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Author Topic: RAW Affects on Image Size  (Read 2148 times)
Piece
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« on: December 21, 2005, 08:32:09 PM »
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I'm using Nikon so the file format is NEF but I'm opening them through CS2.  Basically I'm wondering if shooting in NEF will allow me to increase the output size without losing quality.  Currently I'm getting 40 Picas of height (6.66 inches) at 300 DPI and my final size that I need is 60P6 or 60.5 Picas of height (about 10 inches) at a minimum of 250 DPI.

At the moment I'm changing the file size to what I need with the proportionate DPI (about 198 DPI), then slowly increasing the DPI by 20 DPI incrimints up to 250 (I hear this helps with the quality).  Is there a better way or any way I can take advantage of shooting RAW.
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Dale_Cotton
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« Reply #1 on: December 22, 2005, 07:00:40 AM »
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Basically I'm wondering if shooting in NEF will allow me to increase the output size without losing quality
My answer is a qualified "yes". RAW (which includes NEF) aids enlargement in two ways. One is by eliminating JPEG artifacts, which grow increasingly apparent the more you enlarge. The second is by allowing you to get an image file with minimal sharpening into Photoshop. This is important because you don't want to apply sharpening until after you have done your upsampling. Neither of these benefits of the RAW format is likely to make a dramatic difference in the quality of your enlargements, so you will need to do some comparison prints to see if it is worth your while. In general, the advantages of the RAW format lie more in other areas.

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I'm changing the file size to what I need with the proportionate DPI
There are some who swear by this method, but I read somewhere that those who understand the math say it will magnify any enlargement artifacts that might appear. What you are talking about is upsampling by a factor of 1.5. It very much depends on the content of the image, but I think most of us would consider this a non-extreme degree of enlargement. I suggest starting with the same image file, duplicating it thrice, then applying your 20 pica method to one copy, Bicubic Sharper to the next, and Bicubic Smoother to the third. Print these identically then evaluate.

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Currently I'm getting 40 Picas of height (6.66 inches) at 300 DPI and my final size that I need is 60P6 or 60.5 Picas of height (about 10 inches) at a minimum of 250 DPI
Just to prevent future confusion, most people who do digital imaging use a different convention. We use DPI (dots per inch) only when referring to the actual application of ink by an inkjet printer and use PPI (pixels per inch) when discussing everything else related to the printing process, including enlargement. Also, I am more familiar with inches than picas; I suspect that holds true for others as well, although most Europeans would probably think in centimeters.

Good luck, and don't hesitate to ask if you have further questions.
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Piece
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« Reply #2 on: December 22, 2005, 12:18:18 PM »
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Sorry, I live in a publication world so I think in Picas and Dots.  I wasn't sure what you guys would be more confortable with so I gave them both.  DPI and PPI are the same to my understanding, are they not? The same number of pixels on the screen is the same amount of dots possible on paper?  

What I get from my plant is that we need photos to be a minimum of 250 PPI/DPI.  I think they really only print at like 192 but they won't accept anything below 250.

Thank you Dale!
« Last Edit: December 22, 2005, 12:19:25 PM by Piece » Logged
DarkPenguin
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« Reply #3 on: December 22, 2005, 12:28:28 PM »
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This may or may not be of interest.

http://www.outbackphoto.com/workflow/wf_60/essay.html
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Jonathan Wienke
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« Reply #4 on: December 22, 2005, 12:53:54 PM »
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DPI and PPI are the same to my understanding, are they not?
Actually, they are quite different, though commonly confused. Pixels Per Inch refers to the number of pixels per linear inch of the print surface, while Dots Per Inch describes the number of ink droplets (or halftone screen elements) per linear inch of print surface. Unless the print process is true continuous tone (dye sublimation, minilab, or similar, the DPI must be some multiple of PPI in order to accurately reproduce the image data, due to the dithering involved in creating the appearance of continuous tome. For most inkjets, the DPI setting  is 3-7X the PPI setting. This allows between 9 and 49 dots to be dithered together to form one colored pixel with acceptable tonal, hue, and saturation precision.
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