Welcome to City-Data.com Forum!
U.S. CitiesCity-Data Forum Index
Celebrating Memorial Day!
Go Back   City-Data Forum > General Forums > Science and Technology
 [Register]
Please register to participate in our discussions with 2 million other members - it's free and quick! Some forums can only be seen by registered members. After you create your account, you'll be able to customize options and access all our 15,000 new posts/day with fewer ads.
View detailed profile (Advanced) or search
site with Google Custom Search

Search Forums  (Advanced)
Reply Start New Thread
 
Old 10-07-2011, 07:32 PM
 
31,387 posts, read 37,143,291 times
Reputation: 15038

Advertisements

Quote:
Originally Posted by thecoalman View Post
Should be noted that DPI only makes a difference when you specify a physical size.
True, true, but if you noted I did mention that they needed to specify a size and regardless of the size of the print desired, the dpi needed to be 300 (well it could be 240 but that's another story).
Reply With Quote Quick reply to this message

 
Old 10-08-2011, 04:21 AM
 
41,813 posts, read 51,203,594 times
Reputation: 17866
Quote:
Originally Posted by ovcatto View Post
True, true, but if you noted I did mention that they needed to specify a size
I'm sure you understand this but pixel or a physical size? When someone asks me what the size of an image is I never think in inches because there is no physical size. This is one of my pet peeves, it goes back to my local newspaper insisting on 300 DPI images for print as if a 8MP image from Canon DSLR wasn't suitable for print because it was 72DPI. I saw a lot of images they printed all screwed up that I'm sure were fine before the user changed it to 300DPI.


Quote:
the dpi needed to be 300 (well it could be 240 but that's another story).
Yes it is, 200 to 300 is about what the human eye can see at "viewing distance" and if you're scaling up it's a can of worms to do it right.

I could write a book on this subject but I'm sure many would still be scratching their head. Most people have trouble wrapping their head around the concept.
Reply With Quote Quick reply to this message
 
Old 10-08-2011, 01:07 PM
 
28,803 posts, read 47,821,038 times
Reputation: 37907
Quote:
Originally Posted by thecoalman View Post
I'm sure you understand this but pixel or a physical size? When someone asks me what the size of an image is I never think in inches because there is no physical size. This is one of my pet peeves, it goes back to my local newspaper insisting on 300 DPI images for print as if a 8MP image from Canon DSLR wasn't suitable for print because it was 72DPI. I saw a lot of images they printed all screwed up that I'm sure were fine before the user changed it to 300DPI.


Yes it is, 200 to 300 is about what the human eye can see at "viewing distance" and if you're scaling up it's a can of worms to do it right.

I could write a book on this subject but I'm sure many would still be scratching their head. Most people have trouble wrapping their head around the concept.
Every time I try to change the "resolution" of a picture it comes out not-as-expected. You'd think a reasonably intelligent person would "get it", but it seems to go right past me. I need study aids.
Reply With Quote Quick reply to this message
 
Old 10-09-2011, 05:11 AM
 
41,813 posts, read 51,203,594 times
Reputation: 17866
Part of the trouble is a lot of the terminology gets thrown together, "resolution" is sometimes used to mean DPI and sometimes it's used to describe the pixel size.

The first and most important thing to understand is your images are sized in pixels, that is the real size. Second thing to understand is it has no physical dimension. For example this picture here:



If you have two different monitors side by side at the same resolution but they have different physical sizes the physical size of the image is going to change too.

You can change just the DPI, all that does is set default scale for printing. If you take either of the images I posted previously and send them to a printer they are going to print at different scales. You divide the DPI into the pixel size, the first one at 72DPI will roughly print at 3*3 inches and the second on will roughly be 1/2 * 1/2 in.

Image editors will allow you to scale an image using physical dimensions, if you're going to scale an image to 3*3 the amount of pixels is going to determined by the second variable which is the DPI. If you set it to 300DPI the result is an image that is 900px*900px.

Scaling in inches changes the real pixel size of the image and where many people screw up is they don't realize they are lowering the real pixel size of the image in lot of cases. They are under the impression that setting the DPI to 300 is increasing the real size of the image or making it better but that is not the case if you have an image with a high pixel count and scale to small physical size. You're actually reducing the pixel count and now have a smaller image compared to the original.

Having said that keep your originals even if the scale is going to increase the pixel count, scaling the real size of an image up can be detrimental. There's some really good software out there for that and as time progresses it will be incorporated mainstream. You'll want the most original copy. If you need to scale images for printing make sure you are not overwriting the originals or scale copies if you want to save them.

Last edited by thecoalman; 10-09-2011 at 05:26 AM..
Reply With Quote Quick reply to this message
Please register to post and access all features of our very popular forum. It is free and quick. Over $68,000 in prizes has already been given out to active posters on our forum. Additional giveaways are planned.

Detailed information about all U.S. cities, counties, and zip codes on our site: City-data.com.


Reply
Please update this thread with any new information or opinions. This open thread is still read by thousands of people, so we encourage all additional points of view.

Quick Reply
Message:

Over $104,000 in prizes was already given out to active posters on our forum and additional giveaways are planned!

Go Back   City-Data Forum > General Forums > Science and Technology

All times are GMT -6. The time now is 03:08 PM.

© 2005-2024, Advameg, Inc. · Please obey Forum Rules · Terms of Use and Privacy Policy · Bug Bounty

City-Data.com - Contact Us - Archive 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37 - Top