File type for prints

[ann]

and don't forget to think about viewing distance.

there have been billboards made from 2mp cameras and they look great at more than 100 yards, but up close and personal is another story

 

[Blake.Oney]

Thanks for all the responses. I understand the printing side a lot now.

 

[Boomn4x4]

hahaha oh man all this just made my mind go crazy hahaha i need to learn these terms such as 70dpi and 72 pdi do you do pixle adjustment in photoshop?

Its not really that complicated. The "dpi" is the dots per inch. Its used in terms of printing, as in the number of dots of ink the printer puts down per inch. This number is variable based on how detailed you want the picture to be.

You've probably seen this quite easily in things like text books and magazines.... where you can actually see dots of color. This are printed in very low DPI.. where there are only a few dozen dots per inch. When you are close to the image, you can see them... but if you move further away, they blend in and become pretty much invisible.

Pixels are the number of dots of information are on the picture. This is fixed in stone when you take the picture (though you can change it by enlarging or reducing the image later on) A 6 mega pixel camera will take a picture that is 2848 pixels wide and 2136 pixels high (2848 x 2136 = 6,083,328... rounded to 6Mp)

You need to put those 2 together to figure out what printing will look like.

That all being said, they eye is capable of detecting about 300 dots per inch... any more and they eye isn't senstive enough to distinguish any better. So divide the resolution, by the dpi and you get your picture size at that dpi.
A 6 mp image:
2848 / 300 dots per inch = 9.49"
2136 / 300 dots per inch = 7.12"

So you could print a 6 mp picture at MAXIMUM resoltion.... perfect photo quality at 9.49" x 7.12"

HOWEVER.... and here is the important part..... As displyed in the image above, the further away the image is... the less important the dpi is. This is where viewing distance comes in important. If you have a 4x6" picture you are going to view it from a distance of about a foot or two... so the resolution has to be tighter... but if you are printing out a 24 x 36" print... you can afford to not print so many dots per inch. You could easily drop down to 70 dots per inch (which is probably more than your monitor displays) and when viewed accross the room hanging on a wall, it will look just fine.
2848 / 70 = 40.68"
2136 / 70 = 30.51"

A 6mp image would print out a "computer monitor" resolution image that's 40" x 30". Granted, if you held that image in your hands, you would blatently see the dots and it would look like crap, but you aren't going to do that, you are just going to hang it on a wall.

Even going a step further, look at road side billboards. You could easily print a billboard at about 5 dots per inch.

2848 / 5 = 569"
2136 / 5 = 427"

That would be a 47' x 35' sign.... which would look fine from 500' away passing it at 70mph... all taken with a 6mp camera.