Image resolution

Started Jan 28, 2013 | Questions
PGSONY Forum Member • Posts: 64
Image resolution

Hi,

I have a question which might be very stupid but I need to ask you pro's.

I am making my wedding album using indesign.  I have jpegs from my photographer @ 300 ppi.. which I’m using to make my own album.  My lab requires that they also get the album layouts as jpegs at 300 ppi.  So when I export the layouts from indesign as 300 ppi in jpeg format.. am I reducing the quality even further? Is indesign taking my already 300 ppi res files and downgrading it further or does adobe know that this is already at 300 ppi and export as is?  How does this exactly work?

Also, I exported jpeg files at 300 ppi from lightroom to test a photobook from black river imaging.  The pictures look great on the computer screen, however the pictures on paper came out quite dark and noisy.  Is it something I did wrong?

I want to make sure I correct any mistakes before I sent my wedding album to print to this other lab.

Thanks a lot!!

ANSWER:
This question has not been answered yet.
Biggs23 Veteran Member • Posts: 4,109
Re: Image resolution

Rather than focus on the ppi number, what actual resolution are you sending the files at? (1000px X 1000px, for example.)

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OP PGSONY Forum Member • Posts: 64
Re: Image resolution

Hmm is that when you resize the image?  I leave that blank usually and only select 300 ppi for resolution.  If I need to do it that way.. can you guide me in exactly what I need to do .. which options I need to pick?  The album I am creating will be a 12 by 12.

I think the pictures my photographer gave me are 2000 X 3000 with 300 ppi. I could be wrong.. not in front of my computer.

Biggs23 Veteran Member • Posts: 4,109
Re: Image resolution

PGSONY wrote:

Hmm is that when you resize the image? I leave that blank usually and only select 300 ppi for resolution. If I need to do it that way.. can you guide me in exactly what I need to do .. which options I need to pick? The album I am creating will be a 12 by 12.

I think the pictures my photographer gave me are 2000 X 3000 with 300 ppi. I could be wrong.. not in front of my computer.

2000X3000 is roughly an 8x10 size image. A 12X12 album when open is 24 inches long, neasrly 2.5 times larger than the image files you have. As such, any images that are stretched across an entire spread are going to have to be upsampled to fill the space adequately. The quality of that process is dependent on many factors. I would personally prefer to upsample the images manually in PS before letting another program do it automatically.

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BAK Forum Pro • Posts: 23,797
Not stupid at all

First, don't even think about this being a stupid question. It drives everyone nuts, until they get theri heads around it.

Re > I have jpegs from my photographer @ 300 ppi.. <

This probably is not true.

What you do have is images 2000 pixels by 3000 pixels.

PPI only gets involved when the image moves from being a computer file to being reproduced so you can see it.

When you reproduce the image on paper, following the printing company's request for 300ppi, that 2000 x 3000 pixel image becomes 6.7 inches x 10 inches. (that's 6.7 inches x 300 pixels per inch = 2000 pixels) And 3000 / 300 = 10 inches.

If you took the same 2000 x 3000 pixel original and reproduced it at 240 pixels per inch (ppi) the image would print at 8.3 inches x 12.5 inches.

I have not used modern versions of InDesign. I prepare photos for printing by using Adobe Photoshop Elements.

It has a dialogue box that allows you to type in a resolution whitch will tell you how big the image will be, ONCE YOU REPRODUCE IT somehow or other.

Default is 72 ppi, and you'll see an indication on your image saying what you see is 12% or 25% or 50%, and less and less of the image will appear on your monitor, and more and more will be (in your imagination) extending off the sides and top and bottom.

And there will be some indication that your image is, say 20 inches by 30 inches.

When you prepare the files for InDesign you set the size for 300 ppi  which does not change the actual file, but lets you see how much of the image would be visible, say, if you put it into a four inch wide hole. If there were 300 ppi, and the hole was four inches, you'd see 1200 pixels worth of the original 3000, meaning lots of the picture would be cut off.

And that brings you to resizing and cropping, and other complicated things.

QUESTION: there are a lot of photobook and album companies that offer sotware that is easier to use than InDesign. HAve you tried them?:

ANSWER: About moving files around. what matters is how many pixels are in your image. Monitors use fewer pixels per inch than printing machines, so an image that looks good on a monitor will not print as well. But it gets complicated becaue software does all kinds of automated resizings.

This probably just confused you more. Sometimes, just do as the instructions say, and do not try to understand.

BAK

OP PGSONY Forum Member • Posts: 64
Re: Not stupid at all

Thanks for this reply.  Yes I am confused even more, I need to re read this until it makes sense.

