Resolution, dpi, & pixelation for printing.

Discussion in 'Digital Photography' started by Ben Bowen, Nov 16, 2006.

  1. Ben  Bowen

    Ben Bowen Guest

    Hi all. I just sent out a bunch of pictures to get processed. They were
    taken with my new Canon A640 (10MP). I re-sampled the pix using Corel
    Photopaint to 1024 x 768 to print 4" x 6" prints, because 10MP are too
    big to upload. I believe that is the correct resolution to use,
    however, a lot of the pictures are pixelated. So now, I'm trying to
    debug what I did wrong. I previously had a Canon Powershot S300 (2MP)
    and never had these problems. I camera takes pix at 72dpi and the
    re-sampled pix have 72dpi too, so I doubt it could be that. Did I
    decrease the resolution too much? Should I make it 1200x1600? When I
    print the images at home (from orignial not-resampled images) I have no
    problem, but the re-sampled images I uploaded are no good. I will try
    various combos of re-sampling to experiment, but I'd like to have an
    idea of what I'm shooting for.

    Thanks...
     
    Ben Bowen, Nov 16, 2006
    #1
    1. Advertising

  2. Ben  Bowen

    bugbear Guest

    Ben Bowen wrote:
    > Hi all. I just sent out a bunch of pictures to get processed. They were
    > taken with my new Canon A640 (10MP). I re-sampled the pix using Corel
    > Photopaint to 1024 x 768 to print 4" x 6" prints, because 10MP are too
    > big to upload. I believe that is the correct resolution to use,
    > however, a lot of the pictures are pixelated. So now, I'm trying to
    > debug what I did wrong. I previously had a Canon Powershot S300 (2MP)
    > and never had these problems. I camera takes pix at 72dpi and the
    > re-sampled pix have 72dpi too, so I doubt it could be that. Did I
    > decrease the resolution too much? Should I make it 1200x1600? When I
    > print the images at home (from orignial not-resampled images) I have no
    > problem, but the re-sampled images I uploaded are no good. I will try
    > various combos of re-sampling to experiment, but I'd like to have an
    > idea of what I'm shooting for.


    Your S300 was generating (as max) 1600x1200, so I'd aim
    for that.

    BugBear
     
    bugbear, Nov 16, 2006
    #2
    1. Advertising

  3. Ben  Bowen

    Ken Weitzel Guest

    Ben Bowen wrote:
    > Hi all. I just sent out a bunch of pictures to get processed. They were
    > taken with my new Canon A640 (10MP). I re-sampled the pix using Corel
    > Photopaint to 1024 x 768 to print 4" x 6" prints, because 10MP are too
    > big to upload. I believe that is the correct resolution to use,
    > however, a lot of the pictures are pixelated. So now, I'm trying to
    > debug what I did wrong. I previously had a Canon Powershot S300 (2MP)
    > and never had these problems. I camera takes pix at 72dpi and the
    > re-sampled pix have 72dpi too, so I doubt it could be that. Did I
    > decrease the resolution too much? Should I make it 1200x1600? When I
    > print the images at home (from orignial not-resampled images) I have no
    > problem, but the re-sampled images I uploaded are no good. I will try
    > various combos of re-sampling to experiment, but I'd like to have an
    > idea of what I'm shooting for.


    Hi Ben...

    1024 isn't sufficient to produce good 6x4's. If you must resize,
    then shoot for at least 200 and preferably 300 - meaning that
    6 inches x 200 = a minimum of 1200, and 6 inches x 300 = the
    more preferable 1800.

    If you're resizing only because 10 megs is too big, you might
    try leaving the size alone, and reducing file size by slightly
    increasing the jpeg compression. I suspect you'd like this
    better.

    Fortunately prints are cheap, do yourself some experimenting :)

    Finally, forget that 72 dpi thing. For what you're doing now,
    it's meaningless.


    Take care.

    Ken
     
    Ken Weitzel, Nov 16, 2006
    #3
  4. 200 image pixels per printed inch is a reasonable target to aim for, though
    300ppi would be ideal. 1024x768 is under 200ppi, so you could get some
    pixellation. If you are worried about upload sizes, resize to 1600x1200. But
    I would also consider trying a different online service as most decent ones
    will accept full size images now and others will compress your full size
    images as part of the upload process.

