How Many pixels do I need?

[HeyItsJoel]

I'm not entirely sold on upsizing prints from my current 6mp camera to produce enlargements.

Camera brands aside, how many pixels do I need to print a 12"x18" at its NATIVE resolution? No upsizing, no downsizing whatsoever.

 

[renato]

I print 13"x19" from my 12mp pictures - the prints look simply fantastic! I would say 16mp would be sufficient for anything reasonably large.

 

[hetedik]

I'm not entirely sold on upsizing prints from my current 6mp camera
to produce enlargements.

Camera brands aside, how many pixels do I need to print a 12"x18" at
its NATIVE resolution? No upsizing, no downsizing whatsoever.

Depends on the print quality, i.e. how many DPI you need.

If you take 300 DPI, which is pretty good quality, than you simply need 300 pixels for each inch

(12x300) x 18x300)
3600 x 5400 = 19.440.000

It looks like the new 5D-II

 

[Dallas Woody]

20 MegaPixels if you prints at 300 DPI

I also print 13x19 prints from my 5D and they look great, they will look even more great with the Mark II

Honestly. 12x18 inch prints at 300 DPI which is what most professional printers use comes out to be 5400x3600 pixels which is 19.44 Mega Pixels

 

[Its RKM]

I'm not entirely sold on upsizing prints from my current 6mp camera
to produce enlargements.

Camera brands aside, how many pixels do I need to print a 12"x18" at
its NATIVE resolution? No upsizing, no downsizing whatsoever.

Native resolution depends on the print medium and, in many cases can be much higher than required resolution.

To view with an unaided eye from the standard close viewing distance (10") you require at least 250pixels per inch (ppi), so 12"x250 x 18"x250 works out at 13.5Mpix.

Many printers (HP, Canon etc) use native resolutions of 300ppi, which requires 19.4Mpix to print at 12x18".

Epson use 360ppi (and the desktop printers can go up to 720ppi in some modes) requiring 28Mpix (or 112Mpix!) for that size.

The printer drivers will resample to these resolutions in any case, even if you don't implement resizing yourself.

--
Its RKM

 

[hunk]

I've did some tests on various printers and if you want to be certain you deliver the absolut maximum quality you should use 360dpi.

It depends on a lot of factors though. I've made great prints at

I'm not entirely sold on upsizing prints from my current 6mp camera
to produce enlargements.

Camera brands aside, how many pixels do I need to print a 12"x18" at
its NATIVE resolution? No upsizing, no downsizing whatsoever.

--
wild images and such at my website
http://www.x32.nl

 

[Nicholas_H]

Let's remember that more megapixels doesn't just equate to bigger printing sizes! It also equates to being able to crop a smaller portion of the image and have it be acceptable.

I hardly ever print, but in shooting lots of subjects from far away, more megapixels (as long as they are good pixels!) helps as I don't have any mega-monster glass (and probably never will unless someone wants to lend me $5K).

 

[clarksbrother]

I'm going to concur with those who say 300DPI. If you want high quality professional prints, 300DPI is pretty much the threshhold.

I've done posters and such at 150 or so and that looks fine from afar but you can definitely tell the difference once you get closer.

 

[Daniel Browning]

Camera brands aside, how many pixels do I need to print a 12"x18" at
its NATIVE resolution? No upsizing, no downsizing whatsoever.

The "native" resolution of 12x18 at 300 ppi is 5400x3600, or 19.44 MP.

However, using a 19.44 MP sensor would not deliver the maximum amount of detail possible for that print size/ppi, for one of the following two reasons. If the sensor is engineered correctly with an expensive optical low pass filter (AA), then it will have approximately 75% lower resolution and still some aliasing/bayer artifacts will make it through. If it lacks the OLPF due to cost or poor engineering, then it will be riddled with artifacts.

To fully compensate for the OLPF and remove artifacts almost completely, 34.5 MP (7200x4800) would be sufficient.
--
Daniel

 

[Marco_W]

...is almost everybody here so keen on counting blades of grass on poster sized prints? - because this is what you end up doing with the some above mentioned MP numbers.

