Low light printing issue – advice wanted please

[toasty]

I just had the picture below printed 30” x 12” and there is heavy pixellation (almost 8-bit like) in the dark sky above the buildings.


Hong Kong skyline by Jason Cross, on Flickr

On screen (27in Mac) in Lightroom, there’s very little evidence of this but some banding can be seen if exposure is raised very high.

It probably won’t be noticed from a normal viewing distance but I wondered if there was anything I could have done either in-camera or in post processing to minimise this effect?

I'm assuming it's an issue with the image rather than the printing which was done by Loxley Colour.

Any ideas?

Edited by toasty on Wednesday 22 June 08:41

[Simpo Two]

May be JPG compression coupled with attempting to lift exposure on the sky, which would then reveal the artefacts. Is your monitor calibrated?

[toasty]

Simpo Two said:

May be JPG compression coupled with attempting to lift exposure on the sky, which would then reveal the artefacts. Is your monitor calibrated?

Thanks for replying Simpo. The monitor isn't calibrated, it's just a standard 5K Mac screen. Is this important for printing? My old Mac was calibrated as I borrowed the kit from a friend but didn't notice much difference. I'll see if I can borrow again or get my own kit.

Looking at the jpeg image I can make out the bands in the darkness though it's nowhere near as blocky. It's as though the printer went to 50dpi for this area but it's all in shades of dark purple and black and only really noticeable up close under light.

[Beggarall]

How big a file do you have - maybe 30" is stretching it a bit?

[toasty]

Beggarall said:

How big a file do you have - maybe 30" is stretching it a bit?

It was an 11MB jpeg from a 5D MkIII RAW File. I had another daylight picture printed and it's fine, the issue is in the very dark shading.

[Pixel Pusher]

I'd say Simpo is right. JPEG artifacts.

If you have the RAW file, it would I'm sure be a much better result printing from a 300 dpi tiff file. You could use LZW compression if you are sending it remotely for printing as this is lossless. Then ZIP it to reduce further, again lossless.

Are you printing RGB or CMYK?

30" should be no issue at all.

[toasty]

Pixel Pusher said:

I'd say Simpo is right. JPEG artifacts.

If you have the RAW file, it would I'm sure be a much better result printing from a 300 dpi tiff file. You could use LZW compression if you are sending it remotely for printing as this is lossless. Then ZIP it to reduce further, again lossless.

Are you printing RGB or CMYK?

30" should be no issue at all.

Thanks PP. I'll try re-exporting as tiff format and see if I can tell the difference.

I'm getting frames made up for the two pictures printed. If the artifacts are noticeable once framed on the wall then I might try for a reprint.

No idea on RGB or CMYK. It was whatever Loxley used.

[The_Jackal]

If there is no detail in the sky you could try selecting it, removing any colour and give it a bit of a Gaussian blur just to try reducing the chance of artefacts when printing.

[K12beano]

The_Jackal said:

If there is no detail in the sky you could try selecting it, removing any colour and give it a bit of a Gaussian blur just to try reducing the chance of artefacts when printing.

...that sounds a good call...

When you're viewing on screen, you're viewing from the RAW? I mean, before it's even converted? And even if you're looking at a viewer showing the jpeg I'm not sure your monitor will show the subtleties.

But ... Have you tried talking to the printers? A good one like Loxley might help you find the right solution???

[toasty]

I looked at the image on screen again last night and at 4:1 there's quite a bit of dark noise in the sky. ISO was at 100 so I didn't expect much. Noise reduction did help a bit but maybe I'm expecting too much from the camera.

Exporting in TIFF produced a larger file but on my monitor I couldn't really see the difference. Loxley only take JPEG so I checked all of my settings to their recommendations and apart from not sharpening for print, they were OK.

I doubt I'll get a reprint but will take on all the advice before getting some more prints done. Cheers all.

[Lynchie999]

K12beano said:

..
But ... Have you tried talking to the printers? A good one like Loxley might help you find the right solution???

Yeh, call them up they should be able to sort it out for you! they were good when i spoke to them on the phone...

[The_Jackal]

Just check your software isnt exporting jpgs at a lower compression. Make sure it is set at 100%

[Pixel Pusher]

Lynchie999 said:

K12beano said:

..
But ... Have you tried talking to the printers? A good one like Loxley might help you find the right solution???

Yeh, call them up they should be able to sort it out for you! they were good when i spoke to them on the phone...

http://www.loxleycolour.com/help/Preparation

[toasty]

Pixel Pusher said:

Lynchie999 said:

K12beano said:

..
But ... Have you tried talking to the printers? A good one like Loxley might help you find the right solution???

Yeh, call them up they should be able to sort it out for you! they were good when i spoke to them on the phone...

http://www.loxleycolour.com/help/Preparation

Thanks, I cross referenced that with my settings last night. Only the sharpen for print option was unchecked.

I'm pretty confident nobody will notice once on the wall but wanted to ensure my prep was all in order.

[Zerotonine]

First of all, excellent photo.
Not really much to add which hasn't already been said, but there was an old rule of printing which I am not certain still applies, but it used to be that if you scale your image on screen to 150%, that is what the print quality will look like.
But I have been out of the printing game for a couple of years now, and I know that the tech has improved exponentially in that time.

[Pixel Pusher]

One other thing (and this could be over thinking) but have you also considered the glass that the frame will have?

A dark subject like that would probably benefit from the clear UV non reflective glass and a non gloss finish paper stock.

[FurtiveFreddy]

I'm not sure what's described is jpg artifacting.

What dpi & bits per channel setting is the jpg you sent to the printer and does it differ from the original once you finished editing it?

Could you possibly take a close up photo of a section of the print showing the pixellation and post it here?

Edited by FurtiveFreddy on Thursday 16th June 19:02

[Simpo Two]

If uncropped, that image should be 192dpi - more than enough.

What matters filewise is pixel dimensions, compression and pixels per inch (ppi). You don't get dpi until it hits paper as digital images don't have inches, just pixels

I also think that a hi-res JPG from that camera should be more than 11Mp - so again, this points to compression IMHO.

[FurtiveFreddy]

Simpo Two said:

If uncropped, that image should be 192dpi - more than enough.

What matters filewise is pixel dimensions, compression and pixels per inch (ppi). You don't get dpi until it hits paper as digital images don't have inches, just pixels

I also think that a hi-res JPG from that camera should be more than 11Mp - so again, this points to compression IMHO.

Sure, I'm aware of these points. Just trying to simplify the question a bit.

So why would there be jpg compression artifacts visible only in some areas of the print? Is there a selective jpg option in Lightroom?

Edited by FurtiveFreddy on Thursday 16th June 20:16

[Simpo Two]

FurtiveFreddy said:

So why would there be jpg compression artifacts visible only in some areas of the print? Is there a selective jpg option in Lightroom?

Because the most compression happens in the areas of least information - in this case, the sky.

I have no idea about Lightroom; Photoshop, or at least my version, has 12 levels of compression.