72dpi - resolution - resampling - dpi - ppi

[tomorrowstreasures]

So, I shot in camera raw + jpeg lg... reviewing the jpeg files in Adobe Bridge - it says 72dpi.... WHAT???? :eek::confused:I thought I would be getting the 300dpi... can anyone help me understand this?:confused:

[jjeling]

I think all jpeg files recorded by camera's are recorded in 72dpi. I think it is something you have to do in PP. My Pentax and my Sony record all the jpegs in 72dpi. Maybe I am wrong, but thats what my experiences have told me.

[kat]

This is a great question.

I tried the Raw+JPeg and couldn't get the Raw to upload and the JPeg was low dpi. Can't remember what, it was a while ago.

I've also notice that I have some images pop up at 240 dpi and others 300 dpi. And I haven't changed the settings on my camera for the last year (nor the computer - but then again, we do have two and I use both).

I'm curious to know...

[Gatepc]

I dont mean to be rude ( and i could be wrong so correct me ) but dpi is only a measurement that tells a device how big to display or print something and does not mean anything!!!! since the only thing that matters is resolotion when you go to print it it will STILL print at 300 dpi ( or what ever your printer prints at ) its only a guideline so to speak for devices which doisint really matter anyway.

a image at 3600x2700 res and saying 72dpi on the exif will give you identical results to file with the same res saying 5000dpi becouse the printer recognizes that this "size guidline" is false and writes its own before printing


sorry for spelling using touch screen device

[Iguanasan]

According to Page 170 of the owner's manual you should get the following resolutions:

1535

Now, if I understand this correctly, DPI is dots per inch and whether it's 300DPI or 72DPI will depend upon how big the resulting photo is when it is displayed or printed. If you print the photo on a 4x6 and you do not lose any of the pixels then you are going to get

4368 / 6 = 728 DPI horizontal resolution
2912 / 4 = 728 DPI vertical resolution

So you are at 728 DPI.

That same photo printed at 8 x 12 will get you

4368 / 12 = 364 DPI horizontal resolution
2912 / 8 = 364 DPI vertical resolution

This is 364 DPI.

Remember, no matter what we do the image only has 4368 horizontal dots and 2912 vertical dots. The more inches that it's spread across the smaller the DPI.

Computer screens are generally 72 DPI because that's the largest number of pixels they can fit into 1 inch worth of screen "real estate". Note that newer monitors can go higher (96 and 120) and you can see the DPI of your screen in the advanced display properties (in Windows).

To make a long story short, you might be seeing the display properties of your image showing 72 DPI because it's being displayed on your monitor which really has little to do with the DPI of the image since that is completely dependent upon how big it is when you print it.

[tomorrowstreasures]

Nice that I read these replies on Valentine's day so I can say Love you guys with out too much brow raising!

Thanks for all of the feedback! !!! ! Very,very helpful!

[mindforge]

DPI is a screen and printing term. Dots per inch. It has nothing really to do with the images in your camera. Even the lowest can run at 300dpi at size and look good.

72 DPI = Screen Resolution
172 DPI = Newspaper images (highest quality papers) Keep in mind that most newspapers now have ink optimizers that cut down on the dpi on the plate so they use less ink. So newspapers can print 100 dpi on some plates and 172 on others. DPI is just a term for formatting images for internet use 72-120 DPI and formatting for printing.
200-300 dpi = most trade magazines
300 dpi = high quality printing


Also, if you have a printer capable of printing higher than 300 - you can't see the difference, even at 600 dpi. The only reason you would ever print at high DPI is large format imaging and only if you shooting with a FF camera.

[kat]

Hey. Back to this thread again. So I'm looking into getting some printing done but was told that I had to send my images at 300 dpi.

Some of them, for some reason are 300 while others are at 240. These I got from looking up the image size on PS. I was told that to go from 240 up to 300 was a no no. That it does alter the image negatively. So how do I get my images to 300 from the camera. I don't understand why there is a difference.

[kat]

Ok..and I just read this..does this make any sense?

