Is hi-res + shrink better than taking lo-res?

Discussion in 'Digital Photography' started by veg_all, Feb 1, 2007.

  1. veg_all

    veg_all Guest

    If i take pictures in hi-resolution 1600X1200 and then shrink to
    800X600 is it better quality to just take picture in 800X600 mode?
     
    veg_all, Feb 1, 2007
    #1
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  2. In a word, no.

    Unless cramped for disk space, take highest possible resolution and
    downsize later for various purposes.
     
    John McWilliams, Feb 1, 2007
    #2
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  3. veg_all

    bluezfolk Guest

    On a similar note, is it better to use digital zoom or to just crop
    later? or is this just chicken or the egg?


    Eric
     
    bluezfolk, Feb 1, 2007
    #3
  4. I'd never want to use Digital Zoom for anything. I'd take the
    pic and save the original and crop later and then saveas that
    cropped file to a different name.
     
    Paul D. Sullivan, Feb 1, 2007
    #4
  5. veg_all

    Ken Lucke Guest

    Digital zoom is nothing more than in-camera crop and enlarge. You
    don't gain anything at all, really, except a larger image of a smaller
    portion of the sensor.

    --
    You need only reflect that one of the best ways to get yourself a
    reputation as a dangerous citizen these days is to go about repeating
    the very phrases which our founding fathers used in the struggle for
    independence.
    -- Charles A. Beard
     
    Ken Lucke, Feb 1, 2007
    #5
  6. Yes and no. It really depends on the noise level of the image. Shooting say
    a 6MP image and resizing it down to 800x600 will give you a better picture
    (noise wise) than shooting it at 800x600. The reason is the reduction in
    size basically squeezes out most of the noise.

    ljc
     
    Little Juice Coupe, Feb 1, 2007
    #6
  7. Digital zoom is crap. If you have the MP but need to make the image look
    like you had more optical zoom you are better of cropping later than fooling
    with the digital zoom. The digital zoom resample's your image to work its
    magic. Cropping doesn't resize it just cuts away.

    ljc
     
    Little Juice Coupe, Feb 1, 2007
    #7
  8. And a nice hit in overall picture quality.

    ljc

    --
    Do not assume that because I didn't reply to your comments that you are
    correct or that I am wrong or that I am correct and your are wrong. You
    can assume that you bore me!
     
    Little Juice Coupe, Feb 1, 2007
    #8
  9. veg_all

    Just D Guest

    When I had to resize a few relatively small images for my job to a smaller
    size and the resize dimensions were pretty close to the original ones, I
    used the following trick. If your computer RAM allows you to do that then
    you can try it but it can take some time. Less RAM, longer transformation
    because in this case it will involve the hard drive.

    First of all if you resize these images in one step up or down you'll get a
    very bad quality of the target images if the sizes can't be divided by 2, 3,
    etc. Try to increase the original image in a few times, depending on what
    the computer you have keeping in mind that 2 times increase really increases
    your picture in 4 times because of 2 dimensions, and only then decrease to
    the target size. For example if you have the original image like 500x300
    pixels try to increase the image up to 5000x3000 and then decrease to, say,
    80% from its original size. You will see the difference comparing to the one
    step decrease. Also I'd increase not in 10 times, but in 3, 5, 7, 9, or 11
    times, etc. to preserve more thin lines. That's my own feeling based on some
    mathematics and geometry. I don't think anybody needs the theory here.

    Just D.
     
    Just D, Feb 1, 2007
    #9
  10. veg_all

    Marvin Guest

    The answer to both parts is that resizing later and cropping
    later give you more control than having the camera do the
    tasks. Taking the photo at maximum resolution does make the
    file sizes larger, but that won't matter much for most
    photographers. Hard drives and memory cards are both low in
    cost. I just bought a 160 GB external HD for $50 after
    rebate, and not long ago I got a 1 GB memory card for $20
    after rebate. And yesterday I saw a 1 GB memory card for
    that price, without the need for getting a rebate.
     
    Marvin, Feb 1, 2007
    #10
  11. If i take pictures in hi-resolution 1600X1200 and then shrink to
    It depends on how much you lose in JPEG compression. If you compress
    the 1600x1200 image, then uncompress it, scale it, and recompress it,
    you'll probably end up worse than if you'd just shot at 800x600. If
    you use your camera's "fine" JPEG setting, though, you probably won't
    lose much, and you may gain a lot of you decide you want to crop the
    1600x1200 image instaed of shrinking it.

    -Joel
     
    Dr. Joel M. Hoffman, Feb 1, 2007
    #11
  12. On a similar note, is it better to use digital zoom or to
    I've also never used the digital zoom, but, again, depending on JPEG
    compression, the digital zoom may give you better results than
    cropping after a round of compression and uncompression.

    -Joel
     
    Dr. Joel M. Hoffman, Feb 1, 2007
    #12
  13. This pretty much flies in the face of at least conventional wisdom. On
    what basis to you speculate??
     
    John McWilliams, Feb 1, 2007
    #13
  14. Yes, but as the Dr. says, "Don't do that."
    If
    Even if one is merely downsizing the resolution and/or number of pixels,
    one is best off starting with the highest resolution the camera is
    capable of.

    Joel- in my question of you upthread, there's a typo....
     
    John McWilliams, Feb 1, 2007
    #14
  15. I've also never used the digital zoom, but, again, depending on JPEG
    If you are going to crop the image anyway, so that, either way, you'll
    only be using --- let's say --- the middle 50% of the sensor, then you
    have two choices:

    1. Take the information from the entire sensor, JPEG encode it, JPEG
    decode it, take the middle 50%, and then re-encode it. There's no
    way you can avoid getting some noise from the outer part of the
    image (which you aren't even using) and there's no way you can
    avoid the degredation from the JPEG encode decode.

    2. Take the information from the middle 50% of the sensor, and JPEG
    encode you. You don't get noise from the part of the image you
    don't need, and you don't suffer an encode/decode cycle.

    Now, it may be that the noise from the outside of the image is
    negligible, and it may be that the degradation from the encode/decode
    cycle is minimal, and it also may be that a good computer program
    can do a better job upsizing the image than the camera's software can,
    but these various assumptions are not obvious, nor, do I believe,
    always true.

    To take a concret example, if you take a picture of a deer, and the
    deer only occupies half of the frame, and you want to a make a 6x8
    printed photo of just the deer, you only have 800x600 of image data,
    or 100dpi. If your printer prints at 150 dpi, you need to fill in the
    missing dots. I don't know if the improvements you can make with
    advanced computer software outweigh the disadvantage of encoding and
    decoding the image an extra time. I also don't know if the camera can
    optimize the upsampling by working with the raw un-JPEG'd data.

    -Joel



    Joel M. Hoffman, PhD
    http://www.lashon.net/JMH
     
    Dr. Joel M. Hoffman, Feb 2, 2007
    #15
  16. I tested this (but some time ago) and found that 2:1 digital zoom was
    indeed better than cropping after compression. The larger image in the
    viewfinder may also help composition or focussing.

    I would suggest testing on your own camera, though.

    David
     
    David J Taylor, Feb 2, 2007
    #16
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