In Indesign, I am making my own layouts..lets say a 3x3 square and just dropping the pictures in there and using the "fit content to frame option" to make the picture fit.  So if the layout is larger than 6.75 x 10, the picture quality will not be the best?  Did I understand that correctly?

OP PGSONY Forum Member • Posts: 64
Re: Image resolution

Not sure what this process is exactly, but I will look into it. Thank you!

Lin Evans
Lin Evans Forum Pro • Posts: 17,390
Re: Not stupid at all

The thing you need to keep in mind is that "dpi" is only relevant to the size of your print. The important thing, in terms of print quality and assuming proper focus, exposure, etc., is the pixel dimensions of your original file.

Think of it this way: if you had an image consisting of only 300 pixels by 300 pixels in an original capture and these pixels are half an inch from each other and you could print them this way, the print would be 150 inches by 150 inches. This would equate to a density of 2 dots per inch (2 dpi). Were you to print this image 1 inch by 1 inch your print density would be 300 dpi. So which would "look" better?  Of course the one inch by one inch print would look much better than the 150 inch by 150 inch print.

It follows then, that with all other factors being equal, the more pixels in the original capture, the larger you can print and maintain a print density (number of "dots" or pixels per inch) which will result in a pleasing photographic print.

To tell how large you can print and maintain your desired 300 dpi print density, then you divide the number of pixels which you have available horizontally by 300 and the number of pixels you have available vertically in your file by 300. This result is the size in inches of your best print.

But there is a bit more to the story. When a print is made, the "actual" number of pixels per inch in print density is determined by the type of printing device. For example, in "best quality" prints, Epson inkjet printers will add pixels to give you a print density of 720 pixels per inch. Canon inkjet printers will add pixels (interpolate) to give you a print density of 600 pixels per inch. Most continuous tone printers will do either 300 or sometimes 400 pixels per inch. This is all done by the printers firmware.

What you need to keep in mind is that adding pixels does not diminish the quality of the print "unless" the native maximum print size is exceeded at the desired print density. So, for example, if your camera produces a file with say 4288x2848 (a Nikon 12.2 megapixel camera) then following the formula for a 300 dpi print size, you divide both sizes by 300 and get 14.29 x 9.49 inch print. Of course that's not "exactly" a "normal" print size so you can say that you could safely print 8x12 or even a bit larger at 300 dpi without any loss of quality. And, if the print driver interpolates to 720 ppi (dpi) then it will look even better under magnification because the print density is being increased without losing any original data (detail). It is said that the naked human eye can only see detail to about 300 dots per inch. Perhaps that is so, but astute observers can see the difference between 300 dpi laserjet text and 600 dpi laserjet text when viewed side by side, so perhaps having slightly more print density vis the print drivers is a good thing.

So remember that the "dpi" is not changing the actual image resolution, it's just determining how many pixels are to be fitted into an inch of print space. The actual amount of detail in the image is a function of many factors including the number of pixels in the file, the quality of each pixel, the focus, the exposure, available lighting, ISO, micro-contrast, presence or absence of anti-aliasing filters and last but certainly not least, the quality of the lens. Though we typically use the term "resolution" and "megapixel" as equated, in reality they are only correlations. Optical resolution is measured by photographing standardized resolution charts in black and white and in color. Then a reference number corresponding to the number of "line pairs" visible gives one the measured optical resolution. But then optical resolution is only one of several factors which contribute to image quality.

Best regards,

Lin

PGSONY wrote:

Thanks for this reply. Yes I am confused even more, I need to re read this until it makes sense.

In Indesign, I am making my own layouts..lets say a 3x3 square and just dropping the pictures in there and using the "fit content to frame option" to make the picture fit. So if the layout is larger than 6.75 x 10, the picture quality will not be the best? Did I understand that correctly?

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BAK Forum Pro • Posts: 23,797
Let's see ifthis helps.

a/ the printing company wants to use 300 ppi

b/ your photo originally is 2000 x 3000 pixels

c/ your image on the page is 3 inches by three inches

d/ therefore you need 300 pixels per inch times 3 inches across the image. That's 900 pixels across

e/ And because it is square, you need 900 pixels up and down.

f/ Go to your cropping tool and set it for a square, and crop your image into a square, chopping off some of the image on one end, or the other, or both.

