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Resize vs Resample (Photoshop CS4)


Lulu01 5 156
15 Jun 2011 3:17PM
Hello

I am putting together some artwork to be printed for a friend's exhibition and have got myself confused about resizing and resampling in Photoshop CS4. I have been reading about it online on ePhotozine and elsewhere, and the sites are all very helpful, but I'm just not getting it today Tongue

I have several large files in that they are 1 - 4Mb and 16 x 22 inches, but most of them are only 72 ppi in the Document Size dialogue box. The images only have to be around 3 x 3 inches so my thinking was I could just amend the Resolution to 300 with Resample Image unchecked and this would be ok. Have I got that right or should I have Resample Image checked?

Also, any thoughts on my workflow - I have been doing the following but think I may have got the steps out of synch re the physical document size and resolution:
1. Save copy of image as a tif file
2. Make any changes re levels
3. Adjust the document size
4. Adjust the resolution

Any help would be really appreciated.

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User_Removed 10 3.3k 4 United Kingdom
15 Jun 2011 3:49PM
It's easy to muck stuff up. Remember ppi is just a label which your monitor and your printer don't take any notice of anyway.

First off understand more about ppi here
Then have a look at this guide http://www.rideau-info.com/photos/changesize.html
User_Removed 10 3.3k 4 United Kingdom
15 Jun 2011 3:52PM
This too, will be most useful to you
Lulu01 5 156
15 Jun 2011 5:09PM
Thanks, Chris. I'll have a read and see if I can get my head round it all.
roy5051 13 11
16 Jun 2011 6:24PM
An image 22" x 16" @ 72 pixels per inch is 1584 x 1152 pixels. If you go to Image Resize, untick the Resample box and change 72 to 300ppi the size will change to 5.28 inches x 3.84 inches. If you want the shortest side to be 3" long, retick the Resample box and change the 3.84 inches to 3 inches; the other side will then change to 4.125 inches. It will then print at 4.125 x 3 inches at 300 ppi. NB this assumes the Constrain Proportions box is ticked at all times.
User_Removed 10 3.3k 4 United Kingdom
16 Jun 2011 11:23PM
Hope the links helped. I'll try my RealSimpleŽ explanation

It's really as simple as counting the pixels and converting them to inches. It's so simple that people get confused.

To get a good print you need to print about 300 pixels to an inch of paper. So it follows that if your image is 300 pixels wide then you can print it one inch wide. If it's 600 pixels wide you can comfortably print it at 2 inches wide. If it's 900 pixels tall you can print it at 3 inches tall. If it's 9000 pixels tall you can print it 30 inches tall.

So let's say your image is 3000 pixels wide by 6000 pixels tall. How big will that print at 300ppi? Do it in your head.

If you worked out 10 inches by 20 inches then you've cracked it, you now understand it and you can see how simple it actually is

That resolution figure in the Photoshop image resize box only helps do the maths for you and helps you resample to a specific size at a specific ppi. It doesn't really change anything on its own.
Lulu01 5 156
17 Jun 2011 7:31AM

Quote:An image 22" x 16" @ 72 pixels per inch is 1584 x 1152 pixels. If you go to Image Resize, untick the Resample box and change 72 to 300ppi the size will change to 5.28 inches x 3.84 inches. If you want the shortest side to be 3" long, retick the Resample box and change the 3.84 inches to 3 inches; the other side will then change to 4.125 inches. It will then print at 4.125 x 3 inches at 300 ppi. NB this assumes the Constrain Proportions box is ticked at all times.


