Challanging assumptions about scanning B&W

[Ed Richards]

I have been working on optimizing scanning of 4x5 black and white on a Canon 9950. I do not do color and am not addressing color issues.

Conventional wisdom, reflected in recent View Camera articles, is that you should do a lot of processing in the scanner software, and that many people think Silverfast, with its many bells and whistles, is a good scanning choice.

My prejudice is for scanning once to generate a master file with as much info as possible. I quit using Silverfast and moved to Vuescan - which gives the most control over the scanner and the output file. I oversample - I scan at 4800, even thought this does not really improve resolution much over 2400, because it gives me 4 data points to average to reduce noise. I output the raw file - the linear output from the CCD. I set Vuescan to generate the data from the green channel because that is the sharpest one on my scanner. You can change this based on your scanner's characteristics.

Unless your scanner supports different exposure values, the raw file contains all of the possible info the scanner can put out. I downsample the raw file in Photoshop or PWP, using bicubic sharpening. I shoot for about a 4 fold reduction in file size, from about 770 megs for 16 bit B&W to 180 megs. This averages out a lot of the noise and gives a sharper and smoother image than does a 2400 dpi scan that is used at native resolution. Once I have resampled, I rotate the file and flip it to get the orientation right - I scan emulsion side down, so I get a mirror image. I then invert the image and save this as my master file.

You use levels to set the white and black points and use the gamma slider to set the midtones. You can do this as a layer if you want to tinker with it later. At this point you can see the detail so it is the time to do spotting. You then use curves to fine tune the contrast.

Vuescan has a free trial - give it a run. I think this gives a very good result and makes the best of the technology in the better consumer scanners. I am sure a drum scanner does a better job, but the costs are high, unless you want to take the time and trouble to run your own. I will be doing a comparison at some point to determine what print size it takes to really see the difference. With properly exposed negatives I do not think the better handling of dmax with a drum scan will matter much, nor should the blooming you see with chromes be as much of a issue with negatives.

[tim atherton]

Ed, I basically do this but use NegPos to convert the RAW file once it's in PS (for both B&W and colour neg) - I find it does an exellent job

Bit of a learning curve - it's rather like early Vuescan - but you really need to read the manual and docs with it as it's slightly counter intuitive (to me anyway...) - as a friend said about it; " if you are a Machead who expects an iCute version, you'll have a shock, but if you thought win 3.1 was a great operating system :-) you'll be fine!"

http://www.c-f-systems.com/Phototips.html

http://www.c-f-systems.com/ColorNegs.html

http://www.c-f-systems.com/Docs/NegPos103.zip

http://www.c-f-systems.com/Docs/NegPosManual103.pdf

and if you hunt around there are some very good docs/theories on scanning color on there too

[Denis Pleic]

Ed, Vuescan does not work with my scanner (Microtek ScanMaker 6100, which is a USB scanner).

What I do is rather similar to your process, but I'm using Silverfast AI. I use "16-bit Greyscale HDR" setting, which is basically a RAW scan. I open the scan in PS and invert it (it scans as a positive when you use HDR), and start from there.

Gives perfect results - or, at least, the results with which I'm quite happy

Silverfast's various presets and "adjustments" never yielded the best possible results, and I realized that the way to bypass any in-scanner processing is to use the HDR scan setting in Silverfast AI. The cheaper Silverfast version, which usually comes bundled with new scanners, is the "SE" (i.e. "Lite") version, and does not provide 16-bit grayscale HDR scanning.

BTW, the HDR scan (TIFF) of a 4x5 B&W neg on 1600 dpi is about 100 MB.
I could use higher resolution setting (goes up to 6400 dpi), but I think it's an overkill for Web display and sending JPG scans by e-mail to friends, which usually end up being about 100-150 Kb in size.

If I were to prepare a scan for lab printing, I'd probably use the highest resolution possible (6400) in combination with HDR scan to produce a large high quality JPG.

Denis

[Kirk Gittings]

I have extensively compared Silverfast and Vuescan. SF controls are far superior to VS. The only place VS shines is in its single pass multisampling. Does that mean that you can't get a good scan with VS-of course not, but for me I need SF to get what I need from a scan.

Ed I agree with you about your workflow, but only on drum scans. With scans from say an Epson 4990 (or a Canon 9950f which I have tested extensively too) or an Imacaon, I approach this differently. I do allot of adjustment in the scan, because I want the sampling to be done with my final output in mind. For instance a flat negative that I know I want to print slightly contrasty (like with a steep midtone curve), I will do the scan with the tones pushed "in the direction" of the final out put. Because I manipulate tone and contrast allot. This approach gives me fewer artifacts in the transitionary tonal areas of the final file. This is especially true in the sky areas that I want to "Burn" in allot. The transition areas of tone pick up allot of granularity if you start out with a low contrast scan and then apply a steep curve. Look at the last example in the Scan Around and you will see what I mean about applying a steep curve in low end scanners. This is especially true with scans from like Epson 4990, Canon 9950 f or even an Imacon vs. a drum scan.

