Are all professional prints done at 300 DPI?

[splproductions]

When I walk into a professional photo gallery, are all of the images I see on the wall printed at 300 DPI? If so, is there ever any upsampling done to achieve enough pixels? Or are the very large prints achieved via panoramic stitching?

The reason I ask is because it seems like until just the last few years, most DSLRs were around 20MPs, and I know there were plenty of pros using digital at that time. This would mean that their max print size would be apx. 18x12, unless the were printing at a lower resolution, upsampling, or sticking frames together.

Not sure if the type of work matters... I'm thinking wildlife/landscape photography in particular.



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[tirediron]

No, they're not. The larger the print, the greater the distance from which is intended to be viewed, and therefore the lower the print resolution needed to achieve "photo quality". Think of billboards; many were shot on <5mp cameras in the early days of digital photography, but they look fine as you drive by. It also depends on the medium and quality of the lab doing to the work. Coarse canvas requires much lower resolution than metallic paper and I've had paper prints from my lab at ~200dpi which look just fine in 11x14.

 

[Advanced Photo]

No. Most really big photo printing companies like Snapfish, Shutterfly and others all run presses that use a 150 line screen. So the print is laser imprinted on electrostatic rollers or belts as a 150 dpi image and then transfered to the paper at that resolution.
I have made prints at 150, 300, 600, 1200, 2400 and 4800 dpi depending on the use and size.

 

[alexis.alvarez]

No. I've printed 20x30 prints from pictures I took with my 5-megapixel iPhone 4 (and exhibited them). The prints were amazingly sharp.

 

[KmH]

There are different types of print.
The OP is inquiring about PPI, not DPI, but doesn't yet know that.

DPI (dots per inch) is an inkjet print device resolution specification, not a digital image print resolution specification, which is PPI or pixels per inch.
Indeed, most inkjet prints cannot print at the same DPI resolution in both the vertical and horizontal directions.

It takes many dots to print a single pixel.
At it's most basic it takes 3 inkjet dots to print a single pixel, but a print made that way would not look very nice.

So inkjet printers today use hundreds of dots to print a single pixel.
The most basic inkjet printer has 4 colors of ink/dye - cyan, magenta, yellow, black.
High end inkjet printers have as many as 12 or so colors of ink/dye.
Inkjet printers spray ink through tiny nozzles, and are typically capable of 300–720 DPI. A laser printer applies toner through a controlled electrostatic charge, usually in a range of 600 to 2,400 DPI.

The type of print head in an inkjet printer, thermal or piezoelectric, has a lot to do with how many dots the print head makes per pixel.
Epson piezoelectric print heads have something like 175 nozzles for each print head (color of ink/dye). If one of those printers uses 4 print heads (to mix 4 colors) to print a pixel that is up to 700 dots just to print 1 pixel.
Professional high-volume, production inkjet printers range in cost between $35,000 or so up to about $2 million.

Note that most digital photographs are made using one of the many color spaces in the additive RGB color model, while printing is done using the subtractive CMYK color model.
When red, green, and blue light (RGB) is combined in equal amounts white is the result.
When cyan, magenta, and yellow ink/dye (CMY) is combined in equal amounts black is the result. However the black produced is not as dark as we want for a print so they also use black ink/dye so they can produce nice deep blacks.

Many consumer outlets sell chromogenic prints (C-print).
Chromogenic prints are made on light sensitive paper that has 3 layers of color (Cyan, Magenta, Yellow) sensitive emulsions.
C-prints have no dots, but the print size is still a function of the image resolution (pixels dimensions) and the assigned print resolution (ppi), but many chromogenic printers are effectively limited to an equivalent of about 250 ppi.
Once a digital image has been projected onto the paper, using either red, green, and blue lasers or LEDs, the paper is then chemically processed (RA-4 process) to develop the print.
The 2 most common C-print papers used are Kodak Endura, and Fujifilm Crystal Archive.
Most of the quick print machines (mini-labs) used in places like Walmart, Walgreen's, Staples, etc are Fuji Frontier mini-labs.

Then there are 4-color off-set prints and half-tone prints, neither much used to produce personal, professional, or gallery quality prints..

 

[splproductions]

KmH... you are smart.

