Giclee PPi

JK
Posted By
John K
Sep 13, 2004
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518
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4
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Closed
Hi group,

Is there any sort of formula that exists for how many PPI I should figure for images that will be output as Giclee prints?

For example, for images destined for a printing press, as a general rule of thumb I double the line screen, which in almost all my cases wouldn’t surpass 150 lpi, so my images are saved at 300ppi… That’s the formula I use.

Is there a similar formula for giclee printers depending on the output size or the dpi of the inkjet printer? Is there a certain "optimal point" where more PPI is overkill?

I’m asking because I may be preparing hundreds of images that will be output (eventually) as Giclees, at different sizes. I don’t know which company will do the printing so "check with the company doing the work to see what they want" isn’t really a good answer. I figured I’d save them all at 300ppi, but a guy I know said that is WAY overkill and I’m wasting space and that 150ppi is all I’d ever need for Giclee no matter what the size… Is he wrong?

I don’t have much experience with Giclee printing, but I would think that a big 4 x8′ poster would need less resolution in terms of PPI than a small 8 x10" that one would look at up close. Is this correct?

Thanks in Advance.
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CC
Chris Cox
Sep 13, 2004
In article , John K
wrote:

Hi group,

Is there any sort of formula that exists for how many PPI I should figure for images that will be output as Giclee prints?

That depends on what inkjet printer you’re using and what sort of halftoning it does.
(Giclee == inkjet)

Chris
O
Odysseus
Sep 13, 2004
In article ,
John K wrote:

Is there any sort of formula that exists for how many PPI I should figure for images that will be output as Giclee prints?

For example, for images destined for a printing press, as a general rule of thumb I double the line screen, which in almost all my cases wouldn’t surpass 150 lpi, so my images are saved at 300ppi… That’s the formula I use.
IME that’s a safe ‘rule of thumb’ but you can almost always get away with less: 1.5x the screen ruling is almost always fine, and gives you a better preview of the image’s sharpness as reproduced. Beside wasting space — less of a concern these days than a few years ago! — an excessively oversampled image tends to lose sharpness in print. But halftone screens are a very different animal from inkjet dot patterns.

Is there a similar formula for giclee printers depending on the output size or the dpi of the inkjet printer? Is there a certain "optimal point" where more PPI is overkill?

I’m asking because I may be preparing hundreds of images that will be output (eventually) as Giclees, at different sizes. I don’t know which company will do the printing so "check with the company doing the work to see what they want" isn’t really a good answer. I figured I’d save them all at 300ppi, but a guy I know said that is WAY overkill and I’m wasting space and that 150ppi is all I’d ever need for Giclee no matter what the size… Is he wrong?
For most images, on most inkjet printers that produce ‘dithered’ rather than halftoned images (the printer’s nominal resolution is relatively unimportant), I agree that 150 ppi should be fine. For type or very fine details you might see some benefit from going higher, say 200 ppi.

I don’t have much experience with Giclee printing, but I would think that a big 4 x8′ poster would need less resolution in terms of PPI than a small 8 x10" that one would look at up close. Is this correct?
If the big poster is only intended for viewing at a distance, certainly. (For something like a trade-show display that people can walk right up to, you might want to be more generous.) I used to output film for store displays that were produced by silkscreening: not the same thing as an inkjet, but illustrates the principle. We’d output 175-lpi film from 300-ppi images, then the film would be enlarged by a "blowback" system — which I gather is basically a specialized overhead projector — to 400% to make the screens. The resulting ~44-lpi (now in effect based on 75-ppi data) images looked just fine — from at least two to three metres away. An inkjet print of the same size, from a source of similar resolution, would most likely look smoother than the results of this process.

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Odysseus
B
bhilton665
Sep 13, 2004
From: John K

Is there any sort of formula that exists for how many PPI I should figure for images that will be output as Giclee prints?

Do you know which printer model you’ll be using?

Is there a similar formula for giclee printers depending on the output size or the dpi of the inkjet printer? Is there a certain "optimal point" where more PPI is overkill?

Older LightJet laser printers like the 5000 lay down 12 dots/mm (res 12) which comes to 304.8 ppi and this is optimal for them, anything higher gets resampled down. You can also send them res 8 (203 ppi) and that will get sampled up with very little loss in quality. Newer LJ printers are Americanized for 300 ppi.

Durst Lambda printers are rated at 400 ppi native and will also accept 200 ppi and upsample.

Inkjets like say the Epson Pros (4000, 7600, 9600) are different in that whatever you send them gets resampled to the printer’s native rez, but no one at Epson is on record as saying exactly what the ideal rez is. I’ve seen some tests on vector-type patterns that indicate very small improvements in print quality up to 720 ppi but most shops say 360 ppi is all you need, and some feel that for large prints you can go as low as 200 ppi and still get very good quality. 300 ppi seems to be the most common compromise but if you have more native (ie uninterpolated) pixels like say from a drum scan of medium format or large format film there’s no reason not to go as high as 360-400 ppi, especially for smaller prints.

I figured I’d save
them all at 300ppi, but a guy I know said that is WAY overkill and I’m wasting space and that 150ppi is all I’d ever need for Giclee no matter what the size… Is he wrong?

I’d definitely save ’em at 300 ppi instead of 150 ppi myself. But if it’s important to you to reduce the file sizes to 25% then run a couple of early tests to see if the lower number is acceptable to you. I can definitely see the difference between 200 and 300 ppi on 16×20" prints on my Epson 4000 for example.

I don’t have much experience with Giclee printing, but I would think that a big 4 x8′ poster would need less resolution in terms of PPI than a small 8 x10" that one would look at up close. Is this correct?

Absolutely.

Thanks in Advance.

Good luck. Best advice is to send off a couple of test images for printing at 150 and 300 ppi and see if 150 is enough for your requirements.

Bill
T
tacitr
Sep 13, 2004
I figured I’d save
them all at 300ppi, but a guy I know said that is WAY overkill and I’m wasting space and that 150ppi is all I’d ever need for Giclee no matter what the size… Is he wrong?

Yes, he is wrong…for some giclee printers. For others, 150 ppi is the limit of the effective resolution.

Different giclee printers have effective pixel resolutions that range from 150 to 280 pixels per inch (or so). Above 300 pixels per inch at the final size, you aren’t doing any good, but there’s no compelling reason to go below 300 pixels per inch.

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