Jump to content

Lamplighter55

Members
  • Content Count

    8
  • Joined

  • Last visited

About Lamplighter55

  • Rank
    New member

Recent Profile Visitors

The recent visitors block is disabled and is not being shown to other users.

  1. ... in time for Christmas ... ;-)
  2. I think this is what we call 'challenging lighting conditions' - winter in the UK - grey day lighting. Nice grade - has a interesting rich textural quality to the colours.
  3. The transform from 4K to HD (in camera) basically is a 2x2 sample of the 4K frame pixels going into one HD pixel - so effectively 1/4 the spread of noise. Essentially averaging to the mean each set of 4 pixels in the 4K to create one pixel in HD. The 'neat' thing about this is that you can (canon can) also use this to sharpen (increase luminance contrast) as part of the process as the chrominance noise is variable for each colour channel. So we end up with less noisy but slightly sharper images in HD. I still think Canon should be able to improve on the 'ghosting' or 'temporal' quantisation/sampling problem - if they are not then they should be using a fast optical flow algorithm to integrate the frames at low frame rates - to get better filmic motion blur. As seen with our examples there is some kind of 'stepping' and 'kneeing' at the transitions from dark to light and visa versa - this is like the effect you get on CRTs when a high key signal drops to base black. Along the edge of the transition you see an over-shoot and undershoot of the image signal. Apart from the scan-line look, this is what gives an old analogue video signal it's characteristic 'Video' look - odd dark lines around things. It is quite possible that the required level of processing is beyond the single Digic chip's spec for the XC10/15 and is only implemented in the higher end cameras (C100/C300/C500/C700 etc.) - can but hope otherwise.
  4. Humm could it be that the luminance gradient from the zebra cross-over values are much brighter than in previous shoots? Light being logarithmic the values could easily rise to a 'burn-out' level if you are shooting on a bright sunny day - for example any direct specular sunlight reflections will be orders of magnitude above 'correct exposure'.
  5. ... the artefacts are quite characteristic of 'Temporal aliasing' but obviously some processing has been done as it does not seem to be global to each frame and seems to to be more pronounced when there is a pronounced difference in contrast from the preceding frame onto an area with less contrast. There should be a firmware adjustment that can solve the problem. (There's an interesting page on 'Red's site that helps explain temporal aliasing and their solution (hardware) in using an lcd layer between lens and capture chip that controls the light levels at a pixel level across the exposure of each frame.) It is a tricky problem though, that all digital recording devices have to deal with - the question for Canon is were in the image pipeline, can be mitigated. Assuming this is indeed the problem then in theory we can reduce it by capturing a flat but brightly lit image (reducing contrast but also pushing more of the pixel values towards the mid-point exposure value), running at a higher shutter speed and keeping camera nodal movement to a minimum (to reduce spatial aliasing). I'll also try some tests to see if I'm correct - at least in part ;-) [Link to Temporal Aliasing on Red's site: http://www.red.com/learn/red-101/cinema-temporal-aliasing]
  6. I bought my XC10 back in January (2016) and have been very happy with the quality of the images/footage. This 'Ghosting' or temporal noise reduction (possibly) has also shown up on my footage (see bellow) - and I've been following this thread on the issue. Having had a close look at the artefact I can pretty much say with certainty its an error in the calculation of how Canon integrate values from one frame to the next when calculating for motion blur. Basically the maths is off and creating a 'rounding error' so the pixel bins either hold an 'over shoot' or 'under shoot' value - so you get this characteristic 'zoning' of luminance values. Its a bit like the posterising effect (thresholding) one can achieve when reducing the bit depth of an image. So what is causing this ... hopefully it's a firmware only issue, in which case the frame to frame integration algorithm needs re-writing, or it is something done in hardware ... which means a fault in the DIGIC DV 5 chip. Canon will need to check in the later case if it is a batch issue or systemic. Let's hope it only requires a firmware update! The 'good' thing is that if it is (as I surmise), then the solution is just a question of maths - but the problem is how that is implemented - at chip level in hardware or a firmware 'bug'. (I should add, this could also will explain why this is less evident on HD footage as it has 4x more 'integration' as a reduction from 4K in spatial resolution - equivalent of averaging down to a quarter sized image.) One test we could try is running at a higher frame rate (HD only) and seeing if the artefacts are reduced or increased further for the same amount if spatial moment - in other words more samples over a given time frame and spatial transfer.
  7. I recently bought an XC10 having researched the pros and cons and also taking advantage of the 'January sales'.. So far am pretty happy getting used to its capabilities. I have a question ... I have been trying to find out if any of the 3rd party 1D 'cube' LUTs available for the C100*/300* are compatible with the Clog setting of the XC10? Anyone edited with these in FCPX for example? They seem to work but I'd prefer to be certain, as when it comes to 'pushing' the limits when capturing I'd like to know I can get a safe recovery of the footage with out bias, once I've transcoded it for editing. So any ideas or feedback most welcome. Thanks!
×
×
  • Create New...