How to change my file from A3 to A2 and keep the best quality?

[alfie285769162t0j]

I'm making a poster which at first I had intended to print in A3 size. So I created a 300dpi photoshop file with 297mm x 420 mm which is 4961px x 2508px.

Now, I'm thinking I want to print it at A2 size. So I guess one option is to keep creating the file at 4961px x 2508px, and print it scaled. Am I right that this will be 150dpi and therefore wouldn't be noticeably any worse quality because quality printers have a maximum of around 150dpi.

The file contains many png images. Most of which are scaled down a lot, so if they were to be doubled in size, they wouldn't be any lower resolution.

Or is there a way to scale my photoshop file and have all the layers and objects be redrawn so they are at the best quality?

What's the best way to do this?

[kevin stohlmeyer · Accepted solution]

Hi @alfie285769162t0j 

This page gives an overview of options:

https://helpx.adobe.com/photoshop/using/resizing-image.html

There is also the SuperZoom Neural Filter, you can create a smart object combining all your layers then enabling that feature to help with the low res layers.

https://www.youtube.com/watch?v=bL-x6GIDL7o

[davescm]

The file contains many png images. Most of which are scaled down a lot, so if they were to be doubled in size, they wouldn't be any lower resolution.

Yes they will, unless those higher resolution images have been placed as Smart Objects. Ordinary layers are scaled down and the excess information discarded, so scaling back up does not replace that information.

That said you have two choices.

1. Increase the size without resampling which will give 150ppi. That has the advantage that no scaling artifacts will be introduced but there is a small risk that when viewed very close then the pixel structure might be visible. However you really would need to stand close - good eyes could resolve 150ppi at 45 inches whereas 300ppi would be 23 inches. (both are the equivalent of 60 lines pairs per degree).

2. Resample to A2 at 300ppi. That does not replace missing picture information, although placed smart objects will be recalculated,  but interpolates the missing data from that image data which exists. Different algorithms do that in different ways and some can look good. All though do introduce their own artifacts. Whether they are obtrusive depends on the content.

Dave

[alfie285769162t0j]

I see. I can't seem to work out if my images are smart objects or not. How can I tell? I have an option to convert to smart object but the same option is there even when I click to convert it.
I changed the image size to A2 at 300 dpi and it caused my computer to run very slow. So I don't really think I have any other option than to finish designing it at A3 size and then scale and resample at the end.
When I did it, it looked good. I think the objects are resampling nicely.

[kevin stohlmeyer]

Hi @alfie285769162t0j Smart Object layers have a little page icon on the lower right corner

[alfie285769162t0j]

Thank you. Yes mine are smart images, with the exception of the background which I made my filling a pattern I defined. So I guess I can just redo that one manually after the resizing.

[jane-e]

Yes mine are smart images,

By @alfie285769162t0j

To confirm they were smart objects before you scaled them, do this:

• Select SO layer
• Cmd+T for free transform
• Look in options bar (Window menu):
  does it give a percentage for the W and H?
  • If yes, change the scale to 100% for both
  • If no, choose cancel and report back to us for further instructions

Jane

[alfie285769162t0j]

Yes, it shows percentages and they can be scaled to 100%.

[davescm]

Don't bother converting ordinary layets to Smart object then upscaling. The smart object would still be limited by the layer size before upscaling.

Where it might have helped is if you had added high resolution images using Place - Embedded. In that case your smart objects could have contained images at higher pixel dimensions than displayed in your A3 image. They would have been used to create the new size when upscaling.

Dave

[NB, colourmanagement net]

I agree with @davescm - I too would try first increasing the size without resampling which will give 150ppi

IMO: 180 or 240ppi would be better if it's a commonly found Epson inkjet, since those numbers are factors of the native print resolution [maybe 2880 x 1440], maybe try 180 or 240ppi next time.

1440 / 300 = 4.8 (not a whole number, meaning pixels are invented)

Of course, first check the printer rez. some new Epsons (some SC-P models like 20,000) are, I believe, based on 1200x2400, in which case 300 or 150 would be better. 300 x 4=1,200 150 x 8 = 1,200

I hope this helps
neil barstow, colourmanagement net - adobe forum volunteer - co-author: 'getting colour right'
google me "neil barstow colourmanagement" for lots of free articles on colour management