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DPI - Photography

Good People, I need some advice from you very clever people out there, what dpi should I be saving my pictures ? for printing purposes. Joe...

  1. #1

    Default DPI

    Good People,

    I need some advice from you very clever people out there, what dpi
    should I be saving my pictures ? for printing purposes.

    Joe Guest

  2. #2

    Default Re: DPI

    One other question to go with this topic si to do with format for
    saving. What is best to save in ? ie jpg, bmp etc etc


    On Mon, 22 Sep 2003 23:21:22 +1000, "Joe Seaham"
    <> wrote:

    Joe Guest

  3. #3

    Default Re: DPI

    JPEG 300 DPI


    "Joe Seaham" <> wrote in message

    NF Guest

  4. #4

    Default Re: DPI

    Joe Seaham wrote:

    Where's that string?

    As big as you scan or record in digital.

    300dpi at the print size as a general rule.

    Wiz Guest

  5. #5

    Default Re: DPI

    Joe Seaham wrote:

    Tiff is lossless. RAW.

    Wiz Guest

  6. #6

    Default Re: DPI

    "Joe Seaham" <> wrote in message

    There is a proper formula used to work this out. If you know the final size
    of the image required, for example 13cm x 18cm
    The size of the original eg = 35mm (Dimensions are 36mm x 24mm)
    You first work out magnification, which is always the largest side of the
    image, divided by the largest side of the object.
    In this example the image is the print.
    Its largest side is 180mm divided by the largest side of the object, which
    is the neg 36mm
    Therefore m= = 5
    Industry Standard is 300dpi.
    (Then there is a "fudge factor" this is usually 2 for colour or 1.5 for
    black and white) although these days most just use a factor of 2.
    So the formula is :
    Scanning Resolution = Output Resolution X fudge factor X magnification
    = 300 X 2 X 5 = 3000ppi.
    If your scanner doesn't offer this figure (3000ppi) use the next closest
    In regards to file format question TIFF without a doubt

    Graham Guest

  7. #7

    Default Re: DPI

    How do you make a 72dpi 3mpx shot from a S2 Pro cam to be 300 dpi ?

    Re-populating them in PS is not a really good way someone said.


    "NF" <com> wrote in message

    [BnH] Guest

  8. #8

    Default Re: DPI

    "Joe Seaham" <> wrote in message

    dpi is irrelevant. ppi is irrelevant. liines per inch IS relevant but the
    damned printer software (thank YOU mr software driver writing-dood) doesn't want
    to know such things!

    ppi is how things appear on your computer screen and depends on two things, how
    big the image is in pixels, and what screen resolution you have set.

    dpi is how many dots the printer can splat down on the paper (hint, if your
    printer can do 2400 dpi then it will select 2400 dots of whatever colours it
    needs to make up the colour you want for that 1 inch. to put it another way, if
    you weant to print a 1mm beige dot, the printer will use 944 dots of various
    colours to make that 1mm dot :-) This has nothing to do with how big your
    picture is.

    lines per inch is too hard for me to explain at the moment and won't do you any
    good anyway... the closest thing you can work with is ppi, pixels per inch but
    instead of asking the computer to write this image to the monitor, you are
    asking it via a print driver to write it to paper

    hint. download Irfanview and print ALL your pics through this small program and
    then follow the simple rules outlined below.

    1. decide how big you want the image to be.
    2. remember these two false numeric values <240dpi> and <300dpi>

    now to put these two together. You want an 8x10? 300dpi looks really good at
    8x10 (at close range, 300 pixels per inch are indescernably small - more than
    300 however and you may force the prnter to restrict it's colour choice when
    making the decision which inks are used to make which pixels and the image can
    actually look worse)
    OK, back again - you want an 8x10..
    8 inches x 300 = 2400.
    10 inches x 300 = 3000

    your image should be saved to be 2400x3000 pixels - bugger the dpi.

    lets say you want a 30x40 inch image, here the pic will be so big that the lower
    240 dpi will look fine ('cause you're standing back further to look at it)
    30 inches x 240 = 7200
    40 inches x 340 = 9600

    your image should be 7200x9600 pixels in size.

    when you go to print it in irfanview, you simply tell the printer to print the
    first image and make it 8x10 inches, the second you would say make it 30 x 40
    inches. Simple, and you don't need a single dpi :-)


    k Guest

  9. #9

    Default Re: DPI

    Someone will correct me if I'm wrong :o)

    DPI is irrelevant, other than for printers - that is, it's a printing
    function, not a file function.