    Ian

    Digital Photography Now
    http://dpnow.com

    "Ben Bowen" <> wrote in message
    news:...
    > Hi all. I just sent out a bunch of pictures to get processed. They were
    > taken with my new Canon A640 (10MP). I re-sampled the pix using Corel
    > Photopaint to 1024 x 768 to print 4" x 6" prints, because 10MP are too
    > big to upload. I believe that is the correct resolution to use,
    > however, a lot of the pictures are pixelated. So now, I'm trying to
    > debug what I did wrong. I previously had a Canon Powershot S300 (2MP)
    > and never had these problems. I camera takes pix at 72dpi and the
    > re-sampled pix have 72dpi too, so I doubt it could be that. Did I
    > decrease the resolution too much? Should I make it 1200x1600? When I
    > print the images at home (from orignial not-resampled images) I have no
    > problem, but the re-sampled images I uploaded are no good. I will try
    > various combos of re-sampling to experiment, but I'd like to have an
    > idea of what I'm shooting for.
    >
    > Thanks...
    >
     
    Digital Photography Now, Nov 16, 2006
    #4
  5. hi ben, try downloading yor pics from the cam at 300dpi, and then
    resize to 1800 x 1200px, that would give you an imagesize of 4x6, i
    found a great utility for this type of calculation

    http://auctionrepair.com/pixels.html


    i hoped this helps


    Ben Bowen wrote:
    > Hi all. I just sent out a bunch of pictures to get processed. They were
    > taken with my new Canon A640 (10MP). I re-sampled the pix using Corel
    > Photopaint to 1024 x 768 to print 4" x 6" prints, because 10MP are too
    > big to upload. I believe that is the correct resolution to use,
    > however, a lot of the pictures are pixelated. So now, I'm trying to
    > debug what I did wrong. I previously had a Canon Powershot S300 (2MP)
    > and never had these problems. I camera takes pix at 72dpi and the
    > re-sampled pix have 72dpi too, so I doubt it could be that. Did I
    > decrease the resolution too much? Should I make it 1200x1600? When I
    > print the images at home (from orignial not-resampled images) I have no
    > problem, but the re-sampled images I uploaded are no good. I will try
    > various combos of re-sampling to experiment, but I'd like to have an
    > idea of what I'm shooting for.
    >
    > Thanks...
     
    www.thephotoboard.com, Nov 16, 2006
    #5
  6. Ben  Bowen

    Ben Bowen Guest

    > If you're resizing only because 10 megs is too big, you might
    > try leaving the size alone, and reducing file size by slightly
    > increasing the jpeg compression. I suspect you'd like this
    > better.


    I hadn't considered that. I will give it a shot. Corel allows to adjust
    "Compression" and "Smoothing". Are there big differences between the
    two that should be known, vis-a-vis file size vs quality?
     
    Ben Bowen, Nov 16, 2006
    #6
  7. Ben  Bowen

    Cgiorgio Guest

    Ben Bowen wrote:
    > Hi all. I just sent out a bunch of pictures to get processed. They
    > were taken with my new Canon A640 (10MP). I re-sampled the pix using
    > Corel Photopaint to 1024 x 768 to print 4" x 6" prints, because 10MP
    > are too big to upload. I believe that is the correct resolution to
    > use, however, a lot of the pictures are pixelated. So now, I'm trying
    > to debug what I did wrong.


    Hi, Ben,

    I've prepared a table showing the paper formats popular in Europe and the
    number of pixels required in each direction for printing at 300 Pixels per
    inch. 300 is optimum, for large prints which are normally viewed from a
    larger distance 150 - 200 Pixels per inch give very acceptable results.

    I use Pixels per inch to avoid confusion with the dpi claimed by inkjet
    printers, which are a different story.

    for conversion to inches divide cms by 2,54

    Cms Cms Ratio Pixel Pixel Total Din
    v h v h Pixels Format
    9 13 1,44 1063 1535 1.632.153
    10 15 1,5 1181 1772 2.092.504
    13 18 1,38 1535 2126 3.264.307
    18 24 1,33 2126 2835 6.026.412
    20 25 1,25 2362 2953 6.975.014
    24 30 1,25 2835 3543 10.044.020
    24 36 1,5 2835 4252 12.052.824
    30 40 1,33 3543 4724 16.740.033
    40 50 1,25 4724 5906 27.900.056
    14,9 21 1,41 1760 2480 4.364.964 Din A5
    21 29,7 1,41 2480 3508 8.700.632 Din A4
    29,7 41,9 1,41 3508 4949 17.359.833 Din A3
     
    Cgiorgio, Nov 16, 2006
    #7
  8. Ben  Bowen

    Ken Weitzel Guest

    Ben Bowen wrote:
    >> If you're resizing only because 10 megs is too big, you might
    >> try leaving the size alone, and reducing file size by slightly
    >> increasing the jpeg compression. I suspect you'd like this
    >> better.

