Best Scan resoloution (FrFathi)

User

Fri 20-Apr-01 05:11 AM

HI,

Does anyone has an idea about the best scan resolution for prints.
When I scan an image with 300 dpi for example, its a large file and I dont know how can I reduce resolution or size to both make it small and keep the quality for publishing on web.

Thanks for your help.

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Subject	Author	Message Date	ID
RE: Best Scan resoloution	vfnewman	20th Apr 2001	1
RE: Best Scan resoloution	User	20th Apr 2001	2
RE: Best Scan resoloution	vfnewman	20th Apr 2001	3
RE: Best Scan resolution	jrp	20th Apr 2001	4
RE: Best Scan resoloution	User	22nd May 2001	5
RE: Best Scan resoloution	User	22nd May 2001	6
RE: Best Scan resoloution	User	22nd May 2001	7
RE: Best Scan resoloution	User	22nd May 2001	8
RE: Best Scan resoloution	User	22nd May 2001	9
RE: Best Scan resoloution	User	22nd May 2001	10
RE: Best Scan resoloution	User	23rd May 2001	11
RE: Best Scan resoloution	User	23rd May 2001	12
RE: Best Scan resoloution	User	23rd May 2001	13

vfnewman
Is from: Forest, US
5308 posts

#1. "RE: Best Scan resoloution" | In response to Reply # 0

vfnewman Charter Member

Fri 20-Apr-01 08:21 AM

According to everything I've heard and read, scanning a print at a resolution higher than 200 ppi doesn't gain you anything. There is a very good website that will probably answer many of your questions at:

www.scantips.com

If all you are doing is posting to the web, you should be able to use a scan resolution much lower than 300 dpi.

Victor Newman

My Nikonians Gallery

www.nikonians.org - Worldwide Home for Nikon Photographers
Visit my Nikonians gallery.

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- User
  
  #2. "RE: Best Scan resoloution" | In response to Reply # 1
  
  Fri 20-Apr-01 04:45 PM
  
  Thank you for your tips victor.
  Usually I do both, post to web and make prints.
  
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  - vfnewman
    Is from: Forest, US
    5308 posts
    
    #3. "RE: Best Scan resoloution" | In response to Reply # 2
    
    vfnewman Charter Member
    
    Fri 20-Apr-01 08:54 PM
    
    No matter what the final use of the scan will be, my understanding is that you won't gain anything by scanning a print at greater than 200 or 300 dpi. If you are going smaller, like to the web, you can go much lower. Again, scantips.com and any sites provided in the links will give you a wealth of information. I learned a tremendous amount from that site and others referenced there.
    
    Victor Newman
    
    My Nikonians Gallery
    
    www.nikonians.org - Worldwide Home for Nikon Photographers
    Visit my Nikonians gallery.
    
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    - jrp
      Is from: San Pedro Garza García, MX
      46140 posts
      
      #4. "RE: Best Scan resolution" | In response to Reply # 3
      
      jrp Charter Member
      
      Fri 20-Apr-01 09:15 PM
      
      My method is to scan at 300 dpi, then downsize to 450 pixels height but at 72dpi; my 6X8 original prints become a less than 40Kb jpeg files with a little compression.
      Have a great time
      JRP (Nikonian at the north-eastern Mexican desert)
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User

#5. "RE: Best Scan resoloution" | In response to Reply # 0

Tue 22-May-01 08:30 AM

For printing, you should use 300 dpi and set the image size you are going to use for printing. Afterwards you can print a smaller picture, but not a larger one. Save it as TIFF.
For use on a website, scan at 100 dpi. Save it as JPEG (quality around 5)to keep the files small.

Good luck

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- User
  
  #6. "RE: Best Scan resoloution" | In response to Reply # 5
  
  Tue 22-May-01 12:39 PM
  
  Actually, I find that overscanning and then downsampling to web resolution produces a considerably superior image than scanning it directly to the target size.
  
  I don't bother scanning any image at less than the full resolution of the scanner. You won't save much (if any) time making a lower res scan and you may as well not have to go back to rescan (and retouch, and color correct) an image later.
  
  Save the full res file as a TIFF with LZW compression for a lossless image file and use a colorspace like Adobe RGB (1998) for that image (which provides a color gamut that's appropriate for a CMYK printer). A CD rom burner is the best way to deal with keeping big image files from building up on your hard drives.
  
  Create a separate file at 72 pixels per inch for web use and convert the file to sRGB colorspace (to keep your colors from shifting when viewed using a browser) before saving it. The compression level you can get away with is dependent on your tolerance for jpeg artifacts and the content of your image.
  
