Please lift me out of my ignorance - scanner resolution

Discussion in 'Digital Darkroom' started by peter_sage|1, Jul 6, 2011.

  1. Say I buy a dedicated film scanner that says "xxxx optical dpi"and scan a film frame.
    If I buy a flatbed that says also "xxxx optical dpi" and I scan that same film frame, with its film adapter, do I get the same resolution?
    I suppose so, an inch is an inch, but maybe I am neglecting a technical detail?
     
  2. Yes you should get the same size and resolution in the image file. Some users feel that the claimed resolution for flatbed scanners is somewhat optimistic, they may effectively only deliver around half of the maximum claimed in terms of actual image detail. They scan through glass and the focusing may be less accurate than a dedicated film scanner.
     
  3. Well, not all flatbed scanners scan through glass. Those with glassless film holders inserted into the scanner body do not (like my cranky old Microtek 1800f.) That said, flatbed scanners are still a compromise, and only work really well with MF and LF film. Scans of 35mm film are disappointing and do not come up to the quality of dedicated film scanners. Those issues may or may not be related to max optical resolution of the machines...
     
  4. Scanners only have a true optical resolution based on the pixel density of the sensor. Its an array that then moves up or down the scanner bed via a stepper motor. So when you see 6000x8000, the first (smaller) value is the optical resolution. The 2nd is the steeper motor. Since pixels are square, you can only get 6000x6000 (optical scan) OR 8000x8000 (interpolated data from the 6000 actual pixels).
     
  5. The manufacture's rated resolution and the actual measured resolution are two different things. This is what causes the confusion. Here are links to 3 tests of various scanners. You can see that 2 are exaggerated and only one is close to its stated value.
    Epson V600 - Stated Resolution 6400ppi - Measured Resolution 1560ppi.
    http://www.filmscanner.info/en/EpsonPerfectionV600Photo.html
    Nikon 5000 ED - Stated Resolution 4000ppi - Measured Resolution 3900ppi.
    http://www.filmscanner.info/en/NikonSuperCoolscan5000ED.html
    Plustik 7600i - Stated Resolution 7200ppi - Measured Resolution 3250ppi.
    http://www.filmscanner.info/en/PlustekOpticFilm7600i.html
     
  6. I see...very interesting
     
  7. You can see that 2 are exaggerated and only one is close to its stated value.​
    I'm sure the fact that the linked site sells scanning services has no impact on the objectivity of their results.
    I've seen a number of supposed "experts" claiming that flatbed scanner resolution is much lower than the manufacturers' claims. So they're accusing the manufacturers of lying and false advertising. I'd love to see one of these experts on a witness stand repeat that nonsense under oath.
    Scanner resolution is a function of sensor design. There are a certain number of sensor elements per inch. You can count them if you have a microscope. This is not some kind of smoke and mirrors (well, mirrors yes, but no smoke).
    There are many factors that will influence the resolution of your results, but scanner dpi is not one of them.
    Let's take a simple example, using a scanner that has 1000 sensor elements per inch.
    Suppose you put a target with exactly 1000 lines (500 line pairs) per inch on the bed, and align it such that each sensor element sees half of one line and half of its neighbor. The resulting scan will be a uniform gray, with no discernible detail. This does not mean that the 1000 dpi spec is wrong, it means the test methodology is flawed.
    - Leigh (using an Epson V750)
     
  8. Leigh,

    I agree. There are more than a few inaccuracies on the German's website.

    If anyone has access to the test pattern negative he uses, I'll buy one and test, and post results. Ironically of all the
    scanner stuff he sells, I could not find him selling that. Personally, I don't think he uses a negative at all, but does his
    tests with a printed card of some type and tests using reflective scanning. Which I think is a false test.

    His suggestion to scan at lower settings because there is no difference in the output, is absolutely wrong when I've
    tested my new Epson V500. I will state this, the resolution of the V500(at highest settings) is greater than using my
    Beseler 67 with EL Nikkor 80mm on Ilford paper. And the response curve/dynamic range is spot on to the negative,
    which it is not with paper.
     
