Preparing an image for canvas printing

The cost of full colour printing on fabric, usually canvas, has plummeted over the last eight or so months with the cost of a 16” x 20” canvas print now around the $55 mark (plus postage); depending where you get it done. Earlier in the year this sized fabric print was around $120 (Australian prices). But, and this is a BIG but, this price is for ‘final supplied’. This means that you have to provide the finished final digital file for printing and that the people doing the printing take no responsibility for colour casts, insufficient resolution, or sharpness in the ‘final’.

So if your picture comes back and people have greenish or over-yellow faces and this was in the final supplied, then don’t ask for your money back. Ditto if you get your picture back and the resolution was so low it looks as grainy as gravel; unless you were going for that look.

So what do you need to do to ensure you are going to provide a useful final?

Note that the following assumes you have an image of sufficient
size and resolution to begin with.

Firstly, check the Web site of the service you are going to use and see what, if any, specific instructions they provide for preparing your final; then consider . . .

You need to ensure that the final is colour correct, or, if you are not going for colour correct (i.e., you are going for sepia or duo-tone or grey scale, etc.) that the colours—when viewed on a trusted near-colour correct screen—are as you intend them to be in the print.

A year or so ago the general advice was to slightly over-saturate the colours for fabric prints however modern inks and fabric printers have improved and over-saturation is generally not required. However check the instructions for the particular service you plan to use and see if they advise that you do this.

You need to ensure that you have sufficient resolution built into the final for the size of print you are doing, and this also needs to factor in the viewing distance. The greater the typical viewing distance the lower the resolution can be. For a 16” x 20” print with a typical viewing distance of 1.0 to 1.3 metres I would recommend a minimum resolution of 150 dpi. If your starting image does not permit you to resample to 150 dpi I would recommend strongly against trying to up-sample the image. Unless you know what you are doing then up-sampling (adding pixels where none existed before) almost always provides an unwelcome outcome. It is always better to just go for a lower resolution print—say 130 dpi.

Finally you need to sharpen/un-sharpen*. This is a little tricky and also subject to personal preferences and the subject. Some subjects are better printed soft. Others need to be printed hard/sharp. It is difficult to advise on sharpening/un-sharpening but the general advice is to sharpen more than you think you should when printing on fabric.

One note on un-sharpening. You only ever do this when you have completely finished resizing/re-sampling the image.

Actually there is one more thing you need to consider with fabric printing: What do you want to do with the wrap-around edges? This is called canvas-wrap or gallery-wrap and there are two options. You can include the wrap around edges in your final which means your final will be slightly larger than 16” x 20” (this is called an ‘image border’), or you can usually instruct the print service to simple extend the edges—which means they don’t use part of your final for the edges but they extend the colours of the edges of your final for the wrap-around (this is called a ‘mirror border’). There is a third option some services offer. This is to simply colour the edges using a colour from the print—like blue if there is a lot of blue sky (this is called a ‘colour border’, or for my American readers it’s a ‘color border’).

When you save your final ready I suggest saving it as a PSD or TIFF (no compression) and not as JPG. Saving as a PSD or TIFF will ensure no quality is lost from the file. If you save as a JPG, even at the highest setting, you will lose IQ (image quality) information from the picture. However this will depend on what file formats your printing service supports, but seriously, if they don’t support PSD and TIFF then I would be wondering just how good they are.

Saved as an uncompressed TIFF or a PSD file a 16” x 20” image at 150 dpi is going to be about a 20MB file. Saved as the highest quality JPG file the file size is 6MB.

All sound too hard? Alternatively, if you are using a ‘local’ service, you can sit down with a consultant and they will work through this with you on their computer. But this service is generally (almost always) not free. Also, and I shouldn’t say this (but it’s true), some of these consultants are not as knowledgeable as they should be about what they are doing.

You can also Google the Web for more hints and tips on preparing a fabric final.

I am about to try a couple of fabric prints. I will let you know how I get on.

* Sharpening of colour images actually requires un-sharpening. Confusing I know, but such is life.