Printers require 300 dpi - A different question/issue about 72 dpi

[writerinpjs]

Hello,

I've read through many of the threads on 300 ppi/dpi. I understand the solutions offered such as batch processing and how the printer will print the image size that equals the 300 dpi. However, I have a different issue. I purchased just this week a Rebel T5 with the assumption that I would be able to take 300 dpi images not 72. I create books for print and my printers require 300 dpi. They will not do the conversion. My options in the past have been film camera to CD (old, I know) or the iPhone. I was spending a lot of time in Photoshop getting the images to printer requirements. So imagine my dismay uploading the first batch of photos into Photoshop and seeing 72 dpi. Yes I was able to change them 300 - but this is exactly the production work I had hoped to not have by purchasing the new Rebel. 

There has got to be a better way?

Or is it a different digital camera I need to purchase?

Thank you for your help.

[hsbn]

Camera doesn't shoot a photo at any DPI, 72 or 300 or 30000000. It just produced image with pixel dimension. It's the same for $50 camera or $5000 camera. Again, it's not your camera.

[writerinpjs]

Okay. 

[TCampbell]

Camera's don't have "DPI".  There is no "default" DPI that the camera sets, nor any conversion.  The concept of DPI doesn't exist as far as the camera is concerned.

DPI gets introduced when you open the image in your post processing software.  DPI has no meaning until you try to send an image to an output device... a printer, a monitor, etc.    You could send native resolution, but if you wanted an image to show up at a specific size then you want to know the resolution of the output device so you could figure out how to scale the actual resolution to the image, to the resolution necessary to achieve the size you want on the device you want... and that's DPI does.  As the camera is not an "output" device and it doesn't send images directly to output devices, it has no need for the concept...  but your post processing software needs the concept.

I don't know what version you use... I use Photoshop 5.1 on a Mac.  If I go into Photoshop's "Preferences" panel, I can set the default DPI that I would like to assign to a new file.

Any DPI settings you see where introduced by something OTHER than the camera.  Or stated differently... changing which camera you use still wont change the DPI.  You'll need to figure out which software is adding DPI to your images.

[Skirball]

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@TCampbell wrote:

Camera's don't have "DPI".  There is no "default" DPI that the camera sets, nor any conversion.  The concept of DPI doesn't exist as far as the camera is concerned.

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I thought that too, but from what I read yesterday it seems that they do assign a DPI (72) for jpg.  I haven't confirmed it yet on my camera as I never shoot jpg, but I believe that's where the 72 came from.

Regardless, this is a trivial issue with a multitude of mostly automatic solutions.  Which is why I'm surprised the OP came to the conclusion to return the camera.

[TCampbell]

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@Skirball wrote:

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@TCampbell wrote:

Camera's don't have "DPI".  There is no "default" DPI that the camera sets, nor any conversion.  The concept of DPI doesn't exist as far as the camera is concerned.

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I thought that too, but from what I read yesterday it seems that they do assign a DPI (72) for jpg.  I haven't confirmed it yet on my camera as I never shoot jpg, but I believe that's where the 72 came from.

Regardless, this is a trivial issue with a multitude of mostly automatic solutions.  Which is why I'm surprised the OP came to the conclusion to return the camera.

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Hmm... I'll go test that.  I never shoot JPEG either and any JPEGs I have are converted from RAWs for printing or posting.  I'll flip the camera into JPEG mode and see what it produces.

[RobertTheFat]

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@Skirball wrote:

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@TCampbell wrote:

Camera's don't have "DPI".  There is no "default" DPI that the camera sets, nor any conversion.  The concept of DPI doesn't exist as far as the camera is concerned.

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I thought that too, but from what I read yesterday it seems that they do assign a DPI (72) for jpg.  I haven't confirmed it yet on my camera as I never shoot jpg, but I believe that's where the 72 came from.

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It's probably for use by the camera's direct printing capability. And that's not something the OP (or any of us) is likely to use.

[Skirball]

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@RobertTheFat wrote:

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@Skirball wrote:

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@TCampbell wrote:

Camera's don't have "DPI".  There is no "default" DPI that the camera sets, nor any conversion.  The concept of DPI doesn't exist as far as the camera is concerned.

---

I thought that too, but from what I read yesterday it seems that they do assign a DPI (72) for jpg.  I haven't confirmed it yet on my camera as I never shoot jpg, but I believe that's where the 72 came from.

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It's probably for use by the camera's direct printing capability. And that's not something the OP (or any of us) is likely to use.

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I don't know why they'd choose 72 for a printing setting, and there's too much coincidence with 72 being the web standard.  I poked around on the nets and read a couple different theories, but no one knows for sure.  The most plausible that I read is that the EXIF standard won't allow a null value and that Canon just settled on 72, presumably because of predictably large web use for images, especially for those shooting jpg.  I don't know if EXIF truly doesn't allow null values, but it seems logical.

I also read that Nikon's default is 300.

It's interesting, but I don't think there's much practical impact in real world use.  A testament to that, is that there are several people involved in this thread that have spent quite a bit of time working with images for print and publish and none of us have ever noticed that Canon defaults to 72 dpi for jpg.

[TCampbell]

I just did the same thing... apparently the standard says the field is supposed to be populated with a value, so they populate it with 72 (which used to be the most common video DPI although modern monitors have moved on a bit from there.)

While the camera doesn't need it, apparently some poorly written software would be upset if the field was left null.  So they populate it.

Whenever DPI actually becomes meaningful (sending to print), everyone just sets the value they need in Photoshop (or whatever they happen to be using).

If you are using Photoshop, you can create an action to fix this automatically upon opening any image.

You'll go into their "Actions" panel and tell it you want to record a new action.  Name the action something like "Set default DPI to 300".    With recording started, anything you do in Photoshop will be recorded to that action.

There's just one step to do... in the Photoshop main menu bar, click "Image" -> "Image size..."  

This pops open a panel to let you resize the image.  UNCHECK the box that says "Resample Image" (it will be near the bottom), then type in the DPI that you want the image to have (e.g. 300) and click "Ok" to set the value.

Now go back to the Actions panel and click the stop button (to stop recording).  

You have just created a Photoshop action with one step... that step is to change the DPI.  BTW... this wont change ANYTHING in your image (no pixels are modified)... it just changes the DPI property to make your printer happy.

There's one more thing left to do... the action wont actually run unless you go into an Actions panel and manually invoke the action.  To automate it, do the following:

Go into:

File -> Scripts -> Scripts Event Manager...

Click the checkbox on to "Enable Events to Run Scripts/Actions"

Change the Event to "Open Document" (in other words these are events that will automatically be invoked just because you opened a document)

Check the radio button on "Action" (the choices are "Script" and "Action" and you want "Action"

"Default Action" will probably already be picked, and the action you want on the pull-down menu is whatever name you gave  your action when you created it (e.g. "Set default DPI to 300" was what I named mine.)

Click "Add"

Click "Done"

That's it.  

Anytime you open an image in Photoshop, it will now automatically invoke that action... changing it's default DPI to 300.  You wont need to click anything... just opening the file will do it (of course this change wouldn't get saved until you 'save' the image after opening it.)

[ebiggs1]

Although, we now know hwo to make an Action in PS, I doubt the OP will ever read it.  He and Elvis have left the building!