Digital Lens Optimiser (DLO) improves picture quality

The latest version of Canon’s Digital Photo Professional software v.3.11.26 includes Digital Lens Optimiser (DLO) on the lens tab in the tools panel.

DLO goes much further than the peripheral illumination aka vignetting, chromatic aberration, colour blur and distortion settings found in the Lens tab of DPP. DLO takes in to account the specific characteristics of not only the lens, subject distance, focal length and aperture but adds in specific knowledge of the low-pass filter configuration of the camera. The result is better quality images, since with this approach even diffraction effects can be corrected.

Digital Lens Optimizer (DLO) precisely imitates lens operation, with a series of complex mathematical functions replicating each stage of the journey of light through the optical path. Using this information, DLO can correct a range of typical optical aberrations, and loss of the resolution caused by a low pass filter, by applying an inverse function to each shot that takes the image closer to how the scene looks to the naked eye. This creates exceptionally detailed, high-quality images with highly manageable file sizes, providing photographers with maximum image quality and greater flexibility in post-production.

- Canon Europe, EOS 5D Mark III Technologies Explained

To be honest I was a bit sceptical at first, the images from the latest lenses are typified by being much improved over their predecessors. When it comes to RAW conversion tools, there is often several options available to a photographer and these days they all do a good job in the main. Only Canon DPP software is programmed using exact knowledge of what the camera writes in each file, and what each element of the data in a RAW file is intended to be used for. Factor in that the DLO works with a large number of EOS cameras past, present, and probably future too, it’s worth exploring.

When using DLO for the first time it needs to connect to a Canon server to download the lens profiles, this is a first for Canon, and I hope that it means that DPP will soon auto update the main program direct from Canon too (hint, hint ) There is currently over thirty lens profiles available and each one is quite large, seems to be around 25MB per profile so it’s best to download only the ones you need for lenses you use or own.

Canon software engineers are unique as they have access to many of the teams around the product, they will have been able to get the complete design information of each lens and then work with image processing specialists to all but eliminate small deficiencies that are normally accepted as part of modern lens design. We all want perfect lenses, but perfect is too big, too heavy and too expensive so we get “almost perfect” lenses.

More megapixels, more diffraction

With the advent of high megapixel digital cameras, the laws of optics and physics also bring diffraction to the pictures. Diffraction results in a softening of the image as the aperture gets smaller. It’s interesting to see Canon provide a solution to diffraction with software, but in all practicality it’s the only real way to do so.

Eight types of correction

In discussion with some “folks in the know” I heard that there are eight specific effects that DLO is designed to correct. The eight kinds of correction apply to different parts of the frame. In the centre of the image; spherical aberration and axial chromatic aberration, the edge of the image; curvature of field, astigmatism, comatic aberration, sagittal halo and chromatic magnification aberration. Diffraction effects appear throughout the image, and these are also corrected.

Can you see a difference in real images?

Keen to see if there was a marked difference in my images I followed the advice in the DPP manual and re-processed some RAW images shot last year with the EOS-1D Mark IV and the EF 70-200mm f/2.8L IS II USM lens. Reading the instruction manual for DPP – yes I’m the one who does – it suggests that the effect is best reviewed when sharpening is set to zero. If you sharpen the image, the sharpening may well mask the improved resolution that the software achieves by reversing the effect of diffraction, however sharpening is not the only improvement that DLO makes. Once you have used the DLO function it’s fine to set the sharpening settings, they might be a bit weaker than you are normally using.

DLO adds a lens mark with a “+” symbol to the thumbnail displays.

Shooting motorsport is a long time passion of mine, so last year I was able to join the world rally event in Finland, known locally as the Finnish Grand Prix. The Finns certainly love the sport, and warm weather is a good way to get plenty of shutter speed to freeze the action.

Setting the DPP sharpening to zero I processed out the images as full resolution 16-bit TIFFs and then opened them in Photoshop. Spotting the difference was not easy, it’s not night and day kind of different, so I put the two images in one Photoshop file and set the blend mode to subtraction. I would now easily see the difference between the two pictures! Except that the difference was not easily visible, but there were some clear areas that looked to have some difference.

To enhance the difference I added a very steep curves layer on top of the image, it showed me exactly where the differences between the two images was happening. Kind of as I expected the obvious difference is the sharpness of edges in the picture, things like around the car, windscreen, competition number etc. But on further inspection I found more detail available in the foreground and background also.

• Difference between normal and DLO version
• DLO effect enhanced
• Curve used to view differences

The effects are not easily visible, but they are definitely better and when I made an A2 size print of my images it’s possible to tell the DLO from the non-DLO version. What’s more i’m now interested enough to try some more challenging images, in fact if you have a RAW file from a recent Canon DSLR taken with a lens in the list below why not give DLO a go for yourself? I think that DLO is a tool for those portfolio images and exhibition prints where you want the last word in quality, rather than something you would use each and every day.

The following lenses are improved by DLO

RAW images from the following cameras can be used with DLO