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by Bart Arondson

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52

Generating High Quality Ink Jet Prints Making effective use of professional photographic ink jet printers is tricky business, especially when the statistics that are commonly used to describe these printers are vague and misleading. Learning how a ink jet printers function, how to properly interpret their capabilities, and make the most effective use of ...


35

You ask if there is a practical difference. So the answer is yes, albeit a very small one, but some of the other answers have missed it. You're right that the only difference is in the metadata: if you save the same image as 300dpi and 72dpi the pixels are exactly the same, only the EXIF data embedded in the image file is different. (I've even verified this ...


28

There are some general rules you can use to determine the "maximum" (I use that term loosely) print size. Keep in mind that the quality of a print is often more dependent on what is being printed than its size in megapixels, and even if your image size is not dense enough to mathematically fit onto a certain page size, you can still blow most images up ...


19

Emprical Study: Extreme digital upscaling For all of the theory above, thats all it currently is...theory. It is the end result of days of research on the physical characteristics of printers, the theory behind printing and ink, the concepts of DPI and PPI, etc. The real question is, how does it stack up against empirical evidence? Does it withstand the ...


16

The straightforward answer to your question is very simple arithmetic: 32×300 = 9600 and 18×300 = 5400, so 32 inches by 18 inches at 300 dots per inch is 9600 by 5400. However, it gets a little more complicated when you consider a more complicated relationship between pixels and colored dots in your output medium. For details on this, take a look at ...


16

The information above is quite good, so I won't try to compete, but here is a nice infographic: The boxes are the number of megapixels for a print of the size in inches according to the scales on the axes. This is at 300ppi, which is a standard for the print resolution of many images. This great graphic comes from an article at D215.


14

Generating High Quality Ink Jet Prints: Summary Making effective use of professional photographic ink jet printers is tricky business, especially when the statistics that are commonly used to describe these printers are vague and misleading. Learning how a ink jet printers function, how to properly interpret their capabilities, and make the most effective ...


14

The values are arbitrary and meaningless, and only serve to confuse people. The EXIF standard seems to imply that if the tag is missing, 72 is the (still-meaningless) default. However, it is apparently mandatory for the TIFF standard, from which the JPEG/EXIF format basically inherits everything. So maybe it has to have some value to properly comply with the ...


13

When it comes to print, terms like DPI, resolution, PPI, etc. get thrown around without much care or concern as to what they truly mean. So, before I send you off to a more in-depth answer about DPI, PPI, resolution, and print, a quick summary: DPI: Dots Per Inch A 'dot' is a single element of a pixel On a computer screen, a dot is a single 'sub-pixel' ...


13

DPI, or Dots Per Inch relates to the dot density when printing. To help better understand the relationship of DPI to pixel dimensions, take an 800x600 pixel image for example: Using 300dpi, an 800x600 image will print 2.6x2 inches. Using 200dpi, an 800x600 image will print 4x3 inches. Using 100dpi, an 800x600 image will print at 8x6 inches. Notes: As ...


13

jrista has the start of the formula, and it covers images viewed at arm's length quite well. But that 'conventional wisdom' devolves into unreasonable numbers as soon as you get to anything "big", say even a 16x20... requiring 5-6000 px. And if you hit poster size, say 30x40... 9000x12000... 108 MPix?! When you're talking about really big prints, it's ...


10

Emprical Study: Does PPI Really Matter? For all of the theory above, thats all it currently is...theory. It is the end result of days of research on the physical characteristics of printers, the theory behind printing and ink, the concepts of DPI and PPI, etc. The real question is, how does it stack up against empirical evidence? Does it withstand the test ...


10

Does an image edited and saved/exported with 1200x800 pixels at 300 ppi look any different online than the same image saved/exported with 1200x800 pixels at 72 ppi? No. A bitmap produced either on-screen or on paper from the image will be identical. The only difference would be the default print size from some applications, and only then if the image ...


9

DPI stands for Dots Per Inch. It's used to descibe the output resolution of printers, and it's also often used instead of the PPI (Pixels Per Inch) unit, which is more appropriate for describing the resolution of computer screens, scanners and image files. So, a printer might have a resolution of 2400 DPI, but that doesn't mean that you can print an image ...


