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Author Topic: Scannerless Digital Capture  (Read 7245 times)

svein

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Scannerless Digital Capture
« on: November 16, 2014, 03:43:56 PM »

I haven't seen any thread about this article, which I found really interesting. Not much new serious info about scanning anymore, so thanks for the effort! Also, and any follow up about the new V800/V850 would be greatly appreciated.
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MarkL

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Re: Scannerless Digital Capture
« Reply #1 on: November 17, 2014, 08:15:05 AM »

What wasn't mentioned is what kind of quality you can expect out of this process.
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svein

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Re: Scannerless Digital Capture
« Reply #2 on: November 17, 2014, 12:34:00 PM »

What wasn't mentioned is what kind of quality you can expect out of this process.

Did you read the Pdf? I thought it was a lot of useful info.
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Berliner

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Re: Scannerless Digital Capture
« Reply #3 on: November 20, 2014, 02:20:32 PM »

The PDF even has comparison images, at what I presume is 100% size.

And the quality seems to be fantastic.
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Best wishes from Berlin.

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John Camp

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Re: Scannerless Digital Capture
« Reply #4 on: November 20, 2014, 03:07:02 PM »

What I need is to go the other way -- from digital to film. Film projection via good Kodak slide projectors is much better than digital projection, where a 4K projector can cost ~$10,000. Not that this is in any way relevant to the article at hand...   ;D
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amolitor

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Re: Scannerless Digital Capture
« Reply #5 on: November 24, 2014, 07:09:32 PM »

I skimmed it, but they don't seem to have picked up on the fact that by using a good light source and demosaicing in a non-standard way, you can effectively double the resolution of our Bayer sensor.

It takes a bit of fiddling, but if your light source is broad-spectrum you can "demosaic" a known b&w image (e.g. a negative) by simply making small global adjustments to the R, G, and B values the sensor produces. There is, really, no de-mosaic step. Your useable resolution goes up by quite a bit.
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MHMG

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Re: Scannerless Digital Capture
« Reply #6 on: December 04, 2014, 08:52:35 PM »


It takes a bit of fiddling, but if your light source is broad-spectrum you can "demosaic" a known b&w image (e.g. a negative) by simply making small global adjustments to the R, G, and B values the sensor produces. There is, really, no de-mosaic step. Your useable resolution goes up by quite a bit.


Please tell me more :) How exactly do you make these "small global adjustments to the R, G, and B values"?

thanks in advance for your reply.
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Jim Kasson

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Re: Scannerless Digital Capture
« Reply #7 on: December 04, 2014, 09:26:39 PM »

Please tell me more :) How exactly do you make these "small global adjustments to the R, G, and B values"?

Pretty much the same way as with infrared:

http://blog.kasson.com/?p=3034

If your camera has an AA filter, I don't think it's worth it.

Jim

PS. The adjustments are not what I call small. At least a factor of two between the brightest and the dimmest of the RGGB channels, with a D55 light source.
« Last Edit: December 04, 2014, 09:34:49 PM by Jim Kasson »
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amolitor

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Re: Scannerless Digital Capture
« Reply #8 on: December 04, 2014, 11:06:34 PM »

Well android sticks so I can't paste the link.

dcraw shows you to simply specify scale factors to apply to the three color channels. So if you can illuminate the b&w negative with a suitably balanced white light, you can use dcraw to skip the Bayer interpolation.



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deejjjaaaa

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Re: Scannerless Digital Capture
« Reply #9 on: December 05, 2014, 12:23:24 AM »

Please tell me more :) How exactly do you make these "small global adjustments to the R, G, and B values"?

thanks in advance for your reply.


you can use RPP raw converter (runs in OSX, either on Mac on in VmWare on PC) -> it can run w/o demosaicking and WB there is applied as directl mutliplication on raw channels and you can switch off any color transform too... no need to use command line tools like dcraw.
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amolitor

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Re: Scannerless Digital Capture
« Reply #10 on: December 05, 2014, 12:25:29 PM »

If your camera has an AA filter, I don't think it's worth it.

What makes you say that? Surely skipping the Bayer interpolation where possible is always a noticeable win?

I feel like I am missing something!
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Jim Kasson

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Re: Scannerless Digital Capture
« Reply #11 on: December 05, 2014, 01:56:19 PM »

What makes you say that? Surely skipping the Bayer interpolation where possible is always a noticeable win?

I feel like I am missing something!


If you read the post I pointed to above, you'll see that the blurring of the AA filter overrode any increase in sharpness that I saw in my testing, although the AA-less images were somewhat improved. If your camera has a weak AA filter, like the anisotropic one in some Sonys and Nikons, maybe you'll see a small improvement.

I was surprised, too. I think the take home is that modern demosaicing software is pretty darned good when presented with a monochromatic image.

Jim

amolitor

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Re: Scannerless Digital Capture
« Reply #12 on: December 05, 2014, 02:41:05 PM »

Ahh, my apologies. It never occurred to me that the blog post would explain the AA filter comment. Because, apparently, I am a little slow.

Thanks!
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BartvanderWolf

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Re: Scannerless Digital Capture
« Reply #13 on: December 05, 2014, 03:19:14 PM »

If you read the post I pointed to above, you'll see that the blurring of the AA filter overrode any increase in sharpness that I saw in my testing, although the AA-less images were somewhat improved. If your camera has a weak AA filter, like the anisotropic one in some Sonys and Nikons, maybe you'll see a small improvement.

I was surprised, too. I think the take home is that modern demosaicing software is pretty darned good when presented with a monochromatic image.

Hi Jim,

It is pretty good, but that's been the case for some of the more advanced types of demosaicing for some time already. Here's an old (almost 11 years ago) experiment of mine, which shows only a loss of some 6.4% of luminance resolution as a result of 'debayering'. The algorithm I used (Aqua if I recall correctly) was experimental at that time and used a few iterations to control false color artifacts.

