Quesiton About File Size and Resolution

Hello all,

First time posting here. I’m not a professional graphic designer. I’m pretty much self taught. I have decent designs skills and pretty good command of InDesign and basic Illustrator. Haven’t used PhotoShop much. There’s one thing I can’t seem to understand. I apologize if this is a silly question to professional graphic artists, but it’s driving me crazy.

I am making thumbnail images for my news stories on my company’s web site. I created them in InDesign. My document is setup as 760 X 395 px. When I export at 300 DPI, the resulting JPG file is 3167 X 1656 px. Why is that? If I export at 72 DIP, the JPG is 760 X 395 px but the image is not as sharp.

Is it possible to export at 300 DPI but have the file remain at 760 X 395 px? What do you need to do to achieve this? Can’t all those pixels be crammed into that dimension? Do you need to do this in PhotoShop?

Thanks to anyone who has the answer for me!

Open up a PS document to the correct specs in pixels and 72dpi. Check the image size in inches or whatever you use if your not in the US, make your InDesign doc that size. Export out of InDesign as a pdf and open the pdf in Photoshop at 72dpi, it will be the correct pixel size and won’t look horrible.

Pixels are pixels. So a 760x365 pixel image (if created in PhotoShop) remains 760x365 regardless of how many pixels/inch you set it to PPI, not DPI (dots per inch is for print).

Essentially when exporting out an image at 300 dpi from Indesign, if you created it at 760x365 it defaults to 72 dpi. So exporting it at 300 dpi is exporting the pixels out at 416 2/3% (300/72 is 416 2/3%).

In the past, for the most part, all screens displayed at 72 dpi, but now with high-res phones, 4K, 6K, 8K displays etc. 72 dpi is the minimum and can appear fuzzy on certain devices and screens.

You are referring to PPI (pixels per inch), not DPI (halftone dots per inch on a printed page).

The usual formula for print is 300 PPI for a 150 DPI halftone image (a printed photo or screentint). Since you’re working on a website instead of a printed page, the DPI is totally irrelevant. For that matter, the PPI is irrelevant too since there’s no such thing as a fixed physical dimension on a computer display. An old low–resolution monitor might display 72 pixels in a linear inch and newer, high resolution can cram more pixels into the same space.

The only thing that matters in the context you’re using it online are the number of pixels. If your document is, as you say, 760 x 395 pixels, it will do no good whatsoever to try to cram more pixels into the image than that. All you will be doing is adding an oversized image to the website that will take longer to download and that the browser will display at a smaller size that won’t look any sharper than if you’d made it that size to begin with.

What you can do is try to use Photoshop’s sharpening filters to exaggerate the edges in your photo just a bit — sometimes that helps.

Thanks so much! This is very helpful.

©2019 Graphic Design Forum | Contact | Legal | Twitter | Facebook