How to take images at 300 DPI?

[marius]

Can you help me please?

I have my k20d and set the JPG files at 14,5 megapixels and "premium" .jpg quality (4 stars). My exported jpg images are still 72 DPI. How can I obtain 300 dpi jpg images from my camera? I need high dpi for my images because I need to print them.

How should I set the camera for printing purpose? Thanks.

[ftpaddict]

Photshop

File > New

Dimensions of an A4 paper, and set DPI to 300

Import pic from K20D in Photoshop.

Save


There. your picture is now 300DPI.

DPI is just for printing purposes.

[procyon]

The DPI value in the JPG file has no meaning. It is just a value in the JPG file. You can easily change it, but there is no need to do it, because it has no effect on print quality. It is just like a writing on the outside of a bottle - you can change it, but it doesn't change what's inside.
If this explanation is not enough I suggest you do some research on what the DPI really means and then you should be able to calculate what the DPI of your print really will be (regardless of any silly values embedded in the JPG file).

[RBellavance]

Originally Posted by ftpaddict

DPI is just for printing purposes.

That point is too often overlooked.

The DPI in the file are basically *meaningless*. What matters is how many pixels you print on how many inches of paper.

[ftpaddict]

Originally Posted by RBellavance

That point is too often overlooked.

The DPI in the file are basically *meaningless*. What matters in how many pixels you print on how many inches of paper.

Which makes DPI more printer-based than anything else.

[davebris33]

If you have ten million pixels (or any number for that matter) in your file, it follows that you will always have ten million pixels no matter what [i]physical[i] size you make your paper...Unless you specifically ask photoshop to resample your picture to add or subtract pixels from your image using the resample command. (don't do this unless you know you have to, and then never do it more than once, you will ruin your image)

72dpi was a standard set for showing a picture on a screen, because in the day of CRT screens that was the 'dots per inch' on a display, so 72 was the native resolution...If you look at your picture displayed at 72dpi you will notice it will most probably only be showing you 16.67% or something similar, depending on the physical size of your screen. Ask your PC to show at 100% and you will have a massive picture, showing all 10 million pixels present in the picture, instead of an approximation of 16.67% of the pixels that fits your screen

Re-set the dpi to 300, and you will not affect the pixels, just the screen resolution and the physical size of your print. Computer may be displaying at 60% or similar once this has been done.

200 dpi is fine for really large prints if you want to print poster size and the prints will be viewed from a distance.

Someone said dpi is not important, but it is...Do not print at 72 Dpi, because your printer may discard pixels and affect the print quality, giving you a print, no matter the physical dimensions, at true 72dpi.( i.e. automatically resample the picture to fit it to the paper. Not all printers do this, but it's not worth taking the chance.)

[marius]

Thanks for the answers.

I also have a 10 megapixels Nikon D50 and it takes photos at 300DPI

Are you saying that there are no difference in printing quality from an image at 300 DPI(from Nikon) VS 72DPI(from Pentax). There should be a difference !!!!

[kb244]

Originally Posted by marius

Thanks for the answers.

I also have a 10 megapixels Nikon D50 and it takes photos at 300DPI

Are you saying that there are no difference in printing quality from an image at 300 DPI(from Nikon) VS 72DPI(from Pentax). There should be a difference !!!!

Actually there is none, what so ever.

a 2 megapixel camera can shoot 300 dpi, 600 dpi, 1 million dpi.

Because you're leaving out half the equation.

Let's break it down...

DPI = Dots Per Inch, how many inches exist in cyberspace, how do you measure it before it has hit a print.

Let's say a 2 megapixel file or so 1600 x 1200
@ 300 = 5.3" x 4" print
@ 72 = 22.2" x 16.6" print

A 6 megapixel could print an 8x10 at roughly 300 dpi.

Without the output size, the DPI is utterly useless, and as a result a file tagged 300 or 72 are identical in every way possible, because an image 600 pixels wide by 400 pixels high, remains such no matter what the dpi setting is.

The only difference is how your printing software will chose to setup the output by default (meaning if your software is dumb, and refuses to let you set output density other than the dpi marker in the file, then the nikon image will always print smaller than the pentax at the same megapixels)

It's incredibly basic math, and only half an equation so I can't possibly see how hard it is to understand.