Thanks for the info everyone...

 

[Advanced Photo]

Inkjets do not spray ink at all, the ink is charged by the print head and actually explodes (vaporizes) into droplets and is transferred to the paper that way, there is no internal pressure that would be required to spray inks through a print head.

Offset printing is a method that uses a rubber blanket that the image is offset onto and then pressed to the paper under pressure between the blanket and the impression cylinder of the press. The plates are printed in right reading form because of the intermittent step of the blanket. Some of the areas of the plate are water receptive (non image areas) and other areas are oil receptive (inks are oil based product using soy oil as a base) since oil and water don't mix, the plate receives ink only in the print areas and the rest has a coat of water that repels the ink on the rollers as they contact the plate.

There are also presses like the HP indigo that use a combination of laser printing and offset printing techniques to produce an image. The image is laser written to a charge roller and that roller impart the electrostatic charge to the image cylinder which then contacts the first color in the process, yellow and the yellow part of the image is laid on rubber blanket and then on the paper, the process repeats for each of the 4 colors (cyan, magenta, yellow and black (CMYK))and after the paper has gone around 4 times inside the press and received each color, it is moved on through the paper handling path to the output bin or roll in the case of roll to roll presses. In these presses, the ink is carried by an electrostatic charge and since it is mixed with an oil that contains particles of iron oxide (rust) it is attracted to the charged cylinder image areas.

Xerox uses a completely different method (although it it still based on a laser writer charging a belt in this case rather than a cylinder) using plastic powder and iron filings in 4 negatively charged dust clouds of color (CMYK again in the order of M,Y,C and K) that is then pulled electrostaticly to the positively charged belt and then to the paper by a second electrostatic charge under the paper called the plenum. Again, the paper goes past the belt 4 times for each print as the 4 colors are overlayed to the paper. The powder coated paper is then sent through a fuser area where oil heated to 350 is applied to the paper under high pressure and the plastic powder (toner) is fused to the paper permanently.

 

[KmH]

Piezoelectric Print Heads Vs. Thermal Print Heads - Alder Technology

 

[Advanced Photo]

Yep. Since 2014 things have changed somewhat however. More piezoelectrics are in use in various versions. Thanks.

 

[KmH]

KmH... you are smart.

Thanks for the info everyone...

Smart? Nah! I'm just informed.
Print making is a very technical specialty separate from doing photography.
How a digital image destined to be printed is edited differs from how the same image is edited when that image is destined for electronic display.
The difference? A print is fore lit and what we see is reflected light. Electronic displays are back lit and what we see is incident light.
So it behooves the photographer/editor to have a good fundamental understanding of the technical considerations relative to print making.

The notion that all prints have to be made with a print resolution 300 ppi is an Internet perpetrated canard.
Print labs stake their image reproduction reputations on having a minimum print resolution limit of about 100 ppi, regardless the size of the print being ordered.
Also consider, humans can't detect, by unaided eye, any improvement in the image quality of a print made with a print resolution greater than about 340 ppi.

Tutorials on Color Management & Printing

 

[Advanced Photo]

KmH... you are smart.

Thanks for the info everyone...

Smart? Nah! I'm just informed.
Print making is a very technical specialty separate from doing photography.
How a digital image destined to be printed is edited differs from how the same image is edited when that image is destined for electronic display.
The difference? A print is fore lit and what we see is reflected light. Electronic displays are back lit and what we see is incident light.
So it behooves the photographer/editor to have a good fundamental understanding of the technical considerations relative to print making.

The notion that all prints have to be made with a print resolution 300 ppi is an Internet perpetrated canard.
Print labs stake their image reproduction reputations on having a minimum print resolution limit of about 100 ppi, regardless the size of the print being ordered.
Also consider, humans can't detect, by unaided eye, any improvement in the image quality of a print made with a print resolution greater than about 340 ppi.

Tutorials on Color Management & Printing

The lighting source is just one difference. The main difference is printed images have a subtractive color system and video images are additive system.
You could easily light a printed source the same way. Ever use an overhead projector? Ever hear of a light table?

Most printed images are a minimum of a 150 line screen unless we are talking about newspaper printing that can use an 80 line halftone image to print due to the dot gain inherent in the newsprint substrate.