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Ryan
2004-07-15, 11:44
I'm trying to print some photos out, and I want to print them at the biggest size possible, and I am wondering if anyone knows some good guidelines for this kind of stuff, if all the pictures are uncompressed? Most are taken at at least 1600x1200, some 2048x1536.

Brad
2004-07-15, 12:11
For good photo resolution, you want to be printing no less than 250 to 300 dpi.

You can do the math. :)

curiousuburb
2004-07-15, 12:24
1600 x 1200 @ 72dpi (screen res) = 400 x 300 @ 288/300dpi (print res)

2048 x 1536 @ 72dpi (screen) = 512 x 368 @ 288/300dpi (print)

The larger size will get you an acceptable print of 7 x 5 inches, the smaller 5 x 4.

You may be able to enlarge the image another 30% without degradation, depending on its content.
Printer, ink and paper choices will also affect your final print quality.

noleli2
2004-07-15, 12:52
I usually use 360dpi to print. I'm probably mistaken, but I figure there's less interpolation 'cause it's a multiple of 72 and divisible by 1440.

Ryan
2004-07-15, 13:43
Thanks, I think I'll go with 5x7 for all of them.

ast3r3x
2004-07-15, 13:55
I usually use 360dpi to print. I'm probably mistaken, but I figure there's less interpolation 'cause it's a multiple of 72 and divisible by 1440.

I don't really think that is a factor considering how printers preprocess most of the information anyways to my understanding.

Also, I work at a professional photography studio, and we send our pictures to be printed at 300dpi.

thedustin
2004-07-15, 15:24
I don't think there are any consumer, pro-sumer printers on the market that print over 300-320 dpi.

_thedustin

JLL
2004-07-15, 15:45
For good photo resolution, you want to be printing no less than 250 to 300 dpi.

You can do the math. :)

Yes, for offset printing (at around 150lpi).

Printing on ink jet printers, photo printers and so on doesn't require that much.

ATS
2004-07-15, 16:11
Warning: overly detailed explanation follows. Skip to last paragraph for the bottom line.

Let's start by defining DPI -- Dots Per Inch -- which is a term that applies only to printers and never to a digital file, which curiousuburb (http://forums.applenova.com/member.php?u=11) seemed to be alluding to in an earlier post in this thread.

Digital images of the bitmap variety are measured in pixels, and the pixel density is in PPI -- Pixels Per Inch.

Computer printers represent each pixel using several dots, so as a generalization a printer with a high DPI rating will be able to more accurately represent the pixels in your image. The higher the PPI of your image, the less accurately a given printer will be able to represent each pixel.

To visualize this, imagine what it takes for a monochrome laser printer to print a single grayscale pixel, which may have 256 possible shades of gray. The laser printer will need to use an 8x8 grid of dots ('cause 8x8 = 256) to represent each pixel, and for each dot added to the grid the shade of the pixel represented on paper is one level darker, up to the maximum of 256 dots.

So what is the maximum PPI this printer can accurately represent? If the printer has, say, 1200 DPI resolution, it can reasonably represent an image of 150 (or 1200/8) PPI. (Note that if the horizontal and vertical resolutions are different, for practical purposes the lower number is the only one that matters -- 'cause you can't accurately represent a pixel with a grid of dots with different horizontal & vertical measurements.) Increasing the PPI of your image means there are fewer dots available per pixel, and the printer won't be able to properly represent all 256 shades of gray.

This is mostly true with inkjet printers as well, though there are differences in the way inkjets lay their ultra-tiny dots on the paper. Inkjets don't really use a distinct grid, but scatter the dots within a given area according to optimized algorithms.

Now that the science lesson is over, on to the bottom-line answer:

You can probably get away with as low as 200 PPI in your photos. A few years ago, Popular Photography's Mike McNamara did a test of inkjet photo printers. An inexpensive Epson Stylus Photo produced results at resolutions of 200-300 PPI that were nearly indistinguishable from prints produced using a traditional enlarger from a photo lab, even when viewed under a loupe. That was around 2000, if I recall correctly. In the 4 years since then, photo printers of every brand have gone through a couple of generations of evolution, and they all have improved resolution, increased speed, better color accuracy and cost less. So use the best photo paper available for your printer and do some test prints starting at 200 PPI. Play around with the resolution until you can no longer see any improvement, then stick with that. If you have a page layout program, place different versions of the exact same image at different resolutions on a single page and print it out.



Math corrections follow:

"The laser printer will need to use a 16x16 grid of dots ('cause 16x16 = 256) to represent each pixel."

"If the printer has, say, 1200 DPI resolution, it can reasonably represent an image of 75 (or 1200/16) PPI."

Color me embarrassed.

Bones3D
2004-07-15, 23:36
If you really would like to go big with some of your images, you might consider getting ahold of a product like Extensis' PXL SmartScale. I was recently able to take some 5x6 photos and reliably turn them into 16x20" prints (both starting and ending at 300 DPI). While I was initially skeptical of how software could upsample a photo without losing image quality, I learned this product does not depend on between-pixel interpolation. Instead, it converts the entire image into vector data based on patterns in the image, then upscales that before re-rendering the image at the larger size. (Supposedly, images can be increased up to 1600% before any noticeable loss in image quality is noticed)

It's about $200, but does a pretty darned good job if you can't afford having a $1,000+ camera on hand.

Ryan
2004-07-16, 01:04
As I was expeirmenting, I found that printing a 2048x1536 image out at 360 DPI gave me pretty good quality. I printed 8x10.

ATS
2004-07-16, 09:59
If you really would like to go big with some of your images, you might consider getting ahold of a product like Extensis' PXL SmartScale.


I can also recommend Genuine Fractals (http://www.lizardtech.com/solutions/gf/gf_fnb.php) from Lizardtech (http://www.lizardtech.com/), which does the same thing. I used this product back when Altamira was selling it, and it worked like magic.