Canon's Black Dot Issue

Gene Moore

Gene Moore

EF3
Joined
Nov 23, 2005
Messages
295
Location
San Antonio, TX
Before running out to buy a new Canon 5D Mark II I suggest everyone catch up on the latest with the black dots. Canon recently made an announcement about a fix for the problem, but they have also delayed the major release of the Mark II. Meanwhile the war of words continues on Canon Digital Photography Forum POTN - Fred Miranda and other chat groups.

Canon's recent announcement hinted at a software fix, but the delay of the camera in mass indicates perhaps a hardware change?? Here are some links that worked on the preview...hope they come through.

http://www.slashgear.com/canon-5d-mark-ii-early-bug-reports-black-spot-artifacts-0725482/

http://www.amateurphotographer.com/...Mark_II_black_spot_statement_news_273920.html
 
Yuk!
Imagine the long black gash adjacent to bright lightning. It would look like horribly overcooked USM.

(Ain't it funny how you never hear about film cameras suffering nonsense like this? ;) )
 
Fear not, Ms. Spiffypix!
Canon seems to have a fix in the works.


“Thank you for using Canon products.
We have learned that some users of the Canon EOS 5D Mark II digital SLR camera have identified two types of image quality phenomena that appear under certain shooting conditions.
1. “Black dot” phenomenon (the right side of point light sources becomes black)
2. Vertical banding noise


We are currently investigating and analyzing the causes, and examining measures to reduce or eliminate these phenomena by providing correction firmware. An announcement will be made on www.canon-europe.com as soon as measures have been determined."
 
Really too bad that Canon has this issue.

Unfortunately, I think its a hardware issue that will have a software fix to it. I've read that this problem could be related to a voltage 'overshoot' problem..

Its a condition where the A/D converter is rapidly 'sucking off' the values of each pixel sequentially, and when it comes across a rather bright grouping of pixels (a high value), then hits a 'dark' pixel (not so much light) the voltage 'wildly' swings quickly negative...and overshoots its mark, thus showing a real low number (a black pixel) before it can recover. It all has to do with the matching of the digitizer input impedance to ensure the fidelity of the high-speed data coming in. These pixel steps (I'm only assuming the timing) are only a few nanoseconds wide, thus things have to be matched--perfectly--in order to accurately sample each pixel.

In simple words...think this should be a hardware fix (better matching to the A/D converter), but they will likely apply a software fix(filtering out these high-dynamic range shifts)...and the bottom line is that we may lose some fine-scale contrast within the picture.

Let's hope that Canon chooses the hardware fix..and give the option to current Canon 5D MII owners to send their cameras in for the upgrade.

Shame on Canon!

Tim
 
Not sure... some of the forum speak I have seen has shown the black dots go bye bye by turning off some of the processing options with regard to highlights/color. We'll see! After using CMOS so extensively for the past umpteenth models, I have a hard time they would drop the ball on this one.
 
Thanks for the technical brief, Tim. Doesn't it seem a bit odd that they'd screw up something so fundamental? Wouldn't Canon design in some manner of filtration to control this ringing? Maybe they used some bad or out-of-spec components that are causing the circuit to be underdamped?

In the meantime, here's a cool PS action that does a decent job covering up the black blobs of death. It does as good a job as one could hope - masking the missing data and blending it in with the surrounding scenery. http://actions.home.att.net/5D_MarkII_Black_Dots.htm

l
 
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