# In Library: Display image size in inches vs pixels



## mikecox (Mar 14, 2019)

I've checked the Pref and Library Review options but can't seem to find an option to change the display, in grid mode,  to inches. It seems like an option that would be available. But I can' find it /-:


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## Hal P Anderson (Mar 15, 2019)

You can't do it. 
When you export or print, you set the size of your output, but within Lightroom you have to just deal with pixels.


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## Johan Elzenga (Mar 15, 2019)

An image does not have a size in inches, until you define the output and the resolution of that output. That is why you can’t display the image size in inches, but you can export in say 10 x 15 inch @ 300 pixels per inch, or print in that size.


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## mikecox (Mar 15, 2019)

Hal P Anderson said:


> You can't do it.
> When you export or print, you set the size of your output, but within Lightroom you have to just deal with pixels.


I was afraid of that because in all the years I've been using Lr I've never seen an option to convert pixels to inches, but I never looked very hard because I never needed to know in the past.  Guess I'll just have to Edit in Ps to get that or use a pixel converter.
Thanks


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## Johan Elzenga (Mar 15, 2019)

mikecox said:


> I was afraid of that because in all the years I've been using Lr I've never seen an option to convert pixels to inches, but I never looked very hard because I never needed to know in the past.  Guess I'll just have to Edit in Ps to get that or use a pixel converter.
> Thanks


I’m sorry, but that is nonsense. You can’t “convert pixels to inches”. Just like you can’t convert bricks into yards. What you can do is define how many pixels should fit into one inch (pixels per inch) and you do that based on output. So you can do that on export or on print. No need for a round trip to Photoshop.


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## Dan Marchant (Mar 15, 2019)

mikecox said:


> I was afraid of that because in all the years I've been using Lr I've never seen an option to convert pixels to inches, but I never looked very hard because I never needed to know in the past.  Guess I'll just have to Edit in Ps to get that or use a pixel converter.
> Thanks


You seem to be missing the point. Even in photoshop a digital image has no physical size... it is pixels. Inches are meaningless. Display the image on a small monitor and it will be small, display it on a large monitor and it will "appear" to be larger.... even if you change the display details to inches that still has no meaning because that size will change if you change the dpi/ppi setting.

Inches only have meaning when you have a physical object such as a print and the size of your print will depend on the setting *at the time you printed it*. If you output a 3000 pixel wide image at a dpi of 300 dpi them it will be  10" wide. But if you immediately print a second copy at 200 dpi it will be 15" wide.

So. If you want to know the size in inches of an image in Lightroom just divide the pixel lengths by the dpi you will use when outputting.... but just realise that that is only one potential size that the final print could be.


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## clee01l (Mar 15, 2019)

mikecox said:


> I've never seen an option to convert pixels to inches,


That is because pixels are dimensionless.   This holds for both LR and PS and any other image rendering app.  The thing that has dimensions is the display media.    If the display media is a high resolution monitor then the pixels are displayed at the resolution of the monitor (e.g. pii between 100 and 400 )  Your software is going to scale the image to fit the screen. So, 100% equals one pixel from the image to one pixel on the screen.  Inches on the screen are fixed and irrelevant to the app being used.

If the display media is paper, then you need to instruct the printer how many pixels to print per inch.   This is where apps like PS tend to confuse rather than help.   When your ultimate destination is paper, you need to set a target paper scale for the print.  PS will do this math for you in the scaling/ cropping function.  BUT it still needs to have a conversion factor of ppi to do the calculation that you could and should be doing in your head.

To further muddy the water.  Printers print dots of ink and have a fixed or barely adjustable print resolution of dots per inch (DPI)  One pixel can but usually does not equal one dot of ink.  Printers have a default of 300 DPI or 330DPI.   Better printers can scale to 600, 1200, DPI or higher.  This could mean that your 300ppi image will print 2 dots per pixel at a print resolution of 600 DPI.

Knowing the destination media  and destination size is important to determining the scale of the image when still in LR.  Lightroom will always work in pixels until you export to a final medium.   The export panel gives you the option to resize in inches at a defined resolution in ppi.


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## mikecox (Mar 20, 2019)

I really appreciate everyone's input, which was quite enlightening, but a little TMI.  All I really wanted was a simple conversion from, for example, 1024 x 768 to 6 X 4. I just want to know what size the images I import are.


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## Victoria Bampton (Mar 20, 2019)

That's the thing Mike... their size is 1024x768. You could print that whatever size you like, it'll just be fuzzy if you go too big!


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## Dan Marchant (Mar 20, 2019)

mikecox said:


> I really appreciate everyone's input, which was quite enlightening, but a little TMI.  All I really wanted was a simple conversion from, for example, 1024 x 768 to 6 X 4.



That is like asking for a conversion between Oranges and Monkeys. Pixels are dots of light on a screen and 6x4 is an aspect ratio  equal to 1.5:1 - neither are measures of physical size. A 6x4 physical print could be 6x4 mm, 6x4 cm, 6x4", 6x4', 6x4 meters, yards, miles, hectares. The only known factor is that the length of the long side is 1.5 time the length of the short side. Cropping an image in LR to 6x4 doesn't make is a certain physical size... it just means that the long side is 1.5 times more pixels compared to the short side.
As I explained above, if you want to know what size a physical print will be you need to divide the pixels by the number of dots per inch _you intend to print at_. There is no other meaningful way to convert pixels to inches. You have to decide what quality (dpi) you want to print at and what distance you want to view at. If you want to view the image on a gallery wall from 2 feet you need to print at a higher dpi (which means the max print size will be smaller). If you want to view the same image on a giant billboard from 40 feet away then a really low dpi will suffice. There simply is no single measure of physical size for your digital data.



> I just want to know what size the images I import are.


They are NO SIZE - they are digital data - they don't have a physical size. It is like asking "what size are the memories in your brain".


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## mikecox (Mar 21, 2019)

Dan Marchant said:


> That is like asking for a conversion between Oranges and Monkeys. Pixels are dots of light on a screen and 6x4 is an aspect ratio  equal to 1.5:1 - neither are measures of physical size. A 6x4 physical print could be 6x4 mm, 6x4 cm, 6x4", 6x4', 6x4 meters, yards, miles, hectares. The only known factor is that the length of the long side is 1.5 time the length of the short side. Cropping an image in LR to 6x4 doesn't make is a certain physical size... it just means that the long side is 1.5 times more pixels compared to the short side.
> As I explained above, if you want to know what size a physical print will be you need to divide the pixels by the number of dots per inch _you intend to print at_. There is no other meaningful way to convert pixels to inches. You have to decide what quality (dpi) you want to print at and what distance you want to view at. If you want to view the image on a gallery wall from 2 feet you need to print at a higher dpi (which means the max print size will be smaller). If you want to view the same image on a giant billboard from 40 feet away then a really low dpi will suffice. There simply is no single measure of physical size for your digital data.
> They are NO SIZE - they are digital data - they don't have a physical size. It is like asking "what size are the memories in your brain".


Ok   I get it, now.  Thanks for not giving up on me and my confusion.  Lesson learned


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