300 dpi vs 72 dpi

Discussion in 'Digital Darkroom' started by patrice_bennett, Nov 17, 2007.

  1. Okay - here is a quote from someone that is trying to help me fix some images:

    "
    I note, these are exceptionally small files for a digital camera. At this
    size, we certainly can deal via e-mail for all of them. However, I asked for
    high-resolution pics because they turn out better because, their larger size
    provides more detail in them to work on. While these are 300 PPI, which is
    considered high resolution, they are only about 1.5 inches x 1 inch in print
    size! This makes for a fairly small pixel size too, making it that much more
    difficult to get the best results.

    That said, I nonetheless can fix these up significantly, just not the bit more
    I could have done with larger files. Did you do anything to change the dots
    per inch on them to 300? I guess digital cameras can be set different ways,
    but typically they make them 72 dpi and HUGE print and pixel dimensions (with
    those huge dimensions, I can then change the dpi to higher and still have
    large enough print size). Yours are the opposite.

    But this also will mean you need to consider what you will use these pics for.
    The print size is too small for anything but thumb nail pics. The pixel
    dimensions are small but still large enough for reasonable use on the Web. Had
    they been huge pic files, I could have given you pixel dimensions, print size
    and dpi at whatever you wanted. At any rate, I hope you will be showing these
    to the company on the computer -- because as they are, they won't work as
    prints. I note, I can make them large enough for snapshot print size of around
    4.5' x 3 ' -- but I would have to reduce the dpi "

    -----------------------
    I guess I don't understand all of this because it seems to me that the 300 dpi
    should be better than 72 dpi and I always use 300 dpi getting good results at
    larger print sizes.....

    Can someone explain this to me?
     
  2. All that matters in terms of real resolution is the number of pixels high x number of pixels
    wide.

    If your original photo is 2000 x 3000 pixels it can be output as a 6.667 x 10 inch image at
    300dpi or as a 27.778 x 41.667 inch image at 72dpi.
     
  3. What are the pixel dimensions of the files?
     
  4. The "dimensions" in Adobe Bridge say 3872 X 2592
     
  5. I guess my real questions is - can you change the dpi settings on the camera or are these settings interchangeable once you edit in photoshop? Also, is there a difference in the quality of the image (sharpness) if you can change these settings on the camera? Let's say on a Nikon D80 for instance.
     
  6. Do the math 3872/300 = 12.9 2592/300 = 8.65

    So, at 300 dpi the file will print out 12.9 inches by 8.65 inches, without interpolation.
     
  7. You don't need to concern yourself about dpi in camera. It is only an instruction to an output device like a printer. You can change it to your heart's content in Photoshop using the Image Size menu item when you want to print.
     
  8. 3872x2592 @ 300dpi = 12.907 x 8.64 inches

    3872x2592 @ 300dpi = 53.778 x 36 inches

    Unless you've made some mistake whe nyou resized those files (like not checking the
    Resample Image box in the Iamge Size window in Photoshop) when changing the
    resolution) those are numbers you should be seeing.

    Yes you can tell the D80 to make various size JPEG images -- read your manual to figure
    out how to do it-- but doing anything less than full size is generally not a good thing. It's
    like snipping off your toes to make your adult feet still fit to your favorite pair of shoes
    from the third grade.
     
  9. 3872x2592 @ 300dpi = 12.907 x 8.64 inches

    3872x2592 @ 72dpi = 53.778 x 36 inches

    Unless you've made some mistake whe nyou resized those files (like not checking the
    Resample Image box in the Iamge Size window in Photoshop) when changing the
    resolution) those are numbers you should be seeing.

    Yes you can tell the D80 to make various size JPEG images -- read your manual to figure
    out how to do it-- but doing anything less than full size is generally not a good thing. It's
    like snipping off your toes to make your adult feet still fit to your favorite pair of shoes
    from the third grade.
     
  10. 1.5 by 1 inch at 300 dpi mean your printer is saying the file is 450x300 pixels. Did you mistakenly send thumbnails or images for web display?
     
  11. 3872x2592 @ 300dpi = 12.907 x 8.64 inches

    3872x2592 @ 72dpi = 53.778 x 36 inches

    Unless you've made some mistake when you resized those files (like not checking the
    Resample Image box in the Image Size window in Photoshop when changing the
    resolution) those are numbers you should be seeing.

    Yes you can tell the D80 to make various size JPEG images -- read your manual to figure
    out how to do it-- but doing anything less than full size is generally not a good thing. It's
    like snipping off your toes to make your adult feet still fit to your favorite pair of shoes
    from the third grade.
     
