Is this CCD blooming?

[john_simon5]

<p>I was recently scanning some Kodachromes using my Coolscan 5000 and I noticed an odd combing artifact while pixel peeping to fix dust (see picture below - a 200% crop from the area of the slide where it occurred). It happens occasionally at high contrast boundaries like the one shown and is vertical along the orientation of the scan line (the short axis of the slide). But it didn't happen in very similar areas of the same slide and it is certainly not prevalent in my scans. Can anyone identify this artifact? My initial research has suggested this might be CCD blooming. Is it? It is consistent from scan to scan in this manner but is obviously digital in origin and not on the slide. Following the thinking that it might be CCD blooming or something like that I thought that slowing down the scan speed as it moved from row to row might help to give time for the excess charge to drain. Turning on multisample scanning pretty much cures it - 2x is not quite enough, but 4x and the effect is gone.</p>

<p> </p><div></div>

[john_simon5]

<p>In another scan I noticed there was a bit of colour to this. Same effect just slightly different presentment. The picture below is a 200% crop.</p><div></div>

[benbangerter]

<p>I don't know what is going on with the "comb" structure in your first image, but the color fringing in your second image appears to be classic red/cyan chromatic aberration. It is almost certainly present in the image on the slide, and you may be able to correct it to some extent in post-processing.</p>

[john_simon5]

<p>In the second image I'm focusing on the surrounds of the white area and the way it is yellow with a purple line every 8 or so pixels (and the reverse on the bottom of the white area). I don't think that is of analogue origin. You can also see it a bit on the top of the diagonal grey at the bottom.<br>

(If anyone cares, these are closeups of the Myer Music Bowl in Melbourne.)</p>

[roger_smith4]

<p>I'm seeing very similar artifacts when I use Vuescan with my LS-5000. I've switched to Nikonscan because of that. I emailed Ed Hamrick but he didn't respond. Checking fine mode in Vuescan makes it worse. It's the combing/banding I'm commenting on, not the color fringing.</p>

[john_simon5]

<p>It is comforting to know that someone else gets the same artifacts - that suggests to me that it is potentially inherent to the LS-5000. And multisample scanning pretty much cures it so it's not too annoying at the moment. But I'm still hoping to understand it.</p>

[roger_smith4]

<p>I find that 8x multisample limits it but that Nikonscan eliminates it, so it is not inherent to the scanner. When i get on my home computer I can post a comparison I did of Nikonscan vs Vuescan. The main problem with this banding is that it interferes with sharpening.</p>

[john_simon5]

<p>I use Nikonscan, so there are circumstances where you can still get it with Nikonscan - although it sounds like lower levels of multisample are effective in Nikonscan vs VueScan.</p>

[john_simon5]

<p>I just came across an interesting example on the web. While not directed at this issue at all I believe I can see the same effects in the two Coolscan scans shown here <a href="http://www.webweavertech.com/ovidiu/weblog/archives/000448.html">http://www.webweavertech.com/ovidiu/weblog/archives/000448.html</a><br>

The author doesn't mention what driving software was used, but in the 1x scan there is noticeable combing that is absent with 4x multisample.</p>

<p>I must say that I am rethinking whether or not I should have multisample on as part of my default settings. Received wisdom was that it made practically no difference. But with Kodachromes there is a noticeable difference - there is invariably a dark area where multisampling cleans up the noise and with the additional consideration of this combing artifact I'm thinking that the time is worth it.</p>

[berg_na]

<p>The artifacts are not due to CCD blooming, but rather CCD smearing. An <a href="http://www.fujifilmusa.com/support/ServiceSupportProductContent.do?dbid=879932&prodcat=878844&sscucatid=664262">explanation is given by Fujifilm </a>including an example. It's a serious issue in videos since there is no mechanical shutter. </p>

[john_simon5]

<p>Thanks for the info. Reading the description it sounds like what Fuji are calling CCD smear is what I was thinking of as CCD blooming - it may just be a terminological difference.</p>

[tom_mann1]

<p>Blooming vs streaking/smearing discussed here:<br>

http://learn.hamamatsu.com/articles/ccdsatandblooming.html</p>

<p>Tom M.</p>

[john_simon5]

<p>I continue to learn. All very, er, illuminating.</p>

<p>I am thinking, however, that the artifact noted in my OP isn't CCD blooming. It may be related to the electronics in some way but it doesn't look like the sort of examples illustrated in the articles. It is just too regular in its pattern across scan lines - if it was blooming I would have expected it to affect every scan line rather than just every 8th (or so).<br>

Anyone got any other ideas for what it might be? Other than Roger, has anyone else observed this artifact on their Coolscan scans?</p>

[roger_smith4]

<p>Doesn't the LS-5000 have 3 scanlines working together? I think Vuescan's fine mode knocks it down to one which in my experience worsens the problem.</p>

[john_simon5]

<p>When you say Vuescan fine mode worsens the problem - do you mean that the combing affects more lines? That is, you get the same artifact, but instead of it being every 8 lines (maybe it is 9 if it is a multiple of 3) it is every 2 or 3 lines?</p>