Need to capture accurate colors from scanner

Discussion in 'Digital Photography' started by JibeHo, Jul 26, 2015.

  1. JibeHo, Jul 26, 2015
    Last edited: Jul 26, 2015

    JibeHo macrumors newbie

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    Jul 26, 2015
    #1
    Hi, this is my first post. I use os x 10.9 and I have a Canon MX920 series scanner/printer. I use the scanner flatbed to capture images of fabric (cotton, polyester fleece, etc) for product images. When I scan fabrics, in many cases the colors as presented on-screen look drastically different than the colors of the fabric under natural light. My customers require accurate color representation. I have calibrated my monitor (macbook pro) using the built in System Preferences -> Displays -> Color -> Calibrate tool. I chose the expert mode where one must adjust the slides for brightness and so forth. My problem persists.

    As I understand it (which is not very well) I could fix the images ad-hoc using, say, photoshop. I do have photoshop available. But I have hundreds of scans to capture and that doesn't strike me as efficient. I have done some reading and discovered that with the appropriate software, one can calibrate a scanner by scanning an IT8 target and recording the discrepancies in the color representation, creating a "profile" of a scanner. That sounds like exactly what I need, but I'm uncertain what product someone with my limited requirements should be looking at. I've looked briefly at both VueScan and SilverFast. I admit that it is difficult for me as a non-photographer to see through all the detail and find the simplest, most economical product suitable for merely profiling my scanner so I can capture the correct colors.

    Am I missing some native app that will do this one thing?

    If not, what product do you recommend I get, given my seemingly basic requirements?

    Also, is there a more sophisticated way to calibrate my monitor that you would recommend in my situation?

    Thank you, in advance, for your help!

    EDIT:
    Of course, if there's another forum I should take my questions to, please advise. Thanks.
     
  2. swordio777 macrumors 6502

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    #2
    Hi JibeHo,

    Natural daylight is very close to white. The light inside your scanner may not be anywhere near white, so this could be part of the problem.

    Using dedicated colour calibration might help, but unfortunately, no amount of colour calibration will get 100% perfect results.

    You mentioned you had access to Photoshop, so the most convenient way to guarantee that the colours in your scan are 100% accurate (without buying any new equipment) is probably by using a colour histogram to review your scanned images.

    The scanner will always be out by the same amount each time. Scan an 18% grey card, then take the image in to photoshop to view the colour histogram. If the scan is accurate, the red green and blue spikes should overlap exactly. If they do not, use the Channel Mixer tool to tweak until they overlap. (Whatever you do, do NOT use Image > Adjustments > Hue/Saturation, as it will introduce its own colour shift and will not produce consistent results across different colours.)

    Once you know exactly how much you need to adjust the channel mixer by, this value will remain the same for everything you scan using that scanner. From here, you can create a Photoshop action or droplet which will automatically add the necessary changes to any image and re-save it.

    This would allow you to scan everything, then when you have all the images saved to your computer just drop that folder on the droplet and it will do all the work for you.

    When doing this, it's important to trust the histogram and not your eyes. Different monitors will be differently calibrated, but using the colour histogram you know the digital file is definitely accurate.

    I really hope this helps. Good luck!

    Iain
     
  3. MisterMe macrumors G4

    MisterMe

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    #3
  4. JibeHo thread starter macrumors newbie

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    #4
    Awesome information - that sounds like exactly what I need. Thanks Iain!
     
  5. JibeHo, Jul 26, 2015
    Last edited: Jul 26, 2015

    JibeHo thread starter macrumors newbie

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    #5
    I certainly never figured it was magic - it's just that I didn't know how to do it, but thought perhaps amateur and professional digital photographers ought to. I calibrated my monitor, using the only tool I had available. If you think it was insufficient, I'm happy to hear about that. There is neither a camera nor a printer in the domain of this problem. That leaves the scanner. Hence me asking how to calibrate a scanner.

    Thanks!

    EDIT: I realize that I had asked about recommended, more sophisticated monitor calibration tools. I appreciate the link, to that end. I think I will stick with OS X's built in utility, considering swordio777's histogram solution doesn't require any particular monitor color accuracy. Thanks for your reply!
     
  6. ChrisA macrumors G4

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    Redondo Beach, California
    #6
    To calibrate a scanner you need a color test target and some software. The test target is a very accurately printed chart with color samples. It can be expensive and you need to store it well. The key Google word is "IT8" this is the standard. The target will have a VERY wide color and density range, likely wider than your scanner can capture

    Wikipedia lists the places you can get this.
    https://en.wikipedia.org/wiki/IT8

    So you place this chart in the scanner and each square is filed with a known color and the software knows what the scanner SHOULD be sending. So the software can figure out the error and create a color transform that will correct out as much of the error as possible.
     
