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Thread: Drum scanner doubts

  1. #11
    Resident Heretic Bruce Watson's Avatar
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    Drum scanner doubts

    QT,

    To add to what wg said:

    The laws of physics tell you that spot size is what determines sharpness. You can see this by scanning a reference target like the old 1951 USAF resolution test target. Scan at a bunch of scanner resolutions and you'll see that you get a maximum optical resolution that is consistent with the spot size. And spot size is aperture size.

    So if you want the best in sharpness, you probably want the new Screen drum scanner. IIRC it's the only scanner on the market (that is, that's ever been on the market) that has a fully adjustable aperture size. This lets the scanner make an exact match of the spot size to the resolution you need, whatever that resolution may be. It should be very nice indeed.

    Failing that, you should look for a scanner with at least a 6 micron aperture which will give you an optical resolution in the 4000 ppi range (depending on lots of other factors, like the quality of the optics). The high end ICGs and Azteks now have minimum apertures in the 3 micron range, giving an optical resolution that's something less than 8000 dpi. In comparison, the Tango has a minimum aperture of 11 microns IIRC.

    The story I've been able to piece together from several operators and pre-press people is that the Tango was aimed squarely at the advertising and fashion market. It was a reaction to the Howteks, Screens, Optronics, ScanMates, and other scanners that were aimed at the smaller pre-press and short run press houses that couldn't afford the big Hell, DuPont/Crosfeld, and Heidelberg scanners. These new "table top" scanners were much cheaper, and more versatile - both were required by their target market. The Tango met the competition on price (sorta) and size, but was optimized for Heidleberg's traditional market of the advertising and magazine world. As such it was heavily optimized for chromes and for smaller enlargements (thus the 11 micron aperture). It's a marvelous machine for cranking out magazine pages, and the pre-press people just loved it, which is part of it's enduring reputation.

    These days the vast majority of film scanning is by the the fine art crowd -- us. And we don't play to the Tango's strengths. Many of us choose to shoot on negative film, and I've heard that the software (currently called NewColor IIRC) was so optimized for chromes that doing negative work is a chore. Many of us want to make fairly big enlargements, and the larger minimum aperture of the Tango makes for large prints that aren't as sharp as they could be. What doesn't matter to a model's face on a magazine page matters a great deal to a landscape photographer who is after highly detailed and sharp prints.

    The Tango is a fine machine when used as intended. All I'm saying is that it wasn't intended for the fine-art market.

    Also, what would you expect WCI and NancyScans to say about their equipment? Maybe I'm a cynic, but I think you'll be waiting a while for any company to say that their equipment is anything other than the very best, no matter what that equipment is or what kind of a match it is to your needs. I'm just sayin'...

    Bruce Watson

  2. #12
    Founder QT Luong's Avatar
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    Drum scanner doubts

    Bruce, let see if I am following your story well. I don't see why the "Howteks, Screens, Optronics, ScanMates, and other scanners that were aimed at the smaller pre-press and short run press houses" would be better suited for fine-art scanning than the Tango. So is it that subsequently, those companies introduced new scanners targetted for the fine art market ? Also, isn't the reproduction ratio often higher in pre-press than fine art because most of the film used in magazine publication is 35mm ?

    Regarding aperture size, in practice, at what scanning resolution would you notice the difference between the Tango, and the scanners that you mention with smaller apertures ?

  3. #13

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    Drum scanner doubts

    Bruce, excellent analysis....I would like to add a few notes.....

    What confused many about Tango is their high end scan numbers, I think 11k dpi. Well, even an Epson 4990 can scan at some very high numbers, but not effectively, as you end up with a super large file of mush, this is what seperates better scanners from heap - sharpness at small file sizes is the goal of a fine art scanner, and when your in the fine art market making big prints, the difference between 500MB and 1 gig files is huge.... hence, why you pay so heavy for the better scanners, albeit, this is also what makes digital capture so damn appealing, the capture process is so much more efficient, even using the best film and best scanners of today. hence why I can't keep my fingers out of the digital capture world. I feel as if I understand this efficeincy process as well as anyone, which makes me a huge digital fan, yet in these forums, I get bashed for being pro-film, oh well....

