Purple outline

<p>Hi, I have been noticing purple outlining on certain spots of photos. I'm not sure, why or what causes it and how do I fix it?<br>

I'm attaching a photo that has it, for you to look at. Photo is unedited, only converted from RAW to jpg for posting.<br>

I have noticed it more with my Canon 50mm 1.4 than any other lens, but then again, for portraits, I use that lens more than any other. Everyone says how much they love that lens, but I can't say I'm completely in love, maybe, I just haven't found the sweet spot, or how to get optimal results from this len, SO IF YOU HAVE ANY ADVICE ON THAT(THE 50mm 1.4) PLEASE GIVE THAT AS WELL AS ON THE PURPLE HAZING. :)<br>

Exif for this particular photo is<br>

7D<br>

50mm f1.4<br>

f1.8<br>

1/320<br>

ISO 250</p>

<p>Please give me<br>

1. tips, thoughts, secrets, advice on getting best results with 50mm 1.4, also, if I were to trade this lens what would be a comparable, quality, price portrait lens to trade it for?<br>

and<br>

2. What the purple outline is around figure, what causes it and how do I correct it in shooting.</p>

<p>Thank you in advance!</p><div></div>

<p>I see Chromatic aberration or color fringing as they call it. It is usually seen when the light source is coming from behind the subject as it is in your photograph and the aperture is wide open or pretty close to wide open since you showed us an f/1.8. This is a typical digital camera phenomenon that is caused by the microlenses.<br /> Here is a link that explains the problem further. <a href="http://www.dpreview.com/learn/?/Glossary/Optical/chromatic_aberration_01.htm">Click Here.</a></p>

<p>I would imagine if you close the aperture down a little more say f2.8 or even 3.5 or use Sports Mode on the camera you can eliminate the problem. Further testing would need to be done in order to prove my idea.</p>

<p>Duane Loya,<br>

Do you think that my 50mm could be more prone to the fringing then say my 70-200mm 2.8? I use the 50mm most for for portraits, but sometimes use the 70-200mm, and haven't noticed it.</p>

<p>Yes, I would agree with that. The outdoor portrait may have come out a lot better with the 50mm f/1.4 at the aperture set to f/1.8 or say f/2.8, it's really the light behind the subject causing the problem. Nice shot but perhaps a better background or smaller aperture would help correct the issue for you. I haven't come up across the problem myself but my EF-S 18mm - 200mm wide open is f/3.5 an I can't get an f/2.8 on it. Again, some testing needs to be done. I feel that will correct the problem.</p>

<p>Opps sorry I forgot you shot it at f/1.8 so that is a moot point bet f/2.8 might be the next best aperture setting. It's early I am tired out. Sorry about the mistake.</p>

<p>Stopping down for future photos will indeed help. My Canon 85mm f/1.8 has a good amount of purple fringing at f/1.8 in these types of conditions. If you want to continue to use f/1.8 or for the photos you've already taken, there are a number of post-processing tools that can be used for removing or reducing the fringing. For me, I find Lightroom 4's controls to be great but certainly research other options.</p>

<p>You don't mention whether this picture was shot in RAW or JPEG straight from the camera. As others have said, stopping down will help or eliminate CA. Shooting in RAW let's you shoot at a large aperture and take care of the problem in post. I also use Lightroom 4 and it works well. </p>

<p>Oops, upon re-reading your post, I see where you do mention it being a converted RAW file. Previous comments about fixing problem in Lightroom still apply.<br>

Good Luck</p>

<p>I don't have Lightroom, I have PS CS5, can it be fixed in that? And what do you do to fix?</p>

<p>Much (or all) of it can be eliminated with Canon Digital Photo Professional, which came with your camera ;)</p>

<p>Open the RAW file, open the tool pallet, click on the "Lens" tab and then tune using the "Chromatic Aberration" field under "Lens Aberration Correction".</p>

<p>Just mentioning how you might generally get more out of that 50mm lens . . .<br>

Stopping down the EF50/1.4 to about F/2.8 for that half shot will assist in reducing the CA, others have mentioned that: - but also it will give a bit more DoF and better general Image Quality and I believe we have discussed this matter before, a few months ago.</p>

<p>So just re-iterating that point - I do not see any general requirement, for one using an aperture of F/1.8 when using a 50mm on a 7D, for that shot.<br>