  9. Unfortunately even if the Epsons sensors have enough resolution the lenses in the v500 type scanners are not that great.
    Epson V600 - Stated Resolution 6400ppi - Measured Resolution 1560ppi.
    That seems to be about fair maybe a good example may resolve a little more but these are not 6400ppi scanners. They may produce files that are 6400ppi but the is just not 6400ppi of real detail in those scans.
    If you make scans with a v500 at 2400ppi you will get pretty good scans for smaller sized prints, but scans at 6400ppi just won't be that much better if at all.
     
  10. Hi Richard,
    That's a standard USAF 1951 resolution target, available from everybody.
    But to adequately assess performance at the 4800+ dpi level requires a very high quality target indeed. I would certainly expect to use a deposited chrome on optical glass target for this test. They're available from Edmund Optics and other companies.
    I've considered buying Edmund's scanner resolution target, which is made with that technology and goes down to 2-micrometer (12,700 dpi) target sizes IIRC. But it's $450, and I'm not that interested in proving to myself what I already know.
    - Leigh
     
  11. ... these are not 6400ppi scanners.​
    Do they claim to be? Is that optical or interpolated resolution?
    My V750 only claims 4800ppi optical. I find it hard to believe that Epson would bring out new products (the V7xx) with lower performance than previous (V600) models.
    - Leigh
     
  12. Yep the v500 claims to be 6400 ppi optical resolution. I threw my box away some time ago otherwise I would snap a shot of it.
     
  13. One 6400pp scan from a v500 full image plus 100% crop. I don't what others think, for me it is pretty good for a flat bed but it likely is not as good as a Nikon coolscan.
    00Z091-377083584.jpg
     
  14. Interesting.
    What's the maximum size of an original at 6400 ppi?
    - Leigh
     
  15. 8298 x 5141 was the size of that particular scan at 6400ppi. It varies from mounted slides to unmounted slides/negatives as more image is visible on an unmounted slide but there is not much in it. I think to that some brands of mount may mask more than others but 8298x5141 was the size of that scan.
     
  16. Hi Stuart,
    I meant the dimensions of the original. The V750 will do up to 4"x5" at high resolution. I was wondering if the V500 would do that size or if it was limited to smaller originals.
    Thanks.
    - Leigh
     
  17. Sorry just regular 35mm Fuji Chrome. The V500 only scans film up to 6 cm wide so 120 is the limit with a v500.
     
  18. As Andrew pointed out there is the true electronic or optical resolution based on the pixel pitch of the scanning bar.
    So by that standard if the manufacturers are being honest, any 4000 ppi scanner is a 4000 ppi scanner.

    However there is often a difference between resolution of the real detail in the film and what you get in the film. Just
    as with a camera you get more resolved detail with any scanner when it is actually focused on the plane of the film's
    emulsion. If you cannot focus the scanner by either adjusting the height of the film plane or of the scanning bar unless
    you are very lucky you won't get the full amount of detail the scanner is capable of resolving. Focusing the scanner is
    also complicated by the fact that most film has a curve to it, so ideally you want to either hold the film flat or focus
    somewhere in the curve so that (hopefully) there is enough depth of field that the entirety of the frame you are
    scanning is in adequate focus.

    Without getting into the virtues of drum scanners or even the Hasselblad/Imacon Flextight virtual drum scanners there
    are third party fluid scanning options made for various desktop flatbed scanners and Aztek made one for the now
    discontinued Nikon Coolscan 8000 and 9000 scanners. These options let you set the optimal height and hold the film
    flat. Epson also includes a fluid scanning tray with the V750 scanner.
     
  19. Hi
    Here you can find an interesting part of a Epson V750 flatbed scanner review, and one of the conclusions was that the best 35mm film scan seems to come out at 3200 dpi, well below the maximum indicated optical resolution:
    http://www.photo-i.co.uk/Reviews/interactive/Epson%20V750/page_4.htm
    (you can find this conclusion together with the opinion on definition. at the bottom ยงs of page 4)
    This review is quite complete and recognizes the advantage of dedicated scanners, but it also puts things in perspective, namely concerning prices and the intended uses for the scans.
     
