Default D70 PPI? (PS-related Question)

Discussion in 'General Technical Discussion' started by petert053, Nov 24, 2005.

  1. petert053

    petert053

    143
    Nov 19, 2005
    Austin, TX
    I think this is a simple question, but I haven't found an answer I'm satisfied with yet. As the title asks, what is the default pixels-per-inch setting of a D70 RAW file straight from the camera?

    (As usual), I've been playing around with Photoshop, trying to get my "ultimate workflow" down and it dawned on me that I don't ever recall having explicitly setting the resolution PPI in the PS RAW interface window. It comes up with 300 in my system as a default, but I was wondering if that was true-to-life or not.

    As an aside, is the PPI the same for all Nikon NEF images, no matter what camera source?

    Any help would be appreciated...

    Peter
     
  2. The RAW (NEF) image from the D70 is 3008 x 2000 pixels. This image has not yet been given a size like 4"x6" or 8"x12". So there is no Pixel Per Iinch (PPI) until a size is given by Photoshop or Capture. Your default setting of 300 PPI is an industry standard. If you crop, be sure to set the resolution at 300.

    What is the maximum PPI of a 3"x2" print? 1000 PPI
    3000 pixel / 3 inch = 1000 pixel per inch
    2000 pixel / 2 inch = 1000 pixel per inch

    What is the maximum PPI of a 6"x4" print? 500 PPI
    3000 pixel / 6 inch = 500 pixel per inch
    2000 pixel / 4 inch = 500 pixel per inch

    What is the maximum PPI of a 12"x8" print? 250 PPI
    3000 pixel / 12 inch = 250 pixel per inch
    2000 pixel / 8 inch = 250 pixel per inch

    A Print Lab like Mpix can produce good quality at a minimum of 100 PPI
    So the largest they can print is 30"x20"

    3000 pixel / 30 inch = 100 pixel per inch
    2000 pixel / 20 inch = 100 pixel per inch

    Please note: If you crop you are eliminating pixels and no longer have a total of 3008x2000. Therefore you will will not be able to print 30x20
    Hope this helps, got to get back to family & Thanksgiving, Greg
     
  3. Computer monitors do not use a resolution above 72 PPI, so if working with images for the web, set it to 72PPI
    Greg
     
  4. My point is:
    -the image is measured in pixels
    -PPI = Pixels per inch
    -"per" means "divided by"
    -PPI = pixels divided by inches

    Once the image is given a certain size like 4x6 then we can use the term PPI
    But if you set your image to print at 300 PPI you're ok 72 PPI for web.

    Happy Thanksgiving, Greg
     
  5. shootman

    shootman Guest

    It is best to not set the ppi when using the crop tool in PhotoShop. Let the ppi simply respond to the dimensions you are choosing. For example lets say you have a 3008 x 2000 pixel image from your D70 that you open in PS.

    It will default to 300 ppi which will yield you a 10.027 in. x 6.667 in. print. This will be the setting you'll want for reproduction. But, let's say you want to seriously crop in on the image to produce an 8 x 10 in print. By only setting 10 inches as the width and 8 inches as the height (or visa versa depending on the format of your image) you might end up with a final ppi at 164 instead of 300, which could be just fine from your lab.

    If you set 300 as the ppi in the crop field and then draw a tight crop PS interpolates the image in one foul swoop to achieve 300 ppi where there is no data which may not be best for the quality of the image. You might want to use other forms of uprezing to get the final file to 300 ppi.
     
  6. Shootman, boy am I glad you brought that up, I always wondered about that. I didn't know PS would interpolate, or "grow" pixels.
    Thanks, Greg
     
  7. nfoto

    nfoto Guest

    In fact monitors and web browsers do not use "resolution" as such, so feel free to set dpi/ppi to any value you prefer, 72 or 300 or 3000 or whatever. Or leave the setting at its default value, which usually is 300 (you'll find it in the EXIF data header, the tag fields are "X-resolution" and "Y-resolution").
     
  8. petert053

    petert053

    143
    Nov 19, 2005
    Austin, TX
    Sensor Pixel Density?

    First, thanks for the reply and your information...

    I find this an interesting point. If you think of your image sensor as being like a small, gridded filter, it seems that there's an absolute maximum (I think the term is) pixel density - a physically measurable quantity of pixels per unit area. To me, it seems that there would be a "sweet spot" number not based on your final resolution, but based on your sensor... do you see what I mean? If you're trying to sift something (flour, dirt, alien artifacts, whatever), and you use a filter too small, you're wasting your time trying to pass a lot of (whatever) through too small of a hole... the other way seems true too (large filter looking for something much smaller). I guess, to me, it seems that in PS or whatever editor you use, the PPI should be related (in some way) to the pixel density...

    ...and therefore my orginal question... I guess... ouch! ...my head hurts now - too much technology on my vacation-time... need beer... now!

    Peter
     
  9. heiko

    heiko

    May 15, 2005
    Israel
    Hello Peter,

    As Bjorn said already, the ppi setting in ACR doesn't really matter. In fact, it has no meaning unless you prepare the picture for print. As said before, 72 ppi would be suitable for web, but you usually adjust pics for web usage by entering the pixel values (1024 pixels wide, etc.).

    Where ppi does play an important role is in printing. If, for example, you own an Epson 2200 (or 2100), you may want to print at 288 ppi. At a higher resolution you would probably waste ink, and the result may be less than optimal. At lower resolutions, quality will deteriorate.

    Here is an interesting article on it:
    http://www.rags-int-inc.com/PhotoTechStuff/Epson2200/
    (P.S.: This website wasn't available when posting this reply, but I managed to view it via Google's cache feature.)

    If you print pictures outside, you may ask the shop to tell you what's the best setting.

    In essence, the optimal ppi setting for PS depends on the printing process and printer you are going to use. So if you own your own inkjet or whatever printer, it's worth searching the Internet to find your optimal printer settings and ppi for use with your printer - it can make a noticable difference. Don't take the factory default settings or recommendations of the printer manufacturer as the last word - some manufacturers may advertise higher resolutions that actually produce lesser quality than optimal.
     
  10. petert053

    petert053

    143
    Nov 19, 2005
    Austin, TX
    Ok... I've got it...

    Thanks for your comments...

    That site is still down, but I'll try again later tonight. I guess that I'm just surprised that there isn't a recommended PPI from Nikon based on the sensor itself... but, I'll get over that.

    Peter
     
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