  BJ
  
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  - User
    
    #7. "RE: Best Scan resoloution" | In response to Reply # 6
    
    Tue 22-May-01 05:47 PM
    
    BJ,
    Queston on the screen resolution. My Epson and the Nikon 4000 ED both state 96 dpi for Windows, 72 dpi for Apples. Just curious which it should be when scanning in for the web. I have always defaulted to the scanner default (96 dpi), but would like smaller files if possible. On my screen (set to 1280 x 1024) the 96 dpi files look better.
    
    Doug
    
    --Take only photographs, leave nothing but footprints--
    And carry plenty of FRESH batteries...
    
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  - User
    
    #8. "RE: Best Scan resoloution" | In response to Reply # 6
    
    Tue 22-May-01 05:50 PM
    
    BJ,
    Queston on the screen resolution. My Epson and the Nikon 4000 ED both state 96 dpi for Windows, 72 dpi for Apples. Just curious which it should be when scanning in for the web. I have always defaulted to the scanner default (96 dpi), but would like smaller files if possible. On my screen (set to 1280 x 1024) the 96 dpi files look better.
    
    As for the max scan information, from information supplied by you in another thread I started scanning in at max opitical resolution (1600 on the Epson, now 4000 on the Nikon) and then downsizing, and there is a remarkable difference in the scan files. It was amazing what the differences were between a 300 or 600 dpi and the max resolution scan.
    
    Doug
    
    --Take only photographs, leave nothing but footprints--
    And carry plenty of FRESH batteries...
    
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    - User
      
      #9. "RE: Best Scan resoloution" | In response to Reply # 8
      
      Tue 22-May-01 06:35 PM
      
      LAST EDITED ON May-23-01 AT 00:43 AM (GMT)
      96 ppi is new to me. You can easily check that 72ppi is the Windows standard as well by using Photoshop's "actual pixels" selection under the View menu (it will be identical in size to the 100% preview selection) For all my web design work (I'm on Windows 98 SE) 72 ppi is the standard I use with all my web design software and I've never run across scaling issues even at different display resolutions. I'll see if I can find out where the 96 ppi number is coming from.
      
      In any case, the nominal resolution you tag the file with has no effect on how the image will be displayed via a browser. You can set the resolution (pixel pitch) of your image at 4000 pixels per inch on a 640x480 image and it will display identically to the same pixel size image tagged as 72 ppi. The image will also be identical in file size. It won't print identically, however, since pixel pitch does relate to print output dimensions.
      
      It really is amazing how much nicer a downsampled image looks than an image scanned at the target size, especially when you consider the really low resolution of web images. There must be a big difference in how the scanner decides to sample at low resolutions vs. the algorithms that Photoshop uses to scale down an image. No amount of sharpening will make a direct scan look as good as a downsampled scan. My philosophy is that if I'm bothering to do a scan anyway, I may as well go for the gold rather than mess around with intermediate scan resolutions (I treat my digital camera the same way). CD media is cheap...
      
      BJ
      
      I just looked it up and Windows indeed displays images pixel for pixel at 72ppi, but the type rendering engine creates fonts based on 96 ppi (thanks, Bill). That means that type appears larger on Windows machines than on Macs given the same browser font. Apparently these two values have gotten mixed up and confound some tech writers.
      
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      - User
        
        #10. "RE: Best Scan resoloution" | In response to Reply # 9
        
        Tue 22-May-01 08:12 PM
        
        BJ,
        Sorry to pick your brain, but I have another scanning question for you. When a scanner lists 1600 dpi as the optical resolution, what exactly does this mean?
        From my understanding, this is the optical resolution that the scanner always scans images in at; whereas the output resolution is what you chose when scanning in a file. (Determines the file size and dpi of the actual file.)
        For example, on the Epson, it is listed as 1600 dpi optical resolution, and when doing a scan you have a choice of different scan resolutions stated as output resolution. This range goes from around 72 dpi up to 12800 dpi. However, anything over 1600 dpi is interpolate.
        Just as confused as ever on this scanning resolution stuff.
        
        Thanks,
        
        Doug
        
        --Take only photographs, leave nothing but footprints--
        And carry plenty of FRESH batteries...
        
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        User
        
        #11. "RE: Best Scan resoloution" | In response to Reply # 10
        
        Wed 23-May-01 01:24 AM
        
        The optical resolution is the real resolution of the imaging sensor array. Often flatbed scanners have a different horizontal and vertical resolution, slide scanners usually have the same resolution for both axis. A scanner can end up with different resolutions because the stepping motor that moves the imaging element or the film may not have as high a resolution as the array of pixel sensors of the imaging head.
        
        Interpolation is the bane of comparison shopping for scanners. It's like the "digital zoom" in digital cameras in that the extra pixels are merely calculated from the actual scanned pixels. The higher resolution offers no more detail since the intermediate data is faked. Marketing folks love this stuff since it makes a scanner appear to be much higher resolution than it really is optically.
        
