I'd be grateful for some cookbook instructions for editing/sizing/saving photos for publication

Discussion in 'Photoshop Tutorials' started by EBL, May 8, 2004.

  1. EBL

    EBL Guest

    I am a novice (well, actually a beginner) in Photoshop (have access to
    7.0), but need to submit some photomicrographs of blood cells for a
    scientific publication, and I'd like to make them look as good as I
    can, and I'm pretty educable. I am also out of time (past the
    deadline), and can't spend the time I'd normally spend to learn how to
    do what I want to do, so I'm asking for help!

    This is what I've done so far: I have several photographs of blood
    cells. photographed all the blood cells at the same magnification
    (100x oil) using the same lighting conditions; they are currently
    saved as jpgs. They look best when I open them and modify them using
    the AutoColor function—then they look more like what I saw under the
    microscope. I need to have pictures that are 19 picas wide (or 80
    mm). I am interested in showing only a small area of each
    photomicrograph, so I want to crop the images that I have, and keep
    them all exactly the same size when I'm done (and thus the
    magnification will be equal across all pictures). I don't need to
    know the actual magnification on the page compared to the original
    slide. The color images need to be submitted in CMYK format (which I
    figured out how to do on the Photoshop menu). In addition, some other
    images need to be saved as black and white.

    Assuming I don't do a lot of touchup (just autocolor), it seems that I
    could do this as a cookbook exercise, if I only knew how to do it (do
    I guesstimate the millimeters using the tool bars? Once I crop an
    area, how do I save it? Do I crop, then autocolor, then change to
    CMYK? Another order? How do I do this????)

    If anyone is willing to write me cookbook directions, I'd really
    appreciate it!

    Thanks
    EBL
     
    EBL, May 8, 2004
    #1
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  2. EBL

    Tacit Guest

    This is what I've done so far: I have several photographs of blood
    You've already started down the wrong path. JPEG uses "lossy" compression; that
    means it deliberately degrades the image in order to save space on disk. JPEG
    is only appropriate for situations where file size on disk is important and
    image quality is not important. It is not generally appropriate for images
    destined for professional printing.
    What size are they now? What resolution are they now?

    You can crop the image using the crop tool or marquee tool, then use the Image
    Size command (with the "Resample Image" checkbox turned OFF) to make the images
    80mm wide. However, depending on how the image was originally created, this may
    produce an image that is too low in resolution. It should be at least 300
    pixels per inch *at the final size.*

    You can turn on "Resample Image" in the Image Size dialog and make the
    resolution be 300 pixels per inch, but you can never create detail that is not
    present in the original by doing this; the results will not be better. You need
    to CREATE the image with enough resolution in the first place!
    HOW are you converting to CMYK? What kind of paper will the images be printed
    on? This is important stuff! You can't blindly go Image->Mode->CMYK and end up
    with something that will be printable on any kind of paper and press.

    For best results, you MUST use File->Color Settings->CMYK Setup, and use the
    CMYK Setup dialog box to specify the separation parameters for your press and
    paper, EVERY time you create a CMYK separation.

    Also, many colors in RGB can not be reproduced in CMYK. CMYK has a different
    range of colors, or "gamut," than RGB.

    If your image contains out-of-gamut colors, these colors will be converted to
    their nearest approximation in CMYK. The result will be a color which is less
    saturated and somewhat flatter.

    Often, a little bit of color tweaking is necessary in the CMYK image. After
    separating an RGB image to CMYK, you may wish to use the Curves command
    (Image->Adjust->Curves) to increase contrast in the midtones slightly, as the
    separation often becomes flatter in the midtones.

    Specific colors can be tweaked with Image->Adjust->Selective Color. For
    example, if your blues have yellow in them, you can remove yellow from blues to
    make them more saturated and richer.

    When you color corrrect the image, you should, of course, have your Info
    palette open. Look at the numbers in the out-of-gamut colors; see if your
    primary colors have any contaminating color that can be reduced to increase
    saturation. For example, yellow in your blues or cyan in your reds can be
    reduced, if present, to make the colors richer.

    Vivid RGB blues often separate with too much magenta, making the colors appear
    more purple than blue. Using Selective Color to reduce magenta in blues will
    often solve this problem.

    The range and depth of color you can expect to get depends on the settings in
    your CMYK setup, which themselves depend on the kind of paper and press you are
    going to be printing on.

    As for setting up your CMYK separation:

    If you just go Image->Mode->CMYK without changing the values in your CMYK
    setup, the result will look okay on most sheetfed presses and coated (glossy)
    color stocks, but will not be acceptable for, say, newspaper printing.

    For best results, you should talk to your printer about what to do. Most
    importantly, make sure he gives you the values he needs for maximum ink and
    maximum black percentages; if you exceed these values, the image may smear on
    press.

    As starter points:

    For sheetfed presses printing on high-quality coated paper, you can usually use
    GCR, 100% black ink limit, 300% total ink limit, Light or Medium black
    generation.

    For very high quality lithographic output, your total ink limit can go as high
    as 310%.

