Printing defect: mosaic/tiny little boxes instead of blue sky

[MikeOz]

I am printing watercorolor artworks just for myself on a laser printer. 99% came fine but two of them have a defect in small area of the sky. In one place blue washes look like a mosaic/tiny squares, see attached. (this is just an illustration)

The file is in PNG format, 300dpi, bit depth: 32 and I print it in 100% size from both windows and Photoshop on HP color Laser Jet printer. The original file doesn't have this effect even if to zoom it in.

Does anyone know what could be wrong?

Thank you

 

[Craig]

Is the original file a PNG?

 

[MikeOz]

Yes, it was a PNG file... but I also tried to print PSD from Photoshop and got the same issue
It looks like my printer has this glitch with some hues of blue

 

[Craig]

If you change a PNG to a PSD you have the same thing. It's like putting a Ferrari sticker on a Volkswagen. Zoom in to at least 300% to see if you have the pixilation, if you see it there, it will print.

 

[MikeOz]

If you change a PNG to a PSD you have the same thing. It's like putting a Ferrari sticker on a Volkswagen. Zoom in to at least 300% to see if you have the pixilation, if you see it there, it will print.

Thank you Craig. your answer could be helpful. Just give me one more hint.. Here is the original file, see attached. Is there any pixilation? Honestly, I can hardly see the blue color on my monitor, while it's much better visible in print.

Thanks a lot
Michael

 

[Craig]

Is your monitor calibrated? It's there, plain as day!

 

[SlaveToTheMan]

Yeah, looks pretty horrible here too, on even a barely calibrated monitor. That image is pixellated like crazy! It's been compressed at some point, unless you want to get creative with the Brush in Photoshop, it's not going to get any better.

 

[MikeOz]

hey, thank you for your help! I appreciate it. I should probably re-scan it and calibrate my monitor.

How can you see that it was pixellated ? Well, I zoomed it in 300% and I still can't see it.

 

[MikeOz]

Yeah, looks pretty horrible here too, on even a barely calibrated monitor. That image is pixellated like crazy! It's been compressed at some point, unless you want to get creative with the Brush in Photoshop, it's not going to get any better.

how do you know that it was compressed. I took the scan, processed it Photoshop to make it 5"x7" and 300dpi and saved it in PNG format.

 

[Craig]

Why did you save it as a PNG? Just print the tiff. Make sure you scan it at the proper resolution. Scan it at 100% the size you want it, at 300dpi. Don't take a 72dpi scan and re-size it to 300dpi in photoshop. Remember the "putting a Ferrari sticker on a Volkswagen" thing. It applies there too.

 

[gordo]

It also looks like some strong jpg compression has been applied.
If you increase the contrast it looks like this:

Very similar to the effect of high compression (on the right) compared with the original on the left below.

The effect would be exacerbated if you resampled the image in PShop to get the resolution you wanted.

gordo

 

[MikeOz]

Thank you Gordo, this is very helpful for me. Now I see it too.

 

[Possumgal]

png files are proper for the web, not print. Try tiff, EPS, or native Photoshop, or even PDF. Your printer will love you.