  7. ChrisA macrumors G4

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    #7
     
  8. ChrisA macrumors G4

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    #8
    Your post processing method will make nice looking photos but is not going to work as well as simply calibrating the scanner. Mac OS X has built-in color calibration were you can specify a color calibration matrix for each device (monitors, printers, scanners and cameras) Your method assumes the error is linear. You many check at the 18% level but the calibration test target will check each color channels a dozen points, at least. Then once you instal the color correction matrix you do not need to fix the images in PS any more

    You do need to periodically re-calibrate the scanner because the bulb will age over time.
     
  9. MCAsan macrumors 601

    MCAsan

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    #9
    Mac screens are sRGB. If color accuracy is important, you might want to use and calibrate an external AdobeRGB screen.
     
  10. JibeHo thread starter macrumors newbie

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    Jul 26, 2015
    #10
    Thanks for the replies so far. In the spirit of working from least expensive to most expensive, I've ordered a gray card and will attempt the histogram technique in photoshop and see if that produces satisfactory results.

    I'll be sure to inform you all of my results in a few days.
     
  11. JibeHo, Jul 30, 2015
    Last edited: Jul 30, 2015

    JibeHo thread starter macrumors newbie

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    #11
    Well, my gray card came in yesterday and I had a chance this morning to mess around with it. It seems my scanner is heavy on the blue. Using photoshop's channel mixer, I at first simply "moved" the blue over to the left to overlap the red and green. I saved that preset and applied it to my scan of a peach-colored product. It was a noticeable improvement, but still unsatisfactory. I compared the edited version to both the fabric in natural light and downloaded images from the manufacturer and another party. Those downloaded images were both similar to each other in color and to the physical fabric. I consider that a poor man's screen calibration and assume my screen is displaying properly. Next, I tried "moving" the red and green over to the right to meet the blue at the higher level using the channel mixer. This was not significantly more accurate colorwise, but the "brightness" (excuse the imprecision of my language) was a bit more accurate.

    Stumped, and seemingly having reached the limit of the gray card's usefulness with respect to this problem, I decided to simply mix the channels on my raw scan of the product until it looked like the real thing. This got me a remarkable accurate image, and, in my excitement, I thought I'd solved all my problems. The trouble is, this preset that I developed does not work with other colors. Some colors come right from the scanner needing no changes, some come from the scanner needing changes that the preset fixes (the peach color), and others come from the scanner needing changes but are made worse (or, not measurably worse but different looking and still unacceptable) when I apply the preset.

    So I've looked into VueScan and have purchased an IT8 target. If anyone is interested in learning about my results after calibrating, I'll be happy to share. Otherwise, thank you all very much for your advice.
     
  12. ftaok macrumors 601

    ftaok

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    #12
    I would absolutely be interested in your exploits. Please update this thread when you solve the problem.

    Good luck!
     
  13. Designer Dale macrumors 68040

    Designer Dale

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    #13
    Just an observation here. You are scanning fabric on a flatbed which is primarily designed for flat surfaces like photos. The texture of the fabric might be reflecting the scanner light at angles that cause it to distort the true colors somehow. Maybe light refraction? I think you are going about this the wrong or at least difficult way. Your competition, those folks who seem to be able to get the product colors right, are most probably photographing the fabric on a fixed camera stand with even natural lighting.

    Maybe something like this? http://www.bhphotovideo.com/c/product/99444-REG/Beseler_4205_CS_14_Copystand_Kit.html

    You can also get neutral grey backing paper from a photo supplier and pin it to a wall. Light it evenly with a pair of studio lights in soft boxes and use a tripod.

    Having a product studio that is separate from your computer work will help your work flow.

    Dale
     
  14. dwig macrumors 6502

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    Key West FL
    #14
    I is quite impossible to get the scanner, of digital camera for that matter, to produce files, even after using an image editor to "correct" them, to look exactly like the original fabric whether the files are displayed on screen or printed. The best you can do is get them close to correct and still there will be some hues produced by some dyes that won't every be even close. FOL

    Note:
    • You need to tailor your files to fit you client's usage. If they are going to display them onscreen (e.g. web page, ...) then be sure to embed the color profile that you use. Also, using sRGB might be better than AdobeRGB because it better fits most monitors out there. AdobeRGB or ProRGB will be better for most RGB printing.
    • You need to be sure to use an appropriate backing for the fabrics since some light will pass though the weave of most materials. You may find that white is not universally the best. Sometimes you may find that a good neutral middle grey or even black works better.
     
