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Subject: "How to resize image to 300dpi in Photoshop?" Previous topic | Next topic
shutterbugrn Basic MemberTue 22-May-01 06:36 PM
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"How to resize image to 300dpi in Photoshop?"



          

I want to resize my scanned images to get 300dpi for printing. Using the Resize Image Wizard (clicked on Help, then Resize Image), after indicating that I want to resize for print and setting my image width and height (in inches), it asks me for the halftone screen (LPI) to be used to print my image, then on the next screen it shows the pixel-per-inch based on the halftone selected (which is usually twice the halftone when set to highest quality). It doesn't say anything about dpi anywhere. Does this halftone/LPI/pixel-per-inch stuff has anything to do with dpi and how do I get 300dpi for printing? Thanks in advance. By the way, I'm using photoshop 5.0 for windows.

  

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Replies to this topic
Subject Author Message Date ID
Reply message RE: How to resize image to 300dpi in Photoshop?
BJNicholls Gold Member Awarded for his contributions to the community and the Resources
23rd May 2001
1
Reply message RE: How to resize image to 300dpi in Photoshop?
shutterbugrn
24th May 2001
2
     Reply message RE: How to resize image to 300dpi in Photoshop?
BJNicholls Gold Member Awarded for his contributions to the community and the Resources
24th May 2001
3
          Reply message RE: How to resize image to 300dpi in Photoshop?
N80 Silver Member
20th Jun 2001
4
               Reply message RE: How to resize image to 300dpi in Photoshop?
BJNicholls Gold Member Awarded for his contributions to the community and the Resources
20th Jun 2001
5
                    Reply message RE: How to resize image to 300dpi in Photoshop?
N80 Silver Member
21st Jun 2001
6
                         Reply message RE: How to resize image to 300dpi in Photoshop?
BJNicholls Gold Member Awarded for his contributions to the community and the Resources
22nd Jun 2001
7

BJNicholls Gold Member Awarded for his contributions to the community and the Resources Charter MemberWed 23-May-01 04:08 AM
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#1. "RE: How to resize image to 300dpi in Photoshop?"
In response to Reply # 0


Salt Lake City, US
          

LAST EDITED ON May-23-01 AT 04:03 PM (GMT)

The terminology gets confusing.

A halftone is a conversion of a continuous tone image to a pattern of dots (also called a dot screen, or line screen) for use in commercial offset printing. It is specified in dots per inch and existed long before any computer printer started using the dpi term. Typical magazine line screens are 133 or 150 dpi. In graphic design work, the rule of thumb for good screen output is to have your image resolution twice that of the line screen your image will be reproduced with. For most design work, 300 pixels per inch is a good target.

Printing on an inkjet printer depends on entirely different conversion. The dots are reproduced in a random or stochiastic pattern. 1440 dpi Epson photo printers produce the best results with 300 pixel per inch image resolution or more, but will not show pixel artifacts until you go less than 200 pixels per inch.

Assuming your intent is injet printing, forget the wizard and go straight to the Image, Image Size command. Ideally, you don't want to resample your image as you change its size, so uncheck the Resample box. You can then enter a pixel per inch value or enter the target dimension you'd like for either horizontal or vertical print output. If you enter a dimension, the program will automatically calculate the pixels per inch setting that can produce that image. If that value is 200 ppi or more, you're ready to print. If it's less than 200 ppi, you should resample the image to a higher resolution to prevent pixels from becoming visible in your print. To do that, check the Resample Image box and then enter the target resolution you want (300 ppi).

Resampling an image to a higher resolution does degrade image quality, especially as you resample to more than twice the original resolution of the image. There is a program named Genuine Fractals that uses fractal scaling that offers much better "upsampling" results for images that you are preparing for oversize output. These techniques aren't a substitute for having a high res scan for real detail, but they can let you avoid seeing pixellation from images that are otherwise too small for the size you wish to print.

BJ

BJ

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shutterbugrn Basic MemberThu 24-May-01 01:48 PM
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#2. "RE: How to resize image to 300dpi in Photoshop?"
In response to Reply # 1



          

BJ,
Thanks for the explanation. You're correct in assuming that the intent is inkjet printing, specifically I used the Epson 1200 printer. I generally don't like to resample up so I tend to scan at the max. resolution which gets close to 50M on a Nikon LS-2000. I can always put them on CDs when my harddrive fills up. I've been doing pretty much what you suggested, just lucky I guess, different steps but same result. However, I usually print at 400 ppi. It's probably more than necessary but I rather wait a little longer than have a lower quality print. Recently, due to my printer's inability to print certain images accurately, I have looked into having one of my images printed by a local pro lab (they do not use inkjet printers). But in the instruction, they talk about resolution in dpi and that's where I got confused. If I fail to meet their requirements then they would charge me more. So if I understand you post correctly, then for printing purposes when people say dpi I should interpret that as ppi in Photoshop. By the way, do you know of any good Photoshop books that you would recommend? Thanks again.
Rick

  

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BJNicholls Gold Member Awarded for his contributions to the community and the Resources Charter MemberThu 24-May-01 05:52 PM
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#3. "RE: How to resize image to 300dpi in Photoshop?"
In response to Reply # 2


Salt Lake City, US
          

LAST EDITED ON May-24-01 AT 06:53 PM (GMT)

You should ask specifically what the lab means - I'm betting that they're giving you a mimimum resolution or pixel pitch for the image file. I assume that they would charge you more if they have to take the time to resample your file.