    An image of, say, 2100 x 1200 _could_ be printed at:
    600dpi to give 3.5" x 2" print
    300dpi to give 7" x 4" print.
    150dpi to give 14" x 8" print
    75dpi to give 28" x 16" print

    So I guess it's a matter of ensuring your printer knows what you want
    it to do, and you knowing what your printer can do. Will it print
    your image at 1 pixel per inch, or 1200 per inch?

    I tend to save files with as many pixels as I can, with as much detail
    as I can (big file sizes, but disk is cheap!), and then figure out the
    final bits when it comes to printing or whatever I'm doing with the

    So my advice is 'go for the pixels' rather than worry about dpi,
    unless you know exactly what you want the image for.

    As for format, I usually use tiff, although also have many png & jpg

    Andrew Guest

  10. #10

    Default Re: DPI

    "[BnH]" <b18ATiinetDOTnetDOTaus> wrote in message


    The dpi (or ppi) means NOTHING until it is output to a printer or similar
    output device. By resizing a 72dpi image to 300dpi it does nothing at all
    apart from, for example, changing the output print size. While the filesize
    matters, don't even think about what the res is of the file that comes out
    of the camera. 3Mp is 3Mp is 3Mp whether it be at 72dpi, 150dpi, 300dpi or


    Cameron Guest

  11. #11

    Default Re: DPI

    In article <com>, Joe Seaham says... 

    Read this:

    (from reading the replies, it seems a lot of other people should, too).

    Andrew Guest

  12. #12

    Default Re: DPI

    havent read the rest of the replies but....
    it doesnt matter the size you save the photo at, so long as it is saved at
    the maximum size for that photo.

    for example, my digital camera takes photos that when uncompressed (4mp)
    comes to about 11Mb.
    so long as that 11 mb is preserved the dpi doesnt matter.

    you can resize the dimensions of the photo at the printing stage.
    my ~Mb11 should be ok for about 11X14 printed.
    but 300 dpi is a rather arbitary standard.

    I CAN resize my 11Mb so that it is actually bigger but quality will be lost
    as the software will just extrapolate in extra pixels.

    the lesson is to get as good a quality the first time.
    the question is what is reasonable.

    it is best to save in *.tif format as nothing is lost.
    tif's are rather BIG so, *.jpg saved onto a cd

    "Joe Seaham" <> wrote in message

    Andy Guest

  13. #13

    Default Re: DPI

    Well that was the point I stressed to a publishing guy I knew.
    Maybe he need to read his manual books again :)



    "Cameron" <camlaird"NOSPAM"> wrote in message

    [BnH] Guest

  14. #14

    Default Re: DPI

    Most Inkjet printers will produce photo quality output at 100 ~150 dpi so if
    you are only ever going to print on an inkjet that is all you need. The best
    advise is to leave your originals untouched and creat copies of them for
    printing. If you resize a picture to (for example) 6"x4" and 150 dpi. On a
    Canon or Epson printer, you will get photographic output provided you use
    photo paper. This size resolution is also good for creating jpg files for
    the Internet.

    If you intend to get 'real' photos printed at a chemical lab, then save them
    at 300 dpi. The directory structure of a typical CD sent to a lab have
    pictures all at 300 dpi in directories labled 6x4, 10x12 etc and the resized
    pictures in those directories will then print at their intended sizes. It is
    common for hi-quality photo labs to assume the photographer knows what they
    are doing and not make any corrections to colour or density.

    In a perfect world, this would be fine but how many photographers really
    know what ICC profile to use for an Agfa lab and if this is the same profile
    used on a Lambda printer? If you are happy with the variable stuff that
    comes from mini-labs... You will probably find any Frontierer (FUji) or Agfa
    lab offering digital prints can give you 50 cent prints. When your quality
    expectations begin to reach professional or semi-professional, then you need
    to understand about colour profiles and how they effect your photographs.

    (Just another Troll!)

