Jump to content
Overgaard

How to remove Purple Fringing in Noctilux photos (at overgaard.dk)

Recommended Posts

Advertisement (gone after registration)

I updated my 50mm APO article with a section about purple fringing and how to remove it in Lightroom from Noctilux and other lenses. 

 

Enjoy!

 

"What is Purple Fringing in Leica lenses?"

 

 

 

 

Share this post


Link to post
Share on other sites

What kind of contribution is this? Asking people to get out of here, luring them...

 

If it's really about helping, why not copy/pasting your story here?

Share this post


Link to post
Share on other sites

What kind of contribution is this? Asking people to get out of here, luring them...

 

If it's really about helping, why not copy/pasting your story here?

 

Presuming you are an adult, you have the assumed ability to choose whether or not to open a link. If you took that step, you would know that the content is more substantial than would easily fit in a post. If you didn't take that step, you have exercised a right that is inherent to all forum participants.

Share this post


Link to post
Share on other sites

What kind of contribution is this? Asking people to get out of here, luring them...

 

If it's really about helping, why not copy/pasting your story here?

To materials the advertising effort it has to be like this.

Share this post


Link to post
Share on other sites

Advertisement (gone after registration)

Thanks Thorsten. I appreciate your reviews and tips. And I don't mind clicking a link to read them. If that helps support your site then all the better. You provide a wealth of Leica knowledge free for the taking. 

Share this post


Link to post
Share on other sites

What kind of contribution is this? Asking people to get out of here, luring them...

 

If it's really about helping, why not copy/pasting your story here?

 

 

I put it up for free on my website. 

 

For centuries the system of commerce has worked by exchange and when offering articles for free some people buy my books, some does my workshops, some hire me to take photographs somewhere in the world. That's known as economy and that's what pays my bills so I can provide free stuff so you can click on a link and read for free.

 

By having it on my website I also maintain the rights to my material, as well as control to change and update. 

 

The forum here is a great place to find advice and share too. Some become sponsoring members to support that idea. I would strongly recommend to do that.

Share this post


Link to post
Share on other sites

Sorry, Thorsten, as much as I like your articles, I must say there are a lot of inaccuracies in your PF section:

 

- There are two main causes of PF: Longitudinal and Lateral CA. Your examples only show the first type. 

- Longitudinal CA is not dependent on the position of the frame. This type is minimized stopping down.

- Lateral CA is dependent on the position on the frame, but is usually not a problem with modern high quality lenses.

- Usually, the longer the lens, the stronger the longitudinal CA and PF at the same aperture. Just the opposite of what you say. Special APO lenses will have less CA than wider non-APO lenses, but that is just because APO lenses use special glass that is better corrected for this kind of aberration.

- Subpixel bayer artifacts will not lead to PF with modern converters. And old converters will show any type of subpixel color fringing, not only purple.

- The microlenses theory has never been proven.

- Your 50/0.95 vs 50/2 APO shots are focused differently. This makes them not comparable as far as longitudinal CA is concerned. I have never tested a 50/2 APO, and it may be better than the 50/0.95 at f/2, but your example is not proper.

- Strong backlight makes PF more evident, but does not cause it.

- Correcting PF in Lightroom is done in two different ways, depending on the nature of PF: first, enable the "Remove Chromatic Aberration" correction. This takes care of lateral CA. Then, if PF still there, use the "Defringe Correction" sliders increasing progressively up to the point longitudinal CA PF is not annoying anymore. Never crank up the slider to the end, as it may affect other colors (and that is difficult to see without careful examination of the entire image).

- The 90 APO is not very well corrected for longitudinal CA. I don't know why it could be labeled "APO" by any Leica standard.

Edited by CheshireCat

Share this post


Link to post
Share on other sites

Sorry, Thorsten, as much as I like your articles, I must say there are a lot of inaccuracies in your PF section:

 

- There are two main causes of PF: Longitudinal and Lateral CA. Your examples only show the first type. 

- Longitudinal CA is not dependent on the position of the frame. This type is minimized stopping down.

- Lateral CA is dependent on the position on the frame, but is usually not a problem with modern high quality lenses.

- Usually, the longer the lens, the stronger the longitudinal CA and PF at the same aperture. Just the opposite of what you say. Special APO lenses will have less CA than wider non-APO lenses, but that is just because APO lenses use special glass that is better corrected for this kind of aberration.

