Luminous Landscape Forum
Raw & Post Processing, Printing => Digital Image Processing => Topic started by: Kanvas Keepsakes on April 12, 2014, 01:09:38 am
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Hello. I have a quick question. Hope someone can help me out. A photographer emailed me an image in JPG format that she wanted me to print on photo paper for an expo display she will be at this weekend. I opened the image and it was 46"x30" in size and resolution was at 72ppi. Most of the photo's I get are at least 300ppi. So she wanted an 8x10 so I used Perfect Resize Pro plugin for Photoshop to size down to an 8"x10". I left it at 72 and printed it like that. Now when I look at the print around all the edges and curves it looks kind of pixelated. Attached is the picture I took with my phone (sorry for the horrible photo) so you all could see what I was talking about. I printed several other images for other photographers that sent me the images at 300ppi and it seems as if I don't have that problem with these files. Is the 72ppi the problem here? Why in the world would a professional photog be shooting and saving at 72ppi? Maybe I'm a little lost here. I thought the higher the number the better the photo??
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You screwed up...you should have resized without resampling so the 47"x30" @ 72 PPI was resized to 10" x 6.522 @ 331.2 PPI...since the original proportions were not "8x10" you'll need to figure out how to re-propotion the image to fit 8x10.
Ya know, if you're gonna do this stuff "professionally", you really should learn about this stuff...resolution vs. proportions.
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Thanks for the tip. I did what you said in PS and problem solved. When I opened the original image in the Perfect Resize Pro plugin and changed nothing more but to size to 8x10 I could instantly see the pixels around the fingers. So I resized using PS with resampling unchecked and worked. Thanks for the kick in the right direction about what to read up on.
Still wondering why a photographer would shoot and save the image at 72ppi instead of 300??
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Most cameras save the images by default at 72 dpi, which was a common density for web / monitor.
Anyway, a digital image is pixels x pixels. Until you specify the output dimension then the dpi number is meaningless. If you require a different value of dpi after you decide your output size, then you might need to resample
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Most cameras save the images by default at 72 dpi, which was a common density for web / monitor.
Actually, a lot of digital images are set with no output resolution (which in Photoshop defaults to 72 PPI). The key to the OP's situation was the huge size and low PPI resolution. Resizing without resampling solves that particular problem.
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Still wondering why a photographer would shoot and save the image at 72ppi instead of 300??
Because that value is meaningless as you saw when you correctly 'sized' the image to 8x10. It's just a tag, a value that has to be there (it can't be empty) but doesn't have much bearing on the output size. Digital images don't have a size expect for the space they take up on a drive. Work with pixels not the resolution tag. 1000 pixels is one inch IF the tag were set to 1000ppi, 10 inches if set to 100PPI then output to produce that size on a print. Yet in both cases, the image is 1000 pixels and that's what really counts.
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... 72 dpi, which was a common density for web / monitor...
Boy, old habits die hard! The last time a monitor actually had such a density was in 1984, thirty years ago, with the original Macintosh (512x342 screen resolution).
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Ok, so Perfect Resize Pro is pointless if Photoshop does it all for you as far as sizing without resampling? I don't see anywhere in Perfect Resize Pro that even gives me the option of whether to resample or not. I'm trying to wrap my head around the logic of the 72 and 300ppi. If an image is 72ppi it's 38x40 or something huge. But if we squeeze more pixles into an inch let's say 300ppi, the image gets small like 8x11 or so. Wouldn't it get larger than the original size if you go to 300 from 72? Why does it go backwards in size?
So I opened a file right now that was 8.27x6.617 at 300ppi. I want to print at 20x24. If I open PRP and size to 20x24, the resolution of 300ppi stays there. It doesn't change. But if I size it using Photoshop's built in resize without resampling, it changes to 99 ppi. If I print both these images side by side, one left at 300ppi at 20x24 and at 99ppi, the one thats 99ppi will be sharper and better quality than the one that PRP left at 300ppi after sizing it up?
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Hi,
You should forget the notion that an image file has a PPI, it doesn't, an image file is physically dimensionless, it's just a collection of pixels. All it has is a placeholder for an output instruction, a PPI tag, but it has no meaning until the image is actually converted to a physical output size.
Output on the other hand can have a PPI, it has physical dimensions, a number of Pixels Per unit length (e.g. Inch).
A file has pixels, and those pixels will be spread over the physical output size. Interpolation (resampling) can change the number of pixels that are used to spread over the physical output size.
Printers deliver better quality when they are presented with the correct number of pixels per unit length, and those numbers are usually fixed per model. So, if for a desired output size the number of image pixels is not adequate (e.g. less than 300 or 360 per inch), new pixels/samples will need to be created/interpolated. Some programs do a better job of creating those new pixels, e.g. Perfect Resize. So you need to set both the required output size, and the required number of pixels per inch, for the program to create the correct number of pixels.
Cheers,
Bart
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Whenever a more or less creative person say "...dpi..." or "...ppi..." I am tempted to shout "stop right there". This seems to cause so much confusion, humanity might be better served if those terms disappeared.
