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DPChallenge Forums >> Hardware and Software >> Pixel dimensions and print size
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05/21/2006 12:36:23 PM · #1
Does anyone know how to figure out what pixel dimensions you need to make a certain size print? My problem is that sometimes after I crop my pics they are screwed up when printing. I just send them to Costco for quick 4x6's or 5x7's but sometimes a head gets chopped in half or in the printed image it's cropped much tighter, etc... I hope this makes sense.....I just want to be able to figure out how to crop my pics if I plan to have them printed out in 4x6, 5x7, 8x10, .......

Thanks!
05/21/2006 12:39:27 PM · #2
I know it in cm... is that ok too?
05/21/2006 12:41:12 PM · #3
To keep it simple, I usually create a new document in PS that is the size I want to have printed.

Fore example: I create a new 5x7 document and paste the photo into that document. Either by using Edit > transform or by trying again with a different document DPI, I get the crop I want.

I found that is the best way for me, as I don't like trying to figure out aspect ratios.
05/21/2006 12:41:21 PM · #4
What software are you using to edit your pix?

I use Digital Image Pro 10 and also Picasa sometimes, and when I use the crop features of both there is an option for "Custom" cropping or "Ratio" cropping (ie. 4x6, 5x7).

A 4x6 image is more rectangular than a 5x7 or 8x10, so there will always be a difference in how much pixel information is included in the image for each of those dimensions.


05/21/2006 12:44:17 PM · #5
4x6 is 1.5:1 in aspect ratio, what that means is that the long side must be 1.5 times bigger than the short side

8x10 is 1.25:1 in aspect ratio, so the long side must be 1.25 times bigger than the short side

5x7 is 1.4:1 in aspect ratio, so the long side must be 1.4 times bigger than the short side

To determine the aspect ratio of your picture divide the length of the short side into the length of the long side.
05/21/2006 12:45:49 PM · #6
I'm relatively inexperienced w/photoshop (just started 10 months ago...from scratch) but that is what I use to crop. I usually bring up a picture, photoshop a little and then crop it how I like it in terms of composing the shot. I have never noticed a custom crop feature on PS but that definitely doesn't mean it isn't there.

biteme - what is CM

fmann - thanks!
05/21/2006 12:46:29 PM · #7
cm - best size - minumum size

9 x 13 - 800 x 1168 - 500x 730
10 x 15 -  975 x 1463 - 600 x 900
11,4 x 15 - 1100 x 1463 - 675 x 900
13 x 18 - 1267 x 1900 - 700 x 1050
20 x 30 - 1500 x 2213 - 983 x 1450
30 x 45 - 1700 x 2550 - 1267 x 1900
40 x 60 - 1900 x 2850 - 1500 x 2250
50 x 75 - 2048 x 3072 - 1700 x 2550

cm = centimetre

Message edited by author 2006-05-21 12:47:18.
05/21/2006 12:47:06 PM · #8
Originally posted by cpanaioti:

4x6 is 1.5:1 in aspect ratio, what that means is that the long side must be 1.5 times bigger than the short side

8x10 is 1.25:1 in aspect ratio, so the long side must be 1.25 times bigger than the short side

5x7 is 1.4:1 in aspect ratio, so the long side must be 1.4 times bigger than the short side

To determine the aspect ratio of your picture divide the length of the short side into the length of the long side.


Or in Photoshop, you can just use the mask tool set to Aspect Ratio and use the actual dimensions, like 8 and 10 for 8x10s. Then crop using that mask and you have your correct size.
05/21/2006 12:48:37 PM · #9
Originally posted by 2hoo:

I'm relatively inexperienced w/photoshop (just started 10 months ago...from scratch) but that is what I use to crop. I usually bring up a picture, photoshop a little and then crop it how I like it in terms of composing the shot. I have never noticed a custom crop feature on PS but that definitely doesn't mean it isn't there.

biteme - what is CM

fmann - thanks!


In PS when you choose the crop tool you can choose the dimensions. Also, when using the rectangle selection tool you can choose the aspect ratio.
05/21/2006 12:48:42 PM · #10
cpan - THANKS!! a bunch

biteme - THANKS!!

05/21/2006 12:49:00 PM · #11
you guys are too quick
05/21/2006 12:49:53 PM · #12
you're welcome!

we work in cm here, so every time I have to make a print, I want to be sure to stay in the "best size" category, so I grab this table.

works fine with me!
05/21/2006 12:49:57 PM · #13
Originally posted by 2hoo:

you guys are too quick


For quick reference:

http://www.dpcprints.com/help.php?faq_id=61
05/21/2006 12:50:41 PM · #14
I usually use the crop tool - how do you use the crop tool to choose dimensions?
05/21/2006 12:51:10 PM · #15
In photoshop, if you click on the crop tool, along the top bar you will see:
width _______ height _______ resolution _______ pixels inch or pixels cm

if you put in 5 in, 7 in, 300 the result will be a 5inch wide by 7 inch tall 300 pixel per inch/cm (300 is the best resolution for printing). Use the crop tool to figure out what you want in the image.