- Subpixel bayer artifacts will not lead to PF with modern converters. And old converters will show any type of subpixel color fringing, not only purple.

- The microlenses theory has never been proven.

- Your 50/0.95 vs 50/2 APO shots are focused differently. This makes them not comparable as far as longitudinal CA is concerned. I have never tested a 50/2 APO, and it may be better than the 50/0.95 at f/2, but your example is not proper.

- Strong backlight makes PF more evident, but does not cause it.

- Correcting PF in Lightroom is done in two different ways, depending on the nature of PF: first, enable the "Remove Chromatic Aberration" correction. This takes care of lateral CA. Then, if PF still there, use the "Defringe Correction" sliders increasing progressively up to the point longitudinal CA PF is not annoying anymore. Never crank up the slider to the end, as it may affect other colors (and that is difficult to see without careful examination of the entire image).

- The 90 APO is not very well corrected for longitudinal CA. I don't know why it could be labeled "APO" by any Leica standard.

 

 

 

Thank you for the insight. I know it's a large subject and if it was easy, we wouldn't see purple fringing.

 

My view on it is a little more practical. I turn the slider all the way and only once have I had changes in the picture that forced me to adjust it or make a choice between fringing and maintaining colors. Or choose other ways to deal with it that are not as simple (changing settings in color channels).

 

The simplicity of my view is that under certain conditions - that are almost predictable - I get purple fringing. And by using the LR slider I get rid of it. That's all I want.

 

I am aware that a few people at Leica has to deal with this on a much more scientific level, looking at glass types, lens designs, sensors, coatings, etc. but my ability as a user is to know when I get purple fringing; and in most cases be able to reduce or remove it.

 

I might take you up on this and see if there is a way to explain the subject in a simple way on my page one day. I think we'll continue to demand lenses without purple fringing and that the lens designers will say it's not possible. Though it has improved over the years. 

 

I had a talk on this some months ago that I haven't put on the website yet. 

 

Thanks so far for addressing it. 

Share this post


Link to post
Share on other sites

It's quite interesting that this article has come about as I've been struggling with this exact issue.  In the photo below, there was quite amount of purple fringing around the street lights at the upper left corner of the photo.  When I tried to remove using the selector and sliders it removed  the blue color within the West 34th St. sign (upper right).    With the sliders pushed all the way to the right, I removed all the purple around the lights, but I loose 100% of  the blue in West 34th St. sign.  I was able to find a happy medium, but it took some time.   It would be nice to de-fringe just for a selected area, but it seems to be applied to the entire photo.  

 

M240P / Nocti f/1 (V4-Coded)

Edited by MT0227

Share this post


Link to post
Share on other sites

It would be nice to de-fringe just for a selected area, but it seems to be applied to the entire photo.  

 

 

There is a "Defringe" setting in the Local Adjustment Brush. Tried that ?

Share this post


Link to post
Share on other sites

There is a "Defringe" setting in the Local Adjustment Brush. Tried that ?

 

I will look into this. Are we talking LR here?  I'm hardly an expert.

 

 

Or the color replacement brush in PS.

 

This would be plan B, I was looking for a one stop shop solution while in LR.  

Share this post


Link to post
Share on other sites

Is it possible to see CA fringing in a scene with the naked eye? I mean the sort which appears in front of or behind the plane of focus in high contrast.

Share this post


Link to post
Share on other sites

Is it possible to see CA fringing in a scene with the naked eye? I mean the sort which appears in front of or behind the plane of focus in high contrast.

 

No. Not with the naked eye because we don't see the 'raw' image produced by the naked eye, we see our brain's interpretation of it, and its interpretation is based on a lot of parameters including experience. So many imperfections such as CA are 'ironed out', except those which the brain cannot deal with such as out of focus areas (short/long sight). Although, even here we are sometimes able to 'interpret' stuff like text which is out of focus but 'read' because our brain can figure out what it may say from experience of such text and its surroundings. The eye and brain might be dealt with as two separate areas within the body, but put together they are extraordinarily powerful and not comparable to any imaging systems we have created so far as far as I am aware.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use. We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue., Read more about our Privacy Policy