Why does images look good on a computer screen, but a print-out even at hi-resolution produces images that don't look as good?

April 14, 2011 3:50 AM

Why does images look good on a computer screen, but a print-out even at hi-resolution produces images that don't look as good?

For the sake of argument, a 1280x1024 size photo looks crisp on the screen with solid colours. But when printed out on my new office printer (free-standing A3 type, 30ppm, with 4 paper trays, big toners... you get the idea) looks inconsistent and speckly when viewed up close (printed at 1200dpi with quality set to high). Example, a solid block of red colours on the LCD, would have some speckles when printed on paper.

The quality I would like to see is at the same level of colour brochures you would find in your mailbox.

What I've been told:
I need to print on full-gloss paper
Image resolution needs to be much higher
1200dpi is not high enough
The machine needs a fiery controller, with pantone colours
Only production level printers can produce this level of quality

Thinking about this makes me believe the answer can be pretty complex... I hope not! I want to simple be able to print on standard white paper, and get good quality and solid colours. I think dpi is not a big factor... i mean if there is a block of yellow on screen, i want to see a block of solid yellow on paper.

This long post proves that a picture is indeed a thousand words! Looking forward to your answers!

posted by gttommy to technology (21 answers total)

Monitors are low resolution devices. If a picture is low resolution it will look OK on a monitor but it doesn't contain enough information for higher resolution devices.
posted by rdr at 4:00 AM on April 14, 2011 [1 favorite]

The DPI on the printer isn't what's the problem. It's the file itself. 1280 on the long side gets you a whopping 5" at the lowest setting I feel ok printing, 240 dpi. Monitors are 72-96 dpi. Printers are much higher. To fill in the gaps your printer driver interpolates; hence, jaggies.

Also, heavy ink on regular paper is gonna look like hell. You need photo paper, and the printer driver needs to know it's photo paper, so make nice even color.
posted by notsnot at 4:09 AM on April 14, 2011

Even at 300dpi, you'd need an image that's 3300x2550 to generate a full-resolution 8.5"x11" image.

The images professional photographers take are absolutely huge when viewed on a monitor, and in their raw format can easily be several dozen megs. 1280x1024 just isn't that big an image.
posted by valkyryn at 4:31 AM on April 14, 2011

Your printer can fit more "dots" into an area than your monitor can; thus it will look sharper on your monitor than it does on the page.
posted by alby at 4:31 AM on April 14, 2011

Are you trying to print at A3 size? That's way too big for 1280x1024. To print at 1200dpi either the picture will come out tiny (like 1"x<1") or has to be scaled up by your software and to do that it has to add in extra pixels/dots to make up the difference. What kind of file is it? That will also make a difference (eg. if its a jpg, what looks like solid red to you may not be)
posted by missmagenta at 4:32 AM on April 14, 2011

Yeah, do the math: the image is 1280 "dots" on a side, and you're printing at 1200 "dots per inch". At that resolution, perfect resolution is about 1" wide. The printer driver or the printer itself is resizing the image before output, creating jaggies and all.

600dpi is about the minimum for dotty-looking images (300dpi can be passable). So the max printable size is {longest image dimension} / {dpi} = {max size of longest dimension}. So, at 600dpi, you're going to expect an excellent 2" wide print and an OK 3" wide print, but anything bigger becomes more pixellated and jaggy the smaller the effective DPI is. So, the answer "image resolution needs to be higher" is the correct one.

...big toners...

My experience is that, while color laser printers are pretty awesome, they don't do as well as a photo printed on photopaper using an inkjet or due-sublimation printer. I used to have a 2MP camera (about 1200x1600) that printed nice 8x10s on an Epson 600dpi photo-specific inkjet printer. When you got up-close you could see the pixels, but framed on the wall was fine. The advantage was that the ink dots blended a little bit on the paper, reducing the sharp jaggy edges. Toner doesn't seep or blend, resulting in dottier images but nice crisp pie charts.
posted by AzraelBrown at 4:35 AM on April 14, 2011

This won't help the "dots" but to help getting what comes out of the printer make sure that you have your photo set to cmyk rather then rgb, and don't forget to calibrate your monitor.
posted by monkey!knife!fight! at 4:38 AM on April 14, 2011

...to help get what comes out of the printer to look more like what's on your screen....sigh.
posted by monkey!knife!fight! at 4:38 AM on April 14, 2011

There's a gap that the OP needs filled in, I think. The resolution of the printer isn't the issue. It's the resolution of the image. You need to resize the image in a photo manipulation program. This will make the prinatable image much smaller than the monitor display.

Let's say for argument that you have a photo that's 1500 pixels wide. You save it, and open it in Photoshop. You discover that it is saved at 72 pixels per inch (pretty standard res for web). You want to print it.