I will not look at large size prints from just 10 inches away, so talking about requirements like 34MP for a 12x18 print is just one of the most stupid things I've read here for a while. (the math may be correct though)

--



http://www.landscapes.at

 

[gdanmitchell]

What do you mean by "native resolution?" That is sort of a meaningless concept.

What you may mean is that you want to print at 12 x 18 with sufficient resolution and no need to upsize/downsize. In general you want to aim for printing at no lower than about 180 ppi resolution in larger prints. You'll get sufficient resolution from just about any current crop sensor body.

Perhaps counterintuitively, you actually don't need as high of a ppi resolution in large prints as you do with small print. You are more likely to hold a small print in your hand and view small details very close. On the other hand you would more likely view a larger print from some distance. While I might make a large print at 180 ppi, I would generally make my smaller prints at much higher resolution levels.

Dan

I'm not entirely sold on upsizing prints from my current 6mp camera
to produce enlargements.

Camera brands aside, how many pixels do I need to print a 12"x18" at
its NATIVE resolution? No upsizing, no downsizing whatsoever.

--
---
G Dan Mitchell - SF Bay Area, California, USA
Blog & Gallery: http://www.gdanmitchell.com/

 

[Sal Baker]

...is almost everybody here so keen on counting blades of grass on
poster sized prints? - because this is what you end up doing with the
some above mentioned MP numbers.

I will not look at large size prints from just 10 inches away, so
talking about requirements like 34MP for a 12x18 print is just one
of the most stupid things I've read here for a while. (the math may
be correct though)

I don't think you're the target audience.

People making 16x20 and 20x30 art prints know that prospective customers inspect expensive prints very closely. 34MP would be pretty extreme for me, but 21MP means I have more data to work with in the files and have less need to interpolate additional pixels.

For reduced size web posting, which seems to be what most people in these forums say they do as opposed to prints, a much lessor camera could be used instead of the DSLRs we all nit-pick at 100% from 6-inches away.

Sal

 

[RedFox88]

I've did some tests on various printers and if you want to be certain
you deliver the absolute maximum quality you should use 360dpi.

I regularly have 4x6's printed from 240dpi files. And you realize that if you send a file to a printer that is 240ppi at the print size, your printer will increase the image size as it prints because it'll use the dpi for the quality of the print you selected in your printer driver.

Similarly if you send a 13MP file to print a 4x6, your printer driver will reduce the image size to be the print dpi/ppi. I've actually found a few times when sending even a 6MP image for a 4x6 print resulted in VERY visible grid patterns in the print. Since then I downsize to the print size at 300dpi if printing at home. If emailing for 4x6 prints it'll be 240/265ppi and about JPG quality setting of 9.

 

[RedFox88]

...is almost everybody here so keen on counting blades of grass on
poster sized prints? - because this is what you end up doing with the
some above mentioned MP numbers.

Just grab whatever is cheapest, right? 400 speed drug store brand is as good as kodachrome 64 or velvia 50, right? You're buying the body and the "film" at the same time so it does matter.

 

[Marco_W]

Just grab whatever is cheapest, right? 400 speed drug store brand is
as good as kodachrome 64 or velvia 50, right? You're buying the
body and the "film" at the same time so it does matter.

I didn't say that there wont be a quality difference visible. I also did not say that there is no appliction for really high res photos.

What I meant was the following: Take a photo of a landscape with 34MP and then take a photo of the same scene with, lets say - 8MP. Print both at 12x18 (let the printer do the up-scaling) Put both photos behind glass, hang them side by side on a wall and look at them from one or two meters away. I am sure the difference you SEE (not saying there is none) is close to zero.

--



http://www.landscapes.at

 

[RedFox88]

What I meant was the following: Take a photo of a landscape with 34MP
and then take a photo of the same scene with, lets say - 8MP. Print
both at 12x18 (let the printer do the up-scaling) Put both photos
behind glass, hang them side by side on a wall and look at them from
one or two meters away. I am sure the difference you SEE (not saying
there is none) is close to zero.