        Photoshop can do a better job of interpolation than the scanner's logic can, so there's no good reason to scan at a setting any higher than the true optical resolution of the scanner. Photoshop bicubic interpolation is good for modest amounts of upsampling, but should you want to create a poster or mural of an image, Genuine Fractals is the software to use. It uses fractal algorithms to increase resolution without showing pixel edge artifacts.
        
        As to whether a scanner always scans at the optical resolution, I suspect that's only true at the sensor itself. Often a scanner will perform a scan faster if you spec a low resolution. I'd guess that the scanner logic discards part of the data from the imaging sensor so it can process an image faster using its limited internal processing and memory.
        
        The terminology inevitably gets confusing because image resolution, printing resolution, and halftone screens all get called "dpi" and they're all describing different but interrelated values. That's one reason I've become anal about using ppi, or pixels per inch when referring to the defined resolution of the image file itself.
        
        I'm still trying to figure out how to make the concept simpler to understand but the terminology gets in the way. You have to segregate the various resolution values and understand them individually before it's possible to figure out how they interact. I'm glad to offer any help I can... It's so much easier to demonstrate than it is to describe.
        
        Best,
        
        BJ
        
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        User
        
        #12. "RE: Best Scan resoloution" | In response to Reply # 11
        
        Wed 23-May-01 06:48 AM
        
        LAST EDITED ON May-23-01 AT 12:49 PM (GMT)
        Thanks BJ, someday I'll figure this out. (It appears this subject is similar to California Emission Laws, no logic due to inconsistency. ) I will say that the 4000 ED does not actually mention dpi, for output scan it displays pixels per (inch), centimeter, and a few others that I can't remember sitting here in my office. The only place that shows dpi is what they call "reading resolution" of 4000 dpi, in the owner's guide and in their advertising brochures.
        They give also give a short, but not so informative explanation of how when scanning for a web page to with either 72 ppi or 96 ppi, and when scanning to a printer use a certain specification, depending on the output of the printer (720, 1440, etc.) In fact, it appears they intentionally stay away from any mention of "dpi" in their owner's handbook.
        There is also a drop down window that you can pick Custom, Printer, or Web, and if you pick Printer or Web it automatically defaults to one spec for printer, and 96 ppi for web. Custom allows you to pick anything you wish.
        I will say that their driver software is not as user friendly as that of Epson; however, after a few hours playing around with the software, it does a lot more and has more features; and yes, a person does get more familiar with it as time goes on. (This is true of anything.)
        So far, from what I have seen just playing and testing the new scanner, I have concluded there is no comparison between the 4000 ED and the Epson 1640SU; which there shouldn't be due to the price difference.
        I will put more in another thread regarding this scanner in a few days.
        
        Have a great day.
        
        (I wonder if there is a book for people like me titled, "Scanning for Dummies" that is available through Amazon??)
        
        Doug
        
        --Take only photographs, leave nothing but footprints--
        And carry plenty of FRESH batteries...
        
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        User
        
        #13. "RE: Best Scan resoloution" | In response to Reply # 12
        
        Wed 23-May-01 09:56 AM
        
        The scantips.com website is as close as I've seen, but frankly I don't think his write-up is particularly clear (or even fully accurate).
        
        http://www.scantips.com/basics02.html
        
        The problem now is that a lot of what you'll read is meant for people looking at offset printing, not inkjet, as final output. This introduces a lot of confusing talk about dot screens, line screens and such that have no relevance for inkjet printing. Ideally, these FAQ's would be specific to your desired end printing process.
        
        I really do advise you forget about using resolution settings in the driver as much as possible. Do a full res scan and then resample for your needs in your image editor. It's much easier to learn how to do the process in one program rather than try to manage it in multiple interfaces. At full res, you can crop with the least quality loss.
        
        Another thing that can help is to dismiss the arbitrary value of the pixels-per-unit tag on a file and deal with actual x-y pixel counts instead. Your new scanner will create an image that's about 5668 pixels on the long side. That's 18.9" print size at 300 ppi file resolution.
        
        If you want to resize this high res image for the web, decide on your maximum dimensions in pixels (640 pixels maximum is what I generally use) and enter that number directly into the dimension field when you do the resampling routine. The resulting ppi value that's assigned to the image won't have any impact on how it's displayed on the web.
        
        When adjusting the size for printing, don't resample unless you have to - just enter the image dimensions you want to print. If you print your 5668 pixel wide file at 10 inches on paper, the image file resolution will be 566.8 pixels/inch - more than necessary for a nice Epson print but the extra resolution not only doesn't hurt anything, it's sometimes visible in the quality of the printed image. 300 ppi is the recommended minimum resolution for the highest quality print, but that's just a suggested lower limit, not a value you have to match.
        
        BJ
        
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