"If you need to change the embedded DPI for some other reason, this can be done within photoshop and most other image editing programs. In Photoshop, the DPI can be changed by: Image>Image Size>Resolution (pixels/inch). Make sure to uncheck the "resample image" box at the bottom, otherwise the number of megapixels in your image will change (using interpolation).:"

[tirediron]

Image size is simple math. For all intents and purposes, DPI (Dots per inch) and PPI (Pixels per inch) are equal. DPI refers to printer resolution and PPI to screen resolution. Therefore, if you have an image that measures 3000x2000 pixels (A 6mp image) it would yield a 300 DPI image (using the long dimension) 10 inches wide. Let's say however that you crop a third of the image in order to achieve the composition you want. You now have a 2000x1300 (roughly) image. If you wanted to print an 8x10, the greatest resolution you could acheive would be 200DPI; if you needed 300DPI, then you would have to limit the size to [about] 4x6.

As far as upsampling in Photoshop, it does work, but depending on the degree and the type of image (bright colours with lots of detail won't upsample as well as dark, less detailed images), it may introduce a degradation of quality.

[Mad Aussie]

Ok..and I just read this..does this make any sense?

"If you need to change the embedded DPI for some other reason, this can be done within photoshop and most other image editing programs. In Photoshop, the DPI can be changed by: Image>Image Size>Resolution (pixels/inch). Make sure to uncheck the "resample image" box at the bottom, otherwise the number of megapixels in your image will change (using interpolation).:"
Yes Kat ... that is the correct way to resize the image. DEFINITELY make sure 'Resample Image' is not checked.
It's fine (and reccomended usually) to have 'Resample Image' checked if you are just resizing for uploading to the net.

Lots of nice technical advice in here.

In short ... your monitor at best will show you about 72 - 96 ppi (dpi) so changing it 300 doesn't look any better on the screen.

The printer asks for 300 dpi to save them work when they print. Like someone said ... it's just a code that tells the printing device what quality to print at.

Many photo labs have a default at 300 dpi so even if you forget and send them a file set at 72 dpi you'll get an image printed at 300 dpi anyhow. I (actually LeAngel) tried this recently and it worked.

[Marko]

Excellent info in this thread.

This part of kat's question is still foggy:

I've also notice that I have some images pop up at 240 dpi and others 300 dpi. And I haven't changed the settings on my camera for the last year (nor the computer - but then again, we do have two and I use both).I've noticed that do and I know how to fix it but why does that happen? Is it a portrait/landscape thing?

Ps. - I added terms to the thread title so guests/members can find it in many ways.

[tirediron]

Excellent info in this thread.

This part of kat's question is still foggy:
I've noticed that do and I know how to fix it but why does that happen? Is it a portrait/landscape thing?

Ps. - I added terms to the thread title so guests/members can find it in many ways.

I suspect that this may be the result of using smaller-size .jpg images.

[Marko]

I don't think so T.I., I only shoot RAW and this happens to me too.

[tirediron]

Okay, I'm confused. A RAW image displayed in the same software will sometimes appear as one DPI and at other times, another? What application, and what, if anything else is different?

[edbayani11]

it may come out 250 or 300 dpi in different softwares but the file size in megabites does'nt change. what changes is the length and width measurement if the dpi changes.

[tirediron]

it may come out 250 or 300 dpi in different softwares but the file size in megabites does'nt change. what changes is the length and width measurement if the dpi changes.

Correct; different applications may have different default display sizes set, but I made the assumption that most people would be using the same application...

[edbayani11]

if you want to resample in photoshop simply because you have no choice, ans you want to increase your measurement (length and width} do it in small increments until you reach the size that you want.
this is from experience when i was still doing billboards that measure 40 x 60 feet. i start the image at around 45mb and when approved for printing in large format printers, i slowly increase the measurements slowly in small increments until i reach 40 x 60feet. the file size sometimes go up to 350 to 470mb. this takes time but i noticed there is little degredation compared to resizing it in one shot.
the resolution for this size is about 20 dpi only but since this will be viewed from a distance, it looks smooth and sharp.
i know you won.t be doing this kind of extreme resampling

[ridicwilco]

actually, dpi does matter. here's an example why: if you scan an object on a flat bed scanner at 300 dpi then you can print that image with a higher level of detail at 20x30in than if you were to scan that same object at 72 dpi, convert it to 300dpi and print it out as 20x30in.

when you change the dpi of an image the file size return is larger. that's because you're adding more information.

you have to think about it in terms of information vs detail

more detail means more information but more information doesn't necessarily mean more detail. yes more detail, but more of the SAME details.

say you change a 72dpi image to 300dpi. you're literally multiplying the same information to make for a larger image vs an actual 300dpi image which has a more diverse information matrix.