    For web-fed presses on glossy paper, or sheetfed presses using high-quality
    uncoated paper at a 110-line halftone or above, use GCR, 100% black ink limit,
    280% total ink limit, Light or Medium black generation.

    Newsprint is a different story entirely. For newsprint, appropriate settings
    might be UCR, 240% to 260% total ink limit, 85% black ink limit. When you
    convert the image to CMYK, it will look washed-out and flat, but newsprint
    darkens *considerably* on press so this reduction in density is necessary.
    You crop whatever area you want, with no regard for size. Then you use Image
    Size with Resample Image OFF to make the image exactly 80MM wide.
    File->Save As. For print, do not use JPEG. Use TIFF.
    Generally speaking, you do coarse color correction on the original, convert to
    CMYK, do final color correction there, crop, unsharp mask, and save for print.
    Unsharp masking is used to sharpen the image; any image destined for press will
    benefit from sharpening using Unsharp Mask.

    Unsharp masking is part art, part science. There is no set way to use it which
    works for all images.

    Generally speaking, however:

    The Unsharp Mask filter works by exaggerating areas of high contrast--ie,
    edges. This gives the appearance of sharper edges, and increases the apparent
    overall sharpness of the image. While it can't make a blurred or out-of-focus
    image sharp (nothing can do this), it can dramatically increase the perception
    of sharpness. And unsharp masking is a requirement to get good-looking images
    in print.

    The Amount slider dictates how much edges are increased in contrast. If the
    value in this slider is too high, the image will appear to have "halos" around
    the edges.

    The Radius slider determines how wide the area of enhanced contrast is around
    edges. In general, the amount you put in the Radius field depends on the
    resolution of the image; the higher the resolution in pixels per inch, the
    wider the Radius.

    A good place to start is (image resolution/200). If the image is screen
    resolution--100 pixels per inch or less--try a Radius of 1. Increasin ghte
    Radius will also create undesireable halos around edges.

    If you are sharpening an image which will be printed on a printing press, and
    your image is the recommended resolution (twice the frequency of the halftone
    you will be using to reproduce the image on press), use a Radius of (halftone
    screen/100). So, for example, if your image is being printed on press with a
    150-line-per-inch halftone, use a Radius value of 1.5.

    The Threshold command determines how far apart two neighboring pixels must be
    in tonal value in order to be sharpened. I usually start with a Threshold of 3.
    Lower Threshold values exaggerate noise along with edges; higher values don't
    sharpen noise, but also produce more muted sharpening overall.

    Note that if your image is intended for print, you should set the Amount value
    so that the image looks slightly over-sharpened on your screen! This is because
    the process of halftoning the image for print decreases the apparent sharpness
    of the image (which is why all images should have USM applied if they are going
    to be used for print).

    Hope that helps!
     
    Tacit, May 9, 2004
    #2
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  3. EBL

    EBL Guest

    WHEW!!! I'm going to have to take a little time to see if I
    understand all this. In answer to some of your questions, the photos
    are 1540x1144 pixels (293 KB), adn the document size is 128 mm. If
    the final picture should be 80 mm wide, and more than 300 pixels, does
    that mean I can take only 2/3 of the image (80 divided by 128), or
    does that mean I can really take 1/5 of the image 300 divided by
    1540)?

    I will check on the setup tomorrow at work to see if I can save as a
    TIFF. I couldn't figure out how when I took the pictures, so I just
    saved at the highest resolution possible in JPG format. If I can
    change it, I will. The microscope is connected via a SONY program
    into an older version of Photoshop. But if I can get away without
    retaking them, it would really be preferable. But if I have to, I
    will.

    I'm sorry--I won't know what type of paper the publisher will use, and
    I don't think I will know. They said simply that the colors must look
    correct using CMYK. The publishing company publishes scientific
    textbooks and reference books. The images will be on a color plate.

    Now I'm going to go read the rest of what you said and try to figure
    it out!

    Thanks!
    *******
     
    EBL, May 10, 2004
    #3
  4. EBL

    Tacit Guest

    WHEW!!! I'm going to have to take a little time to see if I
    That means the image resolution is approximately 305 pixels per inch. To
    calculate resolution, take the width in pixels and divide by the width in
    inches; this'll tell you how big each pixel is, and you'll get the resolution
    in pixels per inch.

    For offset printing, your image should be at least 300 pixels per inch, or at
    least 120 pixels per cm.
    They should supply you with this information. Publications have a "spec sheet"
    that they make available to advertisers and contributors; this spec sheet gives
    you information about the trim size (page size) of the publication, the file
    formats the publication will accept, and the CMYK parameters (total ink density
    and so on) that the publication expects.

    If you do not have this information, then before you convert the images to
    CMYK, it's best to use GCR, 280% total ink limit, 100% black ink limit, Light
    black generation. This will look good on just about any coated (glossy) stock,
    without risk of excessive density.

    The problem is that if you do your separation with the total ink density set
    too high, the image will look absolutely fine on your screen, but it will smear
    on press, because too much ink is being laid down on the paper.
     
    Tacit, May 10, 2004
    #4
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