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Thread: cropping and thumbnail image.

  1. #1

    cropping and thumbnail image.

    hey , I am a IT student and am currently working on Bit depth and sampling rate.

    I am looking for the solution to both questions below as i cannot figure it out myself.

    If I was to crop a image , For example turn a picture of a whole person into just a head shot , Would this be related to reducing the bit depth or reducing the sampling rate? why?

    If I was to turn a image into a thumbnail image , Would this be reducing the bit depth or reducing the sampling rate? why?

    thanks!

  2. #2

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    Re: cropping and thumbnail image.

    So grasshopper, you seek easy answers to a teachers questions without understanding the questions. They are not related. If you look and discover what bit depth and sampling rate are and how they are defined and used you will see the light and know the answers are no. Think "data", not light grasshopper.

  3. #3

    Re: cropping and thumbnail image.

    you have to teach someone something before they can answer in this case it hasn't been , NOT asking for just the answer, Im asking for the explanation to the answer aswell , i have read thoroughly through my text book and online into bit depth and sampling rate with no conclusion as too relativity on either image editing technique.

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    Re: cropping and thumbnail image.


  5. #5

    Re: cropping and thumbnail image.

    I don't believe either are related to bit depth...... but it wouldn't make sense for you to do a piece of work that isn't related to the topic you are currently working on , Bit depth and sampling rate. so in theory one or the other has to be bit depth and or sampling rate .

  6. #6

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    Re: cropping and thumbnail image.

    Quote Originally Posted by webapple View Post
    I don't believe either are related to bit depth...... but it wouldn't make sense for you to do a piece of work that isn't related to the topic you are currently working on , Bit depth and sampling rate. so in theory one or the other has to be bit depth and or sampling rate .
    Well, I'd guess those two subjects were treated together, probably with image size, resolution and required storage space and such... So all the concepts are related to the subject being taught, but that doesn't mean each question has to concern all topics. I'd say this question will show how well the students understand the different concepts.

    If you understand the different concepts (what is 'bit depth' and what is 'sampling rate') the questions are actually easy.

    (you are on the proper track btw)

  7. #7
    Moderator Dave Humphries's Avatar
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    Re: cropping and thumbnail image.

    What I find confusing is the "sampling rate" - if we are talking about still pictures, time (and hence any "rate") doesn't enter the equation. If we were talking about video, sampling rate could be more approrpriate, but we're obviously not.

    For what is being discussed, "resolution" would be a better term to use for a still image.

    webapple - it would be nice to know a first name btw -

    What educational level is this course?
    Who is setting these questions?
    I'm not entirely sure they know what they are asking either.
    Either that, or you have changed the context too much when you paraphrased the question you were asked for us.

    Cheers,

  8. #8
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    Re: cropping and thumbnail image.

    I thought bit depth was a property of the image type, e.g. 24 bit (8 bits per colour channel) for colour Jpegs, so I don't understand the questions. But is this web article any help to you? -

    http://photoshopessentials.com/essen...esampling2.php

    Best wishes.

    Philip
    Last edited by MrB; 11th March 2012 at 11:34 AM.

  9. #9
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    Re: cropping and thumbnail image.

    Quote Originally Posted by webapple View Post
    If I was to crop a image , For example turn a picture of a whole person into just a head shot , Would this be related to reducing the bit depth or reducing the sampling rate? why?
    Neither bit depth nor the "sampling rate" is changed by cropping a picture. Why . . hmm .. difficult to explain. Perhaps by a hypothetical example. Take a shot of a metric ruler. Observe the pic full size on your monitor. Save it without resizing. Crop a few cm and save that image without resizing. Now bring both images up in your favorite photoviewer - compare the bit that you cropped with the same bit in the original picture - you will see no difference at all. If you find it necessary to say "but one picture is bigger" then my explanation has failed to enlighten and you are not ready to snatch the pebbles from my hand ;-)

    Quote Originally Posted by webapple View Post
    If I was to turn a image into a thumbnail image , Would this be reducing the bit depth or reducing the sampling rate? why?
    Reducing the sampling rate as in pixels per unit distance. Why - reducing an image size by any amount is called "re-sampling" by the cognoscenti or also "down-sampling" which is not quite as obvious. Either way, the picture is crammed into a smaller area of pixels and something has to go. In this case, the number of pixels allocated to each millimeter of your metric ruler would be reduced (by algorithmic magic) in proportion to the down-sizing factor. Less pixels/mm = a lower sampling rate.

    regards,

    Ted

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