:1st:

[Alex Wilson]

Some good info here, and I thought I'd chime in:

- Most of the time DPI and PPI are used interchangeably when talking about the pixel resolution -- the exception being when talking about the resolution of a printer. For printers, the DPI output is talking about how small the dots are it uses to make the image. In that case, it is not the same thing, since it take many dots over a larger area to render a single pixel of the source image. If you've got a 1440 DPI printer, you don't want to print your images at 1440 PPI on it.

- On a scanner, the PPI is very important since what you're scanning is of a fixed size. Being able to double the PPI means a higher resolution image.

- For an image file, PPI means absolutely nothing unless paired with the image dimensions. A 300 PPI 8x10in file contains exactly the same information as a 75 PPI 32x40in file.

So why do you need to know or care about PPI for an image?

Photoshop and other image applications will use it for printing. If you've set the PPI (or the setting has carried through from your raw file) then that's the size it will print at -- unless you override the print setting to scale it to fit to the paper, etc.

It also makes it easier when talking about printing formats and such. For the print shop I take all my stuff to, it's much easier for them to say to provide the files at 300 PPI rather than list the pixel dimensions of every possible image size.

[Marko]

I don't think so T.I., I only shoot RAW and this happens to me too.

I guess what I was referring to more precisely is the opening up of an image, in my case using camera RAW or the Bridge part of photoshop which is similar to lightroom. And I only shoot in RAW.

When I double click an image to open it sometimes the image has a default size (which of course can be easily changed) of 240 DPI. Sometimes it has a default size of 300 DPI.

The question is why is this DPI not consistent when opening the image in camera RAW or Bridge. This is a bit of a hassle because people (myself included) may not realize that the image is 240 DPI when 300 DPI was desired, after it is opened in a graphics program. (In my case - Photoshop)

many thanks again for this good and informative thread :highfive:

[kat]

That's exactly what I am wondering!!! Same thing for me!!!

[tirediron]

Okay... ya' got me. I don't have a clue on this one. I'm sure it's something dead simple, but I can't for the life of me, think of what it might be.

[Matthew]

This is such a great forum!
Why sometimes 240 and 300 ppi?
The default settings in Camera Raw may have been changed at some point - the default settings are 240 ppi. My printer (Epson 3800), automatically converts input files for printing to 360 ppi and so I have changed my Camera Raw defaults to 360 ppi. Before I had the 3800 I was not aware of this and consequently I have older images at 240 ppi. If your work flow involves your RAW files first being opened in Camera Raw it will always set the ppi to the default of 240 or whatever you have changed it to.

[Marko]

WOW some progress - thanks so much!!!
Any idea exactly where I can find these default settings, I've looked though what I think are the obvious places (preferences) and still can't locate them.

many thanks Matthew!

[kat]

What is camera raw? Is it a program? Or on the camera..lol. I'm confused. I have a Nikon so to get it on my computer I use either Lightroom or Photoshop. Photoshop I had to download a file to get my files downloaded. So do I change this 240 to 300 when I'm downloading by chaning it in lightroom and photoshop? Yes, where do you find that option? Does this make sense..lol

[Matthew]

Camera RAW options are available in Adobe Bridge. Under the edit tab (I am using CS3). This gives you only some options.

If you shoot in RAW format when you double click (PC) a RAW image file (DNG) in Bridge it should open up first in Camera Raw. Here you can apply sharpening and other useful default "actions" as part of a work flow.

Once the image is open in Camera RAW there is a link you can click at the bottom of the page. This will give you access to the colour space, bit depth, size (if you want to change from default camera resolution) and pixels per inch.

Once you have finished your camera raw PP (for the most part I stick with what I have set up as defaults), hit open image in the bottom right corner and it will open up in Photoshop.

I hope this is clear.