  20. OK. That explains the difference. You need higher resolution for smaller originals.
    Thanks.
    - Leigh
     
  21. I've seen a number of supposed "experts" claiming that flatbed scanner resolution is much lower than the manufacturers' claims. So they're accusing the manufacturers of lying and false advertising. I'd love to see one of these experts on a witness stand repeat that nonsense under oath.​
    I would like to see one objective measured testing result showing a flatbed scanner meeting the manufacturer's rated resolution. Please post a link to the testing results for all to see.
     
  22. Please post a link to the testing results for all to see.​
    Ask the manufacturer. It's their specs you're challenging, not mine.
    - Leigh
     
  23. As you can see from the responses, there are other variables to a scanner's output quality than the resolution. A scanner is sort of like a camera; film size matters. Scanning a smaller negative requires much more resolution (since the image will be effectively 'enlarged' more on printing), and things like lens quality and film flatness become much more important.
    The other thing to keep in mind is that since the image sensor produces many 500x500 dpi images, and then combines them (random numbers there folks), larger images will benefit more from this as well. If a negative is very small, the scanner's sensor may not be able to move itself into enough places to take a full XXXX dpi image without overlapping, and thus wasting pixels. This is why you could scan a print or 4x5 negative and get almost stated resolution, while 35mm negatives may look the same at stated resolutions as they do at half of stated resolution. For instance, I doubt you'll get much more detail out of a 110 negative at 4000 dpi than 1500 dpi for this reason, along with many others.
    Lastly, flatbed scanners almost all scan at a single preset exposure, and digitally alter the exposure to provide 'brighter' or 'darker' scans. This can lead to shallower dynamic range, and more grain in shadow areas. Some dedicated scanners, and most drum scanners, can actually alter exposure time like an enlarger, giving you a MUCH higher-quality scan of even slightly under or over-exposed images.
    Richard Sperry [​IMG][​IMG], Jul 06, 2011; 02:16 p.m.
    His suggestion to scan at lower settings because there is no difference in the output, is absolutely wrong when I've tested my new Epson V500. I will state this, the resolution of the V500(at highest settings) is greater than using my Beseler 67 with EL Nikkor 80mm on Ilford paper. And the response curve/dynamic range is spot on to the negative, which it is not with paper.​
    While this is true, I think you're leaving out some of the story. For starters, I find Ilford paper to be much more contrasty than other brands (I've switched to Kentmere, which is actually almost the same brand, but does expose differently), and that will influence your results. I also find - and my negatives tend to be very dark, so your milage may vary - that being able to have "true" exposure control, rather than a digitally edited single exposure, usually results in much better dynamic range from my negatives. Again, Kentmere paper, low contrast, and often different filters in different sections. I also use Moersch paper developers and I'm printing 6x6, so I really want to stress the 'your milage may vary' part :) Personally, I find that if I really work hard on it and waste a lot of paper, I can get much better tonal range with an enlarger than even with the Coolscans.
    Another thing to remember is that most inkjet printers are extremely contrasty in the shadows, and like to clip details. Even if your scan has great dynamic range, that doesn't always mean that your print will have great dynamic range.
    I'm in no way arguing with you Richard - just pointing out that depending on how your own personal negatives are shot and developed, you may get drastically different results. My guess is that your average shooter can probably expect results somewhere in between what you and I are getting with our negatives.
     
  24. Zack,

    When I view a bare negative I can visually see detail in both the light and dark areas. When I wet print to get that
    detail in both I need to use filters(usually split filtering, with dodging and burning) with Ilford papers. If I straight print for one, I
    lose the other.

    "Personally, I find that if I really work hard on it and waste a lot of paper..."

    I concur. But I have to do neither with the V500. And it really does give me a good idea of what I need to do with a
    negative to achieve the results that I intend.

    Ive purchased Adorama paper(which some say is Kentmere) and will be testing that soon.

    I have no intention or desire to ever inkjet or process print any scans. Film is only a hobby for me,
    and when I do print negatives it will be to gelatin silver paper. I also have no intention of ever buying a $4000 used Nikon scanner, it's just something that will not ever happen.


