dpi

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santacruz11

Number of posts: 0
Written on: 2013-02-21 20:07:49
Where can I see the dpi of the picture? example: http://www.movieposterdb.com/poster/d40728c4

Martijn

Number of posts: 438
Written on: 2013-02-22 15:36:08

santacruz11

Number of posts: 0
Written on: 2013-02-22 16:15:18
but i want to print it, as a poster

PaultjePanter

Number of posts: 0
Written on: 2013-02-23 19:26:04
It says in your example 3500 x 5000 pixels, that's all you need to calculate the max size that you can print. For these pixels sizes: 17x25" (over 40x60 cm) on 200 ppi.
That is postersize. If you are able to use some tools (for instance Perfect Resize 7) you can make even bigger posters.

azulita

Number of posts: 0
Written on: 2013-03-02 04:35:06
Hi Paul, how do you calculate from pixels to cms?

PaultjePanter

Number of posts: 0
Written on: 2013-03-30 20:25:09
Sorry I didn't check back sooner here.
Better for our purposes is: pixels per inch.
You need about 240 pixels per inch to print quality work.
The conversion factor for inches to centimeters is 2.54
240 pixels per inch is almost 100 pixels per centimeter.
That means, if your digital image is 2000 x 3000 pixels, you can print that with a max size of 20 x 30 cm.

MassIllusion

Number of posts: 0
Written on: 2013-04-27 09:15:00
Wrong.

DPI does matter for image quality. Firstly, the link above is basically crap. And Old! If I took a photo with a 2 megapixel camera, and then another with a 16 megapixal camera which do you think would be better? More pixels equals better quality, more dots per inch or pixels per inch also gives better quality due to more colour and detail information in the composition.

Also, If I resize an image of 2000 x 3000 at 72dpi, your calculation @PailjtePanter would be incorrect. You cannot determine the DPI of an image simply by it's size. Most web images are 72dpi.

In Photoshop, you can take a 2000 x 3000 image and save it as 72dpi which will retain enough pixels for home printing. For industrial printing (like in a printers) for Raster artwork a minimum DPI of 300-400 is required for quality. No need to worry about DPI for vector artwork as it's scalable to infinity, but you still need a high DPI for mixed media of raster and vector.

The Poster above for 'Drive' is 3500 x 5000 and has a DPI of 300 and a bit depth of 24 and is an sRGB image. For print, sRGB or CYMK is preferred. The images was created in Photoshop CS5 and brought into InDesign CS5 to add the typography and then saved out.



Last bit of info. DPI is for print, PPI is for Computer Monitors. Print works by spraying dots of ink onto the source material, i,e paper, plastic. PPI is the Pixels per Inch on your display. This is why Video is always something like 720p or 1080i (interlaced, consists of two sequential fields of 1920 horizontal and 1080 vertical pixels).

Martijn

Number of posts: 438
Written on: 2013-04-27 17:30:41
MassIllusion,

I'm not denying that a photo taken with a 16 megapixel camera is better than one taken with a 2 MP one, and neither is the article. The point is that it does not matter what the DPI of the images on this website is: you can simply resample it yourself to a different DPI number; the number of pixels remains the same. DPI is or was rather a setting for printers: how many pixels should be printed on how many inches. As that article puts it: "what counts is that there are enough pixels in the digital photo to meet their minimum PPI (pixels per inch) requirement."

MassIllusion

Number of posts: 0
Written on: 2013-04-28 03:51:36
With today's modern technology of 4k UHD and retina display monitors images at 72dpi do look bad. Even modern budget HD LED monitors are now rich in the 'Colour Experience' that web images look terrible. It's OK if the image is small, but at 5000px + 72dpi just sucks. The article above is full of old info.

As for resampling. When an image is altered, either dpi or ppi the image is made larger to fit in more pixels. If you resize a 72dpi image to say 300dpi the (default) bilinear interpolation resize algorithm guesses where the extra pixels should go by selecting the pixels from its nearest neighbour, thus making the image look blurry. More so if an image has already been downsampled like most web images are resulting in loss of image info.

The post above asked what size the image was because the poster wanted to print the image and DPI matters to printing. So raising the DPI in this instance is useless if you want a good quality, crisp image. No large poster in the world will look good at 72dpi.


Komond

Number of posts: 538
Written on: 2013-05-07 12:25:26
MassIllusion, the difference between a 4mp camera and a 16mp camera is based on the actual pixels of the picture, not the dpi you set them. Both cameras can work on the same dpi and still the 16mp will be better (of course, if we suppose we are also talking about similar quality cameras on their respective sizes and not a great camera with less mp and a crappy with a high mp that would only be a big and blurry picture).

If you don't like a 72dpi picture because it looks bad on your screen you just set it to 300dpi if you are happier with that, but the fact is that a picture on screen won't be different because it's shown based on pixels and not dots, because it's not a printing machine, so there's no difference at what dpi it is.

By the way, changing dpi from 72 to 300 doesn't use any bilinear interpolation, that happens if you change the pixels not the dpi, but both versions of a picture one in 72 and the other one in 300 are exactly the same file except for the info that tells how are they're going to be printed, not shown on screen, so it can't be noticed except if you print them, no matter how 4K or retina or whatever example you want to use your screen is. So any picture 5000px set to 72dpi will suck and any 5000px set to 300dpi will suck less but just because it will be printed smaller. If the one who is printing knows something about PQ and printing he can manage those things and decide himself with the picture set at any dpi what he wants. Any 5000px picture printed on 72dpi will suck, but any 5000px picture set at 72dpi can be changed to 300dpi, and will get you a smaller printing at higher quality.

That link up about can be old, but it's absolutely not crap because it's right.

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