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Thread: Putting LF black and white on the WWW

  1. #1

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    Putting LF black and white on the WWW

    I am curious about the workflow to get decent black and white images in WWW size jpgs. My basic work files start as 190 meg tiff files and I process them in PS CS2. Any tricks to avoid posterized skies when you have a subtle sky gradient? Do you change the contrast from what makes a good print? What sizes work best, and do you down sample the image before saving as jpg?

  2. #2
    Whatever David A. Goldfarb's Avatar
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    Putting LF black and white on the WWW

    I downsample in stages, 50% each stage (except for the final stage where I want the image to be a certain size), and resharpen at each stage in decreasing amounts.

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    Putting LF black and white on the WWW

    First of all, there's no need to make the files any greater than 100 dpi, since monitors can't resolve that. (They are great at displaying colors, but not good at details). Perhaps 72 dpi is enough.

    Flatten the image, then down-size, then sharpen. At such small sizes, a little sharpening goes a long way. If your images are toned, then make sure your images are RGB. If you want B&W to be really B&W, then convert to grayscale before saving.

    Another thing to consider is that nowadays, 1024 x 768 is fairly standard. The desktop and browser takes up a fair amount of that space, so somewhere around 500 or 600 pixels wide is big enough for people to get the idea.

    Unfortunately, monitors are not square, but are horizontally oriented. This limits your ability to display vertical images. Oh well. If you don't take any in the first place, you'll be all set :-)

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    Putting LF black and white on the WWW

    Ken said to sample at 72dpi; and for the typical .28 dot pitch monitor that's good. However, there is a growing number of .25 dot pitch monitors on the market. For these users, a 96dpi image would be better. For the users who only have .28 you won't be hurting anything.

    I'd like to expand on the question to experienced PS users. Would you get better results scanning a fine print and posting a full color scan in order to pick up subtle differences in image color from effects such as selenium toning? I realize this would result in a larger file size, but I would think that procedure would yield a superior image.
    Michael W. Graves
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  5. #5
    Abuser of God's Sunlight
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    Putting LF black and white on the WWW

    Doing your very last sharpening, tonal adjustment, and jpeg conversion in adobe imageready can help a lot. It gives you a live preview of every possibility you try. It also lets you preview on a "typical" gamma 1.8 macintosh monitor or gamma 2.2 pc monitor.

    My policy now is to convert web graphics to the sRGB color space, since it's based on the closest thing to an average among pc monitors. it's limited color gammut isn't a factor with black and white. As far as macs, most mac users now are using browsers that are color managed and that respect the profile, so this takes care of them, too.

    There are probably a lot of ways to get good results ... whatever method you try, be sure to test your results on actual browsers on other people's computers. Be sure to include laptops--i find most laptops are set up with outrageously bright screens.

    The goal is to get your work looking acceptable on a wide range. Abandon any ideas of perfection.

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    Putting LF black and white on the WWW

    Are you asking if the file should be scanned and saved in color, versus B&W ?

    It all depends on how well-calibrated you monitor is. If you can be confident that you are seeing the "real" color space that others will see, then color will be better. If not, then you might be in for a surprise to see how your work appears to others. The same can be said for B&W: the grey values might look great on your setup, but could be way off.

    Makke sure to get a monitor calibration tool. I like Gretag-McBeth's EyeOne.

  7. #7
    Photographer, Machinist, etc. Jeffrey Sipress's Avatar
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    Putting LF black and white on the WWW

    Work in 16 bit as long as you can to reduce gradation banding. I use Fred Miranda's Web Presenter Pro routine to automate the downsizing chores. Then I use his Intellisharpen routine at between 5 and 10%. There are other available similar routes.

  8. #8

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    Putting LF black and white on the WWW

    Small clarification: "Ken said to sample at 72dpi"



    You can sample or scan your image at high resolution, like 2500 or 1800 or whatever - but the jpg you put on the web need only be somewhere around 100 dpi. Anything more, is wasted bandwidth that nobody can see in a browser.

  9. #9
    not an junior member Janko Belaj's Avatar
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    Putting LF black and white on the WWW



    sorry, pardon me, but what have to do dpi with our browsers? AFAIK, Web browsers are asking Web servers for physical dimension of image. And Web-masters are coding with physical dimension i.e. [IMG]photo.jpg[/IMG]



    I have made small test (one ugly picture, was just testing 7mm lens on Oly dSLR) with 72, 96, 150 and 300 dpi resolutions. size 300x400 pixels. and every of my browser (Safari, Firefox, iCab) is showing photo of same size... here is that link: dpi test in new window (html coded without width and height attributes)



    for those who want to force browser to load only the pict, here are links (will open in new window too):
    http://www.belaj.com/unsorted/dpi/72dpi.jpg
    http://www.belaj.com/unsorted/dpi/96dpi.jpg
    http://www.belaj.com/unsorted/dpi/150dpi.jpg
    http://www.belaj.com/unsorted/dpi/300dpi.jpg



    (O.K... maybe browsers on Win systems act differently, I cannot test that right now, but such behavior would be against w3 rules.)


  10. #10

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    Putting LF black and white on the WWW

    Janko -

    You are perfectly right. Your web page is a perfect demonstration.

    As your page shows, there is no reason to send an image to a browser at 300 dpi, if 72 dpi will result in the same quality. That is why we recommend that people send images no larger than 100 dpi.

    Small images occupy less storage on the server, and they travel faster over the wire. This is especially helpful to people who have a slow internet connection.

    If you do not specify the dimensions of an image in the "img" tag, then the image will appear in the original size of the image. The "width" and "height" keywords are optional only. If your photo is 200 x 300, and you want it to appear 200 x 300, there is no need to specify width and height. The "alt" tag is also optional, and so is the "border" tag.

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