[procyon]

You cannot "take pictures at 72/300/whatever DPI".
Cameras just write some DPI value to JPG file.
It doesn't affect anything.
If you want to know the DPI you would get from printing just divide pixels with paper length.
For example: if your pictures longer side is 3000 pixels and you print it on a paper that has a length of 10 inches you would get 3000/10 = 300 dots per inch (DPI) (and actually it is PPI, but that is completely another story).
So just do your own calculations.

[vievetrick]

Just amazed that folks are still saying it does not matter what the DPI it. Take two files one at 72 one at 300 print them. Than post if you think it still does not matter. oh print them at 8x10 or 5x7

[Nesster]

DPI matters - like so patiently and well explained above - in printing. It also matters in scanning, because in scanning DPI affects the size of the resulting bitmap. In printing the DPI affects the size of the resulting print from a given bitmap.

I think the confusion comes when dealing with camera sensors: increasing the "DPI" does NOT change the size of the bitmap. Changing the "MP" resolution, from 10 to 6 MP, say, does affect the size of the bitmap and therefor the digital resolution.

Pat B - you are right but only if the bitmap sizes of the two files are different, or if you choose to bleed out most of the 72 DPI file outside of the printable area. In either, if you set the printer driver to size the image to the media, you'll have the same result. In other words, if you start with a 5 inch length, one file should be 5x72= 360 pixels long. The other should be 5x300 = 1500 pixels long. Only if this is true, that you are comparing the print quality of something 360 pixels vs another 1500 pixels, would what you say is true.

[raz-0]

Originally Posted by ftpaddict

Which makes DPI more printer-based than anything else.

Because monitors are whatever size they are and don't vary. For display on a monitor, the DPI is meaningless. If your picture is 1024x768, and your monitor is set to 1024x768, it fits. If it is set to 800x600, it doesn't. It doesn't matter what the in the image says it is.

Print on the otherhand is a printer printing on a page of not necessarily fixed size. So instead of saying that that postcard is 1500x1200 on that printer, or 6000x3600 on this other pritner, they give you a DPI resolution of the printer. On top of that, if you knwo how the printed object will be viewed, you knwo how many DPI you need the image at in order for it to look good. As long as the printer meets or exceeds that, and the image has enough pixels to be scaled to that DPI at that size, everything will look good.

[procyon]

Originally Posted by vievetrick

Just amazed that folks are still saying it does not matter what the DPI it. Take two files one at 72 one at 300 print them. Than post if you think it still does not matter. oh print them at 8x10 or 5x7

Please let's not confuse the DPI written in the EXIF data of JPEG (meaningless) and DPI set in the program you use for printing or printer driver (this really has meaning). This thread is about the DPI in the EXIF data. It has no meaning whatsoever. I can change it freely with any program capable of changing EXIF data. Nothing in the image changes. Only EXIF data. Different cameras/brands insert different DPI in EXIF data. It does not make the images better or worse.

[marcdsgn]

I'm going to offer my explanation from the print-industry POV:

1) Images captured via a digital camera are usually 72ppi. If you bring this image into a post-processing program without changing its values, it will remain as a 72ppi image, and the physical size is huge (eg: an image from the K10D is 136.03cm x 90.88cm. That's over a metre wide).

2) For professional printing purposes, an image being prepared for print should be no less than 300ppi in resolution if pristine image quality is to be preserved.

Effectively, this means if you were to "squash" a uncropped K10D image so that it contained 300 pixels to every physical inch (300ppi), the actual size of the image would be about 32cm x 21.6cm.

From a practical point of view, this means that your photograph won't lose any evident image quality provided its print-output size doesn't much exceed the size of an A4 sheet of paper.

In reality, loss of image quality is not usually evident to the naked eye(unless you're looking really hard) until print-resolution has dipped below about 200ppi. So you could get away with printing an image from the K10D to a physical size of about 50cm x 33cm (larger than an A3 sheet).

However, if you were to print the image at its unaltered onscreen size (136.03cm x 90.88cm) it would be printing at its original resolution of 72ppi, and of course the image quality would suck! But who has a photo album that big anyway?