In Library: Display image size in inches vs pixels

mikecox

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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 /-:
 

Hal P Anderson

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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.
 

JohanElzenga

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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.
 

mikecox

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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
 

JohanElzenga

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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.
 

Dan Marchant

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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.
 

clee01l

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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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