7

JPEG Quality of 9 ~ 10 out of 12 (or 70 ~ 84 out of 100) is pretty indistinguishable from uncompressed. See this article for an in-depth comparison. In short, if you have less color gradients, you can get away with higher compression (lower quality values). For PPI (what you care about), in general, 240 to 360 PPI is high quality. This depends on typical ...


6

Every digital image has a specific size: the width and height in pixels. The amount of information depends on that. In digital image files, the number of pixels per inch is just a hint. It indicates a proportion that should be used for calculating the actual size of the image when printed. If you have an image of 1000x1000 pixels and you print it at ...


5

It depends on a few factors - primarily the print technology that is going to be used, and secondly what the print is to be used for. The D700 shoots at 4256 × 2832 (12.1 MP), so the largest Square frame you can print at 1:1 pixel ratio would be 2832 x 2832 pixels. Lets say the print is to be at 600 DPI, which is a fairly standard high quality signage dpi, ...


5

Pixels per inch don't actually exist until the image is rendered onto some physical medium such as paper or the monitor on your computer. The device doing the rendering determines PPI and PPI determines how large the image will appear when rendered. Rendering your 4000x3000 on a device capable of producing 240 PPI would produce a 16.6"x12.5" physical ...


5

PNG compression quality varies greatly from compressor to compressor. The standard PNG compression in Photoshop for example can sometimes commonly be beat by large percentage points. This is primarily due to more intelligent switching algorithms when it picks the kind of prediction to do for a certain set of pixels. Most of the "additional" compression is ...


4

The DPI setting coming out of the camera doesn't mean much (if anything). You have a fixed number of pixels coming out of the camera (4272 x 2848, to be exact). Since you're enlarging it quite a bit, you probably want to shoot in raw format to ensure you get everything that camera can produce. Once you've done that, you might want to "upres" the picture to ...


4

I'm going to sort of disagree with all the other answers that talk about DPI or PPI rules of thumb, and suggest two different 'rules' (based on PPD, from another answer of mine) Rule 1 — The 'Retina' rule (aka the Pixels-Per-Degree (PPD) / 'better than your eye can see' rule) This comes pretty much straight from Apple's Retina display designs, the idea ...


4

The number is just a random filler. It has no significance since the camera does not know how big you will print. Most cameras default to 72 which according to the EXIF standard is the default value. Some cameras let you set it yourself. Then again, it has little meaning unless you will print all your images without cropping exactly at the same size.


4

The DPI setting (or PPI to be pedantic) only specifies how the pixels should be translated into absolute metrics. The 5400 PPI for the 900x500 pixel image only means that it represents 0.1667x0.0926 inches (4.23x2.35 mm) in absolute metrics. When an image is shown in the browser, it totally ignores the absolute metrics. The image is shown by its pixel ...


4

An image has no physical size, it is simply a collection of pixels. A 1280 pixel wide image will be rendered 20cm wide on my old computer monitor, but the same image will be rendered just 9cm wide on my phone. The DPI value embedded is metadata recording the "intended" physical size. As such it can be set to whatever value the user desires. The value is ...


4

You can use MS ICE for stitching together 3 photos, or use a 12k px linescan camera, panning over some wood, or go the computer graphics way. Wood textures are pretty common in 3D modelling software.


3

What you're suggesting in terms of resizing sounds correct, and you can use any number of tools to do it. If you're on Windows you can use IrfanView, and naturally almost any of the pro line of tools will do it (such as Photoshop). It's also worth noting that most of these tools will also let you set the width as a function of their physical size (cm, ...


3

For printing, i usually scale photos to 300dpi. Since 10cm x 15cm are approximately 4in x 6in, that means scaling to 1200 times 1800 pixels.


3

In my experience those numbers have no special meaning. The camera makers just pick one and use it in all their firmware.


3

The DPI reported in a JPEG file is just a metadata field. That is, it's intended to offer a hint to software that displays or prints image files, but it's not immutable, in practice it's not authoritative or enforced, and it's usually ignored by most software and photographers alike. The actual DPI of a displayed image is determined by the absolute ...


3

Besides the algorithms described in other answers, small images' file sizes can be reduced by stripping out metadata from the file. EXIF/IPTC data can add up to 64 kilobytes to a JPEG image.



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