    In any regard, film flatness appears to be the limiting factor. Not the optics or resolution.
     
  25. Richard, have you experimented with other papers or developers? Your eyes and the negative are both capable of seeing a much broader dynamic range than either form of paper print can show without a lot of coercion. It's possible that if your paper is too contrasty, you'll lose shadow or highlight detail. Also your average variable contrast paper will have a little shorter tonal range than a graded paper, particularly in the shadow areas. To counteract this, I use a graded paper (usually #2) and make my prints a little bit lighter than I normally would want them. I use Moersch neutral developer, which develops a little more evenly across the tonal range than your average Dektol or the like. Lastly, I use a selenium toner to darken up shadow areas. It's sort of like the analog equivalent of shooting a low-contrast RAW file, and then bringing up the black levels.
    Also, just to play devil's advocate ... if you don't print any scans, and you have no intention of printing them, how do you know if the range really is better than your darkroom prints?
    Since film is just a hobby for you, I'd advise screwing around with some different stuff next time you trot out the camera. I don't know your system and I don't presume to, but I'd try some PanF+ 50 if you havent yet. The film can be really contrasty using standard developing methods, but the tonal range is absolutely phenominal, and it's silly sharp. I find that if you expose it at 25 ISO and develop it at 50, but for lower contrast, you get an even broader tonal range.
    The only downside to this method is that it produces a very dense negative. With an enlarger that's no problem: you just print longer. But with a scanner, the denser negative may result in clipped highlights or shadows, unless it's one of those scanners that can vary exposure times. For what it's worth, the widest tonal range I've ever had was on PanF+, overexposed and developed as mentioned, and then printed with a Rodenstock 150mm at f/11. My printing time was a whopping 5 minutes, but that probably wouldn't have happened if I wasn't printing from a few feet away. It actually got up to about 20 minutes when I decided to vignette the edges and burn in a few areas :p
     
  26. The "resolution" that manufacturers specify reflects only the number of pixels that are generated in the output files, i.e. the Nyquist-limited resolution (though even that can be fudged by using interpolation). These specifications do not say anything about the ability of the scanner to actually resolve features on the negative or reflective medium.
    For those who are interested in a serious evaluation of scanner resolution, I suggest the following paper:
    http://www.aspbooks.org/a/volumes/article_details/?paper_id=30173
    The author Robert Simcoe is an engineer who recently led a group building a specialized high-resolution scanner to digitize astronomical photographic plates. I think it is reasonable to assume that he knows what he is talking about. In this paper, he compares an Epson V750 and Nikon Coolscan 9000, using a slanted-edge method to measure the modulation transfer function (MTF). In brief, the resolution of the Coolscan approaches its advertised Nyquist resolution (4000 ppi), but the Epson falls far short of its advertised resolution. This is almost certainly due to the optical limitations. In addition, Simcoe explains how the advertised resolutions of flat-bed scanners are "padded" by interpolating data from staggered CCD arrays. This also contributes to the difference between the specifications and real resolution.
    I have also used the slanted edge test to measure the MTF of a Coolscan 8000 and an Epson V500. I didn't do it as carefully as Simcoe did, or with as good a target, but my results were quite similar to what he describes.
    The reason that Epson and others can get away with the specifications they cite is that the numbers have a carefully-specified meaning, it's just not what most people would expect "resolution" to mean. Personally, I think that this is unfortunate. The real resolution of inexpensive flat-bed scanners is really very impressive for their cost, without any spec-manship. Not surprisingly, though, the resolution is not comparable to much more expensive film scanners.
    I have a copy of the paper described above, but it is copyright protected. If you send me a personal message, I will send a pdf to you (assuming that I don't get hundreds of requests!).
    David
     
  27. David, this spec discussion reminds me very much of how cheap speakers are rated. Generally speakers are rated in wattage (how much power they can handle), and for the better ones, sensitivity (how loud they are per watt). An inexpensive car subwoofer would very frequently be advertised at 1000 watts. But if you played a song into it from a 1000 watt amplifier, the speaker will blow in seconds. They get the 1000 watt rating because it can handle one very specific frequency at 1000 watts, and not because you can actually pump 1000 watts into it. The actual watt handling might be around 150.
    Isn't marketing great?
     