  12. I think this "problem" will keep happening as long as people wanting copies of digital files keep asking to get them in 300dpi rather than just saying to send them as they are from the camera - would have solved many issues, as it seems to be a lot easier to re-dpi them later than to go back and forth trying to make others understand how the dpi and resize thing in Photoshop works...
     
  13. One possible solution, of course, is if PS made it a default that any changes in dpi didn't resize the image, and if you wanted to resize the image at the same time, then you would you have to check other boxes. That way those who didn't know what they were doing wouldn't accidentally make very small images...
     
  14. I don't know, Hakon. It's easy enough to click on "print size" in Ps and see its dimensions on screen. The Gimp has separate menu items for "scale image" and "print size", but I don't know if that helps if the user doesn't understand the concepts.
     
  15. One can talk in pixels; dollars, Lbs of manure and be clear; or in cans of paint without mentioning the size of the can and "let folks guess". <BR><BR>Or one can talk in dpi with mentioning the number of pixels. Or about so many sacks of manure without mentioning the size of sack. Or one can say one is going to charge 200 bucks per hour to recover lost data on a disc drive without mentioning any time. <BR><BR>If ones pays a person to cut ones lawn, fix a toilet, shoot a wedding; does one dwell on the actual cost in dollars; or dollars per hour?<BR><BR>Saying an image is 2000 x 3000 pixels is clear to all; saying 200 Lbs of cow manure is fairly clear too; or saying one is mixing up 2 gallons of D-76; instead of X or Y packages. <BR><BR>Be aware of the pixel size(s) of your images. Just mentioning the dpi of an image; or number of cartons of milk doesnt give clearly what one has. One can have a 2000 by 3000 pixel image tagged as 72 ; 300; or a 1 pixel per inch image. One can have a gallon of milk as 1 jug; 2 1/2 gallons; 4 quarts; 8 pint cartons. <BR><BR>
     
  16. Probably cooking is a more common event where things can be packaged in many different sizes. A metric thanksgiving meal might require 1.8 kg of one meal; thus one could buy 25 packages at 72 grams; or six packages at 300 grams. <BR><BR>Or one might be making a meal for an army and need 1800 Lbs worth of turkeys. One could either get 25 frozen crates with 72Lbs; or six crates at 300 Lbs. With either purchase one has 1800 Lbs of frozen turkeys. <BR><BR>If one is "downsizing" of "upsizing" a receipe; the size of the cartons, packages, crates still doesn matter. One might be using a receipe for a 18Lb bird; and multipling by 100 to get 1800. Or one might cheat and use less bird; and bird helper. Then one can ask how much can I up size a receipe and thin it out and had have folks not notice that porridge is not really gruel.
     
  17. Kelly, sure you took your medication this morning?
     
  18. Frans; at the print shop tommorrow I probably be explaining dpi or ppi to another customer; usually many a day. Some "experts" will FTP in a scan of theirs of a 35mm slide; scanned at 4000dpi. One gets a approx 1 by 1.5 inch image at 4000 dpi/ppi; "print instructions" will say print at "full size". With a known customer; some want it at 72; another say an attorney may want their standard 24x36" trial prints. Yet another will get "testy" when you have to ask them what they want. If they are snotty; one can be an ass too; an give them some 1 by 1.5 inch prints for their deadlines. Part of education is trying to break the mind sets of folks who get in a rut; and just don't "get it". By providing analogys; sometimes their grey matter gets shook; and they gain understanding. A HUGE part of dealing with the public with digital printing is this dpi/ppi; resolution; "how big can I print with my Acme digital camera" type questions. The sad thing is there Photoshop certified chaps that are confused about a trivial thing like pixels. An ill defined nonsense print order just gets delayed; or never printed. The "72" number is a couple decades old now. The adding of this tag to a digital images header is abit old too. Its "intent: was not to cause confusion; but as very very rough approximation of an images size on a monitor. What ever the number chosen; some folks wont be happy with it and argue.
     
  19. Spearhead

    Spearhead Moderator Staff Member

    at the print shop tommorrow
    Where is this print shop?
     
  20. All about dpi/ppi, read my article:
    Misunderstandings about dpi - www.dpiphoto.eu/dpi.htm
     
  21. One can take VGA 480x640 pixel image and tag one copy as 72dpi; another as 300dpi; both with the same 480x640 pixels.

    Then open these two files in Adobe Photoshop and Adobe Illustrator.

    The two images in photoshop appear the same size on ones screen.

