C300 Color Fringing. Update.

Crop from an over exposed frame clearly showing the large amount of LCA.


I’ve spent some time shooting test subjects with my C300 trying to replicate the green/red pixel issues getting reported elsewhere. So far the only real problem I have found is some pretty extreme LCA (longitudinal Chromatic Aberration) which is significantly worse when I use the ND filters. I have seen CA on my F3, it’s down primarily to lens performance and quality. But I have never seen anything as extreme as this. Below are a couple of frame grabs for you to look at, one full frame and the other a crop. What you can see is that anything closer to the camera than the chosen focal point has a distinct  red/purple fringe and anything behind the focal point (further away) has a distinct green fringe. The lens used was a Canon 24-70mm f2.8 L series. One point to consider is that DSLR lenses were never designed to have extra glass between the back of the lens and the sensor other than perhaps the OLPF  (Optical Low Pass Filter) and combined IR filter, which normal sit right on top of the sensor. The C300 has a clear glass filter and 3 ND filters. Each of these filters is at a different distance some way from the sensor. I suspect that these filters are at least in part causing the CA to be more severe than is typically seen in a DSLR as the extra glass will alter the point at which all the colours are brought into focus. With the filters being quite a distance from the sensor any dispersion of the colours through the filter will be quite well spread out by the time it gets back to the sensor, exaggerating the effect.  On the Sony F3 the ND filters are extremely thin and very close to the sensor, but still I should try the same lens on the F3 to see what happens. It’s also been noted that the problem is worse when you shoot interlace. Now the C300 sensor is quite different from anything we have seen in a camcorder like this before. Some of the image processing needed to create the interlace fields from this progressive scan sensor is done on the sensor chip itself and I suspect this may be why we are seeing more artefacts in interlace than progressive as the processing is possible quite rudimentary compared to what can be done in a dedicated DSP (Digital signal processor). That is speculation on my part. Every now and again I do see some aliasing artefacts on horizontal and vertical high contrast edges that manifest themselves as small (1 or 2 pixels) red and blue blocks. Again this is probably a result of the sensor design. The aliasing artefact is very minor and not something I am concerned about, the LCA is more of a concern.

UPDATE: I tried this same test today with my 24-70mm L series lens on my F3. The results are very close, lots of strong LCA. Now, I’ve never seen this extreme LCA on my Canon DSLR. A bit of digging reveals that when you put this lens on a Canon DSLR, the camera activates a tailored compensation circuit to minimise the effects of the CA, this circuity is not present in the c300. I also tried my trusty Tokina 28-70mm ATX Pro lens on the F3 and the C300 and in both cases I get less LCA with the Tokina (which cost £200) than the brand new 24-70mm Canon lens. The Tokina, being a Nikon mount lens has a real iris ring, so no nasty stepping iris. You know I’m really disappointed by this. One of the big selling points of the C300 has been that you can use Canons “L” series lenses, yet this is a real let down as the lenses won’t appear to perform as well on the C300 as they do on a DSLR and I don’t think many people are aware of this, I wasn’t. This is not a fault or issue with the C300 itself but in my opinion it does further lessen the supposed advantage of having a camera that takes Canon lenses without an adapter.

Frame Grab showing a lot of LCA. Shot using Canon 24-70mm L series lens on C300. ND filter 1.

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24 Responses to C300 Color Fringing. Update.

  1. Pingback: HD Warrior » Blog Archiv » Canon C300 Chromatic Aberrations seem to be with certain older Canon lenses !

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