Last week, the much awaited Canon 5D Mark IV made its debut. The rumor mills have been abuzz for quite some time about the features of the rumored camera and the stuffs that you could do with them. They have all been put to rest after the official announcement of the camera last week. Most of you may have already gone through the features of the camera and what it can possibly do for your photography. Some of you may already have it listed on your shopping list. In the clutter of the long list of new and upgraded features you may have probably missed one that really deserves a mention. Too bad, even the official press release did not have too many words attributed to it.
Dual Pixel RAW
The technology that I am referring to is the Dual Pixel RAW. We all know what the Dual-Pixel CMOS AF technology is all about. Ok, may be not all but certainly most Canon fans will nod in affirmative when they hear about it. This technology is based around the concept of a split pixel sensor. When I say split pixel sensor I mean that the individual pixels on the imaging sensors are divided into two.
The idea is to collect light coming in from two sides of the lens. Each half of the split pixel, each of which is a photo-diode in itself, captures light coming in from a single direction of the lens. The photo-diodes then acts like phase detection sensors allowing the camera to auto-focus even when the camera is in live-view mode, and thus without the need for dedicated phase detection sensors.
This much we know and we understand. So what’s the deal with the Dual Pixel RAW technology?
Canon suggests that Dual Pixel RAW will allow the photographer to adjust focus for an image as well as bokeh and eliminate some ghosting after the image has been made. You can do only one at a time and not all of them at the same time. Intrigued? Well this is not something that is new per se (that is adjusting focus post image taking). We know about Light Field cameras and how they allow a photographer to move the focus point around post image making and during post-processing.
Canon, however, hasn’t quite used the word ‘focus adjustment’ in their press release. That means they don’t want us to get an idea that you can make significant changes to the focus, much like you would expect with a light field camera.
This is just to discourage any unreasonable expectations from the camera and the technology. So, what can you really do with this new addition to the Canon 5D line-up? Well you can do very micro adjustment / corrections to your focus. This would be particularly useful for wide aperture lenses like your f/1.8s or f/1.4s and even the f/1.2s.
If you own one of these lenses or have shot with these you would know that these lenses are very difficult to auto-focus with. The margin of error is very small. It is easy to miss focus often resulting in frustrations when you realize that you are off target when finally getting down to editing your images at the end of the day.
One example would be when your target is a very small area and the camera is likely to get it wrong 9/10 times. Dual Pixel RAW allows you to correct those small errors when your focusing is off. It can probably also be a way to salvage back or front focusing issues with your lens as well, provided that the margin of error is not too much. Another area where this technology can come to the rescue is when shooting macro photos.
This can’t be bad after all?
No, the technology does have its utility. But everything is not quite fine with it. Apart from the fact that the technology has got only limited utility, you have to deal with significantly larger file sizes. Dual Pixel RAW images are around twice the file size than normal RAW files. Round about 72 MG each. Thus, if you are quite often off the mark or planning to use this feature as a standard, you have to rethink your file management architecture.
Another big question mark is the compatibility of the Dual Pixel RAW images with traditional and more established photo editing applications. If your favorite post-processing applications are Photoshop and Lightroom don’t think you can download your images to them and adjust focus or reposition bokeh etc. These changes can only be done on the Digital Photo Professional (albeit the updated version).
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