What causes this bluish tint and other anomalies in this image?

Question

I bought a Tamron CF Macro 28-70mm 3.5-4.5 lens on eBay for $35 AUD plus postage - cheap enough to give it a go and see what it's like.

I took a range of photos with my Sony NEX-C3 to get a feel for it on the weekend, and noticed this strange glow around white and bright colours. For example:

Note the bike's water bottle, the frame under the seat, behind the cyclist's head, and the shoulder of the white t-shirt to the left. They are all surrounded by a bright bluish haze, some kind of distortion.

What causes this? The lens was at widest or very wide aperture - is there simply too much light coming through to the sensor?

Note also the distortion in the trees behind the bicycle seat - is this just a low quality lens? Or is this because it's a macro lens, and not intended for this type of shot?

Answer 1

These are known as Chromatic Aberrations or Colour Fringing. These predominantly occur around areas with high contrast such as sharp edges in photographs or around the white water bottle and dark background in your case.

A wider apeture can affect the lenses sensitivity to aberrations although certain lenses can see this "effect" vary depending on focal lengh and this is more often caused by very slight imperfections in a lens.

Don't worry, even more expensive lenses can suffer from this anomally. The lens surface has varying levels of maginification across its surface so you may notice that this anomally is more prominent toward the edges of the lens/photo.

These can be corrected very successully with software (Such as Adobe Lightroom/Photoshop) and overall should not pose much of a problem except for slight reduced sharpness around high contrast edges. 35AUD was a great buy!

Further reading : http://www.dpreview.com/learn/?/Glossary/Optical/chromatic_aberration_01.htm

How to correct/prevent the problem: http://www.tutorial9.net/tutorials/photography-tutorials/correcting-and-preventing-chromatic-aberration/