    >
    > I hadn't considered that. I will give it a shot. Corel allows to adjust
    > "Compression" and "Smoothing". Are there big differences between the
    > two that should be known, vis-a-vis file size vs quality?


    Hi Ben...

    I don't know Corel, so don't know anything about Corel's "smoothing";
    hopefully others here will tell you.

    For the time being, just leave your pic full size, increase the
    compression until it reaches a reasonable file size, and do some
    test prints.

    I'd suggest two sets of test prints - one a nice landscape with
    lots of sky, the other a portrait type head and shoulders shot.

    Take care.

    Ken
     
    Ken Weitzel, Nov 16, 2006
    #8
  9. www.thephotoboard.com wrote:
    > hi ben, try downloading yor pics from the cam at 300dpi, and then
    > resize to 1800 x 1200px, that would give you an imagesize of 4x6, i
    > found a great utility for this type of calculation
    >
    > http://auctionrepair.com/pixels.html


    You don't choose a download dpi, nor even ppi, from the camera. They
    will download at however many pixels the camera is set to when the image
    is captured. It's often recommended to capture at the highest resolution
    your camera will allow; you can always downsize.

    And, yes, a 4 x 6 sent to the printer at 300 ppi will measure 1200 x
    1800 pixels.

    --
    John McWilliams
     
    John McWilliams, Nov 16, 2006
    #9
  10. Ben  Bowen

    Jim Townsend Guest

    Ben Bowen wrote:

    > Hi all. I just sent out a bunch of pictures to get processed. They were
    > taken with my new Canon A640 (10MP). I re-sampled the pix using Corel
    > Photopaint to 1024 x 768 to print 4" x 6" prints, because 10MP are too
    > big to upload.


    OK.. 1024x768 is bad for TWO reasons..

    The first reason is that you don't have enough resolution to produce a
    good print and the other is that the aspect ratio is wrong.

    1024x768 has a ratio of 4:3 and 6x4 prints have a ratio of 3:2. The
    printer must crop some of the 4:3 image to get it to fit properly.

    I'm not familiar with Corel Photopaint, but it must have a method of
    cropping to a constrained value. If you set that to 3 X 2, the crop
    square will always have the correct ratio no matter what size you drag
    it to.

    Once you figure that out, crop the desired 3:2 chunk out of your full
    sized image.

    Then, sample that crop down to 1800 x 1200 pixels. Now you have an image
    that will yield 300 pixels per inch both horizontally and vertically.

    300 DPI is the generally accepted resolution for quality prints.

    You DON'T have to worry about DPI at all in any step of the way.
    That's the processors job. Just make sure you deliver images that are
    1800 x 1200 pixels.
     
    Jim Townsend, Nov 16, 2006
    #10
  11. Ben  Bowen

    Ben Bowen Guest

    > OK.. 1024x768 is bad for TWO reasons..
    >
    > The first reason is that you don't have enough resolution to produce a
    > good print and the other is that the aspect ratio is wrong.
    >
    > 1024x768 has a ratio of 4:3 and 6x4 prints have a ratio of 3:2. The
    > printer must crop some of the 4:3 image to get it to fit properly.


    Man, what an uber-amatuer mistake to make. I'm usually pretty good with
    the ratios.

    Thanks for all the info everyone, I guess I really did drop the ball
    with regard to the resolution. I'll try it all again. Too bad it took
    220+ prints for me to figure this out. Stupid learning curve.

    Thanks again!
     
    Ben Bowen, Nov 17, 2006
    #11
  12. Ben Bowen wrote:
    > Hi all. I just sent out a bunch of pictures to get processed. They
    > were taken with my new Canon A640 (10MP). I re-sampled the pix using
    > Corel Photopaint to 1024 x 768 to print 4" x 6" prints, because 10MP
    > are too big to upload. I believe that is the correct resolution to
    > use, however, a lot of the pictures are pixelated. So now, I'm trying
    > to debug what I did wrong. I previously had a Canon Powershot S300
    > (2MP) and never had these problems. I camera takes pix at 72dpi and
    > the re-sampled pix have 72dpi too, so I doubt it could be that. Did I
    > decrease the resolution too much? Should I make it 1200x1600? When I
    > print the images at home (from orignial not-resampled images) I have
    > no problem, but the re-sampled images I uploaded are no good. I will
    > try various combos of re-sampling to experiment, but I'd like to have
    > an idea of what I'm shooting for.
    >
    > Thanks...