You need to convert it to print resolution. 300 pixels per inch is standard, but you can get away with numbers in the 200s like notsnot suggests. But we'll go for 300 in the this case.

So the huge, nearly 21-inch picture on you monitor (1500 pixels at 72 ppi = 20.8 inches) becomes a 5 inch wide printable image.

Then you print it at 300 dots/pixels per inch. You get a nice image.

The printer resolution is pretty much irrelevant when it's higher than the resolution of the original. Print a 300ppi image at 600dpi on your printer, and you basically just get two smaller dots of the same color instead of one larger dot. And they're connected, so they look exactly the same magnified as the one bigger dot.
posted by Mayor Curley at 4:42 AM on April 14, 2011

This nifty chart shows how big a print you can make with a 300dpi printer.
posted by tommasz at 5:24 AM on April 14, 2011 [2 favorites]

Basically, we're all just used to onscreen stuff looking like blurry crap, and we all adjust our expectations accordingly. That's why, when the iPhone came out with a 300+ dpi screen, people were so blown away; it looks qualitatively different, not merely better. It's also why so many pen-and-paper arty types are so repelled by computers - they know what high quality imagery looks like, and computer screens are not it.

I'm quite looking forward to the day when I'll be able to buy a used laptop with an A3 size panel with 0.05mm pixels.

The other reason for discrepancies between what you see on screen and on paper is the fact that different colour approximation mechanisms are in use. Screens work by emitting narrow-band light, while ink or toner on paper works by absorbing quite broad spectra.

The colours you see when looking at screens or four-colour process printing are not, in general, spectrally identical to the colours of the original objects depicted. Instead, they're a mix of narrow-spectrum emissions chosen so as to make our retinas respond as if they were exposed to the original colour spectra.

For example, when you're looking at something orange, your retina's red-sensitive receptors will respond strongly, green-sensitive somewhat less strongly, and blue-sensitive scarcely at all. And if you look at a mix of narrow-band red light and narrow-band green light whose intensities are carefully chosen, you can get the same colour sensation as you would from looking at the original orange.

An orange-looking object on a computer screen makes the screen emit just such a mix of narrow-band red and narrow-band green light. The exact colors used for screen displays are chosen so as to cause as much difference as possible between colour sensor responses, allowing for the closest response match to that experienced when viewing natural colours. Even so, there are colours that simply cannot be reproduced by a RGB color display; these are said to lie outside the display's "gamut".

To get an orange effect on paper with four-colour process printing takes a mix of yellow dye (which almost completely absorbs blue light, reflecting only a non-blue portion of the spectrum) and a little magenta dye (which selectively absorbs green). Illuminate that with full-spectrum white light, and what you see you'll interpret as orange - the reflection will be missing almost all the blue portion of the incident spectrum, and some of the green portion.

The four colours most commonly used for printing are cyan (which absorbs red light), magenta (absorbs green), yellow (absorbs blue) and black (absorbs everything). Translating an image containing RGB information for on-screen display to make it contain CMYK information for printing involves a lot of fiddly arithmetic and can't, in general, always be done perfectly; there's only so much overlap between an RGB display's colour gamut and that of a CMYK printer.

Some photo-quality consumer-grade printers use more than four colours (I know Epson makes one with six inks) and this extends the gamut that the printer is capable of and makes photos look rather better.

Laser printers are not as good as inkjets for accurate colour reproduction, simply because fusing toner powders doesn't make them blend as smoothly as inkjet dye or pigment does. Your example of a red region ending up speckly-looking is a good one: look at your printout under a powerful hand lens and you will find a visible mixture of magenta and yellow toners in any red region rather than the smoother blend you'd get from an ink printer. Yellow is quite a bright colour, because the eye's red and green sensors are both quite sensitive and both respond strongly to yellow light; so even though the printer's pixels are small and the toner grains are even smaller, you will see some yellow speckles in your red.

So: what you've been told is pretty much exactly correct. You can't reasonably expect professional-quality colour printing from an office-grade laser printer even if you put really really good paper through it, which you've said you don't want to. There's a reason a four-colour offset press costs more than your laser printer did, there's a reason glossy brochures are glossy, and there's a reason people can still make a living doing printing for others.
posted by flabdablet at 5:44 AM on April 14, 2011 [9 favorites]

Leaving aside the resolution issues everyone else has already mentioned, if you want output that looks like "colour brochures you would find in your mailbox" then you will need to either get it printed on a press rather than a home or office printer, or you'll need it printed on a professional printer that's capable of producing proof-quality output. If output of the quality you're after could be produced with an office laser printer on plain paper stock, then that's how everyone would do it and the glossies in your letterbox would be laser on plain paper.
posted by russm at 5:51 AM on April 14, 2011 [1 favorite]

or, what flabdablet said...
posted by russm at 5:53 AM on April 14, 2011

Just remember...Resolution is not a measure of the raw pixel count of an image. Resolution is the measure of the density of the pixels within a standard square space (usually and inch). It's become a regular thing for people to call an enormous (say, 3000 pixels square) screen image "high resolution", even though its pixel density is 72ppi (screen rez).

