Hi, I've got the following question, hopefully someone can give me some clue.

With Photoshop, I made an image which has the dimensions: 4096 wide on 2048 high. The resolution is 250.

The thing is, I want to print the file (external company will do that)
The desired dimension I would like to have is: 120 cm x 80 cm (or 47.2 inch on 31.4 inch)

So what I did is, I changed the image-size to 120x80 cm (11811px by 7874px) as I would like it to have.
The quality of the image is still good, I'm just not sure if I'm doing it the right way and if it's nessecairy that I do this.
What is disturbing me is that the image-size went up from 35 MB to 1.2 GB

I've searched some on the web for tutorials and tips and I'm reading all different kind of things when it comes to resolution, dimensions etc...
Apparantly most people struggle with this.
Some forums claim that if I want an image to be printed at 120 x 80 cm, I need to make it at 240 x 160 cm (which would result in a 2.5 GB file - sigh)

So anyone who has experience with printing or preparing documents in Photoshop for large printing, I'm very happy to hear your expertise on this.

Thanks.

interested overhere too

yep, I'm no expert BUT I always tell our clients, if you want a nice high resolution print, make sure that the images are about double what you want printed. Going from an original image to double its size is never good. About the only way (I know) around that would be to decrease your dpi to say 125 or 72 from 250 while increasing the dimensions... and really... who wants that?

Vokaris would be a good one to ask this question.

Hmm.. ok, that makes sence.
The only problem is, I've made something in where I use external elements.
The external pictures are all quite large and have 230 DPI, but I think they are way too small for a 120 x 80 image.

I'm talking about this image:



The rocks are 230 DPI and have 2600 - 2000 px dimensions each. Same for the water and the clouds btw. (pictures of my own)
The background is a mixture of googled pictures and way too small resolution I'm afraid.

The image as you see it now, is 1024 - 509 px (it's a small version, just to show you an example)
Basicly, if I want to make it as you suggest (double the size), so that is 240 CM x 160 CM, I will need to go to 23600 px by 15600 px (which is insane... is it?)

Kinda desperate, but I want to make sure I get it right before I make more large ones for printing in the future

This image looks like 120x60 proportions (2:1), not 120x80 (3:2)

Since you already composited it at 4096px x 2048px, the best print you can get from it at 300 dpi will be 13.6cm x 6.8cm

The size of the externals doesn't matter at this point, since you already scaled them down in your composite (unless you kept them as smart objects at their original resolution). Or, you can start compositing from scratch at a higher resolution

For all practical purposes, if you're not looking at the printed image too close, you can get away with 200 dpi, so from this pixel size, you can print a 52cm x 26 cm.

You want to blow it up about 2 times, the default Photoshop bicubic interpolation is not your best friend. Try a spline interpolator - the Andromeda Blow-up plugin does a good job, I believe the results will be plausible

see...

anyway, always start at the dimension you need at 300dpi if you plan to go to print...my suggestion is to start over.

the double resolution thingie is for external images (scanned) if youre gonna print at 300, scan them at 600, and so on.

Thanks Vokaris for the explenation.
I had no idea...
Yes, the image you see above is 2:1, but I have a 3:2 aswell stored on my HD. It was just as an example.

So do you suggest if I want to remake this from scratch, I make it in a 240 cm on 160 cm image-size on a resolution of 300 and every external element I use, I convert to a smart object first and when all is done, resize it to 120 x 80 cm for printing?

Does that sound right or am I still seeing it wrong?

Alright, thank you.

nope, the document you will create is 120x80 @ 300dpi, the double dpi thing is for external scanned images

Alright, I think I'm getting to understand it a little bit.
Next question:

I just restarted the image from scratch, this time at 120 x 80 cm on a 300 resolution.
I imported an external and converted it to a smart object.
Then I enlarged the Smart Object a little bit, to see what it would look like.
When I click on Zoom 'Actual Pixels', it's screwed. But when I click on Zoom 'Print size', it looks quite decent.
What exactly is the difference at this point between actual pixels and Print size?
Does it have to do with my monitor-settings?

If any of your externals are low-res, try upscaling them first with a spline resizer to about their final size.

Crop a small piece (10x10cm) of an area you think doesn't look good and print it on your regular desktop printer to see if it looks ok printed. The 300 dpi mantra is only for images that you are going to see at a close distance (a photograph, magazine, etc.) Do an experiment: get a high res image, crop a piece of it, say 10cm x 15cm at 300dpi and print at the best settings for the printer. Change the resolution (not the physical size) to 200 dpi and print. Place both prints at 1m viewing distance and see it there's any difference.

Hmmm... sounds like a good plan.
Will try that.
Thx Vok!

you're sure they need such a high res? most stuff I produced this size was 720dpi with 1:10 scale. 300dpi is best for a distance between eye and object like holding a book/magazine, kind of how long your arms are. for larger distance, mostly 72 dpi are enough, like signs, posters, banners, stickers. overlarge-productions like huge posters you can find on buildings etc. are often produced with 360dpi and a 1:10 scale. but this only works with very large distance to the object. human eye has its limits!

How do you mean 1:10 scale?
You mean that when you make a poster which has to be printed at let's say 100 CM on 50 CM, you make it on 720 DPI using 10 CM on 5 CM document size?