This is the 'easiest' way but I think it by-passes the bicubic - sharp/smooth part of resizing.

Geez I'm slow today. :)

Message edited by author 2006-05-21 12:52:00.
05/21/2006 12:51:29 PM · #16
I like to crop in the camera as much as poss. With file size of the 20d, if I crop it or let the printing shop do it, I lose the ability to fill the print as in the camera. So how do work with this issue? If this makes any sense.
05/21/2006 12:52:38 PM · #17
Originally posted by 2hoo:

I usually use the crop tool - how do you use the crop tool to choose dimensions?


When you choose the crop tool there will be height and width boxes at the top of the window. Set the width and height (using the units of choice) and blank out the resolution box.

BTW, the PS help is quite good and would give you some explanation of the tools you use.
05/21/2006 12:53:12 PM · #18
Here is a Guide to Print Sizes in Pixels.

Note that sometimes printers (e.g. at Costco) sometimes enlarge the print 1-2% to make sure it bleeds off the edge. If you have important elements near the edge, you should save at a slightly larger size, according to this Table of Print sizes at the bottom of this page on printer profiles from Dry Creek Photo. Most Costco print centers use these profiles, so the rest of the article may interest you too.
05/21/2006 12:55:29 PM · #19
This issue is regarding the aspect ratio of the print store machine x your camera or croped size you had produced.

You have a 3:2 aspect ratio, since you had a Canon 20D. The 5x7 and 8x10 are all 4:3 aspect ratio. This relates with the sensor/film dimensions. The 4:3 (four thirds) is the aspect of the 35mm film, full frame digital SLR and too of Olympus E-series, digital cameras. The Canon sensor with 1.6 crop factor, all produces 3:2 aspect ratio, ready to print at: 6x4 and multiples of this size. Remenber your colege math? The 6x4 fraction can be reduced to 3x2! The same calculations will give you the answer of all kinds of print sizes you can do safely.

All other sizes that not complain with your camera aspect ration needs to be croped to that size, this way you can choose to left out some chest area to keep the head for example.

To crop correctly, in PS, choose your dimension (print size, all of then can be choosed), then put this dimension in the Crop tool panel in inches, then the crop will be done correcly to the size.

Other tip is to check if your print store makes that size of print (phisically). Some print stores with no quality control does any print size, despite of the machine/paper real print capabilities. Resulting in chooped prints too. Or worse that, making more image processing out of your own control.
05/21/2006 12:58:59 PM · #20
Thanks a lot everyone!
05/21/2006 01:01:10 PM · #21
Now that makes sense.....great thread...great advice....thanks..ace
05/21/2006 01:04:04 PM · #22
Reading this tutorial will provide you basic information you need to understand how to better get print sizes correct:

Resizing Pictures to Standard Print Sizes

I'd recommend you always post process your full sized image and save it as your post processed master file. Then you crop from your master file for various web or print output needs.

Btw, the exact image pixel dimensions for any particular print size depends on the pixel density (DPI or dots per inch) that you want to print it at. Higher pixel denisity results in better prints. For example, a 5X7 print is 750 X 1050 pixels at 150 dpi, but is 1500 X 2100 pixels at 300 dpi.

Message edited by author 2006-05-21 13:17:23.
05/21/2006 01:05:50 PM · #23
Originally posted by stdavidson:


I'd recommend you always post process your full sized image and save it as your post processed master file. Then you crop from your master file for various web or print output needs.


Yes, definitely.
05/21/2006 01:08:02 PM · #24
Originally posted by GoodEnd:

The 5x7 and 8x10 are all 4:3 aspect ratio. This relates with the sensor/film dimensions. The 4:3 (four thirds) is the aspect of the 35mm film, full frame digital SLR and too of Olympus E-series, digital cameras.

8x10 is a 1.25:1 ratio
5x7 is a 1.40:1 ratio

"35mm" is 1.5:1 ratio, not 4/3.
05/21/2006 01:25:41 PM · #25
Largest digital print rule states:
To calculate in inches the largest photo-quality print you can make with a digital camera, divide the horizontal and vertical pixels counts by 200. If you want exhibition-quality prints, divide by 250.
If you have 3000x2000 pixel image you could print a quality 15x10 photo.
You could reverse the proceedure to get pixels from inches.
10x8 would be 2000x1600 pixels.
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