    "Joe Seaham" <> wrote in message

    Snaps! Guest

  15. #15

    Default Re: DPI

    On Tue, 23 Sep 2003 00:33:29 GMT, "Snaps!" <>

    So, in other words, your target is for 300dpi, and:
    the 6x4 folder will have images 1800 x 1200 in size
    the 10x12 folder will have images 3000x3600 in size

    dpi is a figment of the imagination until anything goes on paper.
    Size is all that matters.

    Andrew Guest

  16. #16

    Default Re: DPI

    "Snaps!" <> wrote in message


    I hate to have another go at what you wrote but that is simply wrong. Plain
    wrong. I am guessing that most people reading this (considering it is a
    photographic newsgroup) have a photo quality inkjet printer like the Epson
    890 or 1290 or one of the Canon models. There is a clear difference between
    100-150 dpi and 250-300 dpi. DON'T do your images to 100-150 dpi. Do them
    at 250-300 dpi (I stick with 300dpi) and then you can send them to your
    inkjet or to a dig lab. There is a difference however when making large
    prints (i.e larger than 11"x14"). When making large prints the viewing
    distance is increased therefore the resolution doesn't need to be as high so
    I would suggest (as a guide) 250dpi up to about 12"x16", 200dpi from 12"x16"
    up to 20"x30" and maybe 150dpi for larger than 20"x30". (This is for a
    single image.... If you are doing up a sheet with multiple images to send to
    the lab (mainly 5x7's and 8x10's) then stick with 300dpi for each individual


    Cameron Guest

  17. #17

    Default Re: DPI

    Camron, Disagreement is what this group thrives on. If I didn't disagree
    with you at times, how would learn you were wrong?

    I use a Canon S9000 printer and I sometimes use an Epson dye sublimation
    inkjet for prints on porcelain. There is absolutely no difference between
    the quality of a print on Epson Premium Glossy paper made at 150 dpi and one
    made at 300 dpi from my S9000.

    Further... A 150 dpi image resized in photoshop (version 6) to 300 dpi, an
    ICC profile added and sent to an Agfa lab, is indistingusible from the 300
    dpi version which only had the profile added. Just as I did with Rudi (who
    had problems with an S9000) I will gladly send you examples to prove what I
    say is in fact, true.

    (Just another Troll!)

    "Cameron" <camlaird"NOSPAM"> wrote in message
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    Snaps! Guest

  18. #18

    Default Re: DPI


    I have had an Epson Photo EX, 1270 and 2000P and now have a 1290 and a 2100.
    I think that you may have a problem with your photography or eyesight if you
    can't see a difference between an inkjet print on a high quality photo
    printer or a digital lab at 150dpi (remember you also said as low as 100dpi)
    as compared to 300dpi.

    Also, if you resize an image in photoshop from 150dpi to 300dpi it will only
    make the image smaller. To make the image the same size and increase the
    output res from 150dpi to 300dpi is called resampling. Just the same as
    keeping the same output res and increasing the size.

    Time for new spectacles! :-)


    "Snaps!" <> wrote in message
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    Cameron Guest

  19. #19

    Default Re: DPI

    What is is about you Cameron?
    You don't know me from a bar of soap yet you can describe all my
    shortcomings as if I were your father!
    You must be a fair pain in the to live with.

    "Cameron" <camlaird"NOSPAM"> wrote in message
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    Snaps! Guest

  20. #20

    Default Re: DPI

    Cameron wrote:
    Question after the explanation...
    This is what I do... phone the lab I am printing at... find out what the
    MAX DPI of their machine is (400dpi at the new fang dangled? Agfa
    machine at Pronto in Newcastle) then use photoshop to make my images to
    that resolution at whatever print I want (6x4, 8x12 12x18 etc.)

    What would you deliberately make them 150 dpi when the machine can print
    higher... wouldn't this give a "grainy/noisy" effect up close where as
    using PS to interpolate will give a smooth effect??? and yes.. I realise
    that larger prints are not really supposed to be view up close but
    hell... I was looking at a REALLY BIG "Ken Duncan" print the other day
    from about 10 inches away :-)

    PS.. mind you... for smaller print sizes (6x4 and 5x7) I just get them
    printed direct from my burnt CD's at full-size ... I never bother to
    down size them.

    Brenton Guest

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