For printing purposes, a pixel density of 300ppi is the minimum to be considered "high resolution".
posted by Thorzdad at 5:53 AM on April 14, 2011

I think it's mainly about viewing distances. You are viewing your monitor at more than arm's length, but when you pick up a printout you are viewing it at a much closer distance, maybe only a foot. If you take that "crummy" printout and frame it and hang it on the wall, it will look good enough 90% of the time because you won't be able to see the flaws from afar.
posted by smackfu at 6:24 AM on April 14, 2011

Also, viewing distance. I shoot with 10-12 mpx dslrs, and printed on A3 it's not exactly sharp when viewed 3 inches from the surface. Take a few steps back though, bang! However, 1280 for an A3 print is really pushing it....
posted by TrinsicWS at 6:25 AM on April 14, 2011

Yes, what everyone has said.

1- Your photo's resolution is too small. The printer may well be printing at 1200 dpi, but the source only has (at that paper size) 87 dots per inch. That can look fine if it is meant to be a poster, but not if it is meant to be something like an ad sheet. Looking at it as if it was text, that's really only 8 dots per character, and if you remember the old dot matrix printers, you know how rough that can be.

1b- To fill an A3 page with 1200 dpi, you need an image that is 19800x14000.

2- Color laser printers aren't super awesome at doing photo-quality. They can produce some damn fine results, but you really have to get down into the nitty gritty of how it physically produces the images and massage that. You may have to change the format that the image is being sent to the printer in, so that it is more close to the way the printer does its RIP.

3- The way it is doing the halftoning may not be optimal. I wish I could remember the name of it, but there is another method besides the traditional "dots of different sizes" where the "dots" are all at the at the resolution of the printer, and the intensity of each color is produced by laying down more tiny dots. I think it might be called diffusion screening, but googling that doesn't seem to get to exactly what I'm talking about.

4- Monitors versus printers have different color rendering. On a monitor, pure red means turning on the red dot at full and the others at zero. On a printer, pure red means laying down (something like) 75% magenta and 25% yellow. You really shouldn't be able to see the individual dots, but depending on various things, you might.

5- Modern color lasers need a fuck-ton of memory to do a good job. To do four color printing, it needs that 19800x14000, times 4 colors, of bits (about 1gb) of ram to fully render the image. If it hasn't got that, it might be cutting quality corners.
posted by gjc at 7:12 AM on April 14, 2011

Everyone above is right. One more thing, though- You're forcing the printer to upsample your image. There are different ways to interpolate when you upsample, and I would expect your printer to be doing this in a low-quality way.


Use Photoshop or Gimp to scale your image first into the printer's native resolution. 1200dpi is pointless overkill if your source image is much less... so scale it up to 300dpi on A3 and use cubic interpolation.
posted by qxntpqbbbqxl at 7:26 AM on April 14, 2011

Even using photo imaging software to enlarge the image is still going to create subpar results. Interpolation will not create a perfect enlargement and your best bet if you want high quality prints is to start with a high resolution image straight out of the camera.

The image resolution you need to produce a high quality image depends on the printing method you're using. (more information on that here) If you're using a 4 color digital printer, you need the image to have a resolution of at least 225 DPI at the intended output size to get optimum results.
posted by girih knot at 11:38 AM on April 14, 2011

You've gotten some excellent answers already, but I'll add my $0.02.

One reason you're not getting the results you're expecting is because paper and monitors show color by two completely different methods. Monitors are emissive, that is they generate light and color. Think of a flashlight with a sheet of colored cellophane over the bulb. The color is going to be rich and vibrant. However, paper is reflective. Light comes from the environment you're in, be they fluorescent or incandescent or what-have-you, passes through the pigment on the paper, bounces off the paper and hits your eyes. A lot of the light's energy is lost in all that bouncing and color vibrancy is lost in transit, which is one reason printed pieces rarely look the same when compared to a monitor.

Additionally, think of the color of the lights around you; sunlight, fluorescents, LEDs, and incandescent lights all have different light temperatures, and that affects the look of the printed pieces you view.

Lastly, the color gamut of your monitor is considerably larger than the gamut possible through four-color printing, which is to say that a monitor can show more colors than a printed piece. For example, reds are easy to print, but printing rich, pure greens is really hard.

Sorry, it really is a complex issue.
posted by lekvar at 1:18 PM on April 14, 2011

All great answers, thank you very much
posted by gttommy at 6:27 AM on April 26, 2011