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Old Dec 31, 2002, 1:05 PM   #1
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Default Pixels / resolution / Image size ???

Hey everyone. I'm new to this forum and in fact new to digital photography.

I work in a marketing department designing printed sales and support literature. So my background is definitely in the "printed" world. I primarly use CorelDraw, Corel PhotoPaint and Fireworks.

This whole "digital" concept is confusing me.

I'm trying to make the manuipulation / printing of my photos as fast as possible. (I'm figuring if I spend hours on the computer messing with my pictures, I could have taken a roll of film in for processing much easier.

My background tells me all printed pictures need to at 300 dpi resolution. So do I need to resample every digital picture?
I was told NOT to resample as I would lose quality. I was told just to resize my photo to fit my media, 5x7, 8x10, etc. They also told me as I resized, my resolution would increase.

Unfortunately, when I reduce, indeed my photo gets smaller but I never actually see the resolution increase. It seems to stay at 72 no matter what I do, unless I resample.

Please help this old girl understand this whole process. Thanks for any hints you can give me.
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Old Jan 2, 2003, 8:36 PM   #2
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Default comments on resolution and resizing

The issues are with resolution and resizing. The number of pixels
you have stays constant (without resampling) and that is set
by the resolution seting on your camera. However, the 72 dpi that you are getting is the pixel density (DPI or Pixels per inch) and if you resize without resampling you can make the image larger or smaller and change the DPI to a setting you need.

The problem comes about when you want to print a certain size image where you need 300 DPI (as you acknowledged) and the numbers of pixels does not cover the image size at the pixel density you need. Thus your only choice is to resample. Resampling uses
adjacent pixels to add new pixels to your image.

Not knowing the software you are using I cant say for sure how much resampling will hurt your image quality. If you print and have the printer fit into the size you need it will also resample. Thus it is best if you control the process. if you have photoshop, there is an inexpensive resampling action that you can add to PS 6 & 7 from
www.fredmiranda.com.

Otherwise I would just resample, see how it looks and do adjustments from there. Here is an article by Tim Grey on resolution that might help as well.

http://www.naturephotographers.net/a.../tg1002-1.html

Does this make the issue any clearer? What software do you have?

Jim

my photos: www.pbase.com/jimskayak
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Old Mar 19, 2003, 10:52 PM   #3
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Hi! Paint Shop Pro 7.04 has the same problem, but I found a solution! Just increase the DPI until the dimensions are ~6X4.5.

Rememeber the DPI number, then change all your photos to it. BTW, Paint Shop Pro 8.0 is coming out in April, it has a resamlple uncheck box, meaning you don't have to resamle. That way, like the last guy said, you just change the picture size, and it will increase the dpi automaticaly. That way is especialy prefered for cropped images, otherwize you must come up with a new DPI setting.

Also, if you don't want to fiddle around with the numbers tring this and that you can take your long dimension in pixels and divide by 6. Example, a 2.0mp image is 1600x1200 pixels, so all you have to do is divide 1600 by 6 inches and you get ~267 DPI.

Actualy most people (including myself) often confuse terms. A digital image is measured in PPI, Thats Pixels Per Inch. A printer prints in dots, and thats where DPI comes from, Dots Per Inch. Sorry if I just confused you
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Old Jun 15, 2003, 7:13 AM   #4
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CindyN, To change the DPI in an image using Corel Photo-paint (I use photo-paint 7) go to resample, change the image size display to inches or what ever dimensions you work in, tick the maintain original size box and change the DPI to what you want or change the dimensions to what you require. The pixels will be the same but your size when you print will have changed with no qaulity loss.
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Old Jul 2, 2003, 10:33 AM   #5
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Default OK....

Alright... my head is spinning... but the original question posted is really close to the problems I have been having... When to crop, resize, resample... what to do when printing, and how to do it.

I photograph to raw and then have to go through all this conversion crap... I can live with that... but the pictures are huge and often I want to crop down. But what do I do with the cropped photo... it's size is often wrong. How do I get it to convert well to a 5x7, or 8x10?

Help! A good book or a tutorial on this would be very helpful...
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Old Jul 3, 2003, 8:08 AM   #6
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Default Re: Pixels / resolution / Image size ???

Hi,

Quote:
My background tells me all printed pictures need to at 300 dpi resolution.
Many inkjets print at 240 dbi optimum.


Quote:
Unfortunately, when I reduce, indeed my photo gets smaller but I never actually see the resolution increase. It seems to stay at 72 no matter what I do, unless I resample.
The 72 ppi is just a subjective term.
There is not actual ppi or dpi in your digital file. If your monitor resolution is let say 1280x960 then you're about 96ppi or more.
Your digital image size is only pixel count:
(pixel_width x pixel_hight).

Dpi and inch terms make sense only when going for printing.

- One pixel translates to one dot.

So let say that your digital image is 2048x1536pixels and you want to print at 300dpi.
Let's do the math:
(2048/300)x(1536/300)=6.8x5.1 inch.
So if you print your 2048x1536pix image at 300dpi you get a 6.8x5.1 inch print.

If you want a bigger print you've got to interpolate your digital file and add more pixels to it.
How much you can interpolate with acceptable results depends on your image subject. (For example portraits of people can be interpolated pretty much but landscapes with many details not much)
Some tools for interpolation here:
http://pixtool.info

Cheers,

Theo
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Old Oct 9, 2003, 2:18 AM   #7
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I'm not sure where this 300DPI figure comes from, but all the literature I've read suggest that true photo quality can be achieved by maintaining at least 200PPI.
I use Adobe Photo Deluxe to resize & crop, & never resample unless I'm trying to print a size that would mean less than 200PPI if I didn't resample. In this case I resample to 200PPI.
Eg: I have a Canon A70 that has 2048x1536 (3.2mp) resolution.
(2048p / 200ppi = 10.24i & 1536p / 200ppi = 7.68i). So I can resize to about 8x10 inches without resampling (comes to about 196PPI). Only if I was going larger than 8x10 then I would resample.
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Old Mar 24, 2005, 11:51 PM   #8
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Thanks to this forum for all of its education to me for resolving client issues. it seems that there are a number of graphics/ print layout people who are not familiar still with digital images and want extremely high pixels which most affordable digital cameras don't take (but them i'm no expert).

i'm responding the the concerns about upsizing images without losing quality. Once you've expired the upsize with resolution interdependent from the pixels and you still need to go higher without losing quality (as in the example of 72 dpi first mentioned) you can purchase a very affordable plug in for adobe called genuine fractals which uses an algorithm to resize (or so i've read) up to 10x with sometimes even crisper results than what you would have noticed without it.

I haven't yet used it because i'm not the end user, i'm working with the media supplying to end users that don't know things (baffling to me) so i've had to educate myself to educate them. i believe this plug in though to be what everyone needs if they wish to resolve that upsize issue.
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