  15. dadohead macrumors newbie

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    May 27, 2008
    #15
    Okay, so much bad information here. There is no such thing as "natural daylight" being close to white. What time of day daylight? Because the color temperature of "daylight" and thus the nature of "white" can change by several thousand degrees Kelvin from sunrise to noon, and even at noon the color temperature in the shade is very different from the color temperature in the open. White is essentially meaningless.

    You have two separate problems here;

    1) You need a color calibrated workflow. It doesn't matter whether you use Adobe RGB or sRGB. SRGB would probably be a better choice for you, as you have to interface with clients and others who will have even less of a calibrated workflow than you do. Adobe RGB, while having better "gamut" (number of colors), gets tricky in the wild. If color accuracy is important to you, you need to use a hardware calibrator to calibrate your color monitor. Software monitor calibrators are absolutely worthless; anyone who tells you different is not to be trusted. Having said that, any recent LCD panel is pretty flat and will stay that way for quite a while; a CRT will go out of whack if you sneeze near it. A Datacolor Spyder costs about $150. You can also maybe get someone to profile the monitor for you, if you live in an area with a robust tech presence. The hardware monitor will linearize your monitor.

    More important, you also need to profile your scanner. A target composed of many swatches is scanned and run through a piece of software which creates a profile that you attach to the scanned file, usually at the time of scanning, or when opening the file in PS. This process linearizes the scanner and balances the 3 color channels. You are not changing the color nature of the lamp or sensor in the scanner, you are only telling the OS or Photoshop how to interpret the color information in the scanned file. I'm not familiar with the scanner/printer you mention, but VueScan, while not for the faint of heart, will honor and attach custom profiles and run any scanner ever made. You can also profile a scanner using VueScan, but I wouldn't advise my worst enemy to do this. This process works best with higher bit scanning (like 36 or 48-bit) because you have lots of overhead to shift the colors, but with the proper technique 24-bit scans can work without much loss of color info. It depends how out of whack the native color of the scanner lamp and sensor is. The part that poses a problem for you is the printer/scanner. Generally, printer/scanners excel at neither. But someone truly skilled at color management could get acceptable results from one. You should probably get someone to do that part of it for you, but here is a lengthy description of the process http://people.rit.edu/med2823/colormanageproject/scanners.html An ongoing problem for you, however, will be that you could get stone-cold accurate color on your end, but if your clients have not endeavored to create an even moderately color managed system on their end, there's no telling what they might see.

    2) The above system will work great for photos. But it seems like you might be scanning fabrics directly on the scanner. The bigger problem here is lots of fabrics have fluorescence in the dye mix, making the colors pop, or use fluorescence as a brightener. The scanner can't see this (film can't either) and won't record it, making the colors appear dull in the scanned file, especially hot pastels. And, as others have pointed out, the weave itself may make colors look different depending on the angle of the light. Business that need to target colors use what is called a photospectrometer, a device which analyses the spectral qualities of anything reflective and has bypass filters for optical brighteners. These devices can tell the user the exact color values of a color independent of lighting or color temperature, allowing manipulation and replication of a color in a digital file (limited, of course, by the reproduction method) to a target value. The photo spectrometer can also calibrate a monitor and profile a scanner, among lots of other things. An example is an i1Pro by XRite. A Color Munki would also work, but I believe this has been discontinued. The i1Pro solution costs $2000 with the scanner capability. If you did a lot of this, like 100s of samples a month, the i1 would pay for itself in no time. For many years I photographed, scanned and printed fabric samples. It took years to get an accurate system and a lot of it was waiting for the right tools to be developed.

    Honestly, I'd advise you to pay someone to set this up for you, but purchasing VueScan and a target is a good DIY place to start. You would do well to get a copy of "The VueScan Bible." Getting through Ed's documentation can be challenging. Good luck.
     
  16. swordio777 macrumors 6502

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    #16
    Please do let us know how you get on.
    Best of luck!
    Iain
     
  17. JibeHo thread starter macrumors newbie

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    Jul 26, 2015
    #17
    Thanks for the new perspective. That is a cool gagdet, and I will definitely look into something like that if I exhaust all reasonable possibilities of doing this with the equipment I have already (READ: my inexpensive home office scanner).
     
  18. JibeHo thread starter macrumors newbie

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    Jul 26, 2015
    #18
    Gratefully noted. This is for a website, so I will stick with the sRGB, then.

    Also, I'll experiment with using my new gray card for a backing in the scanner.

    Thanks for the tips.
     
  19. JibeHo thread starter macrumors newbie

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    Jul 26, 2015
    #19
    There's a lot of good info here! Without having yet had time to follow the link you posted nor to read the VueScan manual (particularly about calibration), my knee-jerk question is:

    What software, as a substitute for VueScan, would you advise a complete stranger to use?

