Render Size Question

Sean Earley

Hi everyone.

I am working on a DazStudio piece for a client who needs the final artwork to be 250cm x 100cm at 120dpi

I have seen some posts online that discuss some alternate render sizing to get a decent quality image because I think 250cm wide at 120dpi will be a super huge render.

Any suggestions or alternatives?

PS, if this is in the wrong thread category, please move it to wherever it should go.

nonesuch00

Well a typical computer monitor is 72 dpi and typical print quality is 300 dpi with low quality deemed 150 dpi and generally nothing is printed lower than 150 dpi. So basically whatever you render is going to need to be halftoned at 250cm x 100cm to be printed. 

So looking at an image and estimating with a little math means you would need to render about at 30Kx20K image to print at 150dpi at 250cm x 100cm. 

You could render a good image and then use a vectorization program for that render so that it can be scaled to larger sizes. It needs to be a good vectorization though.

I would ask an actual print shop business on the best way to procede.

JamesJAB

Rendering at 100dpi should not be noticable when you resample the image up to 120dpi.  If your final render is going to have a lot of strait lines and sharp edges, you might not be able to get away with resizing.

Fishtales

No matter how you do it the image will  have to be at least 12,000pixelsx4800 to get 120 dpi for printing.

Richard Haseltine

nonesuch00 said:

Well a typical computer monitor is 72 dpi and typical print quality is 300 dpi with low quality deemed 150 dpi and generally nothing is printed lower than 150 dpi. So basically whatever you render is going to need to be halftoned at 250cm x 100cm to be printed. 

So looking at an image and estimating with a little math means you would need to render about at 30Kx20K image to print at 150dpi at 250cm x 100cm. 

You could render a good image and then use a vectorization program for that render so that it can be scaled to larger sizes. It needs to be a good vectorization though.

I would ask an actual print shop business on the best way to procede.

As Fistales says, all you need is the right number of pixels - 120 * 250 / 2.5 by 120 * 100 / 2.5 (that is, Pixels per inch * size in inches). The Pixels per Inch is as etting at the front of the file, it has nothing to do with the pixels themselves. Given that 120 PPI is rather low, unless this is a poster, I suspect the requirement is merely a shibboleth.

SpottedKitty

Also important to remember that D|S does not put any DPI/PPI setting in the image file when you save your final render. Whatever program you use to look at your renders will assume a default value (e.g. 72ppi) when it displays an image that doesn't have one.

Calculate the pixel size you'll need, then, and use an image editor (e.g. Photoshop) or viewer (e.g. Irfanview) to add the DPI/PPI setting.

A word of caution; this setting is frequently (depending on which program you use) part of the "image resize" dialog. Make sure you aren't actually resizing the image, only changing the definition of the pixel size. The image pixel dimensions should be the same before and after.

jestmart

Divide centimeters by 2.54 to get inches is more precise.

Fishtales

jestmart said:

Divide centimeters by 2.54 to get inches is more precise.

Check my pixel dimensions, I just rounded them up a little 

nonesuch00

I stick by my estimate for a poster so large as 250cm x 100cm unless we are talking 70s comic book halftoning.

Fishtales

When viewing a render in any program that shows ppi ignore it as that is the screen resolution of the monitor that it is being viewed on. Unless the image has been saved with a different ppi and then that is the setting shown. For printing you need the correct number, or greater, of pixels to get the print resolution required. A ten by eight picture needs to be at least 3000x2400 pixels to be printed at 300dpi, it can be printed larger using a smaller dpi, say 20x16 at 150dpi, but not at the same quality, it is difficult to add pixels without losing quality. Forty foot billboards can be printed as low as 4dpi because they are viewed from a greater distance, the closer the viewer the higher the dpi has to be so that the dots are closer together and the brain fills in the spaces. Stand directly in front of a poster and the closer you are to it the more dots you will see.

DrNewcenstein

My brother's Mardi Gras posters were printed generally at 18" x 24", and the printer he took them to recommended 144 dpi. This was for traditional printing press, not giclee or other inkjet-style printing.

When I printed his proofs from my HP DeisgnJet 90, they were set to 300 dpi.

SpottedKitty

DrNewcenstein said:

My brother's Mardi Gras posters were printed generally at 18" x 24", and the printer he took them to recommended 144 dpi. This was for traditional printing press, not giclee or other inkjet-style printing.

When I printed his proofs from my HP DeisgnJet 90, they were set to 300 dpi.

Probably due to the different printing processes. The "traditional printing press" means the image is broken down into usually the four standard CMYK colours and printed as four overlapping dot patterns. Inkjet printers like the DesignJet don't use the same kind of dots, even if they do use the same colour split. And both print types require different DPI values for best colour reproduction. It's complicated, and there's a lot of contradictory information floating around out there.

Fishtales

One of the easiest ways to see what size of print you can get from any image is to load it into Photoshop, change the ppi to different settings, and look at the Print Sizes which each setting gives..