How do I take screen shots at my displays native pixel density? ...NOT 72 PPI!

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My Mac (I assume all Mac's, and most computers in general) always takes screen shots at 72 ppi... why is this? Also, it seems 72 ppi is the default pixel density for most image editing software. Again, WHY??? NO display today still uses 72 ppi and I'm pretty sure printers print at 300 ppi/dpi (whatever). Doesn't this seem counter-intuitive when it comes to the image size? I'm not much in to professional photography or graphics design, but from what little I've done this seems like a serious issue!

Regardless, I still need to take screen shots at my displays native pixel density... or I at least need to somehow change the default.
 
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Because 99.9% of the time a screen shot is meant for sharing in email or online. 72DPI is fine for those purposes and provides a small file size. A 300 DPI file size is huge compared to 72 without any added benefit in those 99.9% of scenarios.
 
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Because 99.9% of the time a screen shot is meant for sharing in email or online. 72DPI is fine for those purposes and provides a small file size. A 300 DPI file size is huge compared to 72 without any added benefit in those 99.9% of scenarios.

...umm, an images pixel density has no effect on its file size. (???)
 
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third-party app???

Let me rephrase my question:
If I'm not able to adjust the default pixel density of my screenshots, is there a third-party screen capture app available that would allow this?
...or do I have no resort to manually changing it after the fact using something like Pixelmator or Photoshop? :|
 
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Actually, pretty much all digital cameras (yes, even those 20MP cameras) shoot at 72dpi.

By default, screen shots taken on a Mac open in Preview. Guess what Preview can easily do.
 
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Actually, pretty much all digital cameras (yes, even those 20MP cameras) shoot at 72dpi.

By default, screen shots taken on a Mac open in Preview. Guess what Preview can easily do.

Yeah, I know... 72 is apparently the default everywhere. There is absolutely NO logical reason for this!

...and simply "zooming it fit" in Preview never gets the end products actual size exactly right, (unless I do the math my self and come up with some random number like 87.0086522%). If the pixel density where accurately represented, simply choosing 100% or "actual size" would be all I'd need to do.
 
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Your iMac's display should be about 102ppi. The whopping 30ppi difference is hardly noticeable on the screen. This, to be honest, is why most images for web are 72ppi. So this is actually a very logical reason, and at one point in the not too distant past most monitors were are 72ppi anyway. IMHO it really doesn't matter until you PRINT anyway.
 

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you could try doing a screen recording, and then exporting 1 frame as a picture?
 
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Your iMac's display should be about 102ppi. The whopping 30ppi difference is hardly noticeable on the screen. This, to be honest, is why most images for web are 72ppi. So this is actually a very logical reason, and at one point in the not too distant past most monitors were are 72ppi anyway. IMHO it really doesn't matter until you PRINT anyway.

Actually, mine is 99ppi (to be more precise, 99.28ppi) ...and there is a noticeable difference:
(screenshot uploaded here)
Both images have been scaled to actual size.

Yeah, most monitors were 72ppi... 20 or 30 years ago!!
If you can't see a difference in monitor resolution between then and now, I have nothing to say!

How can purposely using a lower quality than the actual display for a screenshot possibly be "logical"???
 
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you could try doing a screen recording, and then exporting 1 frame as a picture?

How would one do that? Seems even more time consuming than using Pixelmator to edit a regular screenshot.
 
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Way... way too many specs to list.
Here's a legitimate solution then... write something better :D
 
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PPI for VIDEO (as in the monitor that you, and everybody else is viewing the web on, no matter what kind or size of monitor) is irrelevant, and the notion that PPI matters is absolutely false and a HUGE misconception. The ONLY thing that matters is resolution, but resolution of a picture and not the screen. This also goes for scanning.

Your monitor, my monitor and everybody's monitor ignores PPI/DPI values, because those things are only defined for PAPER. The real issue I believe, is how much the screen shot is compressed. You can change the dpi/ppi values all you want (if you could) but that wouldn't make a bit of difference on a monitor.

There are more than a few articles on the web which you can Google, that explains what I'm saying in much more detail. A quote from the article I'll post right below it:
In our world of digital images, dpi is for printing images on paper, or for scanning images from paper or film. Dpi means "pixels per inch" and it implies inches on paper, or film, or someplace where inches exist. Paper is dimensioned in inches, but video screens are dimensioned in pixels, and there is no concept of dpi in the video system.
Read the article, it's pretty good and goes into detail. It was a random one I had come across when searching for what I wanted to explain:

Say No to 72 dpi

Fairly long article, and page 2 has really good info so try and read the whole thing.

Doug
 
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PPI for VIDEO (as in the monitor that you, and everybody else is viewing the web on, no matter what kind or size of monitor) is irrelevant...

The article you provided at times seems to agree that what I'm trying to do is an appropriate use of ppi/dpi... presenting an image at "actual size" on the screen and in print. ("Approximate Actual Size On the Screen" section)
Yet, in its summery, it seems to dismiss that example???
I'm aware that the video system ignores ppi data, relying only on the given pixels, but its rather obvious that the software providing those pixels CAN and often DOES recognize pixel density and it would be stupid not to put that into consideration.


In our world of digital images, dpi is for printing images on paper, or for scanning images from paper or film. Dpi means "pixels per inch" and it implies inches on paper, or film, or someplace where inches exist. Paper is dimensioned in inches, but video screens are dimensioned in pixels, and there is no concept of dpi in the video system.

