85mm f1.8 Purple/Green Fringing and/or Chromatic Aberration?

[littlebill]

<p>Hey all, I just went out and took a set of foliage photos up in my hometown

with the EF 85mm f1.8 lens. Took some lovely photographs of the leaves with the

lens wide open at 1.8 and I'm seeing some annoying purple/green fringing. Is

there something I'm doing wrong, or are there ways to correct this?</p>

 

<p>I'm shooting with a Canon 40D fully manual. Here's an example of the shot:</p>

 

<p><a href=" title="Photo

Sharing"><img

src="http://farm3.static.flickr.com/2111/1565753405_a28985cc7e.jpg" width="500"

height="334" border="0" alt="Maple Tree #1" /></a></p>

 

<p>Thanks!<br />

Bill</p>

[jason_hall4]

Nothing you are doing wrong. Problem this lens has with high lights at times. mine does the same. Usually repaired in post prosting with lens correction feature. That is where it would be done in lightroom. What application are you useing? DPP?

 

Don't dispair, I just had to fix some blue fringing on a 70-200 f2.8 IS from a shot this week end. Out of 250+ only one needed it. It was along the edge of a white shirt in a rather high key shot.

 

Jason

[littlebill]

Jason, I tried to do some lens correction in Photoshop's RAW editor with zero luck. What's DPP?

[gdanmitchell]

I assume we're looking at a 100% crop? (If that is the entire frame, there is definitely

something else going on!)

 

Some fringing is common with many excellent lenses, especially in the corners and

especially when dark and very bright subjects with fine outlines (e.g. - branches and

leaves against sky) are combined.

 

ACR and/or PS will usually do a good job of minimizing the issue if it is even visible in the

print at normal sizes. In extreme cases you can play around with saturation levels at the

borders.

 

Dan

[littlebill]

Dan, that's the entire frame, not a 100% crop. Yeah, I mean, I could go and edit out most of it in CS3... but I don't want to have to.

[howard_slavitt2]

DXO Optics pro automatically corrects for chromatic aberrations based on each specific lens and camera. It does a fantastic job. This is a problem with almost every Canon lens (I have mostly "L" lenses), especially the closer they are to wide open. It depends a lot on the lighting, backlighting with strong contrast between light and dark, makes these kinds of aberrations more likely, all the more so with the lens wide open. Lightroom does a very good job for correcting CA, but not as good as DXO Optics Pro.

[bobatkins]

It's not really CA in the normal sense and it's not the highlight related purple fringing. You['re seeing colors in the defocused areas, not in the in focus areas. That's more likely to be something like spherochromatism, a chromatic compenent of spherical aberration.

 

You may see one color in objects in front of the focal plane and a different color in those behind it. Look to me like you're seeing purple in front and green behind.

 

Lenses are corrected for minumum CA at focus, but the out of focus areas may show show these effects, particularly at wide apertures.

 

There's no way to automatically correct for this in Photoshop, DxO or any other image editor. You can try selectively desaturating the specific colors you see. Otherwise, just take it as an "artistic effect".

[PuppyDigs]

I find this particular artifact much more noticeable on my 40D than 5D, 20D or 10D. I

thought maybe increased density of pixels might have something to do with it.

[gerrymorgan]

I've seen similar problems with my 85mm f/1.8 if I use it wide open. The problem goes away when I stop down a little. Even using it at f/2 makes a big difference.

[gdanmitchell]

The whole frame - yikes!

 

I wonder if you managed to blow out the red channel in a shot that otherwise looked like

a good exposure? I find this is a problem with autumn leaves (e.g. - the aspens I shot last

week) and sometimes with saturated flower colors. (Ever try to shoot a California Golden

Poppy? ;-)

 

Sometimes I find that I must underexpose such shots in order to handle the intense color

in one channel.

[bobatkins]

Can't think of any technical reason why this should differ on the 40D. Spherochramatism (as opposed to the dreaded "purple finging") is not sensor related and is spread out over many pixels, so pixel density (and nature) should have no appreciable effect on it.

[bobatkins]

"...I've seen similar problems with my 85mm f/1.8 if I use it wide open. The problem goes away when I stop down a little..."

 

Very characteristic of spherochromatism. You see it in the out of focus areas with a lot of fast lenses used wide open.

[littlebill]

The orange leaf was the point of focus. It was as close as the lens could focus (not far away) -- I wonder if the focus point could've affected it. Other photos in the series -- which can be found if you click the image above -- don't exhibit the same spherochramatism or fringing or CA or whatever it is.

[ellis_vener_photography]

try the defringe settings in ACR and in Lightroom v1.2

[jason_hall4]

BTW, DPP stands for "Digital Photo Pro". It is the editing software that come with the canon DSLR. I am almost positive it has lens correction ability. Assuming you have no other software like ACR or Lightroom.

 

Jason

[james_taylor11]

"There's no way to automatically correct for this in Photoshop, DxO or any other image editor"

 

 

Thanks!

 

I have been wondering why I could not get this to work in Photoshop or Lightroom. I keep hearing it is an easy fix; I thought I was just a loser in Photoshop (well, I probably am a loser in Photoshop, but that?s beside the point). I get this with my 85 1.2 and my 34 1.4 wide open.

 

James

[bobatkins]

"I get this with my 85 1.2 and my 34 1.4 wide open"

 

I'm not surprised. Those are the lenses I'd expect it from. Propbbaly the 50/1.2 as well.

 

You can sort of correct it by desaturating the specific colors, as shown in the "corrected" example below:<div></div>

[lester_wareham]

"You can sort of correct it by desaturating the specific colors, as shown in the "corrected" example below"

 

As an extension you can mask the desaturation effect to the fringing area, making the mask using select on colour, fill and then add a bit of Gaussian blur.

 

I think I have seen this is the 50/1.4 and 28/1.8 also when wide open but not quite this strong.

 

I did not realise it was a separate mechanism to common CA. Thanks Bob, I looked it up in "Smith" and even understood it.

[jason_hall4]

Same here, Thanks Bob!

 

Jason