    With Illustrator the two images are different sizes on ones screen. This is because graphics arts has a job to do; make brochures, layouts; typically created at one ppi/dpi for the entire print. Thus a layout for a low res handbill might only require a 200 ppi image; images that are *tagged* at 200 dpi are then moved around with the mouse to fit around the text of the handbill. In doing a layout for the maps we create and print; the ppi of the 11x17" image is high; 400ppi. This is because the text is fine; and there are chart & topo dinky symbols and alot of details. Photo images that combined are resized and retagged to 400dpi; then moved in place with the layout software. Having the master layers and added features at the same tagged resolution makes the layout easier to eyeball for looks and fit.


    Many older graphics programs when installed default into a 72ppi world when making a new layout; even Photoshop does this by default. You can change it to anything you want.



    Mentioning that the 72 number is bogus or a misnomer just *tags you* as a abit of a begineer; or you dont have anything to do with printing; or know the history of printing. The 72 number is ancient in printing; its from 1737; before the first camera. Its printers points. The actual 72 number has had a slight waver since their was the French goofy inch. It can be the number before or after the print comes off Ben Franklins press. Prints SHRINK when dried. About 130 years ago the Hawk point came out which is .013838 inches ; ie 1/0.013838= 72.2648 Hawk points per inch.

    Warnock and Geschke started Adobe in 1982 after leaving Xerox. There are also Score points too; another story. The 72.2648 number was then truncated down to a practical interger *72* for usage in a computer; thats Postscript they invented for printers; which the 72 is the natural number. PostScript tends to be device independent; it revolutionized printing in the early 1980's. Mentioning that the 72 number is misnomer is like working at Home Depot and not knowing what a 1/4-20 bolt is; a skill saw is, or a 2 by 4. In a way the 72 number is like a 2 by 4; its been around along time; often missunderstood folks new to the trade. One could apply for a job at Home Depot and rant that a 2x4 is not really 2 by 4 inches. One could apply for a job at an editor and preach that the 72 number is a misnomer too. Its natural for folks new to a field to want to change history; its easy.

    The *72* tag for a cameras image file was added as an aid; but it seems to cause massive confusion. Its just added info that typically doesnt matter to most.
     
  22. Did you read the links in my article. E.g. www.scantips.com/no72dpi.html ?
    Do you agree with this?
     
  23. sorry, the link is: www.scantips.com/no72dpi.html
     
  24. In web design the 72 number was once called "screen resolution"; this is from the UCLA extension courses I tool a decade ago.

    I the 1970's one often did crude graphics in Basic; where a dot matrix printer often had 72 *dot matrix resolution* for 9-pin printers VERTICALLY; and horizontal many different dpi ranges

    In the early/mid 1980's a Mac's screen was almost exactly running at 72 dpi by design and this resolution was doubled to 144 when the image went to an early printers. The Mac/MAC screen of 512 x 342 pixels was purposely displayed so graphics work was the ancient 72 number thats many centurys old; ie 72 points per inch. Aldus PageMaker came out in 1985. Aldus Manutius was a printer who patented the italics type face; he passed away in 1515. The early Mac printers ran at 72 dpi draft; and 144 dpi in high quality. Todays Macs tend to run i the 90 to 105 dpi range for their monitors. Clip Art Libaries folks used in the early Mac days were usually at 72 dpi. In the spirt of rewritting history; its easy to say the folks at Bandley 3 accidentally got a 72 dpi output for the original Mac; and the pixels were square by accident. With older Apple Lisa; the pixel on screen were not even square. Who uses LisaGraf today?

    The vertical PITCH of the typical dot 1980's matrix printer was 9 pins/72 inch; ie 9/72 = 1/8 inch.

    With CorelDraw one can save as a EPS file and set the *tag* on the file to 72, 96, 200, whatever. Mine defaults to 72. The *72* number is also in Quark.



    In photo work keep track of our images size in pixels. One doesnt have to say the 72 number is always a misnomer; or rewrite history like Bluto Blutarsky in Animal House "Was it over when the Germans bombed Pearl Harbor?" :) In printing and graphics the *72* number has been around for 3 1/2 centurys. It was the screen resolution for the first Mac in 1984 for a reason; its was designed for graphics and printing work where folks are use to working in points; like dozens of generations of printers have used for centuries. Its the default resolution of Postscript and often the tag for digital images.
     
  25. Back to the original question: A digital image has only pixels, but no inches, so no px/inch (ppi/dpi).
    A print has inches and pixels, so px/inch (ppi/dpi). Some people above gave the right answer.
    Further explanation on my site (see my first post).
     
  26. Spearhead

    Spearhead Moderator Staff Member

    r weistra has encapsulated the whole story with his last comment. Not much need for anything else, including more history of 72dpi. But where's that print shop located?
     

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