Resolution Information?

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izharqu

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Hello

Just want information on picture resolution, when i take pictures on my canon 40d the resolution comes out as 72dpi

Does it make any difference if this is on 72dpi or 250 dpi?

My friend recently sent me some images and the dimenstions, height & width are all the same as pictures i take however the resolution horizontal and vertical are set at 250 dpi, was this done manually or does the camera have a feature to set on higher dpi

When i increase my pictures to 250 dpi in photoshop, the file becomes over 30mb?

If you can explain dpi resolution it be much appercaited
 
dpi only counts for printing. Your camera takes a picture of x dots by y dots, everything else is based on that.
 
ok, so if i want to print an image say a3 size,do i have to increase its dpi from 72 to 250dpi?
 
Are you taking JPEGs or RAW photos? If you take them as RAW you can use DPP to convert the files to JPEGs and choose the dpi depending on what the final output will be (i.e print, web)
 
im using jpeg

so when i print the image, should i increase it from 72dpi?
 
Where's the 72dpi coming from, I would expect 300dpi straight out of the camera, raw or jpg.
 
Are they straight from the camera, you know, shoot jpg > download to desktop > open with windows viewer, or are you importing to 3rd party software and all that crap..
 
joxby said:
Where's the 72dpi coming from, I would expect 300dpi straight out of the camera, raw or jpg.
Click to expand...


No, some cameras do 72dpi. I alter this in Photoshop or indeed my Sony Camera RAW software to 300 for printing, or someting like 150 for a photo that I'm going to host on a website, much like this site.

I think I read somewhere ages back that 72dpi was about the best that a monitor could show so that's where the 72 came from.
 
joxby, your correct, its straight from camera, imported and saved

= 72dpi




when i create layouts in Page Gallery, i import the pictures which are 72dpi and when i produce the final layouts which imports to photoshop, the actual layout converts the file into 250 dpi however are the pictures i imported still 72dpi print or 250dpi?
 
dpi and ppi are two different things

your camera shoots at say 3000x3000 at 1000dpi your print would be 3inches wide and tall
whereas at 100dpi your print would be 30inches wide and tall

a camera doesn't shoot at a specific dpi it shoots a specific pixel ratio and whatever you set your print sizes document dpi decides the quality

i'm trying to think of a better way of explaining this but i can't really let me know if that makes any sense :P

oh yeah it's 72dpi for screen and anywhere between 180-300+ dpi for print depending on the size of the print
 
If I was going to print at say 6" x 4" then I'd use whatever photo-software package I had to resize the image to 6" x 4" with the dpi set to whatever the printer requires (best results on my R200 are 720dpi).

You could leave the image alone & just tell the printer to resize it to fit the page but the photo software 'probably' has a better resizing algorithm

dpi is just the dots per inch that the printer prints, the 72dpi from the camera is just a made up number to confuse us :)
 
dpi or ppi is a scalar, it's used to calculate the size a print would appear on paper.

If you have an image 3000px wide with a dpi of 300 then it would print 10" wide

3000/300=10

In terms of printing photos you only need to be aware of dpi as a guide to print quality. 300 dpi is generally accepted as the standard value for a high quality print when viewed up to arms length. As the viewing distance increases the dpi can decrease and for very large prints even 50 dpi would still look good.

If you change dpi in your editing s/w it can get confusing because often the values are based on inches/cm and dpi rather than pixels. So if you start with an image 3000px wide at 72dpi and then increase the dpi to 300 the s/w will calculate new pixel dimensions based on the measurement in inches and dpi.

A full size jpeg from my 1DmkIII opens up in photoshop as 54x36" @ 72dpi. If I change the dpi to 300 then the size stays at 54x36" but the pixel resolution increases from 3888x2592 to 16200x10800 and photoshop would enlarge the image adding new pixels based on the existing ones, a process called interpolation.

If I turn off the resample option and change dpi then the pixel resolution is unchanged but the physical size changes instead, it becomes 12.96x8.64"
 
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