Specifically: the Subject's Face and his Hands & Football are much softer than the air pockets on his jersey – the DoF for that shot appears to be about 3inches.<br>

F/2.8 would be much safer IF you wanted only the face to be in sharp focus: but F/3.5 to F/4 would be typically about what I would choose for the range from a Tight Half Shot to an Head Shot.<br>

Those smaller apertures will still provide nice bokeh and shallow DoF.</p>

<p>(Also on an entirely different subject – a reflector at or near the camera bouncing some light into his face would assist)</p>

<p>(Also, if you had a UV filter on the lens – then consider removing it for those shots when you shot into the light.)</p>

<p>E.G. –<br>

<img src="http://d6d2h4gfvy8t8.cloudfront.net/13440514-md.jpg" alt="" width="680" height="486" /><br>

EF50F/1.4 on a 20D, Available Light and Bright B/G behind lens used at F/3.5, White Card Reflector used at camera left.<br>

The image was cropped slightly from a H&S Shot.</p>

<p>WW</p>

<p> </p>

<p>Does anyone know exactly how the "Lens Aberration Adjustment" tool in DPP actually works? I ask because it may use an algorithm that is completely ineffective with purple fringing caused by the microlens array, ie, the problem under discussion here. </p>

<p>To the best of my knowledge, there are only two software methods used to minimize color fringing. The first method separately adjusts the magnification of each of the three color channels so that the images at the three component wavelengths overlay perfectly after application of this tool. This approach is quite effective when the color fringing is due to lateral/transverse chromatic aberration and is available in various RAW converters. Unfortunately, it isn't useful with longitudinal / axial CA, or with purple fringing from the microlenses.</p>

<p>The second software method sometimes offered detects high contrast edges, then desaturates specific color ranges a few pixels on either side of these edges. As far as I know, this is the only method that is effective with purple microlens fringing. The downside is that it is a heavy-handed approach when applied to either of the two forms of lens CA. When applied with sufficient strength to be useful with lens aberrations, the image's color suffers. </p>

<p>Tom M</p>

<p>See if this link will help you out. <a href="http://digital-photography-school.com/how-to-fix-chromic-aberration-in-photoshop">Click Here</a>.</p>

<p>Duane, you must not have understood my post. The link you suggested is nothing more than a manual version of what I described in my 3rd paragraph (ie, "The second software method"). Other than perhaps being a bit more tweakable, the manual version of that method provides all the same benefits and has all of the same limitations of the fully automated versions of that method, such as are provided in several software packages. </p>

<p>The purpose of my post was to caution the OP that DPP, a package recommended to the OP by a previous poster, may not provide this method, ie, the correct one to use for the "purple" fringing due to index of refraction dispersion of the plastic used for the microlenses.</p>

<p>However, one way I can see that link being of use is if the OP doesn't happen to have one of the software packages that includes this method and decides to implement that method manually.</p>

<p>Tom M</p>

 

<blockquote>

<p>"The purpose of my post was to caution the OP that DPP, a package recommended to the OP by a previous poster, may not provide this method, ie<strong><em>, the correct one to use for the "purple" fringing due to index of refraction dispersion of the plastic used for the microlenses</em></strong>."</p>

</blockquote>

<p><br />+1.<br />I am also of the opinion that DPP will not do a good job for the Purple Fringing seen in the sample.<br />In my experience the Lens Aberration Correction in DPP is quite OK for removing Lateral Chromatic Aberration, but not for Longitudinal C.A. nor for Purple Fringing.<br />But I expect it is worth a go, as there appears to be some other, lesser degree CA in the image, anyway - and to learn first hand what DPP can and cannot do.</p>

<p>In answer to Tom’s previous question: No, I do not know how DPP’s C.A. correction works. I have just experienced that it doesn’t work satisfactorily (for me), for Purple Fringing.<br />When necessary, I have Purple Fringing ‘fixed’ using Lightroom.</p>

<p>WW</p>

<p> </p>

<p>Backing up William W's observation, I just took a quick look at DPP's CA tool, and I'm also quite sure it won't work for microlens induced Purple Fringing or axial/longitudinal CA. </p>

