optimal dpi resolution to work at - is 300 dpi still standard?

What bitmap dpi resolution do you work with in your layout software?

Is 300 dpi still the standard for cmyk images supplied for quality offset printing, or is there something to be gained in sharpness and detail by being able to supply higher cmyk bitmap dpi?

 

I recently did a test on this. Offset and digital.

I could not see a difference under a loupe from 300 to 600 to 1200. They all look the same.
I dont see a benefit of raising resolution unless you are doing large format printing.

The test i ran was only on Type, however..

 

Thank you very much for your reply Michael.

I am confused though by your ending with "The test i ran was only on Type, however.." as I thought text would be sent to the digital printer or the press not as raster data and would be imaged at the laser's native resolution (which should be 600+ now) or a much higher resolution on the press plates ???

 

For offset litho, Ideally you should supply images that are twice the 'LPI' (Lines Per Inch of dots) for conventional screening, ie if printing at 200lpi, supply 400dpi images. (this assumes your images are 100% at the size to be output). Stochastic screening requirements are different.
Supplying images that are more than twice - as a ratio, will not benefit the quality, and may even harm it - as the sampling needs to cover more pixels.

http://imagesetting.com

 

Thank you very much imagesetting.

I didn't realize there was such a simple logical mathematical relationship between dpi and lpi! I imagine when 300 dpi was the standard 150 lpi was the standard. My job will be printed at 175 lpi so this would mean I would supply the photographs at 350 dpi following your ratio.

 

Strictly speaking, yes image res. is typically 2x the LPI, in practice you could get away with images @ 300dpi for a 175lpi job, depends how critical you want to be - its difficult to know the break point at which you get pixelisation - sure their are complex mathematics that could explain that. If I could I would always err on the side of caution and follow whats required if you can, ie supply a 350dpi image for 175lpi work.

A 2x pixel sampling means 4 pixels are sampled for each dot (halftone cell), and the more dots and more pixels (in ratio) are sampled the better the detail is you will capture.
If you want to get very technical the screen angle the particular colour plate is sampled at will also slightly affect the correct ratio, and I understand modern Adobe RIPS with live transparency flattening go through a more complex process to decide how pixels are sampled, but I think you not need worry yourself about that - you cant be that finite. 2x LPI = Image Res is the rule.

Obviously the above applies to conventional screening, stochastic will have different rules.

http://www.imagesetting.com

 

My Test was on type that was created in a bitmap program. If the type is Vector than you are correct in that it is RIPed when the file is sent to print.

 

You should really use a page layout application for text, but if your using a bitmap application just testing thats fine.

"I dont see a benefit of raising resolution unless you are doing large format printing."
Vector images are rasterised at the resolution the device is set to, pixel based images are sampled at the ratio for screened images. The two are handled differently

http://www.imagesetting.com

 

It is pretty straightforward. I coded this calculator if you are into being lazy-

http://www.inkfarm.com/DPI-and-Picture-Size

 

if your unsure easiest to go bigger rather than messing around finding optimum if we are printing photo based we try and run it at 600dpi even though you can't really see a big difference if its vector 300 dpi will do just fine.