Excellent Roy5051, many thanks. So if my understanding is correct, providing I don't mind a smaller image (which I don't in this instance), I still have the same number of pixels as I originally had and will be able to print a good quality image. If I were to print the 22 x 16 image it would be poor quality.
Lulu01 5 156
17 Jun 2011 7:33AM
Thanks again for your post, Chris. I think I'm getting there ... slowly!
mikehit e2
5 6.8k 11 United Kingdom
17 Jun 2011 9:57AM
The question comes as to how many pixels per inch you need on your printing. 300ppi seems to be the mantra, but I have seen huge discussion about it and some say that for all but the most critical work there is no advantage to going above 160ppi. Just try it and see.
Lulu01 5 156
18 Jun 2011 7:22AM
Thanks, mikehit. The artwork will be going to a printing company who have asked for 300ppi, but I will try the 160ppi on my own printer. I thought I had read somewhere that it needs to be 240-300ppi, but haven't read anything suggesting 160ppi. Some of the images I've received are very poor quality so I'm just hoping it all works out ok with what I've done.
User_Removed 10 3.3k 4 United Kingdom
18 Jun 2011 12:06PM
It is meaningless to ask for a 300ppi file if they don't also specify a size in inches or pixels. Have they?

Which would they be able to get the best print from: A file that is 300ppi and is 600 pixels wide by 400 pixels tall or a 150ppi file that is 6000 pixels wide by 4000 pixels tall? The reason they ask for 300ppi is that it imports into their DTP software better or they don't know what they are talking about (and many don't). Read What Printers and Magazines Really Want
Lulu01 5 156
18 Jun 2011 5:04PM
Hi Chris, no they have just said 'save at 300dpi at the size it will be printed' so I guess that means 300 dpi regardless of size. I've noticed that sum printers also ask for 1200 ppi for text. Unfortunately I don't seem to be able to specify that in CS4.

I've also noticed that most are asking for CMYK. I've set everything up in RGB so when I convert to CMYK the colours go off which is really annoying. I have tried to set it all up in CMYK but the colour palettes aren't so good (not that it matters if I have to convert them to CMYK anyway). I really wish there were 'industry standards' which everyone adhered to and, more importantly, was easy for the customer to understand.
GlennH 9 1.9k 1 France
18 Jun 2011 6:49PM

Quote:I've also noticed that most are asking for CMYK. I've set everything up in RGB so when I convert to CMYK the colours go off which is really annoying. I have tried to set it all up in CMYK but the colour palettes aren't so good (not that it matters if I have to convert them to CMYK anyway).


If it helps any, it does matter when you convert to CMYK. It's far easier to work in an RGB working space. If you dig deep enough you'll find reference to RGB working spaces being described as 'well behaved', which essentially means they're neutral and predictable to edit with. There's a reason that conversion to print profiles takes place at the end of a workflow.

To help you convert to CMYK, there's a great PDF from Jeff Schewe on the web, which is a classic lesson in softproofing. This is one of the things you can do in the full version of Photoshop. It's here if you're interested.
Lulu01 5 156
19 Jun 2011 8:27AM

Quote:To help you convert to CMYK, there's a great PDF from Jeff Schewe on the web, which is a classic lesson in softproofing. This is one of the things you can do in the full version of Photoshop. It's here if you're interested.


Thanks for the post and the link GlennH. It's very interesting. I was just going to Image / Mode / CMYK Color in CS4 so perhaps that's why my colours are changing so much, although I understand that bright blues are a bit of a problem.
mlewis 10 1.5k United Kingdom
19 Jun 2011 9:58AM

Quote:Hi Chris, no they have just said 'save at 300dpi at the size it will be printed' so I guess that means 300 dpi regardless of size. I've noticed that sum printers also ask for 1200 ppi for text. Unfortunately I don't seem to be able to specify that in CS4.

That's still meaningless. You need to know how big it will be printed. If you don't know how big the image will be printed it could be tagged as 300ppi but when printed it could actually be more or less. Until you know the physical dimensions of the print ppi is completely meaningless as it relates to a physical size..


Quote:I've also noticed that most are asking for CMYK. I've set everything up in RGB so when I convert to CMYK the colours go off which is really annoying. I have tried to set it all up in CMYK but the colour palettes aren't so good (not that it matters if I have to convert them to CMYK anyway). I really wish there were 'industry standards' which everyone adhered to and, more importantly, was easy for the customer to understand.

You shouldn't really be doing the CMYK conversion. The printers should do that as to do it properly would mean knowing about the inks and paper being used in printing. The printers should know more about that than you.

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