# blowing up digital prints



## spiffyandstuff (Oct 16, 2005)

so when you blow film pictures up to big it doesn't really look that bad, the dots are just further apart... but digital looks awful when you blow it up, anyone know of any tricks around this? i've been messing with huge resolutions, 500+ dpi, then applying a 'halftone' filter, but i haven't been able to print anything out yet
also, if i change the standard 72 dpi reolution to 300 dpi without changing the print size, will i get a better print?


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## jadin (Oct 16, 2005)

There's a few things you can do. For starters the method of resampling you use can greatly affect the output quality. For example pixel resize will give a horrible outcome. Instead use something like bicubic, in Photoshop CS2 they have an option called bicubic-si which works even better than bicubic.

You can use programs such as Genuine Fractals, a program that does nothing but resizing. It's results are quite nice. Many stock photography websites require you to use something like that for optimal results. I personally use Paint Shop Pro, which has an option called smart-size, I couldn't tell the difference between a Genuine fractals resize or one inside using smart-size, so I simply use that.

Lastly you can resize slowly. For example resize your photo just 10% larger at a time. This will help you to keep the detail that can be lost by simply resizing to your desired size. This works especially well when you use one of the better resample methods listed above.



			
				spiffyandstuff said:
			
		

> also, if i change the standard 72 dpi reolution to 300 dpi without changing the print size, will i get a better print?



I don't think so, but don't quote me on that. If I remember right if you change the dpi resolution absolutely nothing about the photo will change. Only if you change the print size as well. I've found it's two different modes to work in, stick to what you find easier. 

One method is simply pixels. A 3000 width image can print up to 10 inches at 300 dpi, or 20 inches at 150 dpi. You do the math in your head and it's pretty straight forward.

The other is strictly based on your desired print size. If you want to print at 300dpi and want an 8 x 10, it will resize the photo to 3000 pixels. I find the only time this method is useful is if I'm printing something like a postcard something that _has_ to be exact dimentions.


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## alexecho (Oct 17, 2005)

spiffyandstuff said:
			
		

> also, if i change the standard 72 dpi reolution to 300 dpi without changing the print size, will i get a better print?


DPI is dots (pixels) per inch, so more of them will give a better picture, surely? I think... Maybe... It also depends on the printer, they like a 300dpi image, and stretch pixels if the original is less, but don't quote me, either!


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## Digital Matt (Oct 17, 2005)

If you are printing at 72 dpi, that is your problem.  Photo quality prints should be at 300 dpi.  From there it's the same with film.  The size of your negative (megapixels) will determine how far you can enlarge and still retain detail.


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## Marctwo (Oct 17, 2005)

It seems an awful lot of people get confused over this type of thing and I think a lot of it is to do with the way PS handles/presents the dpi in image size.  You'll find it more simple if you think of resizing in two stages:

*Set the dpi:*  Most people would agree that 300dpi is pretty much standard so uncheck the resample image button in image size then set the dpi to 300.  The pixel count and the image itself will remain unchanged but the software will now interpret each pixel as 1/300 of an inch in printing terms so the print size of the image will change.
*Interpolate the image:*  This is the part that actually changes the image and adds pixels - in other words, it resamples the image.  In resize you can either enter the required size in inches/cm/mm/etc. or you can do the math yourself and enter the pixel size directly, eg. 10 inches X 300dpi = 3000 pixels.  Remember that the resample image button must be checked for this stage.
It's a good idea to include step 1 in a pre-processing action along with anything else that you initially do with all images.


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## jadin (Oct 17, 2005)

That's what that little resample button is for! It makes so much more sense now! Thanks. :sillysmi:

:hail::hail:


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## Marctwo (Oct 17, 2005)

I'm happy to help.


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## fdi (Oct 17, 2005)

I use Qimage to res up my images before printing. I use to print great 13x19s from my 3M D30. My favorite thing about Qimage is not having to store the res-ed up images which end up being enormously large 13x19 tiffs. Even if I do some mods during the printing Qimage just stores an attribute file so I can exactly reproduce the print later.


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## craig (Oct 17, 2005)

Yeah what they said. Always keep in mind the original file size. Part of digi's appeal is the interpolation of pixels. Technology has made great strides in this field. Personally I try not to enlarge or reduce my photos by more then 20%.  Also keep in that photos are enlarged not blown up.


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## fightheheathens (Oct 17, 2005)

keep in mind, color film is equivalent to around a 16 megapixil image.


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## jadin (Oct 17, 2005)

Slight correction. 35mm film is around 16 megapixels. There's more than one size of film.


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## cbay (Oct 18, 2005)

Well i have just been experimenting with this as i didnt realise about the DPI, i printed a image off 10 x 8 @ 72dpi and it was rubbish changed the image to 300dpi and printed and it was exactly the same! 

Any ideas??


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## Marctwo (Oct 18, 2005)

What's the resolution? For 10 x 8 you want 3000 x 2400.

<edit> PS. It's no good just changing the dpi on a previously resized image.  You'll have to go back to a version before you resized it at 72dpi. </edit>


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## craig (Oct 19, 2005)

I would delve into the print dialog boxes. For instance my printer has options for print quality, paper type and size. Also make sure that you have the correct print driver selected.


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## Mumfandc (Oct 20, 2005)

Many people stand by 300 dpi as the standard resolution by which all digital images should be printed. But this need not be the case depending on the printer you are using, particularly high-end lightjet photo printers.

I think this link explains digital image enlarging pretty well.

http://www.westcoastimaging.com/wci/page/info/photoshoptip/tip25.html


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