Nikon D5100 and dpi

Goldcoin79 · Mar 25, 2014

I have noticed a differance between the image size as in dpi when shooting in RAW compared to JPEG on my Nikon D5100 so I'm hoping one of you may have the answer.

When I shoot in JPEG and I look at the image size, it is taken at 300dpi but when I shoot in RAW and look at the image size it is 240dpi. This does not make sense to me as 240dpi means less quality than 300dpi and surely when shooting in RAW the quality as in image size should be at least the same. Am I missing something here , please explain if you have any answers.

James

SCraig · Mar 25, 2014

Looking at DPI alone is meaningless. It stands for Dots Per Inch and is only pertinent when printing an image. If you look at the actual dimensions of the image in pixels they will be virtually the same.

KmH · Mar 25, 2014

What software is it that is calling it dpi? Because it's actually ppi.
The 2 terms - dpi and ppi - are not the same thing. Ppi indicates an input device, like a digital camera. Dpi indicates an output device like a printer.

But as mentioned the ppi (print resolution) has no meaning until a physical print is made.
Until that happens the pixel dimensions (image resolution) of the photo and the electronic display device determine how big a photo is.

It takes many dots to print 1 pixel.
Quality inkjet printers use as many as 9600 dpi to print 300 ppi.

The D5100 is set by default to make images that have pixel dimensions of 4928 x 3264 pixels.

Do the math :
4928 px / 300 ppi = 16.43" and 3264 px / 300 ppi = 10.88" - At 300 ppi you would get a 16.43" by 10.88 " print.
4928 px / 240 ppi = 20.53" and 3264 px / 240 ppi = 13.60" - At 240 ppi you would get a 20.53" by 13.60 " print.

Other than the slight difference in print size, at normal viewing distance you likely could not tell which print was made at 240 ppi and which was made at 300 ppi.

bigal1000 · Mar 26, 2014

As said it is meaningless..................Adjust DPI when you make prints.......................

KmH · Mar 26, 2014

Advanced cropping, resizing, resampling | Photoshop

Note: Pixels per inch (ppi) is the number of pixels in each inch of the image. Dots per inch (dpi) relates only to printers, and varies from printer to printer. Generally, there are 2.5 to 3 dots of ink per pixel. For example, a 600-dpi printer only requires a 150- to 300-ppi image for best quality printing.

Goldcoin79 · Mar 26, 2014

I noticed when I put my RAW files in to adobe camera RAW (I use elements 11) and once I made any changes and saved it into a JPEG file when I looked at the properties of the file it said it was 240dpi however files I took in JPEG say 300dpi. I just expected they would both be the same size regarding dpi.

sifelaver · Mar 26, 2014

Goldcoin79 said:
I noticed when I put my RAW files in to adobe camera RAW (I use elements 11) and once I made any changes and saved it into a JPEG file when I looked at the properties of the file it said it was 240dpi however files I took in JPEG say 300dpi. I just expected they would both be the same size regarding dpi.

Adobe Camera RAW defaults to 240dpi. Next time you have a file open in the RAW editor click settings and change to 300. you can also output the file at 16bit from here (8 is default.)

Goldcoin79 · Mar 26, 2014

Thanks for all your comments and thanks sifelaver that probably explains things.

WayneF · Mar 27, 2014

Goldcoin79 said:
I have noticed a differance between the image size as in dpi when shooting in RAW compared to JPEG on my Nikon D5100 so I'm hoping one of you may have the answer.

When I shoot in JPEG and I look at the image size, it is taken at 300dpi but when I shoot in RAW and look at the image size it is 240dpi. This does not make sense to me as 240dpi means less quality than 300dpi and surely when shooting in RAW the quality as in image size should be at least the same. Am I missing something here , please explain if you have any answers.

James

dpi is meaningless in a camera. The image is dimensioned in PIXELS. The camera has absolutely no clue what size you may choose to print it. dpi only tells the printer how to space the pixels on paper.

But... if you are using Adobe Raw, and if you want to see 300 dpi there, simply click on the text line under the picture in the Raw editor.. (where says sRGB and 240 dpi, etc). Then simply change it to say 300 dpi on all images in the future. It is just an isolated number, it has absolutely zero effect on your picture or its pixels (dpi only tells the printer what size to print those pixels - you will likely decide that differently when the time comes).

KmH · Mar 27, 2014

You might note that Photoshop and ACR both use PPI, and not the incorrect and so very often misused term DPI.

WayneF · Mar 27, 2014

KmH said:
You might note that Photoshop and ACR both use PPI, and not the incorrect and so very often misused term DPI.

Misused says who?

It's been a long time since I heard that protest, I thought they gave it up.

The term for printing resolution was named dpi for years, including before Photoshop. Possibly technical jargon, but dpi always was the formal name of it. Then development of low price scanners and digital cameras started involving lots of newbies who were easily confused. So not all that long ago, someone got the notion it should be instead called ppi. Which is not a bad idea, however of course the name is dpi, and of course the change is no law, and too many old timers are still saying dpi.

Bottom line: It is absolutely necessary that we understand it said either way,

FYI:

In English, words are understood in context of use. If dpi is about ink drops, it is about ink drops. If dpi is about pixels, it is about pixels. Image files do not contain any ink drops, so any discussion about images is about pixels. Seems pretty simple.

Continuous tone printers (dye-subs, and Fuji Frontier types) don't print discrete ink drops of three colors like inkjet printers must - instead they mix the color of the pixel directly, and they print pixels (called continuous tone). There are no dithered ink dots then, just pixels. But these printer ratings still refer to the spacing of those image pixels with the term dpi, simply because dpi has always been the name for "pixels per inch".

Scanner ratings also always call it dpi, also referring to pixels of course (scanners don't use ink dots). You have never heard of a 4800 ppi scanner rating (and there are no ink drops used in scanners - scanners create pixels of course).

The formal technical specifications at the very heart of our digital imaging definitions use dpi:

JPEG file specifications See page 2 and 5, dpi, "dots per inch", meaning pixels.
TIFF file specifications See page 38, "dots per inch", meaning pixels.
EXIF 2.2 specifications See pages 19, 90, 101, 104, 108, 112, "dpi", meaning pixels (the number 72 dpi there has no significance, it just means "blank, no information").

EDIT: Oops! This third EXIF link has gone bad. Here is another with the same specifications:
http://www.kodak.com/global/plugins/acrobat/en/service/digCam/exifStandard2.pdf

All of the above is good enough for me. It is called dpi. It always was called dpi. Those fundamental and elite specification documents do not use ppi one time - because dpi has simply always been the name of it. I always say dpi too, for same reason, simply because that has always been the name for pixel resolution. Instead of telling newbies everything they hear is wrong, it seems much better to help them understand what they do hear.