Fixing your lens imperfections

Some great new software almost hits the mark - DxO Optics Pro

Lenses are nowhere near perfect. There are all kinds of distortions and faults laying in the image that your sensor captures (some from the sensor as well). In this short article Keith reviews a package that may well become the standard in lens correction software.

Topics

What is wrong with your image?

What does the software do?

Does it work?

Is there a downside?

Summary

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Note. Keith has now written a review of the raw processing version of this software and there is now a review of version 3.5 available

What is wrong with your image?

If you have read the article on 'Why use Raw format' you will have seen example of chromatic aberration, and how I was able to 'fix' some of it using Photoshop CS RAW import. Well the false colours are not the only problem you get with a very wide angle lens, like the Canon 16-35L that I use for a lot of shots. There are also geometry problems such as pincushion and barrel distortions.

The picture below was taken of a house wall just around the corner from where I live.

Red brick wall

Brick wall Canon EOS 1Ds 16-35L at 16mm (reduced from 4064x2704)

In many pictures this distortion of straight lines and vignetting would not be too noticeable - but brick walls...

Later I'll show what DxO Optics Pro can do for this image

What does the software do?

If you measure all the distortion that a lens produces, then you should in theory be able to mathematically manipulate the image data from a camera to remove the distortion. Sounds easy, but it is not. Only recently have personal computers become powerful enough to be able to do this intensive number crunching. DxO also produce lens analysis software and are known for their accuracy. The software supports a growing number of lenses and cameras (full list). All three lenses I regularly use with my 1Ds are supported which is great.

Module for 1Ds and 16-35 lens

You get the software in modules which cover specific cameras and lenses.

There are four areas of your image that the software currently addresses:

Geometric distortions - this includes barrel and pincushion distortion, along with more complex patterns.

Vignetting - Where the brightness of your image falls off towards the edges of the picture.

Blur or Lack of sharpness - This corrects some of the blurring introduced by your lens/camera combination. It does not extract detail where there was none, it just gets the best from what there is in the image.

Lateral Chromatic Aberrations. This is a where different colours focus at slightly different places on your image sensor, giving coloured fringes. It is important to remember that some false colours are produced by other means (see the problem of water highlights in Keith's 2nd article on moving to digital)

The software is simple and intuitive to use - it gets lens information from the files EXIF data, and asks you for any additional info it might need. Just drop files onto the conversion window and off it goes - that's it.

Does it work?

In a word - YES. The changes are quite obvious. If you put your mouse over each of these images the corrected version will appear. All were shot with the 16-35 lens on my 1Ds.

35mm

21mm

16mm

Those three images show the correction of distortion and vignetting quite well, what about the chromatic aberration?

The image below shows a heater vent with a reflection of a house over the road. At the size I've had to shrink these images to show them on the web, you can hardly notice the more subtle corrections. However look at the 100% scale crop of the heater - this image is unsharpened.

Section showing increased detail and colour correction

A more realistic shot of an ugly car parked outside of my house

Notice that at 16mm focal length, the perspective is warped enough that you do not notice the distortions as quickly as with the brick wall.

Is there a downside?

From the results above you'd think I'd be using this on many of my images shot with the 16-35? Unfortunately it only (currently) works on 8 bit JPEG images. That's why the examples I've used were specially shot. I tend to shoot RAW format all the time, with lower res. JPEGs saved as well (1Ds RAW+Jpeg mode). I did try to get it to correct a JPEG made from one of my RAW pictures, unfortunately the software spotted this and would have none of it.

If your camera/lens is not covered then the software just won't work - not surprising given the amount of work needed to prepare the correction parameters for the software.

Summary

Wonderful, brilliant software, BUT of limited use to -me- for my most critical work, where it would be most useful.

That's the paradox of the current version - many of the people who would most benefit from the improvements probably can't use it. If you shoot JPEGs in your camera then this is for you. I sometimes only use JPEG, but most of the time I'm looking for the extra flexibility and quality that RAW files give me.

All is not lost however ... DxO promise a RAW processing version in the near future. To me, software like this is one more reason that I keep all my best shots in RAW format. New software and faster computers give me the option of producing even better prints from some of my favourites.

Note- there is now a full review of raw processing version of DxO

There is a time limited demo available and I would recommend that you try it out on some of your own pictures.

Other Info on this site that may be of interest

DxO Optics Pro V3.5
A review of the latest update to the DxO software. It adds many new features to the RAW conversion software that Keith regularly uses for his landscape prints.

Using a tilt and shift lens
Keith has been experimenting with using the Canon TS-E 24mm 3.5L lens on his 1Ds. Lots of images showing some of the effects you can get and why in conjunction with Photoshop it makes a good choice for some interior and architectural work (even hand held).

Focus Magic
Image processing software to fix camera shake and focus blur.

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