-h
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Ok so I'm grasping a better understanding of this whole resolution thing. Thanks for all the info guys. That's why I love this forum. What I am having issues with is laying out multiple photo's onto one canvas in Photoshop and printing. Let's say I have a 36" roll of paper. I create a new file in PS with 36" in width and xx" in length. It asks what resolution to make it at. So what if I want to print 3 images next to each other so I can save paper yet they are all different sizes in resolution as far as ppi? So i open one of the photos and it's originally at 240ppi. Another one is at 300 and the other is at 72. How would I get all 3 of those images on the same canvas next to each other? As soon as I try to move an image into that canvas with a different resolution of the blank file, PS alerts me the size is different.
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Hi, In that case you will have to resize and most likely resample all the images to the same ppi and desired output dimension.
For instance if you want the three prints 8" X 10" (assuming all images have this aspect ratio) next to each other then:
- Create the new file 36" in width at 300ppi
- Resize (with resample if necessary) each image to 8" X 10" and 300 ppi
- Now you can place the individual images onto the 36" wide file without any issue.
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... So what if I want to print 3 images next to each other so I can save paper yet they are all different sizes in resolution as far as ppi?...
You will choose ONE resolution for all of them.
Which resolutions shall it be then? The one that is optimal for your printer and file size (pixel dimensions) of your photos. What is "optimal" for your printer? To simplify it, the rule of thumb is: 300 ppi for Canon Printers, 360 for Epson. What if you do not have enough pixels in your files? Then you can go lower. Another rule of thumb is that most people (read: other than Jeff Schewe ;)) won't notice the difference if you go as low as 180 ppi for paper and even as low as 100 ppi for canvas.
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Francisco has given you the simple solution. But it seems you still have failed to grasp the concept.
So i open one of the photos and it's originally at 240ppi. Another one is at 300 and the other is at 72.
None of these photos has an inherent resolution of ???ppi. They only acquire a resolution (in ppi) after YOU have assigned a size (in inches) to the image. :)
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Hi, In that case you will have to resize and most likely resample all the images to the same ppi and desired output dimension.
Exactly. The physical output needs to be presented with the correct (and same) number of pixels per unit length (PPI) for each image. Allow the image editing software to resample (recreate) the correct number of pixels to allow doing just that, by changing both the PPI and the image output size.
Cheers,
Bart
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Hi,
One more comment: in order to place several images onto a new document, make sure that the Color space and bit depth is the same for all images and the output document
Regards,
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You should have e-mailed back and told her to send her the high rez image by way of Dropbox.
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You should have e-mailed back and told her to send her the high rez image by way of Dropbox.
Ahmmm... she DID send a high-rez image. At least high enough to print @ 270 ppi.
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Hello,
why don't you try Lightroom for printing ? It does the whole job of resizing and choosing the right dpi /pip for you and just simply creates great prints.
Robert
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My d800 gives me an image that's 7,360 × 4,912px per shot. This same image could be either:
20.4"x13.4" @360ppi/dpi or
24.5"x16.4" @300 or
30.6"x20.4" @240 or
etc, etc
This would be "resizing" in Photoshop. The image is still 7,360 × 4,912px (not adding or removing any pixels)
RESAMPLING is actually adding/removing pixels to achieve a certain target output (for print/web)
As said, it's pointless to use Perfect Resize to REMOVE pixels. PS does that just fine.
When it comes to adding pixels, you don't need to run an image through Perfect Resize unless you're adding a lot of pixels.
I just resample in Photoshop (up to about 1.5x original size at most. If I need to make something big big, then I'll use Perfect Resize)
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To do a multi-image print... I resample all to-be printed images to 360dpi@whatever physical target dimension, Create a new document in PS @360 and whatever colorspace, "place" the images, and print. (using 360dpi as the target because I use Epson printers)
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Thanks for the tips guys! Very much appreciated. So would going from 72 to 300 be considered an extremely large upsample to use PRP with?
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Thanks for the tips guys! Very much appreciated. So would going from 72 to 300 be considered an extremely large upsample to use PRP with?
Going from 72(ppi) to 300(ppi) would involve NO resampling (up-sampling) whatever as long as the dimensions of the images retain the ratio of 72:300.
Apparently you still haven't digested the concept. Please go back and re-read this entire thread. :)
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So would going from 72 to 300 be considered an extremely large upsample to use PRP with?
No, up-sampling is something different. That's adding (creating out of thin air) more pixels. Resample is add or subtract pixels. Doesn't matter if that document is 72 or 300. Work with pixels! That's what's really there in the document.
1000x1000 is the same document if set at 72 or 300. IF set to 72, the 'size' if output that way would be 13.8 inches. If 300, the 'size' would be 3.3 inches. In both cases, we started with and ended with a 1000x1000 pixel document.
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Thank you Andrew. I just clicked on your link to your site. Good informative stuff!
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It brings up the question of why so many people in publishing ask me for pictures in "300 dpi". I always feel a bit awkward in asking them how big they want them - they should be the experts not me. Unless I'm mistaken 300 dpi is meaningless on it's own. They seem completely unprepared for the question.