If you go into Photoshop's Image Size control, you can use it to test various combinations of ouput size and resolution. Just uncheck the Resample box if it's checked. Then type in a dimension and the resolution for that dimension will update automatically. Or you can see what print size you can get at a given resolution.

If your lab is providing you a minimum dpi spec for a digitally exposed print, it's probably the minimum pixel pitch for your file below which you'll see pixel edges. Enter that value in the Resolution window under Image Size and you'll see the maximum print size they can do for you without upsampling your file.

The Photoshop books I've used are more oriented to graphic design. They would probably only add confusion for digital darkroom work. Perhaps the book I saw that dealt with Photoshop for photographers would be better. I'll take a look at it and see...

BJ

Zenfolio gallery

  

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N80 Silver Member Charter MemberWed 20-Jun-01 01:53 AM
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#4. "RE: How to resize image to 300dpi in Photoshop?"
In response to Reply # 3


Rock Hill, US
          

BJ

You are right. Most Photoshop books are oriented toward professional print shops for output. I'm reading a great book called Photoshop Grayscale which is great for the mid-level Photoshop user but all output is in line screen, etc.

With the latest inkjet technology, particularly in the area of B&W printing with Quadtones and Piezography (from Cone Editions) there is little need for the serious amatuer to seek professional printing. In this regard it would be really nice to find a Photography/Photoshop/Inkjet book.

I remain confused about inkjet resolution settings. I generally understand the issues of resizing and resampling but my question is this: If I scan an image at a high resolution, say 800 dpi or higher, at the right size so that no resizing or resampling needs to take place, in the Image Size dialog box the resolution will be the resolution I set at the time of the scan, so do I need to change this resolution if I am going to print at max resolution on my printer, 1440 or even 2880 on some newer printers?

George
George (N80)
gebarron@infoave.net

George Barron

My Nikonians Gallery is here:
http://images.nikonians.org/galleries/showgallery.php/cat/500/ppuser/1091

  

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BJNicholls Gold Member Awarded for his contributions to the community and the Resources Charter MemberWed 20-Jun-01 05:26 PM
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#5. "RE: How to resize image to 300dpi in Photoshop?"
In response to Reply # 4


Salt Lake City, US
          

LAST EDITED ON Jun-20-01 AT 06:28 PM (GMT)

The printer resolution is the number of ink dots the printer can put on the paper and isn't directly related to the pixel pitch of the image. One dot of ink does not equal one pixel in an image. Remember also that an Epson printer in either 1440 or 2880 horizontal resolution is still only delivering 720 pixels per inch in vertical resolution. The 720 value is the resolution of the stepping motor that feeds the paper past the print head for each pass. Naked eye comparison of 1440 to 2880 won't detect a difference in the resulting image, although it may be that the smaller ink drop would help in rendering very subtle tones.

For Epson photo printers, all that you need to keep in mind is that for whatever image you're printing, you should ideally have a file resolution of 300 ppi or more at the dimensions you want your image to print. You can get away with less and you won't see pixels until you get under 200 ppi at your output size, but more resolution will increase the apparent sharpness of your print until you get to about 300 ppi.

The "300 ppi at print size" value is derived from making prints and finding the point of diminishing returns for the Epson printer's inkjet resolution. It doesn't hurt anything to print an image that scales to 800 ppi or even higher, but you won't see any signficant increase in sharpness either.

If your image doesn't have enough pixels to print at the size/resolution you want, you can resample the image to a higher resolution. However, resampling can only help prevent obvious pixellation from becoming visible (within limits). The process of "upsampling" not only doesn't add sharpness information to an image, it actually degrades the sharpness of the original bitmap. That's why I recommend that you do every scan at the highest optical resolution of your scanner. Don't go beyond the optical resolution since interpolated resolution is just another name for upsampling. A full res file will give you the maximum size your scanner can provide for a large print, but will print equally well for any smaller print you make.

BJ



BJ

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N80 Silver Member Charter MemberThu 21-Jun-01 01:00 AM
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#6. "RE: How to resize image to 300dpi in Photoshop?"
In response to Reply # 5


Rock Hill, US
          

BJ
Thanks for the explanation. Issues of resolution are impossibly confusing to many beginners so your help is appreciated. My advice to you, as moderator, is to combine your responses here and save them so you can plunk it down without recomposing every time someone asks for an explanation. It probably won't be long until i get confused again myself.

George (N80)
gebarron@infoave.net

George Barron

My Nikonians Gallery is here:
http://images.nikonians.org/galleries/showgallery.php/cat/500/ppuser/1091

  

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BJNicholls Gold Member Awarded for his contributions to the community and the Resources Charter MemberFri 22-Jun-01 07:28 PM
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#7. "RE: How to resize image to 300dpi in Photoshop?"
In response to Reply # 6


Salt Lake City, US
          

Good advice, however mikepoison is the moderator for this forum. I will compile this scanning and resolution advice into an article as soon as I can make the time...

BJ

BJ

Zenfolio gallery

  

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