    I have looked at SilverFast, however: (a) from what I've read so far on their site, software is licensed to a particular device, which is not ideal for someone whose decision to purchase a better scanner hinges on whether their current device will perform, once calibrated; (b) looking through the list of supported Canon scanners for both SilverFast 6.6 and 8, it doesn't appear my humble device made the cut (I am not surprised nor do I think this requires an explanation. I know my scanner was not made for this kind of work), subsuming problem "a", previous; (c) supposing I had a supported scanner and was certain it would perform desirably once calibrated, I would still have analysis paralysis shopping that website.

    I honestly hope it doesn't come to purchasing a photospectrometer, but I will see about whether anyone in my area does this professionally.

    Thanks for all the advice!
     
  20. JibeHo thread starter macrumors newbie

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    Jul 26, 2015
    #20
    As a general announcement, my IT8 target made it to my shop yesterday. I have downloaded VueScan's trial and will see if I can throw together a profile for the scanner.

    Thank you, everyone, for your input.
     
  21. JibeHo thread starter macrumors newbie

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    Jul 26, 2015
    #21
    Unexpected good news:

    Well, I did a test scan with VueScan (trial version) just to see if it's compatible with my scanner and voila! The color is very good. I only tested a creamy pink color and a bright blue, but they look very good on screen. I still intend to go through with the IT8 calibration using VueScan, of course. And I realize that my uncalibrated screen can only be trusted to a certain extent.

    I just want to express that merely operating the scanner with VueScan instead of OS X's built in functionality (and Canon IJ Scan Utility2) got the color of the image very close to that of the real fabric. So close, in fact, that had I started with VueScan instead of the other two scanning utilities I was using, I probably still wouldn't know what an IT8 target is. It's as though the scanner was sending information about color that the generic scan tools were discarding.

    That said, I want to reiterate that I understand the limitations of judging the color that my scanner is reading by what I see on my screen. I still intend to perform the IT8 calibration on the scanner.

    Question for you all: If I'm successful calibrating the scanner, is it still highly recommended that I calibrate my screen? In a sense, if my image files have the correct color encoded, that's the best I can do in terms of ensuring my customers see the real color. Is the utility in calibrating my screen that I will be able to detect when the calibration of the scanner is slipping (due to the lamp wearing out, etc) and will know that the scanner should be re-profiled? In other words, assuming I have correctly profiled my scanner and my image files are good, what would be the most compelling reason for me to purchase a gadget for calibrating my screen?

    Thanks for staying tuned and for all of the very helpful suggestions!
     
  22. Designer Dale, Aug 6, 2015
    Last edited: Aug 6, 2015

    Designer Dale macrumors 68040

    Designer Dale

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    #22
    Welcome. You can piece it together cheaper.
    Stand: http://www.bhphotovideo.com/c/product/438353-REG/Dot_Line_RS_CS920_RS_CS920_Copy_Stand.html

    EDIT: Canon makes good stuff. I love their cameras and used Vuescan in college. If you are going to calibrate your scanner, please do so with your monitor. As for ensuring that your customers see "true-ish" color that is beyond your control. Macs and Windows handle color differently and that goes for different monitors too. Just do the best you can.

    Dale
     
  23. dimme macrumors 65816

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    #23
    How are your customers viewing your files, Hard copy or on their own screen?If they are viewing the samples on their own computer you will have no control over the calibration of their hardware so all your hard work will be in vain. I used to do scanning and copy work for a living and fabrics were always the hardest to get right. What works for one fabric/dye combo will not work for another. But you do seem to be on the right track for the capture part.
    Good Luck
     
  24. JibeHo thread starter macrumors newbie

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    Jul 26, 2015
    #24
    They'll be viewing the images through a web browser on their own hardware. I do expect that the occasional dye/material/pile will require special attention, but if I can get most fabrics to look good without special, ad-hoc editing, I'll be happy.
     
  25. JibeHo thread starter macrumors newbie

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    #25
    I just finished profiling the scanner. It was actually very easy. Just load the target, crop to fit using the built-in tool, and press profile. I'm simplifying only very slightly.

    My target came with both a standard reference file and one that's, while non-standard, is optimized for scanners with white backgrounds (per the documentation).

    My monitor (macbook pro) is using Apple RGB, and VueScan has a very neat functionality where one can select the color space for the preview, but save the image file in a different color space. I.e., preview in Apple RGB but save in sRGB.

    It seems the consensus is to use sRGB, so I may invest in a piece of hardware to calibrate my screen to sRGB, so that I can check my images outside the preview function of VueScan (say, from my browser).

    All good stuff. Thanks again, everyone.

    EDIT: Of course, I tested my work by scanning the originally-very-offensive fabric and applying the ICC profile. I saved it in Apple RGB color space and it looks amazingly accurate on my screen.
     

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