Jim
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It brings up the question of why so many people in publishing ask me for pictures in "300 dpi"...
I've been perplexed as well. One of possible answers is that it has become a code word for "high resolution," "printable" images. In other words, YOU are supposed to know or guess how big they want to print it and multiply it by 300 ppi to find the right file dimensions.
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It brings up the question of why so many people in publishing ask me for pictures in "300 dpi". I always feel a bit awkward in asking them how big they want them - they should be the experts not me. Unless I'm mistaken 300 dpi is meaningless on it's own. They seem completely unprepared for the question.
Yes it's rather meaningless but something has to appear in the tag. We usually see a 'defaut' of either 72 or 300, both really old values that were based initially on needs that don't fit all purposes in the modern digital world. For example, at one time, 72 was the value for the very old Macintosh display output. Some still think that's a pertinent value today but of course it's not. As for 300, I believe it was due to the large majority of output to a halftone dot using a 2X quality factor with a 150LPI screen. You'd never use that for newsprint. But for a lot of pretty good color repro work, where a linescreen was commonly 150LPI, applying the 2X QF gave you a value of 300. Is that necessary today? Well yes, if you're using a 150LPI screen and a 2X quality factor. You decide 1.5X is OK, the value would of course change. There is no one or two correct values, you first have to define the output device!
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Yes it's rather meaningless but something has to appear in the tag. We usually see a 'defaut' of either 72 or 300, both really old values that were based initially on needs that don't fit all purposes in the modern digital world. For example, at one time, 72 was the value for the very old Macintosh display output. Some still think that's a pertinent value today but of course it's not. As for 300, I believe it was due to the large majority of output to a halftone dot using a 2X quality factor with a 150LPI screen. You'd never use that for newsprint. But for a lot of pretty good color repro work, where a linescreen was commonly 150LPI, applying the 2X QF gave you a value of 300. Is that necessary today? Well yes, if you're using a 150LPI screen and a 2X quality factor. You decide 1.5X is OK, the value would of course change. There is no one or two correct values, you first have to define the output device!
Hi Andrew. The problem with the requests I get are where they say "could you e-mail me the picture at 300dpi". So starts the questioning about what it will be used for etc.
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The problem with the requests I get are where they say "could you e-mail me the picture at 300dpi".
"Sure, could you e-mail me the physical dimensions of the planned print so that I can calculate what meaningless ratio of downsampling to apply to my image so that meaningless meta data in the file will satisfy your requirements"
Or
"I take it that 300dp is a code for 'high-resolution'. I'll mail the image in its native resolution and await your response."
-h
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Hi Andrew. The problem with the requests I get are where they say "could you e-mail me the picture at 300dpi". So starts the questioning about what it will be used for etc.
Be fun just to send them a document with 300 pixels by 300 pixels with the 300 DPI tag.
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Be fun just to send them a document with 300 pixels by 300 pixels with the 300 DPI tag.
That would be cruel..... ::)
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So, AdoramaPix has a currently-running contest which specifies as one of the submission rules:
Every entrant must submit one image – jpeg 300 dpi
Luckily, they have a comment section, so I said:
I can not believe that professional photo sites still resort to such an incredibly lame, totally useless and meaningless description of file size as "300 dpi" !? It means nothing, people! Besides, the "d" in "dpi" refers to "dots," as in "dots per inch" and is related only to printers, describing how many dots the printer head will spurt per inch, i.e., it does not describe the file size. If you insist on using it, then it should be "300 ppi" or "pixels per inch." But even that does not say anything about file size, as you have to add how many inches there will be (remember the "per inch" part?). So, you can say, for example, 300 ppi for an 8" x 10" printout. Which then translates to 2400 x 3000 pixels file, the only way to meaningfully express file size. In other words, why not just simply say what is the minimum acceptable file size in pixels to begin with?
They answered (emphasis mine):
We are not concerned about the file size, that is why it is not stated. If it were an issue we would have stated it. We just ask that it be 300 dpi for printing purposes- since top 12 will be printed. Only the top 12 need to be concerned about size. If it's too small we'll ask for a larger size.
Then one guy joined the debate (emphasis mine):
Yes but at this point we all know that "300 dpi" is just another way of saying "high res image" - otherwise we are just being pedantic
And the AdoramaPix staff concluded:
We have a lot of people ---hobbyists to professionals entering contest. If we were to be more specific with size, we would get a lot more questions on how to size the images properly to meet the requirements. So that is why we keep it more general and only ask that for our printing purposes (top 12) the image be at 300 dpi. If they are not, we will ask them to submit a larger file.
So, there you go. We've been just ignorant of what "everybody else knows" already. Or pedantic ;)
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So, there you go. We've been just ignorant of what "everybody else knows" already. Or pedantic ;)
Hilarious really. They can't be serious (or consider themselves to be professional printers). Where can I go to ask them about sending a 300x300 pixel file at 300 DPI? I'd love to hear what they have to say.
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Or even a 1x1 pixel image at 300x300 ppi ;D