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Photography Question 
A C
BetterPhoto Member Since: 12/6/2004
 

Resolution: how many ppi for printing photos?


What kind of resolution do I need when preparing my pictures to take to the lab? I'm a Graphic Communications student and I'm used to doing every thing at 300 ppi - for halftone printing. However, I've been told different things about what kind of resolution is required for printing photos.

A book I have said that "the target resolution of an image depends on whether or not it will be screened during output" (O'Quinn, Donald - A Hayden Print Publishing Shop Manual).

So, what is it? Is it still 300 ppi? If so, my 6.3 Megapixel camera can't really do over a 8x10.


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7/9/2005 6:02:05 PM

 
John P. Sandstedt
BetterPhoto Member Since: 8/8/2001
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  Your printer, regardless of manufacturer, will work just fine at 240-300 dpi. Most folks set 300 dpi as the standard. More than 300 dpi is defintely a waste as the rpinters won't do any more.

dpi and megapixels are not the same so you really shouldn't have a problem unless you shoot in JPEG at too low a resolution to begin with. Check your manual. You should be able to get reasonably large prints with a 6.3 mp camera, maybe even 16 X 20's.


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7/10/2005 3:43:33 PM

 
anonymous 
BetterPhoto Member Since: 2/7/2005
  Yep, my 8.3 megapixel camera will only do a 8x12 at 300dpi on Large Fine. Maybe it is bigger if you shoot in raw, not sure, but I know, that it doesn't really matter and give it a test run, as where I print, the guy who put up the example prints did a huge A1 print, with his 6.3 megapixel 300D and the print looks great. I asked him how he did it, and he said it was set at Large Fine jpeg, he just took the photo and then printed it out, didn't change anything!

The print is HUGE and looks amazing!!! Although I am standing about 2.5 metres from it, so I can't see it close up, but who looks at a print like that anyway!


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7/10/2005 6:10:49 PM

 
Swapnali Mathkar
BetterPhoto Member Since: 1/3/2004
  Hi,

If you simply change the DPI to 300, you will get a print size as 8x10 or so. if you really want to get a very big print, you can interpolate the image. It means upsizing. In Photoshop / elements, you can check resize option and select bicubic (This is best alogorithm to do) and increase your resolution.
I heard that, you should increament in small steps, instead of big leap. and dont increase it beyond 100%, though I never tried even 50%.
Yes This certainly reduces quality , but you just do slightly, this should work. Also when you get a print of A3 or greater, people look at it from some distance , so slight reduction in quality is acceptable.

PS. This all is what I read. I have never taken a big print to check this out.


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7/10/2005 6:55:59 PM

 
John P. Sandstedt
BetterPhoto Member Since: 8/8/2001
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  If Natalie's and Swapnali's responses are correct, then evrything I've read at innumerable websites is wrong. But, again, here goes -

3 mp - a 4X6 print
4 mp - a 5X7 print
5 mp - an 8X10 print
6+mp - larger.

If these folks aren't able to print "large" prints they're doing something wrong and the whole printer industry is WRONG. Frankly, I tend to side [this time] with the printer makers.


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7/10/2005 7:25:30 PM

 
anonymous 
BetterPhoto Member Since: 2/7/2005
  John

You have every option to print as large as you like, you definitely aren't limited. But!! Obviously, the quality of the print goes down as the print size goes up!!! I swear on my brothers grave, this print was A1 size and taken with a 300D Canon camera on Large Fine jpeg. I spoke to the guy who took it!


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7/10/2005 9:08:48 PM

 
Swapnali Mathkar
BetterPhoto Member Since: 1/3/2004
  Hi John,

It is not a question of wrong and right.
The things you have read are facts. The thing I am saying are calculations underneath this fact.
If you open up photoshop (or any tool) and select Image Resize option. If you change the "Print Size" to 300, the image size is reduced and if you change the "Print Size" to 72, image size becomes huge. This "Print Size" is the DPI, Dots Per Inch. It says that if the printer prints 72 dots per inch it can print so and so size of image. If the printer prints 300 dots per inch, it can print say 8x11 size of image on paper.
Obviously if you print at 72 DPI , the print size is really big (I dont know if A1 or not) and at that big size, nobody takes a lens and check the quality (as said above) . People will see such print from a distance so Ideally you can take a print at 72 DPI also for bigger sizes. It means "larger prints" as per you had read.
This is all pure mathematical.

I guess this answers Natalie's point also. as that in camera fine jpeg might be at 72 DPI and making such a large print and seeing good quality from 2.5 mtrs is possible.


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7/10/2005 9:28:10 PM

 
Vince Broesch   As you know, for press you want about 1.5 pixels to the halftone dot. So 300ppi is fine for separations if your going to press at 180 dpi or so. That resoulution of 300ppi is also fine for photo labs. Most photo printers these days, that print on true photo paper, use ether a CRT or LED to expose and they image at about 240 DPI. As said, you could certainly print a much larger picture, especially since you will view it from a grater distance. The "average print viewing distance" is twice the diagonal messurement of the print.

Vince


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7/10/2005 10:45:30 PM

 
Swapnali Mathkar
BetterPhoto Member Since: 1/3/2004
  Sorry I used term
"Print Size" to 300 & Print Size" to 72
it should be "Document Size" -> "Image Resolution"


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7/10/2005 10:51:18 PM

 
anonymous 
BetterPhoto Member Since: 2/7/2005
  Yeh, the A1 print I saw must of been printed at 72dpi to get it that large, I think ISO setting would also play a huge part in it!


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7/10/2005 10:59:22 PM

 
A C
BetterPhoto Member Since: 12/6/2004
  Thank you everybody for responding! This has been very helpful.


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7/10/2005 11:20:30 PM

 
Terry  R. Hatfield
BetterPhoto Member Since: 1/4/2003
  The Key To Printing Is Interpolation I Have 13x19 Images Printed And Framed From a 5.47Mp Camera That Looks Very Good! As Size Of Image Goes Up DPI Can And Should Go Down, I Have Seen 20x40 Images Printed At 150 DPI Looking Like Medium Format Material,Its The Viewing Distance,A Large Image Is Viewed At A Further Distance Thus The Lower DPI!


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7/11/2005 9:30:48 AM

 
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