Sizing your image file in Photoshop

Metroprint is a professional online printing service that works best with images that are sized by the photographer before upload. Although you can upload any file and allow the system to decide your print size by determining the data in your file ('original from file'), it is better to do this yourself before upload.

This brief tutorial shows you how to use resampling to preserve the data (MB) in your file whilst setting the correct (cm or inches) size for printing. If you would like to understand more about the terms used in describing the process, they are explained at the end.

The trick to getting a good quality print is to make sure you don't unneccessarily lose quality when you change your document size to a print size. A loss of pixels, would mean lower resolution, which is image quality. But here's the rub: each printer has its own resolution and you cannot exceed this. So your file should be the correct resolution, at your chosen width and height. The correct resolution also comes in to play with getting the borders you want so it's useful to learn as much as possible about how to keep your files in line with teh printer settings.

So firstly, to find out the right resolution for your print type (size, paper,type) always use the Technical Help Calculator.


The calculator will tell you the right resolution (dpi) for your chosen print type (eg C Type, Giclee, black and white) and size (different printers are set up for specific sizes, for example the Lambda is 200dpi, the Lightjet 245dpi). Now you know the correct resolution, you can set your document size to your chosen width and height.

1. Go to Image> Image size



2. Make sure that Constrain Proportions is checked.



3. Uncheck Resample Image. The symbol to the right shows that width, height and resolution are now linked.



4. Keep an eye on the Pixel Dimensions (16.3M in this example) you will notice that now they remain constant when you adjust the width and height. If you add extra (cm) size, the resolution (pixel/inch) will go down, if you remove (cm) size, your resolution will go up.



In this illustration I have taken the size down to 6 inches and the resolution has gone up to 418 ppi. This is over the correct resolution for a Giclee print which is 300dpi.

So set your (cm or inches) document size, and observe the resolution. If the resolution is over or under
the correct resolution go to stage 5.

5. Check the Resample Image. Now the link symbol will return to just width and height.



Change the resolution for your print type to the correct resolution given by the Technical Help Calculator.

In this example, I have changed the resolution to 300dpi. You will notice that the pixel dimensions have gone down from 16.3Mb to 8.38Mb. This is because my file was too big for my desired print size. Photoshop is using Resampling (in this case, resampling down) to take away unneccessary pixels. This will make upload time quicker and my file easier for the printer to handle.

If your resolution is lower than the correct resolution for your print type, you have two choices: either add in pixels at this stage by using Resampling (up) or make a smaller print and keep within the limitations of your file. Most professionals would feel that this second option is the lesser of the two but resampling can be an easy shortcut to the right resolution if used in moderation.

Having set up your preferred width and height at the correct resolution for your media type, you can now set up custom borders in Photoshop.

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