  28. IMO Epsons are really only able to capture 2400 dpi, expecting more is just setting yourself up for disappointment.
    Why, just as some have said: lens, light surce, ccd, stepper motor, film holders, and scanning through glass. Why can
    they claim higher? Because they can give you a file of a higher "resolution", so they meet the truth in advertising idea.
    No where does it say that those higher "resolution" files have a one to one relationship between a pixel and a sample
    site.

    Should you buy Epsons? That is up to you, if the tool fits your needs then it might be ok to use it. Be careful in
    evaluating examples. I found that after being on the scanning learning curve for a little while that I became aware of the
    effects of over post processing of images, I missed that a lot of examples were not living up to the standards I wanted
    to achieve. So, I bought wrong and wasted a good amount of time.

    Of course take my opinion in it's contex, I wanted to get all the detail I could out of the film I shot. To be frank the Nikons fall a little short in that regard as well, but still more than twice as good as the Epsons.
     
  29. David,
    Thanks for posting the link. I downloaded the article. It gives the best explanation for the lower resolution found on flatbed scanners that I have read.
    This is the type of information that enhances our understanding of the scanning hardware available. I think this can aid buying decisions that match the user's needs and budget.
     
  30. IMO Epsons are really only able to capture 2400 dpi, expecting more is just setting yourself up for disappointment.​
    Scanning at 6400 and 2400 respectively produce two different apparent images, the 2400 has larger pixels at the same size magnification.
    Also, if what you say is true, then all that is happening is that the scanner is splitting the same pixel to make more than one, say 4 for convenience sake. Magnifying down to say a block of 4 pixels in the 6400 scanned file, should reveal that the pixels are the same color. And that does not occur.
    Additionally, if you are repeating the German's conclusion that one should limit scanning dpi to 2400 with the Epsons; one should keep in mind post processing(who would print a raw scan?). For example, Unsharp Mask a 2400 scan and a 6400 scan at the same setting, or even converted/comparable setting, reveals two very different results.
     
  31. Here is a 35mm scan, on the Epson V500(at $160), at the PNet max size of 700px inline.
    [​IMG]
    Here is a 100% selection for comparison(700x700).
    [​IMG]
     
  32. Additionally, if you are repeating the German's conclusion that one should limit scanning dpi to 2400 with the Epsons; one should keep in mind post processing(who would print a raw scan?).​
    Richard,
    I couldn't find where the German site specifies that one should limit scanning to 2400dpi on any of their Epson scanner tests.
    Typically in their tests they make resolution tests at various settings to see if there is any improvement in using a higher setting. If all you get is a larger file then they recommend using the lower setting. This is what happened with their Epson V600 test. They found that using the 3200ppi setting gave the maximum resolution along with a smaller file size.
     
  33. Marc,
    I get a much better scan at 6400dpi at a lower percent size, say 25%, than with lowering the dpi; while decreasing scan time and file size. With the V500; considering that the V500 and V600 have similar specs, I will assume that they are scanning relatively the same.
    I couldn't find where the German site specifies that one should limit scanning to 2400dpi on any of their Epson scanner tests.​
    I was in error, this is what he wrote.
    In order to achieve the maximum resolution of 1560ppi, one does not have only to scan the with the highest optical resolution but it is sufficient to digitalize the original with 3200ppi. The effectively achieved resolution does not differ, no matter if one scans with 3200ppi or with 6400ppi - in both cases, an effective resolution of 1560ppi will be achieved! By this way, it does not make sense to scan with the Epson Perfection V600 Photowith 6400ppi.​
    From, http://www.filmscanner.info/en/EpsonPerfectionV600Photo.html
     
  34. ...in both cases, an effective resolution of 1560ppi will be achieved!​
    Given that they only wanted 1560 dpi in the first place...
    how could their opinion possibly be relevant to the maximum achievable resolution of the scanner?
    - Leigh
     
