Advice on Summarit 35mm f/2.5

[ghealey]

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I am using a new Summarit 35mm f/2.5 wide open on my M9 - auto lens detection, ISO 160, uncompressed DNG. I was shooting midmorning on a bright, but overcast day.

 

The issue I have is the nasty CA in the leaves on the backlit trees (see attached sample shot). I do my processing in Lightroom 3, and can reduce the CA somewhat with the software CA tool, but it is still there. I am assuming it is CA as that is what it looks like to me.

 

This is dissapointing as I have observed this CA before when using the M9 with a CV 15mm Super Wide Hellar. I was unable to remove the CA then, and put it down to a CV characteristic. But now it is appearing with my new Leica glass.

 

There are several possible causes/remedies I can think of...

1 - Operator error - I am relatively new to Leica - any advice on settings, technique, etc?

2 - Avoid backlit situations with lots of high frequency detail (i.e. trees/leaves) - not really practical as I live in Singapore and the whole island is either buildings or trees

3 - Processing the DNG - I use the latest version of Lightroom 3 - I am not an expert - perhaps someone has a better workflow to remove CA. Perhaps there is a better software alternative for dealing with CA (Capture One, other)?

4 - I might be expecting too much from the Summarit 35mm and should embrace this as a characteristic? Is this lens prone to CA? Alternatively, the lens may be a lemon, and should be exchanged? It seems fine otherwise.

5 - Might be an M9 fault? or characteristic? It too seems fine otherwise.

 

I would appreciate any feedback you may have.

 

Geoff

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[hobb3]

I have the same promblem in almost every shot against a white background. I find it impossiblr to clean the images in Lightroom, at least not with my current PP knowledge. Capture One 6 is much better in that regard and removes these pirple fringes automaticaly. I would love to hear other opinions.

[thighslapper]

Some degree of this is inevitable with a white background and high contrast sharp edges.

 

See the current noctilux thread...... it's usually a mix of sensor and CA issues....

 

but .... most of the time it's not an issue unless you pixel peep or do big prints or crops. The slider controls on Aperture/Lightroom etc will only get rid of the worst......

 

In practice it's pretty easy to guess which situations are going to produce this, and I tend to bracket so that I always have a relatively underexposed version which minimises the artefacts..... you can then boost the shadows in processing to get back the detail. May be a little 'flatter' than ideal but at least you have an acceptable image.

 

In very tricky situations you can always resort to HDR..... but remember to dial out the fringing on the overexposed images before you merge them.... and there are few HDR programs that produce natural results (Oloneo Photoengine is ok) so you might end up with a mess if you are not careful.

 

Best solution is nice weather and blue skies......

[01af]

I am using a new Summarit-M 35 mm f/2.5 wide open on my M9—auto lens detection, ISO 160/23°, uncompressed DNG. I was shooting midmorning on a bright, but overcast day.

 

The issue I have is the nasty CA in the leaves on the backlit trees ...

That's no chromatic aberration but purple fringing, and it has nothing to do with lens quality. It's a sensor issue. It usually can be reduced by shooting at a smaller aperture because then the sensor will get hit by narrower light cones—this has nothing to do with lens aberrations but is pure geometry, albeit lens aberrations can add to it. The reason for the fringes always being purple (magenta) is the basic structure of the sensor's Bayer mosaic. It has twice as many green pixels as red or blue ones, and the de-mosaicing process then creates these magenta fringes which is the complementary colour to green. I once read a detailed explanation as to why this happens but I'm sorry I can't recall all the details.

 

Another effect that also will lead to purple fringes is over-exposure of the specular highlights which will 'spill over' into adjacent darker areas. Again the fringes will be mostly purple due to the fact that Bayer sensors have more green pixels than red or blue ones. This effect can be reduced by giving less exposure.

 

In real life, the two effects leading to purple fringes often will occur in conjunction and add to each other.

 

To remove the fringes in post-processing with Photoshop, add a Saturation adjustment layer to the image, set it to affect magenta tones only, and paint the desaturation effect into the relevant areas as appropriate, using a soft-edged brush. For this kind of retouche, a pen tablet comes handy but is not utterly required.