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Please explain 100% crop

Discussion in 'Open Discussion' started by simonz, Nov 18, 2011.

  1. simonz

    simonz Mu-43 Regular

    Jul 20, 2010
    New England
    I see the term "100% crop" all the time in various forums when this refers small portion of a large photo posted. Suppose I have a 12mp m43 camera that has 4000x3000 jpgs, what size crop of that picture would represent the 100% crop? Is there a formula to calculate this?
  2. sprinke

    sprinke Mu-43 All-Pro

    Apr 5, 2011
    Pasadena, CA
    100% crop would be when a single pixel of your picture is displayed as a single pixel on your monitor.

    Monitors display information at 72 pixels per inch.

    For example, a 4000x3000 image file displayed at 100% on a computer screen, would require a monitor 55.55 inches by 41.66 inches in size. Obviously that is impossible, but you can show a smaller part of that same image at 100%.
  3. ~tc~

    ~tc~ Mu-43 Hall of Famer

    Oct 22, 2010
    Houston, TX
    careful with blanket statements, each size/resolution monitor is going to be different.
  4. snkenai

    snkenai Mu-43 Top Veteran

    Sep 5, 2010
    So "how do" you create a 100% crop to display?
  5. John M Flores

    John M Flores Super Moderator

    Jan 7, 2011
    It's when you place your nose up against a photograph to determine if it's a good photo.

    On a serious note, you can view your 4000x3000 pixel photo on a monitor that can display 2000x1500 pixels in a number of ways:

    A - You squeeze the entire photo onto the screen
    B - You don't squeeze the entire photo onto the screen, instead viewing what can fit and scrolling to see the rest.

    B is a 100% crop. In this case you'll only be able to see a quarter of the photo (2000x1500 pixels) at a time.
  6. sprinke

    sprinke Mu-43 All-Pro

    Apr 5, 2011
    Pasadena, CA
    True ...

    Depends on what software you are using.
  7. WT21

    WT21 Super Moderator Subscribing Member

    Feb 19, 2010
    I zoom in 1:1 in Lightroom, then take a screen grab. I'm assuming that's a 100% crop, but would love to hear from those in the know, if that is truly a 100% crop?
  8. RobWatson

    RobWatson Mu-43 Hall of Famer

    Crop means to cut. Cut you photo to the size you want. The scale of the pixels remains unchanged so objects 100 pixels in size remain 100 pixels in size. Crop tools work just like scissors in your hand - draw a box around the pixels you like and the crop tool creates a new image using only those pixels. Scissors cut away the parts you don't want and you are left with whatever you didn't cut away.

    The other method is to resize by altering the size of the photo by enlarging or reducing. This operation changes the scale of the pixels so objects that are 'normally' 100 pixels become represented by fewer/more pixels when reducing/enlarging the photo.

    How to do it? Use the crop tool! Every piece of software I ever used for manipulation of digital images has had a crop tool-gotta be at least 500 SW packages. Draw a box (some tools have other shapes that can be drawn) and everything inside the box is made into a new image.

    100% crop just means crop with no resizing.

    See post #2 here for full versus cropped
  9. snkenai

    snkenai Mu-43 Top Veteran

    Sep 5, 2010
    Thank you. I think I got it now.
  10. Ned

    Ned Mu-43 Legend

    Jul 18, 2010
    Alberta, Canada
    What software are you using? The easiest thing to do is to use Photoshop, choose the Crop Tool, input the height and width you want in "px" (pixel) units, then crop and save. Don't use print resolution (dpi/ppi), just pixel dimensions.
  11. shnitz

    shnitz Mu-43 All-Pro

    Break it up into 2 parts. 100% means that the image is the original size, 1 pixel from your screen is showing 1 pixel from your photograph. The opposite of this is resized, which is most pictures that you see. Let's look by going to Flickr's GH2 stream:
    Flickr: Panasonic DMC GH2
    If you click on any photo, then click the magnifying glass, you can view multiple resizes, from 75x75 pixels, often to original size.

    Crop means to cut a piece out of the original image. For example, I could take a full-body photo of a person and then crop the image down to include only their head.

    As an example of a crop, here is a photo I took in RAW, so its size is 4000x3000 pixels. Putting it here in all of its glory would be very obnoxious, because only a small number of pixels fit on your screen. My laptop, for example, is 1280x800, or just over 1 megapixel of display space. So, I resized it to 800x600 so that you can see the whole picture without scrolling around.
    Subscribe to see EXIF info for this image (if available)

    Now here is a small portion of the image, at the 100% level, so that pixels are correctly represented on your screen.
    Subscribe to see EXIF info for this image (if available)

    When you say take a screengrab, do you use printscreen? Yes, that it a 100% crop, but you can stay in LR and do it just as easily. Go to the Develop mode, and press "I". This will show you information, and you can see the size of your crop. This way, you can easily do whatever size you like.
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