  35. Leigh,
    The German states that the 1560dpi is the maximum resolution of the V600. While theoretically it doesn't make any sense to scan at 6400 when max resolution is 1600, and 3200 should suffice.
    Experimenting with actual scanning results with different results than his conclusions. The scans look different, and behave different with typical post processing, say Unsharp Mask at the very least.
    I definitely do not think that a 4000 dollar scanner is needed for negative proofing and posting film images to the web. I know I am in the minority here in supporting cheap low cost scanners, but I am just going off what I see. A Coolscan 9000 scan, sent out, is going to cost me about 40 dollars per 6x6 negative; that equates to 4 scans to buy the V500 new for my self.
    Honestly, the thought has crossed my mind to buy one just as back up for when they are discontinued, and this one breaks down, as a spare. For all you pros, who sell enough prints to justify a 9000 scan or buying a drum scanner, by all means do so.
    But it is certainly not the only option for a hobbyist photographer.
     
  36. Richard, Leigh, etc. :
    I'm just guessing here, but comments about the limitations of a scanner's dpi might have less to do with sensor resolution, and more to do with lens/processor resolution. I don't know the engineering specs of each model so please feel free to disagree with my point, but not my math. I know these are arbitrary numbers :)
    Let's say you have a very small black to white gradient, and the scanner records that as a line of ten distinct pixels at a given resolution. That gives you ten distinct 'objects' in your scan of a given size. If you sharpen the heck out of your image, each one of those ten objects will have a slight border. Let's assume worst-case scenario, and say that the lens or the processor can only see those ten colours. I know that no scanner in the world is that bad, but go with me here.
    If we quadruple the resolution while keeping the lens and processor the same, each 'object' recorded by the scanner will be four pixels. However, the image will look identical, because the scanner can only see ten colours. The resolution jump would imply that we are now getting 20 colours (since there are twice as many pixels going from black to white), but the lens and/or processor limitations are still 'squishing' that into ten colours. If we sharpen the image, we'll still get ten distinct objects of the same size, although the border will now be slightly smaller, since the pixels are all smaller. We won't get any more actual information that the original scan though.
    The only thing we might get is more grain pattern in the scan, as the scanner is looking for smaller and smaller objects of the same ten colours. In other words, scanning at a higher resolution than the lens and/or processor can support may actually degrade your image.
    I suspect is that this is what various people are talking about when they say that 'scanner X only has half of the listed resolution.' Obviously you can right click it and see that it really has more resolution than the review says, but it might not contain as much detail as the resolution numbers would indicate. This is probably lose in the German to English translation.
    My thinking, Richard, is that the reason you're getting a better scan at 'full resolution, partial size' is because you're essentially giving the processor a larger sample space. By setting it at 25% you're throwing out 3 out of 4 pixels, but scanning at full res allows it to see more pixels and make a better decision about which three to toss out. Sony claims that the compression on their AVCHD movies works this way, and that it results in better image quality.
     
  37. Sorry,l Zack, but you're totally missing the point.
    You're confusing post-processing with what the scanner does. They're two entirely different and unrelated subjects.
    You can't "quadruple" the resolution, or double it, or whatever. It is what it is. You can reduce it if you wish to get a smaller file size, but you can't increase it.
    - Leigh
     
