Color halos, out of focus

[erkuchera]

Hi all!

So whenever I shoot, the photos look great until I upload on the computer and view at 100%. Sometimes I get weird color halos, and every other time I just can't get crisp lines. (See photos)

I use EOS Rebel T2i. I use manual and auto focus depending on the situation, and have tried it with a multitude of settings, including automatic. It happens with all my lenses.

Any help is greatly appreciated!

Beth

[TCampbell · Accepted solution]

The color-fringing issue you see is called "chromatic aberration" and it's caused by the lens (so the good news it's not the camera.)

As light passs through glass at an angle (such as a prism) it it split into it's constituent wavelengths with blue wavelengths bending more than red and this causes color separation.  The edges of any typical lens element would do this.  But in a high end lens that corrects for it, additional lens elements are used to reverse and control the effect.

It's somewhat common to see this happen in consumer-priced lenses (where keeping costs low is a design goal.)

It might be possible to damage a lens in such a way as to mis-align the elements from the optical axis (but often that would manifest as more obvious problems such as jamming the focus and zoom capabilities... and also having non-uniform focus (one side of the image is focused and the other side is soft).   I don't really see evidence of that in this image.

You'll typically see a reddish fringe on one side of an object and a bluish fringe on the opposite edge, but it's all relative to the center axis of the lens (the middle of the image) so that if you look at a subject on the opposite side of the image it will be reversed (and in your case, it is reversed... as expected.)

Which lens were you using?

[RobertTheFat]

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Those pictures don't have much depth. When you take one that does, is everything out of focus, or just the subject you're trying to capture? If everything is blurry, it often means that the shutter speed is too slow. Or it could mean that the viewfinder is somehow out of alignment. How long have you had the camera? Has it always done this, or did it start more recently? Has the camera ever been dropped or otherwise damaged? Is the problem equally pronounced if you're using automatic or manual focus? Any further details you can supply might turn out to be helpful

[erkuchera]

Thanks Bob!

The photos I attached before were zoomed in to just under 100% on the "in-focus" area. Attaching larger versions here, but they look fine zoomed out and compressed. 

• I've owned the camera for 5 years.
• I believe it started a few years ago, but I didn't notice until recently.
• I have (regretfully) dropped my camera. Possibly around the time this started.
• Equally pronounced on auto and manual.

Other details: 

• Sometimes the autofocus doesnt work, especially in far range.
• I've lent this camera out.
• I used a telephoto lens on the color halo example.
• I could be expecting too much? Maybe this is normal?

[TCampbell · Accepted solution]

The color-fringing issue you see is called "chromatic aberration" and it's caused by the lens (so the good news it's not the camera.)

As light passs through glass at an angle (such as a prism) it it split into it's constituent wavelengths with blue wavelengths bending more than red and this causes color separation.  The edges of any typical lens element would do this.  But in a high end lens that corrects for it, additional lens elements are used to reverse and control the effect.

It's somewhat common to see this happen in consumer-priced lenses (where keeping costs low is a design goal.)

It might be possible to damage a lens in such a way as to mis-align the elements from the optical axis (but often that would manifest as more obvious problems such as jamming the focus and zoom capabilities... and also having non-uniform focus (one side of the image is focused and the other side is soft).   I don't really see evidence of that in this image.

You'll typically see a reddish fringe on one side of an object and a bluish fringe on the opposite edge, but it's all relative to the center axis of the lens (the middle of the image) so that if you look at a subject on the opposite side of the image it will be reversed (and in your case, it is reversed... as expected.)

Which lens were you using?

[diverhank]

I got the chromatic aberration on the bird but not so sure what's wrong with the leaf though...I think that is how leaves look like under magnification...

All lenses exhibit chromatic aberration to a degree.  It gets much worse when the object is highlighted by the sun.  Even really good, expensive lenses have this.  A friend of mine just scolded me for not getting rid of it in post processing in one of the pictures I posted...I was using one of Canon's best, the EF 24-70 f/2.8L II lens...and it has color fringing too, pretty bad at that.

Chromatic aberration can be filtered out in post processing even though not always perfect...

[TCampbell · Accepted solution]

On the leaf the description is that you're not getting "crisp lines".  I see on the larger view of the leaf that the upper and right sides seem focused... the left edge and bottom seems a bit soft.  

The "depth of field" governs how much will be in focus (relative to the actual focused distance).  But as you get close that depth of field gets narrower.  Depending on lens focal length, distance, and focal ratio, it can easily be just a couple of millimeters thick.  That means that if the plane of the leaf is not within the plane of focus for the camera lens, it (or at least a part of it) will go soft.

Macro photography often benefits from use of tripods to make sure the camera is exactly in the position needed, and sometimes even a focus-rail to allow for multipel images and focus stacking.  Without knowing a bit more about how the photo was taken (lens, focal length, focal ratio, focused distance, hand-held vs. tripod?, etc.  I don't see any EXIF data in this image) there isn't enough information to offer a specific reason for the softness. 

[ebiggs1]

Tim Campbell is correct. It is CA.  What lens are you using?  When you crop to 100% you are doing what is referred to as pixel level editing.  It is intended to show all the worst,... or the best.

I think you need to start saving for a better lens.  If you are really in to and like shooting birds check out the Canon EF 400mm f/5.6L USM Lens.  It works absolutely great on a Rebel for birds.  It is a unique lens and one of the best lenses made a any price.

[RobertTheFat]

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@ebiggs1 wrote:

Tim Campbell is correct. It is CA.  What lens are you using?  When you crop to 100% you are doing what is referred to as pixel level editing.  It is intended to show all the worst,... or the best.

I think you need to start saving for a better lens.  If you are really in to and like shooting birds check out the Canon EF 400mm f/5.6L USM Lens.  It works absolutely great on a Rebel for birds.  It is a unique lens and one of the best lenses made a any price.

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Beth, it's usually worth listening to Ernie in matters like this. He's owned more lenses than most people have ever seen.

[erkuchera]

Wow, thank you so much Bob, Tim, Hank and ebiggs1! You have all answered my questions plus some.

Tim, I'm sure your right about having too narrow a depth of field. I didn't realize it could be that small. Also didn't realize lens abboration can be corrected. Time to tweak my photoshop skills! Great lens recommendation. 

I can't thank you all enough!!