[Ed Richards]

Kirk

My point with Vuescan is that I can set it to do nothing but the scan and output the file with the unscaled CCD data. There is really no reason to treat the raw output any differently for the 9950 than from the drum scanner. There is no intrinsic contrast to the scan at all if you use the raw output. (Again, I could never tell whether Silverfast was doing anything with the HDR, so I cannot speak to its use.) For Vuescan, it is better to not have the software do anything to the file. The fewer times you do adjustments, the better. Using photoshop on the raw file skips one level of processing, and using levels and its gama control will let you combine the processing you are doing with scanner software and the processing with Photoshop.

[Bruce Watson]

There is really no reason to treat the raw output any differently for the 9950 than from the drum scanner.

There might be. It depends on the scanner and the software of course. But... I suspect that you'll get better results if you at least set your black and white points to reflect the density range of the film in question, and your contrast as well, in the scanning software.

The reason for this is that you want to give the software the best use of available resources. If you only have 12 or 14 bits of real data capability, you want to use it all - you don't want an output file that is half zeros.

If your scanner/software generates a raw file that "has room for" the full dynamic range the scanner can generate, say the density range of 0-3.4, and it scans a B&W negative with a density range of say 0-1.4, then your file is more than half zeros. The file's density range from 1.5-3.4 will be zeros. Looked at another way, you could say that you are effectively scanning at 5-6 bits or so (no, I'm not going to sit here and do the math and give you and exact answer!). This is sort of like craming all your film's information into the toe of the response curve. It's not a good thing.

I think Kirk is right on this one. Tighten down on the film's density range as much as you reasonably can at scan time, erring on the side of caution to avoid leaving any actual image information behind. Then clean up the scan in an image editor.

FWIW, this is what people get when I drum scan film for them. I wouldn't necessarily consider it "raw" output, but rather output that is ready for image manipulation.

[Henry Ambrose]

Ed,
I'm with you on getting the full info from the scanner into Photoshop and doing so at as high a bit depth as supported by your machines and software. You are absolutely working in the right direction but Kirk and Bruce do have solid ideas that you can add into your mix. Setting black and white points just outside of your film's scene information range is a good idea for sure! Beyond that I suggest that you continue to reserve most of your adjustments for Photoshop. The less you rely on the scanning software and the more you use PS the better off you are in terms of controlling your files and not having to learn and re-learn each time you buy a different scanner.

[Kirk Gittings]

You guys know that I am not really technically minded. If things work i don't really care why.

My point is based soley on extensive anecdotal experience from Epson 3200, 4870, 4990, Canon 9950f, Imacon 848 and dozens of drum scans for comparison and Silverfast and Vuescan and the native software of each scanner. I am currently doing about 1250 4x5 and 6x9 scans s a year about 2/3rds of which are NPS color negatives and the rest FP4. All the b&w pigment prints for my current show were done on either a 4990 or an Imacon. These are the kinds of tonalities I am talking about. The b&w files for this portfolio were taken directly from the files used for the show prints.

www.portfolios.com/profile.html?MyUrl=KirkGittings

If you apply a steep curve to a flat unclipped, unsharpened, downsampled "raw" scan from those mentioned scanners (say in a sky section that you want allot of drama in-less so in the Imacon in b&w mode) you WILL get allot of granularity (similar to noise) in the transition areas between tones that are being stretched or compacted. This does not happen in good drum scans. If you scan with those scanners closer to the tonalities you want in the final output the sampling is done closer to those final tonalities, less expansion and contraction is done to achieve the final results and less granularity appears. I have struggled with this issue allot and decided that Ed's workflow will not work for my imagery.

[Ed Richards]

Bruce

Let's black box this. We have one box that is the sensor. The output from the sensor is 12/14 bits - as you put it, a lot of zeros. We can process it through a second black box inside the scanner that scales it by spreading the data over the entire range from 0 to 32,000, instead of, say, 0 to 6,000. All it is going to do is multiply the data with some function to scale it. We then take that data to our second black box (Photoshop) and multiply it by another function to scale it a little more accurately, then perhaps twiddle the contrast by applying yet another function. Each time we run it through a function we lose data with rounding errors. From a computer perspective, there is nothing that the computer in the scanner box can do that cannot be accomplished by the editing software - we are combining the two functions into one function and thus removing one set of rounding errors. (We just combine our Turing machines, for the fossil geeks out there.) I have also run this past Ed Hamrick, who writes Vuescan and knows a bit about the innards of scanners.

One more thing that I find fascinating with working with the raw output from Vuescan - you realize at once how much info is in the negative. Most negatives look pretty dark, meaning that the data is compressed into fewer zones. Some are full range, showing the data is spread across more zones. Those are going to produce better scans. What I have not yet done is work out whether the ones that look good are much higher contrast than you would want for silver printing. I had originally assumed that the best scanning negative would be relatively flat, but after scanning a step wedge I realized that the scanner could sort out much greater densities than I had assumed.

[Henry Ambrose]

Kirk,
You may not have the time or inclination for this but I'd love to see a straight "raw" scan and one using your current method of working on the same negative.

I think there are lots of ways to get to the same place. I'd most likely start using layers and mode: multiply and layer curves to get the hard worked sky effects if they were not there in the straight scan. Obviously you do it quite differently.

This is not a contest............ I'm just curious.

Also I'm headed to Chicago this weekend for the marathon. Do you have any pictures up there?