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04/16/2004 11:40:55 AM · #1 |
I just got a Rebel and am playing around with downloading photos etc. I noticed that as a default my images are saved as something like 96 dpi. I am taking photos at the highest res setting. Should I change the default to 300 dpi for printing?
Message edited by author 2004-04-16 11:41:15. |
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04/16/2004 11:44:23 AM · #2 |
Originally posted by smayman:
I just got a Rebel and am playing around with downloading photos etc. I noticed that as a default my images are saved as something like 96 dpi. I am taking photos at the highest res setting. Should I change the default to 300 dpi for printing? |
I half wonder if it isn't the editing program that decides things like that...my files open at 180 dpi. |
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04/16/2004 11:52:24 AM · #3 |
Do you mean ppi? Because there is a pretty important difference.
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04/16/2004 11:55:57 AM · #4 |
I don't know of any camera that saves images at 300dpi by default. When you open a downloaded image in Photoshop, you'll generally get a large image at a low dpi (Rebel images come in at 180dpi, I have other cameras that open at 72dpi). Just change the image size to 300dpi without resampling and you're ready for a printing press (150-200dpi is fine for inkjet, so that may be why the default is 180). A 4x6" image at 180dpi is the same as a 2.4x3.6" image at 300dpi- they're both 2.22MB files.
EDIT: High-resolution RGB images from a Rebel yield an 18MB file in Photoshop (about 6.827 x 10.24 @ 300dpi). You can safely res-up the image another 10-20% in Photoshop (sometimes more depending on subject matter). For a printing press, you should also change the color to CMYK mode.
Message edited by author 2004-04-16 12:02:47. |
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04/16/2004 11:58:28 AM · #5 |
I believe the Canon cameras put 180dpi into the EXIF as a default value. An editing program can ignore/override that of course.
really makes not difference at all if you're not printing the image, and if you are, you will prolly want to optimize that yourself anyway.
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04/16/2004 12:36:13 PM · #6 |
Yup - what everyone else said.
The resolution settings you use are entirely unrelated to the dpi settings.
Resolution specifies how many pixels you record in the saved image.
Pixels are dimensionless. They are just a number of typically square blobs of colour. They have no inherent size.
To translate that into something that can be printed, seen on a screen etc, you have to pick a size for each pixel - that's the number of pixels (or loosely dots) per inch that you'll show.
Screens normally use 72 or 96 dpi, printed material is often in the 150-300 dpi. This is why you can see an image big on the screen, with 80 odd pixels per inch of screen, and then when you print it, it would seem much smaller - because you cram more pixels of information in to smaller areas.
When you talk about printers, particularly dot matrix printers, there is a further layer of confusion. The printer lays down dots of ink, to create the image. often it will lay down 1440 to 5000 dots of ink, per inch of page. Each pixel therefore is being drawn with about 4 to 16 drops of ink - so you have to be slightly more careful about pixels per inch and dots of ink per inch.
Message edited by author 2004-04-16 12:36:41.
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04/16/2004 12:54:18 PM · #7 |
A tips:
Make an action in photoshop where you e.g.:
1. Flatten image
2. Make CMYK
3. make 300dpi (without resampling)
4. save a copy in folder (c:\pictures for printing)
I have one that I use for pictures that to be imported into the image bank and on for pictures that are going to the printer. |
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04/16/2004 01:00:57 PM · #8 |
I found this article to be of great help to me:
Understanding Resolution |
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