<p>Also, re his comment that LR 4 does a good job of reducing microlens induced purple fringing and axial/longitudinal CA, below is a screen shot from that panel of the Develop module. As I described in my earlier posts, it allows you to select a couple of color ranges, and then desaturate them when they occur near high contrast edges. LR4 is particularly nice because it also has automatic reduction of (lens) transverse CA. A very good explanation of the LR4 fringe tools is here:<br>

http://blogs.adobe.com/lightroomjournal/2012/04/new-color-fringe-correction-controls.html</p>

<p>HTH,</p>

<p>Tom M</p><div></div>

<p>Just be glad that we no longer have to use the entirely manual tool for reduction of transverse CA provided in the Tiffen DFX package. As you can see from the screen shot below, it has a zillion parameters / sliders that all need to be adjusted to work well. The Adobe databases for transverse CA correction are infinitely more convenient.</p>

<p>Tom M</p><div></div>

<p>I was interested to see what people posted in this thread. As Tom says, fixing lateral chromatic aberrations is relatively easy (by independently scaling the colour channels), with the proviso that the colour filters don't just record a single wavelength and that the result will be necessarily softened. The fix is often good enough, which is why many cameras now integrate this into their JPEG processing, and many recent lenses are designed not to prioritize correcting for this aberration.<br />

<br />

Longitudinal chromatic aberration, caused by different wavelengths having different focal lengths, is harder to fix - an attempt can be made heuristically, but since the actual effect is dependent on the distance of image detail from the lens and a conventional camera does not record per-pixel depth information, a perfect automated fix is impossible. Stopping down the lens improves longitudinal chromatic aberration, since it reduces the size of the circles of confusion caused by the different wavelengths focussing either side of the focal plane; it has no effect on lateral chromatic aberration. Of course, this only helps if you don't mind changing the aperture - if you <i>want</i> the background that blurred, it's hard to do much about it.<br />

<br />

That said, longitudinal chromatic aberration is generally exhibited as green edges behind the focal plane and purple edges in front of it - most lenses are <a href="http://en.wikipedia.org/wiki/Achromat">achromats</a> and correct for two wavelengths and rely on everything between being close enough; <a href="http://en.wikipedia.org/wiki/Apochromatic_lens">apochromats</a> tend to do better, but - for fast lenses - cost more. This is pretty much the entire reason I own a 200 f/2 and use it to blur the background in preference to my 135 f/2. I don't believe anyone makes an apochromatic 50mm, which is pretty much why the only 50mm lenses I own are relatively cheap f/1.8 options; if Nikon were to produce an apochromatic equivalent to Canon's f/1.2 USM, it'd be on my shopping list.<br />

<br />

There's a chance that the fringing you're seeing is more due to UV light than visible - I'm trusting to <a href="http://en.wikipedia.org/wiki/Purple_fringing">wikipedia</a> for this, but it makes sense. Stopping down should help, but you may find a UV filter does as well - so long as it's a good, coated one that avoids adding too many of its own aberrations (and, unlike some, actually does block UV).<br />

<br />

My preferred means of fixing LoCA in Photoshop (other than buying expensive lenses that don't show the problem) has been to convert to L*a*b* colour space, deselect the luma (L) channel, then smudge the a* and b* channels with the smudge tool to pick up nearby colours. I guess the clone tool might work as well, especially for larger regions. I don't like the desaturation solution, since this (obviously) throws away valid colours at the edges. Automated options may do an acceptable job - I've only limited experience with them.</p>

<p>I know Tom. The Op also said this.</p>

<blockquote>

<p ><a href="../photodb/user?user_id=6747438">Pix All</a> , Aug 15, 2012; 03:03 p.m.</p>

</blockquote>

 

<blockquote>

<p>I don't have Lightroom, I have PS CS5, can it be fixed in that? And what do you do to fix?</p>

 

</blockquote>

<p>So I wanted to give him a solution other than the DPP and something different to try in Just plan Photoshop, I tired it out on his photograph and with a little tweaking it worked. So that is where I was coming from. Didn't want you to feel discounted so I keep it small.</p>

 

<p>Hi Tom,</p>

<blockquote>

<p>Duane, you must not have understood my post. The link you suggested is nothing more than a manual version of what I described in my 3rd paragraph (ie, "The second software method"). Other than perhaps being a bit more tweakable, the manual version of that method provides all the same benefits and has all of the same limitations of the fully automated versions of that method, such as are provided in several software packages.<br /> The purpose of my post was to caution the OP that DPP, a package recommended to the OP by a previous poster, may not provide this method, ie, the correct one to use for the "purple" fringing due to index of refraction dispersion of the plastic used for the microlenses.<br /> However, one way I can see that link being of use is if the OP doesn't happen to have one of the software packages that includes this method and decides to implement that method manually.<br /> Tom M</p>

