300dpi setting not giving 300dpi images in render

Started by markw, October 05, 2011, 01:21:09 AM

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Ive searched for answers, but cant find the exact one I need.
I need a 300dpi image, or so our printer tells me.

I set the render window to 300dpi, but in photoshop the image is reported at 72dpi

Can you help how I achieve this?

Thanks Mark



Hey Mark W,

Let me try and explain how I understand things: Keyshot renders at what ever resolution you tell it to as in 1600x963 pixels. That means that you have an image made up of 1600 px wide by 963 px tall. That's physically how big it is. You adjust this setting in the drop down box, am sure you've seen it. Now, you can display that image at whatever 'resolution' you wish ie. If you want it to be detailed you want it at 300 dpi (or 300pixels per inch of image), therefore the image you just rendered out will be physically small in size. If you want it lower quality, you can display it at 72 dpi and the actual size of the image is as big as you see it on screen as screen resolution is 72dpi.

When you select a resolution to render at (dpi wise) in Keyshot, you're not really changing anything, the physical size of the image just changes in the boxes next to the dpi drop down selection box. It simply tells you how big the image that you are rendering will be I you display it at the given resolution.

To cut to the chase, define the size of the image to be rendered by the eg. 1600x963px drop down box, and then select 300dpi. That will tell you how big the image will be at 300dpi (what you want for printing). If it's not big enough, increase the image to eg. 2000x10??px. Render the image. Create a new empty photoshop file and make sure you select 300dpi when you create it. Now, drag the newly rendered image into the empty photoshop document and it will no be an image at 300dpi. It's probably easier to create the blank photoshop document as an A4 page, and then you get an understanding of how big the image will be at 300dpi in real life.

Hope you followed, and please disagree anyone if you feel my explanation is incorrect.




Yes, your understanding is correct. For the purposes of working with your images on a computer, DPI is meaningless. Image size in pixels is everything. More pixels = more detail. PhotoShop also doesn't care about DPI. DPI is only related to how many pixels per inch will be printed. In PhotoShop DPI can be set for the image. It can be set for any DPI without changing the pixel dimensions of the image. Depending on where the image is going to be used will determine how large in pixels the final image needs to be. Most of the images we present to our clients these days are through PowerPoint presentations and therefore do not have to be very large. This has the advantage that they will render quickly. That said, we tend to make our images large enough to be printed at "B" size (11x17" here in US) at 100dpi - 150dpi. While not great for text, color images print well on our Epson 4000 at this res.


Don't worry about why.  Just compute what size you want, and what dpi you want.  Example- an 8" x 10" at 300 dpi would be 2400 x 3000.  Set it and render it.  When you take it into Photoshop, go to "Resize Image", UNCHECK "Resample" and change the 72 (as KS imports) to 300 and that's all there is to it. 
Bill G


Here's an table I'm keeping in excel.  I can change the 300 to other values and then check which dimensions are requested by the DTP guys and then I know which res I need to render.  If you use inches, you could make an excel in inches.

300   dpi      118,1102   d/cm
5   cm   =   591   pix
6   cm   =   709   pix
7   cm   =   827   pix
8   cm   =   945   pix
9   cm   =   1063   pix
10   cm   =   1181   pix
11   cm   =   1299   pix
12   cm   =   1417   pix
13   cm   =   1535   pix
14   cm   =   1654   pix
15   cm   =   1772   pix
20   cm   =   2362   pix
25   cm   =   2953   pix
30   cm   =   3543   pix
50   cm   =   5906   pix
100   cm   =   11811   pix
60   cm   =   7087   pix
120   cm   =   14173   pix
170   cm   =   20079   pix