    My local Photographic Club has a good .pdf file worth reading on this
    subject................
    http://www.eastwoodps.com/tutorialspage.html

    DP
     
    Dennis Pogson, Nov 17, 2006
    #12
  13. Ben  Bowen

    Roy G Guest

    "Dennis Pogson" <> wrote in message
    news:ell7h.1645$...
    > Ben Bowen wrote:
    >> Hi all. I just sent out a bunch of pictures to get processed. They
    >> were taken with my new Canon A640 (10MP). I re-sampled the pix using
    >> Corel Photopaint to 1024 x 768 to print 4" x 6" prints, because 10MP
    >> are too big to upload. I believe that is the correct resolution to
    >> use, however, a lot of the pictures are pixelated. So now, I'm trying
    >> to debug what I did wrong. I previously had a Canon Powershot S300
    >> (2MP) and never had these problems. I camera takes pix at 72dpi and
    >> the re-sampled pix have 72dpi too, so I doubt it could be that. Did I
    >> decrease the resolution too much? Should I make it 1200x1600? When I
    >> print the images at home (from orignial not-resampled images) I have
    >> no problem, but the re-sampled images I uploaded are no good. I will
    >> try various combos of re-sampling to experiment, but I'd like to have
    >> an idea of what I'm shooting for.
    >>
    >> Thanks...

    >
    > My local Photographic Club has a good .pdf file worth reading on this
    > subject................
    > http://www.eastwoodps.com/tutorialspage.html
    >
    > DP
    >
    >

    Hi.

    I did not know you are a member of EPS. I used to be, but now live in Ayr.

    Roy G
     
    Roy G, Nov 18, 2006
    #13
  14. Roy G wrote:
    > "Dennis Pogson" <> wrote in message
    > news:ell7h.1645$...
    >> Ben Bowen wrote:
    >>> Hi all. I just sent out a bunch of pictures to get processed. They
    >>> were taken with my new Canon A640 (10MP). I re-sampled the pix using
    >>> Corel Photopaint to 1024 x 768 to print 4" x 6" prints, because 10MP
    >>> are too big to upload. I believe that is the correct resolution to
    >>> use, however, a lot of the pictures are pixelated. So now, I'm
    >>> trying to debug what I did wrong. I previously had a Canon
    >>> Powershot S300 (2MP) and never had these problems. I camera takes
    >>> pix at 72dpi and the re-sampled pix have 72dpi too, so I doubt it
    >>> could be that. Did I decrease the resolution too much? Should I
    >>> make it 1200x1600? When I print the images at home (from orignial
    >>> not-resampled images) I have no problem, but the re-sampled images
    >>> I uploaded are no good. I will try various combos of re-sampling to
    >>> experiment, but I'd like to have an idea of what I'm shooting for.
    >>>
    >>> Thanks...

    >>
    >> My local Photographic Club has a good .pdf file worth reading on this
    >> subject................
    >> http://www.eastwoodps.com/tutorialspage.html
    >>
    >> DP
    >>
    >>

    > Hi.
    >
    > I did not know you are a member of EPS. I used to be, but now live
    > in Ayr.
    >
    > Roy G


    Small world! Does Ayr have a Camera Club?
     
    Dennis Pogson, Nov 18, 2006
    #14
    1. Advertising

Want to reply to this thread or ask your own question?

It takes just 2 minutes to sign up (and it's free!). Just click the sign up button to choose a username and then you can ask your own questions on the forum.
Similar Threads
  1. Angelo DePalma

    pixelation; optimal settings for different sized prints

    Angelo DePalma, Sep 4, 2003, in forum: Digital Photography
    Replies:
    3
    Views:
    408
    Angelo DePalma
    Sep 4, 2003
  2. Coolpixel

    Pixelation problem with the Cool Pix 5700

    Coolpixel, Jun 10, 2004, in forum: Digital Photography
    Replies:
    5
    Views:
    403
    misifus
    Jun 14, 2004
  3. DS

    Should File DPI Match Printer DPI?

    DS, Jul 5, 2004, in forum: Digital Photography
    Replies:
    8
    Views:
    646
  4. Boooger

    96 dpi x 96 dpi?

    Boooger, Nov 29, 2005, in forum: Digital Photography
    Replies:
    8
    Views:
    2,631
    Bill Hilton
    Nov 29, 2005
  5. Giuen
    Replies:
    0
    Views:
    1,255
    Giuen
    Sep 12, 2008
Loading...

Share This Page