  38. I definitely do not think that a 4000 dollar scanner is needed for negative proofing and posting film images to the web. I know I am in the minority here in supporting cheap low cost scanners, but I am just going off what I see.​
    I absolutely agree! But, there really is a difference between a flat-bed scanner and a film scanner. I mentioned before that I had performed slanted-edge MTF tests on an Epson V500 and a Coolscan 8000. Here are graphs from those measurements.
    For those who aren't used to graphs of this sort, the vertical axis represents the fraction of the orginal contrast that is recovered in the scan, and the horizontal axis represents different spatial frequencies in cycles per inch. For the Epson, the maximum frequency is 3200 cycles per inch (one half of the maximum number of pixels per inch), while the maximum for the Coolscan is 2000 cpi. The individual curves are from scans made at different resolution settings.
    For the Epson, the curves with scan resolutions of 6400, 3200 and 2400 ppi are essentially identical, meaning that no additional information is gained by using a setting greater than 2400. At 1200 ppi, the Nyquist limit (600 cpi) is reached before the optical limit is. The relationship between MTF and resolution is somewhat arbitrary, but one interpretation is to say that the maximum frequency at which the MTF is greater than 10% corresponds to the maximum resolution. In this case, this occurs at about 700-800 cpi, which would correspond to about 1500 dpi. This is pretty close to what www.filmscanner.info says for the V600, using a different method (a resolution chart).
    For the Coolscan set for 4000 ppi, the MTF curve reaches 10% at about 1400 cpi, or 2800 dpi. Reducing the scan resolution to 3000 dpi causes a noticeable loss in information, and the MTF curve just reaches the Nyquist limit. With a 2000 dpi scan, the result is clearly limited by the scan resolution.
    For my slanted edge, I used a double-edged razor blade in a glass slide mount. This may not be ideal, since the blade is very reflective. But, I think that the comparison makes the relative performance of the two scanners pretty clear.
    Whether or not this difference is important, depends entirely on the user and application. In my experience, one of the practical differences is that scans from the Coolscan require minimum sharpening, with correspondingly less artifacts.
    As always, YMMV.
    David
    P.S. For more about MTF and the slanted edge test, see this page:
    http://www.imatest.com/docs/sharpness.html
    00Z0sX-377909584.jpg
     
  39. Here is the graph for the Coolscan 8000
    00Z0sY-377911584.jpg
     
  40. David,

    Do you have any scans, that can be posted, of the same negative from both scanners for comparison?
     
  41. Richard,
    Funny you should ask! 2 1/2 years ago I started what turned out to be a very long thread, very similar to this one, by posting scans from the V500 and a Coolscan V:
    http://www.photo.net/medium-format-photography-forum/00RS5y?start=0
    (Depending on your browser you may have to go to the fourth page of the thread to actually see the scans. I had some file format problems.)
    There are lots of other comparisons like this on the web, and one can pixel peep to justify just about any conclusion one wants! As demonstrated by the this and other threads.
    David
     
  42. Thank you David for the link.
     
  43. Leigh B. [​IMG][​IMG], Jul 08, 2011; 08:46 p.m.
    Sorry,l Zack, but you're totally missing the point.
    You're confusing post-processing with what the scanner does. They're two entirely different and unrelated subjects.
    You can't "quadruple" the resolution, or double it, or whatever. It is what it is. You can reduce it if you wish to get a smaller file size, but you can't increase it.
    - Leigh​
    Leigh, I think you may be misreading my post. With the exception of sharpening, I didn't discuss post-processing. The scanner itself processes the images. When I was discussing processors, I was referring to the one built into the scanner. If the processor built into the scanner is only able to process X amount of tones, then it will continue to see a maximum of that number regardless of how much resolution you give it to use as a sample size.
    As an anology, take the Nikon D40 and similar cameras. My experience is that those cameras are much more likely to blow out highlight detail than the larger Nikons, even shooting in RAW. The sensor (the camera's eyes) may be the same as in a more expensive camera, but the processor (the camera's brain) in unable to comprehend the entire gamut of tones. Thus, highlights and shadows are occassionally clipped, even though the camera technically 'sees' the same thing, and you're theoretically not processing the image. To take the anology a step further, I have a friend who is legally unable to drive. He has better than 20/20 vision, and has no felony history. The reason he can't drive is that for some reason his brain (his processor) can't take the images from his eyes and create depth. Even though his eyes are great, he has no depth perception whatsoever, and can only guess at distances based on relative sizes.
    I'm not saying that all, or any, flatbed scanners are this limited. I am, however, saying that the ability of the scanner to actually parse the information it is seeing is just as important as what it sees.
    You can't "quadruple" the resolution, or double it, or whatever. It is what it is. You can reduce it if you wish to get a smaller file size, but you can't increase it.​
    Again, I wasn't referring to quadrupling the resolution in post. I was referring to scanning the image at a resolution that is four times higher. If the processor is maxed out at a given scanning resolution, scanning at a higher resolution will give the same or only slightly better results.
     

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