Upscaling images and fonts for large image

[rjt76]

Hi,

I'm working on a project to be printed at 89x119cm. The image I've designed is composed of a 300dpi image, text and a couple of AI/EPS. I'm working in Photoshop CS. The final image is to be at 200dpi. My questions are should I change the dpi before upscaling? Does the text need to be embedded? Any tips for upscaling an image aprox 8x larger?

Thanks in advance

 

[RallyPC]

because photoshop is a rastor based (pixel based) program your going to lose resolution when up scaling an image and once you start at a low res like 300dpi you can't gain resolution, you should have started at about 1,600-3,000dpi for something that large or else it will look pixelated, and changing the resoultion to say its higher won't really work because you don't have that much pixel data, you can try to use the sharpen image filter but no guarantees that will work, good luck. post how it works out for you.

 

[rjt76]

Thanks. The orig image is 300dpi, so are u suggesting I convert this to 3000dpi first then begin the upscailing, then change the dpi to 200 as printers requested.

Also, the text used in the image has just been typed straight in via photoshop and the file needs to go as a PSD. The text looks fine blown up but will it print OK or does it need to be rasterized or embedded or something prior to printing?

 

[duncdude]

No - he is not suggesting you convert up to 3,000 dpi first. That is madness. Remember one thing - the artwork you have on your machine is as good as it gets. You can maybe apply trickery when enlarging the image to fool the eye - but you will always reduce the quality of the image. This can be a strange concept to grasp. Even in the case of an old photograph that requires doctoring - the muddy looking original is the picture in its best state and any alteration of the picture, even though it may appear more pleasing to the eye, is reducing the quality. Too many alterations can pretty much destroy the image. RallyPC said "you SHOULD have started at ..." not "go ahead and resample the image up to 3,000 dpi". i.e. it's probably too late now. You might, however, be lucky in the case of text on layers as they might not be rasterised yet. Why not just do what you think you need to do, cut a section out, print it at the output size - but on a A4 laser/inkjet. See what you think once you have output the snippit of the picture. Hope this load of crap makes sense!!!


Kind Regards
Duncan

 

[TrojanWarBlade]

I think you'll find that you'll be limited in terms of resolution to your lowest common denominator.
In other words, if you're mixing a number of images together that are in different resolutions, you will need to resize some to fit at the right scale into the final image.
If your lowest resolution image is at 300dpi then you should be ok but in general it is a bad idea to resize anything at all if you can avoid it. Scaling down a not good and can lead to imperfect lines but scaling up is much worse.
The ideal is to have all your images at the right resolution for the final output or to at least have them at a vastly higher resolution and do one scaledown at the end.
If you try to scale from 300dpi to 200dpi then basically you're gonna lose every 3rd pixel. Try it. Create a white image and draw a diagonal line across it and a shallow angle and then resize to 2/3rds (66.667%) normal size. See what happens. That should give you some idea of what we are trying to say.




(slowly healing) Trojan.

 

[duncdude]

Hi Trojan - not that it is particularly relevant but something that was quite interesting many years back was that i actually tested out a cheap scanner i had and found that i got better results scanning at 300 dpi than 400 dpi. Simply because the scanner had awful hardware resampling and that 400 dpi was not a multiple of the 600 dpi of the scanner. I always used to scan at 1200, 600, 300 and 150 from that point on - never an arbitary resolution. This post demonstrates how difficult it can be to explain basic prepress concepts over a site like this.


Kind Regards
Duncan

 

[TrojanWarBlade]

Absolutely, good point. I have always done the same for exactly the same reasons. You can often get a better 400dpi image by scanning at say 1200dpi and using software to rescale.

The other point worth noting is that rescaling in x and y with the same ratio is important. If you rescale with different ratios in x vs y then the errors are much worse.




(slowly healing) Trojan.

 

[rjt76]

Thanks guys,

The main image I'm having the dilemma with is a piece of stock art (300dpi), I have tried Smartscale and GF Print pro with similar results. I will try the idea of printing a small area at 100% on A4 and see how that works. Is rasterizing the type not a good idea then....I thought that if using the type tool in PS what ur typing is automatically a raster?

 

[TrojanWarBlade]

The type will be rasterised but it's best to do that on the final image at the appropriate resolution since it may not resize well.
When you add text, the font is usually some form of vector and is converted to raster at the size and resolution you specify. This allows the machine to anti-alias and kern the font to make it look as smooth as possible at that resolution. Rescaling can only ever degrade from that point on as suggested earlier.
In short, if your adding text, do all imaging work first, resize to final scale and add text to taste.




(slowly healing) Trojan.

 

[rjt76]

Thanks again.....I thought perhaps bringing the fonts as large AI's would be better than just typing them in....