</blockquote>

<p>My post had nothing to do with the DPP or your explanation of it. I was just putting something else for the Pix All to try out. Something he or she could do with photoshop like the question Pix All told us about not having Lightroom.</p>

<p>In the beginner's Photography forum from carefully posting here in the past, we the people answering the questions are suppose to be as accurate as we can. Op doesn't have lightroom and asked about photoshop, I could have gone into several other ways to manually corrected the purple fringe in photoshop and selected one that I was able to use to correct the purple in his or her photograph. After testing it, I put the link up for the procedure. I think a step by step is what the Original Poster is looking for as Tom Mann explained the DPP and I with a little research on fixing it with just plain old Photoshop manually. Maybe I am totally wrong just seems we are moving away from the OP's original questions and going off explaining software that the OP may not even have available to them or use.</p>

<p>Ahh. I understand. I should have stated explicitly that it probably would need to be a DIY effort in CS5, and then listed specific suitable software products immediately instead of talking about the principles behind how they worked, and not mentioning LR4 or DFX till a later post. Thanks.</p>

<p>Tom M</p>

<p>PS - For completeness, I probably should have also mentioned that there is the Layers -> Matting -> Defringe tool in CS5 (and earlier versions) for composites. Unfortunately, I've never been happy with it, at least without a lot of fiddling. </p>

<p>Thanks for all of your imput guys.<br>

Duane, my name is Hannah, so it would be 'she' not 'he' ;)<br>

So what is your opinions on the Canon 50mm 1.4?<br>

Is there another lens that you would replace it with, that's not way out of that price range?<br>

I have Canon 70-200mm 2.8 IS, I like to use, for portraits, but I don't. Sometimes too restricting, due to distance from subject you must be. I'd really like to have the 16-35, but that's out of my price range right now. ;) </p>

<blockquote>

<p>"So what is your opinions on the Canon 50mm 1.4?"</p>

</blockquote>

<p>Good lens, one of my most used lenses.</p>

<p>***</p>

<blockquote>

<p>"Is there another lens that you would replace it with, that's not way out of that price range?"</p>

</blockquote>

<p>No.<br>

<br />Even if you bought the 16 to 35, that zoom will not 'replace' the 50/1.4. If you wish to extend your cache of Primes, then a 35/1.4 or 35/2 and the 85/1.8 would fit nicely with the 50/1.4: but the 85/1.8 is perhaps a little extravagant purchase, as you already have the 70 to 200/2.8L IS. But saving for the 16 to 35/2.8 if you want that lens seems a good move.</p>

<p>WW</p>

<p> </p>

<p>Hannah - for what it's worth, I notice the defringe support has made it into ACR in the latest version of Photoshop, so if you update you should get some automated functionality. I appreciate that updating Photoshop is not a cheap option...<br />

<br />

I'd stress that there's nothing wrong with Canon's 50 f/1.4, but most people's 50mm f/1.4 lenses were basically the same design (at least until recently - Nikon updated theirs slightly, and Sigma and Leica have been a little more exotic, but none of these solves the issue at hand). The design is generally pretty good, but - like almost all fast lenses - is prone to longitudinal chromatic aberrations. This fact put me off owning any kind of f/1.4 50mm lens, but I find I can live without that focal length anyway. Stopping down, or just avoiding very bright backgrounds, are the main solutions - although I'll be interested to see how well Adobe's post-processing works.<br />

<br />

Sigma's 50mm f/1.4 is very well regarded if you're looking at alternatives, but I don't think it'll solve this particular problem - I know of no 50mm lens that does. If you want to blur the background, one option is a longer, slower lens, like the f/2.8 you mention; if you want the same field of view and small depth of field with a smaller aperture - and hopefully therefore less visible chromatic aberration - you need to go to a larger image format (e.g. shooting at f/2.8 and 80mm on a 5D, or 140mm and f/5 on a 645 camera).<br />

<br />

Sorry not to have a better solution. I'll be interested if anyone else has one.</p>