    Although micron size began to be the holy grail to resolution for fine art / large enlargement work, just like photographic lenses, there is points of diminishing returns. Your correct about the Screen and Azteks improved micron size, but I found this the following interesting...... with film, say color film, it will only hold a max. of 30 - 60 lp/mm of detail, based on the film being used. So the key for scanning color film is sharpness at these frequencies, which is under 4000 dpi. At these levels, I have spoke to operators who use both the Screen 8060's new drums and the Screens Cezzanne Elite flatbed. They have done a ton of comparisons, and their conclusion is, unless a scan has to be made over 5000 dpi, such as super detailed B&W shots which holds 2 - 3 x the detail vs. color film, it gets done on the flatbed. As for Dmax, they claimed the differences were in the 1 - 2 % range, not even detectable to the eye. So, my point is, there is more to the equation, just like other optical mechanical devices that have so much complexity from film to file. BTW, Screens software is optimized for color neg scanning, and whats neat is they have it profiled for the new color negs films using the new bases optimized for scanning, which started with Reala in the Fuji line.

  4. #14

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    Drum scanner doubts

    QT, some cross posting, i will try to respond.....

    You are correct that in magazine repros., a 35mm piece of film can be pushed to its limits for a full size two page display.... and the Tango certainly catered to that market, hell, that was their only market, mainly pre press companies, but the scanners were small potatoes to them, as they were after the presses and computer to plate systems.

    There is a mathamatical relationship between micron size and point size on film. There is 25,400 microns to the inch, so an 11 micron sensor (Tango), is equal to a spot on the film of 1/25,400 * 11 = .00043.... now, in ppi world, this is, 1/.00043 = 2,309 dpi. So if one buys into the micron = spot size, in theory, the Tango sensor is only capable of seeing 2300 dpi, however, there is more to the equation then this and we all know, no optics is linear in its ability to resolve, the fall off is dramatic towards the higher frequencies.

    In drum scanners, the ability to tighten the threads of the scan (drum scanner is nothing more then threads on a screw), is also a determining factor of resolution. The Tango probably did an excellent job in its ability to tighten the threads on the film, which is probably how they attain the 11k dpi claim. But the optics will need to interpolate this data a lot, as its not as precise as the hardware would have liked. But as with all optics, specially with LF lenses, we see the same fl, the same aperture, the same target, etc, and yet digitar lenses our resolve other LF lenses by a factor of 3. And there still is the MTF issue.... of course, none of these numbers are ever published, and its my guess, since the market came and went so fast, even the makers do not know them. hence why the easiest determining factor boils down to side by side tests with the actual film you plan to scan as well as the software for both machines. Then, we have the tuning issue, so the variables are a witches brew of possibilities.....

    for resolution, sound testing invovles scanning targets, as real worls subjects are to subjective in the analysis process. As in the sybold tests, they took scanner targets, and made each scanner perform scans at a given dpi, then made an analysis of the digital file, and made conclusions of the scanning efficiency. Meaning if they scanned at 100 lp/mm, but could only resolve 95 lp/mm, the scanner is 95% efficient. Which, btw, is the best of the batch, many of the expensive models were in the 75% range, while many consumer models can be at the 30% range.

    To me, as for resolution aspect of a scanner, this test is the culmination of all the factors involved in scanning. Plain and simple, this is the test that determines what the scanner is really resolving at a given scan resolution. My guess is, you would see Tango scans start degrading vs. their better competitors at around 1500 dpi, something less then its optical potential. But remember, most color film doesn't have more then 2500 dpi to begin with, so these numbers are not too rediculous, unless you are scanning Velvia for big enlargements, then the differences begin to surface. In my case, I saw noticeable differences in the 8x + enlargement range, i.e. Tango vs. howtek. Considering the market for film scanners have been reduced to ebay sales selling for pennies on the dollar, (other then a couple of makers that still exist on the high end) I doubt we will ever see any more analysis, life has moved on to digital capture :-) It's only us dinosaurs left !