Having somewhat balanced RGGB levels helps demosaicing, and should be achieved by adjusting the lightsource filtration, especially for masked color negative film 'scans'. Proper anti-aliasing by low-pass pre-filtering helps to reduce false color artifacting. Even crude Gaussian blur and USM are quite effective, but we can do much better nowadays.

Cheers,
Bart
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Jim Kasson

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Re: Scannerless Digital Capture
« Reply #14 on: December 05, 2014, 03:48:52 PM »

It is pretty good, but that's been the case for some of the more advanced types of demosaicing for some time already. Here's an old (almost 11 years ago) experiment of mine, which shows only a loss of some 6.4% of luminance resolution as a result of 'debayering'. The algorithm I used (Aqua if I recall correctly) was experimental at that time and used a few iterations to control false color artifacts.

As usual, Bart, you've gone at least one level further than I did. I actually have the means to replicate your work with my camera simulator, and probably would have done it by now had my initial testing been more promising. I recently added AHD to the simulator, using the inventor's Matllab code. I still have no way to write simulated raw files that a standard raw developer program can handle.

Having somewhat balanced RGGB levels helps demosaicing, and should be achieved by adjusting the lightsource filtration, especially for masked color negative film 'scans'.

Dust off those 30CCM filters!

Proper anti-aliasing by low-pass pre-filtering helps to reduce false color artifacting. Even crude Gaussian blur and USM are quite effective, but we can do much better nowadays.

We won't see false-color artifacting with balanced monochrome images if we bypass the color conversion process, will we? Iridient Developer makes that easy. DCRAW, too.

Jim

amolitor

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Re: Scannerless Digital Capture
« Reply #15 on: December 05, 2014, 04:30:42 PM »

I am surprised by how much blur the AA filter adds, but in hindsight it makes a lot of sense.

I think it's difficult to build a good brick-wall low-pass filter in the optical domain, so it would make sense to push right up against the limits imposed by demosaicing, in order to get the best possible performance out of your fairly slow rolloff filter.
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Jim Kasson

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Re: Scannerless Digital Capture
« Reply #16 on: December 05, 2014, 05:16:08 PM »

I am surprised by how much blur the AA filter adds, but in hindsight it makes a lot of sense.

I think it's difficult to build a good brick-wall low-pass filter in the optical domain, so it would make sense to push right up against the limits imposed by demosaicing, in order to get the best possible performance out of your fairly slow rolloff filter.

A 4-way Lithium Niobate beam-splitting anti-aliasing filter is not at all close to a brick wall. It has a zero that's usually placed at the monochromatic Nyquist frequency or a little beyond. It rolls off quite a bit on the low side of the zero, and there's a rebound after it:

http://blog.kasson.com/?p=5832

However, if it were a brick wall filter, it would ring like crazy, so it's a good thing that it isn't.

Jim

ColSebastianMoran

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Re: Scannerless Digital Capture
« Reply #17 on: January 19, 2015, 09:31:13 PM »

I haven't seen any thread about this article, which I found really interesting.

I read this article and the PDF with interest. Much appreciated, especially the commitment to testing and comparison, not just finding something that works well-enough. I'm especially delighted to know how to create a linear TIFF from the camera-raw file.

When I've experimented with this, I had trouble getting good color, I thought in part because the raw scan had so much red/organge.  I set up a color-head (from a Beseler Dual-mode Slide Duplicator), shot with the strobe illumination and filtration to get a lot of blue to offset the orange mask. With the strobe, filtration at 110C and 60M, I could get a reasonably neutral scan with a setting of 4000K in ACR. Then I inverted and adjusted in Photoshop.

I have a question for the authors (Mark Segal and Todd Shaner):  Have you tried illuminating your negatives with bluer lighting so that the color balance adjustments are not so extreme?

Here's a sample for judging color only. Film boxes look OK, but there's plenty of casting (wall, paper towel, bottle). Overall, I was encouraged. I would like to find a reliable way to get reasonable color from a scannerless process.



Again, thanks for the article. 
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trshaner

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Re: Scannerless Digital Capture
« Reply #18 on: March 22, 2017, 11:51:36 AM »

I just happened across this old post and can provide an update on my findings. I did try using CC correction filters to white balance the color negative image, but experienced similar cross-over color casts. This is using Lightroom (or ACR) for initial raw file processing and then Photoshop with the workflow outlined in the article. The PV 2012 Basic panel controls are image adaptive and apply Highlight compression and Black Point setting with all controls at their 0 default setting. What I found works best is to use the WB tool in LR or ACR to reduce the dynamic range of the raw film scan. The objective is to place all three RGB channels into the linear mid-tone region to prevent compression of the highlight and shadow area image data. You can download an addendum PDF with more details here:

https://www.dropbox.com/s/6j3emoq40kqkymb/Color%20Negative%20Camera%20Raw%20Image%20Processing%20In%20Lightroom%20%26%20Photoshop.pdf?dl=0
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ColSebastianMoran

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Re: Scannerless Digital Capture
« Reply #19 on: March 22, 2017, 01:15:48 PM »

Thanks for the tips and the additional writeup.

I understand your notion you get better results by bringing all three histograms into the middle range, based on "things are more linear in this range."

My thinking is this: Recent mini-labs were digital, and the vendors had their machines calibrated to the different color negative films. The calibration produced pretty good color most of the time, some tweaks by operators, and the operators weren't master print makers. I wish we had some calibrations (color temp of light source, CC correction at "scan," color profiles, and post-processing parameters) that would give us the same color quality we had from mini-labs.
« Last Edit: March 22, 2017, 01:19:10 PM by ColSebastianMoran »
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