Artistic judgement now needed.

g/ Let's say you want to use three quarters of the up and down part of the image, and want to cut off one quarter of the image.

h/ adjust the cropping of the square in f/ so you now have 3/4 of the original height. Because the original was 2000 pixels high, you now have 3/4 of thoe pixels in the up and down direction. That's 1500 pixels.

i/ Because the image is square, you also have 1500 pixels from side to side.

j/ But rememb er, the printer was 300ppi, for3 inches, equalling 900 pixels.

k/ Use the software resizing tools to resize the new cropped area, changing it from 1500 x 1500 pixels  to 900 x 900 pixels, and adjust the resoolution box to say 300 ppi.

YOUR COMPUTER WILL DO THIS WHILE MAINTAINING ECELLENT QUALITY.

l/ The dimension box on your software will now say the image is 3 x 3 inches, has 900 pixels in width and 900 pixels in height, and will print at 300 ppi.

BAK

MaxTux Regular Member • Posts: 449
"dpi" values in the image file are only a "hint"

All kinds of useful information was given to you above; but one important thing was not mentioned, at least not explicitly:

When you have an image in a form of a computer file, that image file has two characteristics:

1: Resolution in pixels on the horizontal and vertical axis; for instance 1200x800 pixels.

Most image processing and viewing programs on your computer will quite readily display this information, or it may be possible to just use an operating system function to do this (possibly something like "right-clicking" on the file icon and selecting "properties" on the menu that appears...?). This is a "hard quality" of the file, if you use some image processing program to change it, you are either throwing away information (when you reduce the numbers, "down-sampling") or forcing the program to "invent" information that does not exist in the file, if you are increasing it ("up-sampling").

2: Anticipated display size, expressed as "dots-per-inch" or "dpi". This is just a "hint" of intended file use, and consequently, changing it in the file, is almost always inconsequential. Why? There are two reasons: different display devices operate at different dpi values: a computer screen works with about 75 dpi, medium-quality printing with 300 dpi, high quality printing with 600+ dpi. When an image is displayed, almost all software and devices that does the display will quietly ignore this value in the file: if the display is on the computer screen the software will "fit" the image to the window size (by down-sampling "on the fly") until and unless you explicitly request something like "display original size"; if the display is by printing, it is determined by the requested paper/page size that the image is to be fitted onto.

Therefore, unless there is some specific and unusual reason for dealing with dpi "hint" values in the image file, these are best ignored. Any required processing should be done by changing the resolution: down-sampling if the display can't possibly use high-resolution of the original file (for instance, before posting a 5000x3000 camera image on a web-page, or up-sampling, and that only if absolutely unavoidable.

MaxTux

JulesJ
JulesJ Forum Pro • Posts: 45,443
Re: Image resolution

Biggs23 wrote:

PGSONY wrote:

Hmm is that when you resize the image? I leave that blank usually and only select 300 ppi for resolution. If I need to do it that way.. can you guide me in exactly what I need to do .. which options I need to pick? The album I am creating will be a 12 by 12.

I think the pictures my photographer gave me are 2000 X 3000 with 300 ppi. I could be wrong.. not in front of my computer.

2000X3000 is roughly an 8x10 size image. A 12X12 album when open is 24 inches long, neasrly 2.5 times larger than the image files you have. As such, any images that are stretched across an entire spread are going to have to be upsampled to fill the space adequately. The quality of that process is dependent on many factors. I would personally prefer to upsample the images manually in PS before letting another program do it automatically.

Why would anyone think you did represent DPReview?

Robert J. Gonzalez Senior Member • Posts: 1,173
Re: Image resolution

Biggs23 wrote:

PGSONY wrote:

Hmm is that when you resize the image? I leave that blank usually and only select 300 ppi for resolution. If I need to do it that way.. can you guide me in exactly what I need to do .. which options I need to pick? The album I am creating will be a 12 by 12.

I think the pictures my photographer gave me are 2000 X 3000 with 300 ppi. I could be wrong.. not in front of my computer.

2000X3000 is roughly an 8x10 size image.

Very roughly.  8x10 at 300dpi would be 2400x3000.  This is 6 2/3 x 10.  You should still be able to get reasonable prints but maybe you could ask your photographer to give you non-resampled images.  No camera puts out exactly 2000x3000.

A 12X12 album when open is 24 inches long, neasrly 2.5 times larger than the image files you have. As such, any images that are stretched across an entire spread are going to have to be upsampled to fill the space adequately. The quality of that process is dependent on many factors. I would personally prefer to upsample the images manually in PS before letting another program do it automatically.

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wazu
wazu Senior Member • Posts: 1,407
Re: Image resolution

Your problem with getting dark prints is not resolution. It's gamma and calibration. Here is an article on how to first set gamma and whitepoint so your monitor more closely matches photographic prints.

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