...this quote does a good job of summarizing my example, but again, it confuses the basic points.


If I take a screenshot of my screen, I expect the saved image to include all correct data available about the shot, including screen size (as pixel density).
 
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chas_m

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Yeah, I know... 72 is apparently the default everywhere. There is absolutely NO logical reason for this!

Well, yes there is -- it's called the Lowest Common Denominator. Not that I'm defending it, I'm just saying there is some rationale behind it.

You may have missed the second part of my post, where I mentioned that Preview can resize the screenshot to be pretty much whatever dpi you want. It's in the Tools menu under "Adjust Size."
 
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...umm, an images pixel density has no effect on its file size. (???)

Um, actually it does, unless you plan on shrinking the 300DPI version down to a tiny postage stamp size compared to the original 72DPI version?

Is that what you want to do?
 
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Well, yes there is -- it's called the Lowest Common Denominator. Not that I'm defending it, I'm just saying there is some rationale behind it.

You may have missed the second part of my post, where I mentioned that Preview can resize the screenshot to be pretty much whatever dpi you want. It's in the Tools menu under "Adjust Size."

At this point I'm having to settle with a folder action that takes a new screenshot and modifies the pixel density in Pixelmator. Adds about 5 seconds of "lets stare at the screen while automator moves the mouse around".
I guess replacing Pixelmator with Preview might take off 1 or 2 seconds.

But wait, if Preview can modify pixel density, you would think you could change the system default somewhere. ???
 
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Um, actually it does, unless you plan on shrinking the 300DPI version down to a tiny postage stamp size compared to the original 72DPI version?

Is that what you want to do?

No, actually it doesn't at all. Go ahead and try this for yourself. Export a RAW image with 3 different DPI/PPI sizes. The file size will be exactly the same. The only thing which affects file size is jpg quality and resolution size NOT pixel density.


If you'd like proof, or don't have the time for such an endeavor, here you go: Each of these files is the same resolution. I re-sized by dividing the original resolution by 3. One of them was exported @ 10 ppi the next at 150ppi and then finally the last at 300ppi. Each one has a file size of 705kb (well, 688.something according to Imageshack .. and imageshack does not resize) Just click on each link and look at the image properties.

Just to clarify, if what you're seeing when increasing the "perceived" pixel density is an increase in file size, it's because the software/program you're using is actually up sizing the resolution, and NOT the PPI/DPI. The PPI/DPI is really just a made up and non working element in the equation, which for all intents and purposes can absolutely be ignored up until the point of when you're going to PRINT.


http://img546.imageshack.us/img546/1200/10dpi.jpg
http://img847.imageshack.us/img847/3308/150dpi.jpg
http://img40.imageshack.us/img40/9079/300yk.jpg

And David, you're mixing concepts up a bit, and not reading carefully enough. You're making it out to be what you want it to be and not what it really is.

Furthermore,
What Preview is doing by what you perceive as increasing the pixel density for a larger preview (resolution) is not actually increasing the pixel density at all, even though it will assign the new file with an corresponding ppi value to which it can "relate". What it is doing actually, is up-sizing the resolution all together. There's a very big difference between these two actions, as again... pixel density or dots per inch (as there is no such thing as an inch in regard to measurement here) ONLY relates to the amount of pixels needed in order to maintain a proper value for printing on PAPER.

I wish you guys would understand that, because it totally changes the perspective of this entire issue. If you knew this, then all you'd have to do is tell OS X to up-size the screen shot. Perhaps there is a way to do this via a terminal command.

Doug
 
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Um, actually it does, unless you plan on shrinking the 300DPI version down to a tiny postage stamp size compared to the original 72DPI version?

Is that what you want to do?

Again, NO...

72ppi ... 300ppi ... 1000ppi (...image links.)
You should find that all three images have the same file size: 1.47 mb (or 1,544,958 bytes), and the same number of pixels: 1202 x 1354, but different pixel density values. Because of this, they each have different image sizes when viewed on screen or in print at "actual size". (…not actual pixels. Preview and many other image viewers seem to mistakenly do that by default. To make Preview show images at their real "actual size" (assuming the author of said image used an accurate pixel density value, not "72ppi"), in preferences, for both "Images" and "PDF", change "Define 100% scale as:" to "Size on screen equals size on printout".)

At the very least, one might expect 72ppi to have a larger file size since it has the largest apparent actual size. I'm aware thats probably the opposite of what most people assume (greater ppi, larger file size), but that goes to show you just how misinformed people are about this topic. Either assumption is wrong, pixel density has absolutely NO EFFECT of an images file size.

(...and, it should be worth pointing out that 1000ppi is closer to the stamp's original size than 72ppi.)
 
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And David, you're mixing concepts up a bit, and not reading carefully enough. You're making it out to be what you want it to be and not what it really is.

What concepts am I "mixing up" exactly?
What is it, really?????

I'll repeat myself... If I take a screenshot of my screen, I expect the saved image to include all correct data available about the shot, including pixel density/screen size. My display is NOT 72ppi!
Why does that concept seem so alien to everyone?


... pixel density or dots per inch (as there is no such thing as an inch in regard to measurement here) ONLY relates to the amount of pixels needed in order to maintain a proper value for printing on PAPER.

...or, presenting the image on screen at it's "actual size", in the same way it would be printed on paper.
Why do you keep ignoring that example?
 

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