PNG file sizes much smaller 2020 vs CC 2017?

[JaddahKing]

I make designs for print-on-demand t-shirts. The printing company accepts PNG files (and JPG which I don't use).

Saving in PS CC2017 using Save As... PNG with no compression gave me huge files typically over 20MB at 3,000 x 3,000 (300 dpi).

Saving similar files (text on transparent backgrounds) in PS 2020 using Save As... PNG Large File Size (fastest saving) is gving me files of less than 1MB at 3,000 x 3,000 (300 dpi).

Everything seems okay as far as stated size and resolution but the disparity has me scratching my head and I don't want to run into a problem with printing that I can't see from lack of knowledge.

Was there some sort of massive improvement in PNG saving implemented from CC2017 to 2020? Was my CC2017 just whacky?

Thanks for your attention,

JD

[Test Screen Name]

"Saving in PS CC2017 using Save As... PNG with no compression" I have no idea what you mean by this. PNG is always compressed, there is no such thing as a PNG without compression.

[JaddahKing]

Sorry. I no longer have CC2017 installed and I was trying to recall the terminology on the popup at the end of the Save As procedure. I guess I remembered it wrong.

There are three choices, similar to the choices in 2020 but worded differently. Whatever the popup says in that version that will give the largest file with least compression.

Thank you,

JD

[Abambo]

Looks like you are saving as JPEG with PNG extension. Could you post one of your 1-mega files here as attachment?

BTW: Correctly done, there is no drawback using JPEG against PNG for the final output picture, except that PNG allows for transparency, if that is important.

[JaddahKing]

Here is one of my PS 2020 "Save As... PNG, Large File Size (fastest saving)" files, as requested.

I do need the transparency, to avoid printing the backgrounds.

Thank you,

JD

[Test Screen Name · Accepted solution]

Ok, it is indeed a 3000 x 3150 PNG. Hmm. I tested with Photoshop 2017 and found some interesting things.

1. Photoshop does indeed offer a choice of "None/ Fast" even though it's nonsense to talk of "None"! 

2. Your file has large expanses of white, and other solid colour which should compress extremely well. I created a 10,000 x 10,000 pixel, entirely white image and saved it as PNG. "None/fast" - 286MB. "Smallest/slow" - 323KB.  So the first setting made a file 900 times larger. This is extraordinary. [One might almost imagine that, having made a new "smallest" setting and being disappointed by it, that the programmers deliberately broke the normal setting to make the new one look better]. Anyway, what this shows is that PNG compression is broken in PS 2017, not that it's wrong in PS 2020!

[JaddahKing]

Anyway, what this shows is that PNG compression is broken in PS 2017, not that it's wrong in PS 2020!

By @Test Screen Name

This is a load off of mind and a load off of my bandwidth!

Thank you so much for your time and your help!

JD