  5. #15
    Resident Heretic Bruce Watson's Avatar
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    Drum scanner doubts

    So is it that subsequently, those companies introduced new scanners targetted for the fine art market? To the best of my knowledge, no company has ever sold a drum scanner aimed at the fine art market. My point is that the general purpose machines may do a better job with the demands of the fine art market than machines that are specifically aimed at the advertising market. This is particularly true when you get to negative films.

    isn't the reproduction ratio often higher in pre-press than fine art because most of the film used in magazine publication is 35mm? It could be about the same. When people are trying to maximize image quality, they tend to stop at about 10x enlargement. If they need bigger, they go up in format. It's the advertising industry that gave rise to the 645 format after all.

    More importantly, the advertising and magazine markets often will trade sharpness for smoothness. For example, if you are showing a model's face, would you choose sharp grain or smooth tones? Heidelberg knew the answer to that one which is why they picked that 11 micron minimum aperture. They optimized for smoothness over sharpness to meet the requirements of the target market. And that's not at all a bad thing. But if you want to use a Tango for fine art work, you should recognize that this trade off was made.

    Regarding aperture size, in practice, at what scanning resolution would you notice the difference between the Tango, and the scanners that you mention with smaller apertures? Like most things, it's going to depend on the image, the scanner, the software, and the operator. As wg says, it's a complex system. All other things being equal (an impossibility, but still), I suspect that you would start to see differences in the 2000 ppi range, and will certainly see them by the time you hit 4000 ppi.

    I suspect that the Tango's sharpness limitations are one reason that a number of "name" photographers say that "you can get all the detail off film by 2000 ppi." Because with a Tango, that's probably true. Unfortunately, this is the kind of half-truth that spreads easily. Before you know it, people are applying this litany to all scanners, true or not.

    Bruce Watson

  6. #16

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    Drum scanner doubts

    Bruce, actually, I think these half truths have some reality to them, BUT, under the right curcumstances. The confusion usually exist with the application of whats being scanned and how efficient the scanner is.

    For example, if you shoot a test target with color chrome film, with the best LF lenses (NOT MF or 35mm lenses) you will record between 35 - 50 lp/mm throughout the different areas of a 4x5 (not 8x10) piece of film (non velvia, an exceptionaly high resolving color film). So if you shot a flat subject, this is what you can record throughout the film, so lets use 43 lp/mm as an average, which equates to 43 * 50.8 = 2,184 dpi. Assuming the scanner records at 90% efficeincy, you would need to scan at 2184/.90 = 2427 dpi. This would record approx. 80% of all the rez throughout the film, if you wanted to scan for the higher resolving center portion, so maybe 2800 dpi. This is where the mis understandings begin, very few of us shoot test targets in a lab.

    Since very few shots are of flat sujbects, once you add DOF to the image, both the defocus principle and aperture difraction both severely degrade the recorded resolution. If you averaged near to far, the 43 lp/mm would be closer to 30 lp/mm, or 1700 dpi scan after efficeincy. At this scan rezolution, you would only loose a very tiny bit of resolution at the "point of exact focus", which usually represents less then 15% of the total scene, but regardless, the scan levels are relatively low.

    Now, if you use Velvia, it will kick up the numbers up to 30%, if you add an inferior scanner in the mix, say 70% efficiency, you divide by .70, and the required scan resolution grows again, which will create a larger file, but not contain anymore useful information. (just more cumbersome to work with) If you use good MF, such as M7 lenses and Velvia, the numbers can jump another 30% just for arguments sake.... so there is a need for higher resolving scanners indeed, but, for LF scenes with no lens tilt, and shot at f32, the numbers are a bit less then most think. Of course, it never hurts to scan a bit higher then needed, assuming you are not exploiting the grain of the film, then, you can down-size the file and gain a bit of resolution with a slightly smaller file.


    So, it's the application of several factors that dictate the optimum scan resolutions. (optimum = pulling all resolved data off the film without overscanning to the grain) In the color film world, to exploit everything in the film, a high / low scenario can be something like this....