First off, people usually don't view prints as small as 12x18 from nearly 7 feet away. One of the first things they'll do is look at it up close. Now if you're talkinga bout a 20x30 inch print now that's a different story, but people would still want to look at the print close up.

I notice the difference in 11x17 prints from a 6MP vs. a 13MP dSLR at a viewing distance of "arm's length" and it is pretty easy to pick which is which.

 

[rhlpetrus]

Steinmuller, who worte a nice book on digital printing, has the following rule of thumb:

the ppi you need is given by 300 divided by viewing distance in feet. So for book reading, about 1 ft distance, 300ppi is needed, for wall viewing, typically 2ft disctance is ok, one would need 150ppi.

I find this a bit too optimistic, I'd say 240ppi would be good enough for wall diplays, since there are people who get close to image to look at some part of image.

Thus, for the OPer who asked for 18x12":

300ppi would give 5400x3600 pixels, which would be a little under 20MP. But this the resolution that makes it impossible, even at very close distance, to see any signs of printing dots.

At 240ppi, the count would be: 4320*2880 = 12.4MP.

This, except for close-up inspection, should be good enough for all purposes, so 12MP looks like pretty nice.

18x12" is 45x30cm, a very large image, pretty good for wall display. People should go more to museums and galleries and check Ansel Adams, Edward Weston, Cartie-Bresson and Eugene Smith images. All I've seen up to today are smaller than that.

So, unless you are into selling poster size images, 12MP looks quite good, if you are really obssessive, 21Mp is about all you need.

What I meant was the following: Take a photo of a landscape with 34MP
and then take a photo of the same scene with, lets say - 8MP. Print
both at 12x18 (let the printer do the up-scaling) Put both photos
behind glass, hang them side by side on a wall and look at them from
one or two meters away. I am sure the difference you SEE (not saying
there is none) is close to zero.

First off, people usually don't view prints as small as 12x18 from
nearly 7 feet away. One of the first things they'll do is look at it
up close. Now if you're talkinga bout a 20x30 inch print now that's
a different story, but people would still want to look at the print
close up.

I notice the difference in 11x17 prints from a 6MP vs. a 13MP dSLR at
a viewing distance of "arm's length" and it is pretty easy to pick
which is which.

--
Renato.
http://www.flickr.com/photos/rhlpedrosa/
OnExposure member
http://www.onexposure.net/

You cannot depend on your eyes when your imagination is out of focus
(Mark Twain)

 

[Its RKM]

I've did some tests on various printers and if you want to be certain
you deliver the absolut maximum quality you should use 360dpi.

That depends on the printer.

Send 360ppi to an HP or Canon printer and it will be resampled to 300ppi usin bilinear interpolation, making it lower quality than printing at 300ppi directly.

On an Epson, 360ppi is fine, but even that isn't maximum quality. I follow on from an archiving convention that I began with film, where I print contact sheets of images. Nowadays, instead of archiving the contact sheet with the sheet of negatives, I store it with the DVD of the original data. I print those contact sheets at 720ppi because the Epson desktop printer can cope with that resolution and the difference is clear when the images are viewed with a lupe or magnifying lens.

There is no point in going higher than 360ppi, even on an Epson printer, if you are only viewing the prints with the naked eye.
--
Its RKM

 

[Its RKM]

The only issue that is a matter of interpretation is what he means by "native resolution".
--
Its RKM

 

[RedFox88]

Steinmuller, who worte a nice book on digital printing, has the
following rule of thumb:

the ppi you need is given by 300 divided by viewing distance in feet.
So for book reading, about 1 ft distance, 300ppi is needed, for wall
viewing, typically 2ft disctance is ok, one would need 150ppi.

Even though you may send an image to a print shop or your printer at 150ppi, the print shop or your printer will enlarge the image so it meets its dpi requirements, i.e. 265, 300, 360 ppi as needed.

150 dpi on a home injket would probably be "draft" print setting and you wouldn't print a photo on photo paper on that setting, would you? So your home printer prints at its photo quality dpi setting no matter if you sent an image file that is 100 ppi at print size or 450 ppi at the print size. Dig?