus is at about 15 ft, and

this is background at about 30 ft, causing

the back lighting to "carve" hard contrasty

edges onto the tree branches. If you see

something like this on enlarged viewing it

shouldn't be alarming.

  

  

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[Coast]

Thanks Golem; I'm coming to that same conclusion, which is amazing to me.

I guess I'm going to have to figure photoshop, unfortunately

 

thanks again forum

[Austerror]

Try f/8 on the Zeiss (not using it in Auto mode).  The CA will be reduced.

[Coast]

that's the conclusion I'm coming to, hand held it's going to raise my ISO

thanks 

[Guest Jaf-Photo]

If it's any consolation, branches against bright sky is the worst case scenario for CA. It is often used in lens testing to bring out even the smallest tendency for CA.

 

One thing you can do is to check the measurement tests for your lenses to find out which aperture setting gives the least CA. For zooms that must be cross-referenced with the focal length. Then use those lens settings.

 

Lightroom and DxO Optics have good tools for automatically or manually removing CA. CaptureOne has CA removal profiles for some lenses.

 

If you use a combination of camera settings and software you can get CA down to a level where it's negligible.

[Coast]

If it's any consolation, branches against bright sky is the worst case scenario for CA. It is often used in lens testing to bring out even the smallest tendency for CA.

 

One thing you can do is to check the measurement tests for your lenses to find out which aperture setting gives the least CA. For zooms that must be cross-referenced with the focal length. Then use those lens settings.

 

Lightroom and DxO Optics have good tools for automatically or manually removing CA. CaptureOne has CA removal profiles for some lenses.

 

If you use a combination of camera settings and software you can get CA down to a level where it's negligible.

 

Thanks for the advice, there's a lot of wisdom

I'm going to step down my f stops, which puts me into higher ISO,  and lower speed, even w my f.2, especially on cloudy, foggy days, like at the Redwoods 

I have Elements 12, so I don't know how far that gets me. But I'm going to work on it

[Guest Jaf-Photo]

Sound good. CaptureOne is free to download for Sony users. It has CA correction for most major Sony lenses and a few third party ones. You can also do unprofiled CA-correction, but it's on the weak side.

 

The funny thing about CA is that it behaves different in different lenses. Some lenses have optimal CA at f4 while some may need to go down to f8-11. In a few lenses, CA increases as you stop down. So it's always worth checking the technical measurements.

 

I write down the main optimal lens settings in my little black notebook that I keep in my camera bag. That way I can quickly reference the lens if I want optimal photos. Unfortunately, I have too many lenses or to small a mind to remember them all.