    High Scan scenario
    35mm sharpest lenses, flat subject, Veliva, high contrast subject, low eff. scanner
    65 lp/mm * 50.8 / 70% = 4,700 dpi scan required, quite high indeed.....

    Low Scan scenario
    8x10 format, ISO 200 film, avg sharpness lens, f45 for DOF, low contrast subject, high eff. scanner
    20 lp/mm * 50.8 / 95% = 1,100 dpi scan required, quit low indeed.

    As you can see, this is a 400% swing in required scan resolution, quite extreme. So, in general, the image capture details is what should drive the scanning requirements (other then scan eff. factor), not vica / versa. For those who pay for scans, this can save some big $$, and for those whow work on large files on undersized PC's, it is also helpful to keep file sizes at their smallest but most optimum levels.

    Just my $.02 .... your mileage may vary

  7. #17
    Founder QT Luong's Avatar
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    Drum scanner doubts

    Do those numbers imply that for 35mm film, besides Dmax there is little point of scanning on the Tango rather than on a desktop film scanner ?

    I understand that the labs have to say that their scanner is the best, but why would they choose the Tango to begin with, when they cater to the fine art market like WCI and Calypso does ? Calypso for instance makes huge prints from 35mm for the late Galen Rowell and Franz Lanting.

  8. #18
    Resident Heretic Bruce Watson's Avatar
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    Drum scanner doubts

    wg, I did say it's going to depend on the image, the scanner, the software, and the operator. IOW, I think we generally agree. Clearly smaller formats need higher scanner resolutions, and therefore smaller apertures. But my experiments with my own 5x4 Tri-X shows me (and the 10 other people I showed it to in a highly unscientific experiment) that there's a visible difference in sharpness of prints when the only difference was the 6.25 micron aperture vs. the 12.5 micron aperture that my scanner has available (I was scanning at 11x, output at 360ppi (overkill, but I wanted to take up-rezing software out of the equation). For sharper films in this size I would expect it to be even more visible. For smaller formats I can see a need for a 3 micron aperture, but I can't imagine that anything below 6 microns has any meaning for LF users ;-)

    QT, scanning providers have somewhat different needs than individual artists. They are betting their business on the scanner, so they need service contracts and parts availability. They also need throughput, and a Tango runs significantly faster than my old ColorGetter 3 Pro. Also, as pre-press houses continue to shut down, used Tangos are available a significant savings over new ICGs and Azteks. But it's the first two things alone will drive them to stay with currently available scanners.

    As parts and service become more of a problem, I imagine that they'll move on to scanners from the last manufacturers standing - ICG, Aztek, and Screen. And they will say that whichever one they bought is the best. But they'll still mean the best for them, not necessarily the best for the artist. But that's not necessarily a bad thing as long as there is still film that needs to be scanned and companies that are willing to scan it.

    Bruce Watson

  9. #19
    Resident Heretic Bruce Watson's Avatar
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    Re: Drum scanner doubts

    Mea culpa. Boy did I screw this thread over. Turns out I was factually wrong about the Tango's minimum aperture. The real answer is that Tangos have an aperture wheel with 25 apertures available. The smallest aperture is 10 microns, not 11 micons.

    This doesn't much change my conclusions about the Tango, but it's still misinformation that needs to be corrected. So I'm correcting it now. Better late than never I hope.

    My information comes from Karl Hudson of Hudson Grafik Services, Inc., a guy who makes his living repairing and maintaining these (and other) machines. He should know is anyone does.

    Bruce Watson

  10. #20

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    Re: Drum scanner doubts

    Quote Originally Posted by Marco Frigerio View Post
    is there a way so that I can understand if the unit I'm purchasing is fine tuned or not?
    Marco
    When I bought my last scanner, I had it sent directly to Aztek for tuning/maintenance. I also made a deal with the seller that if Aztek said it was a useless bucket of bolts that I wouldn't pay for it - I was only out the shipping costs.

    Lenny
    EigerStudios
    Museum Quality Drum Scanning and Printing

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