DPI and images

galax · 08-03-2024, 05:52 PM

Greets,

I had a question related to dpi setting with images for epubs.

Let's say the screen specs says 300dpi, how does this tranlates for images?

Should 300pdi be set only for images fullscreen, that is, the complete screen resolution?

I the case that I want to put two images side by side on one page, does the dpi halves for each image (since images became half screen)?

Or does is it possible to set 300pdi to all images regardless of size for a 300dpi screen?

I am trying to find the optimal settings for an epub.

Thanks in advanced

JSWolf · 08-03-2024, 07:01 PM

Forget DPI. It doesn't mean anything. Just make sure your images are high-resolution.

That's all you need to do. You don't need to worry about DPI at all.

Karellen · 08-03-2024, 07:46 PM

I don't use dpi either. I know my Libra2 has a screen resolution of 1264 x 1680 so I ensure my images are at least 1000w for landscape or 1500 for portrait images.

Nothing worse than using piddly little images like 300x450 which are then upascaled and look blurry and hazy and any small details or text are unrecognisable.

Turtle91 · 08-03-2024, 08:39 PM

From what I understand, DPI is a printer resolution....it will set 300 dots of ink per inch (DPI) for an image regardless of how big the image is, 3x5 inches or 3x5 miles.

On a screen you don't want to have an image resolution that is significantly less than the resolution of the screen, otherwise it will get all blurry if it is expanded to fullscreen... so a 20x30 pixel image would look like crap if it was blown up to 100% of a 1264 x 1680 screen.

Thus, use a good high-resolution image that looks good on your target devices...but don't overdo it unnecessarily ... no need for a 6000x10000 pixel image if it will only be displayed on a phone with 720p.

I personally use about 1600px high images for images intended to take up the full screen inside the book....and about 2200px high for a cover image.

Quoth · 08-04-2024, 07:10 AM

DPI of images is only a meaningful setting in a source when intending to output a PDF for paper printing.

Images in ebooks are a number of pixels in source and then px (which are not always 1 px = 1 pixel) or % (of a width or height)

galax · 08-05-2024, 02:10 PM

Thanks all for the explanations. This greatly simplifies the process.

Now my question is whether to remove DPI information altogether from the images.

Turtle91 · 08-05-2024, 02:38 PM

You CAN remove it if you really want to, but it is unnecessary.

Quoth · 08-05-2024, 03:04 PM

Quote:

Originally Posted by Turtle91

You CAN remove it if you really want to, but it is unnecessary.

I agree. Any dpi or other embedded info is irrelevant in this application.

08-03-2024, 05:52 PM	#1
galax Enthusiast Posts: 36 Karma: 10 Join Date: Sep 2023 Device: none	DPI and images Greets, I had a question related to dpi setting with images for epubs. Let's say the screen specs says 300dpi, how does this tranlates for images? Should 300pdi be set only for images fullscreen, that is, the complete screen resolution? I the case that I want to put two images side by side on one page, does the dpi halves for each image (since images became half screen)? Or does is it possible to set 300pdi to all images regardless of size for a 300dpi screen? I am trying to find the optimal settings for an epub. Thanks in advanced

08-03-2024, 08:39 PM	#4
Turtle91 A Hairy Wizard Posts: 3,225 Karma: 19000635 Join Date: Dec 2012 Location: Charleston, SC today Device: iPhone 15/11/X/6/iPad 1,2,Air & Air Pro/Surface Pro/Kindle PW & Fire	From what I understand, DPI is a printer resolution....it will set 300 dots of ink per inch (DPI) for an image regardless of how big the image is, 3x5 inches or 3x5 miles. On a screen you don't want to have an image resolution that is significantly less than the resolution of the screen, otherwise it will get all blurry if it is expanded to fullscreen... so a 20x30 pixel image would look like crap if it was blown up to 100% of a 1264 x 1680 screen. Thus, use a good high-resolution image that looks good on your target devices...but don't overdo it unnecessarily ... no need for a 6000x10000 pixel image if it will only be displayed on a phone with 720p. I personally use about 1600px high images for images intended to take up the full screen inside the book....and about 2200px high for a cover image. Last edited by Turtle91; 08-03-2024 at 08:41 PM.

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08-03-2024, 07:01 PM	#2
JSWolf Resident Curmudgeon Posts: 76,491 Karma: 136564766 Join Date: Nov 2006 Location: Roslindale, Massachusetts Device: Kobo Libra 2, Kobo Aura H2O, PRS-650, PRS-T1, nook STR, PW3	Forget DPI. It doesn't mean anything. Just make sure your images are high-resolution. That's all you need to do. You don't need to worry about DPI at all.

08-03-2024, 07:46 PM	#3
Karellen Wizard Posts: 1,363 Karma: 6794938 Join Date: Sep 2021 Location: Australia Device: Kobo Libra 2	I don't use dpi either. I know my Libra2 has a screen resolution of 1264 x 1680 so I ensure my images are at least 1000w for landscape or 1500 for portrait images. Nothing worse than using piddly little images like 300x450 which are then upascaled and look blurry and hazy and any small details or text are unrecognisable.

08-04-2024, 07:10 AM	#5
Quoth the rook, bossing Never. Posts: 12,378 Karma: 92073397 Join Date: Jun 2017 Location: Ireland Device: All 4 Kinds: epub eink, Kindle, android eink, NxtPaper11	DPI of images is only a meaningful setting in a source when intending to output a PDF for paper printing. Images in ebooks are a number of pixels in source and then px (which are not always 1 px = 1 pixel) or % (of a width or height)

08-05-2024, 02:10 PM	#6
galax Enthusiast Posts: 36 Karma: 10 Join Date: Sep 2023 Device: none	Thanks all for the explanations. This greatly simplifies the process. Now my question is whether to remove DPI information altogether from the images.

08-05-2024, 02:38 PM	#7
Turtle91 A Hairy Wizard Posts: 3,225 Karma: 19000635 Join Date: Dec 2012 Location: Charleston, SC today Device: iPhone 15/11/X/6/iPad 1,2,Air & Air Pro/Surface Pro/Kindle PW & Fire	You CAN remove it if you really want to, but it is unnecessary.