Resize Without Pattern

[nater973]

How can I resize a photo without the sensor grid pattern becoming evident?

I'm using Affinity Photo 1.8.5.703 on Windows 10. I have a 5520x8288px, 45.75MP, RGBA/16 photograph of the Milky Way. I've done lots of work on it and I've saved it as a TIFF (241 MB). At some point I'll probably print it, but for now, I'd like to add it to my SmugMug page, which means converting it to a JPG. Even exporting it as a JPG at 90% quality means the file is still very large. Typically before exporting as a JPG I'll use Document > Resize Document and scale it down. However, for this particular image, when I scale it down to 12" x 8" the sensor grid pattern (I think that's what it is) becomes very evident in the image, even when I use Lanczos 3 Non-Separable and Resample.

Any suggestions?

Thanks.

[Dan C]

Hi @nater973,

Sorry to hear you're having trouble!

This isn't something I've encountered before, so I'd like to request a copy of your file so I can look into this further.

Can you please upload your TIFF to the below link for me?

https://www.dropbox.com/request/u0wOif42gyiYgvrK3JzA

Once uploaded, please reply here to let me know.

Many thanks in advance!

[nater973]

Thanks Dan. I've uploaded both the TIFF and the resized JPG that displays the grid pattern. One thing to note-- the TIFF was created by stacking 21 NEF files in Sequator prior to working on it in Affinity Photo.

[James Ritson]

Hi @nater973, there are a couple of things to dissect here (I'm internal staff so the samples have been shared with me, hopefully that's OK?).

Firstly, are you seeing the grid pattern with a particular image viewer, or perhaps when uploaded? I've checked your output JPEG in Photo and macOS Preview and cannot see any grid artefacting. I've also tried resampling the TIFF you've provided using different resampling methods (Bilinear for softest resampling, for example) and cannot see any particular grid patterning.

What's in your layer stack when editing? Are you using any live filters for example? Perhaps try flattening your document before using Document>Resize Document to see if the results differ?

Whilst I can't see any grid patterning, I can see shimmering when moving between different zoom levels. There is a lot of high frequency content in your document as a result of the noisy sky. Have you applied some additional sharpening as well?

I would propose at the very least removing all the colour noise—this may help with your grid pattern issue, since it should hide obvious bayer pattern noise, but it will also help greatly with compression efficiency when you come to export. You can de-noise destructively (Filters>Noise>Denoise) or non-destructively (Layer>New Live Filter Layer>Noise>Denoise). Whichever method you use, just bring the Colour slider up to about 15% and you should find it gets rid of the colour noise without sacrificing your star colour information.

For export, I would also recommend using a small amount of luminance de-noising as well (before resampling your document, if you choose to do so). This will just take the "edge" off all the high frequency detail and make it more compressible. If you want to go further, some kind of low pass may help as well (e.g. small amount of gaussian blur).

Just by de-noising, I managed to halve the file size of the eventual export at full resolution (JPEG, at 90 quality): it went from 31MB to 15MB.

Hope the above helps—if the issue persists, could you perhaps capture a screengrab of however you are viewing the image when the grid pattern is visible?

Finally, to give this post some interesting visuals, here's a comparison of the image before/after de-noising in the frequency domain! You can see this by using the Scope panel (View>Studio>Scope) and selecting Power Spectral Density. Useful for finding out the frequency "composition" of your image (and potentially how noisy it is).

[nater973]

Hi James, and thank you for your valuable input. I found part of the grid pattern problem and your recommendations took care of everything else. When I received your response indicating that you weren't able to see any particular grid pattern, I was baffled. I even reproduced the issue again-- seeing the grid pattern in Affinity Photo itself-- to make sure I wasn't crazy, and it did indeed appear again. Which led me to wonder why I was seeing it but you weren't. Then I wondered it if it could be the different monitors. I do most of my work on my main monitor, which is a BenQ SW271, 3840x2160 @60Hz in Adobe RGB. After reading your response and puzzling over it, I moved the Affinity Photo window over to my Dell 1920x1200 @60Hz monitor in sRGB. I literally dragged the window over to the Dell monitor and the grid pattern disappeared-- I was able to move it back and forth and see the pattern on the higher resolution monitor. I'm not saying your monitors are low quality-- they're probably better than my BenQ; however, this indicated to me that my grid pattern was a display issue and not an Affinity Photo issue.

That said, I greatly appreciate your dissection of my photo. I'm primarily a landscape and bird photographer and had the opportunity to be in a pretty dark spot out in Nevada, USA where I took this astrophotograph. I actually used some techniques from your Astrophotography workflow video to stretch this image (admittedly a bit too far). To answer your questions/comments/recommendations:

• The image came from stacking 21 photos in Sequator. I did not do any additional de-noising in Affinity Photo prior to re-sizing.
• My layer stack consisted primarily of curves adjustment layers (I may have had a Levels one in there too). 
• I did flatten the document prior to resizing.
• I did not apply any additional sharpening because when I did so, it seemed to accentuate the stars, and I was already fighting too many stars obscuring the Milky Way.
• I went back to the document and implemented the colour and luminance de-noising you recommended. That helped the overall image quite a bit, thank you, and it alleviated the grid pattern issue when re-sizing-- even on the higher resolution monitor.
• I appreciate the tip to use the Scope panel!

I consider this issue resolved, thanks again.

Always learning,

Nathaniel

 

[James Ritson]

Hi again @nater973, that's interesting regarding the monitor difference. I have a 4K monitor which is running nearer 5K (4608x2592) before being downsampled, and I saw no issues. I wonder if your BenQ has some artificial sharpening being applied, or whether it's some kind of retina scaling issue within Photo on Windows. I'll try and hook my 4K display up to my Windows box later and see if I can reproduce it. Just something to try if you have time—in Edit>Preferences>Performance you'll see a Retina Rendering option. Does the grid pattern change/disappear if you set this to Low or High quality rather than Auto? If it prompts you to restart, you can instead just go to View>New View for your settings to take effect.

If that's the noise level from stacking, what did your original exposures look like? There's still a lot of chromatic noise in your final image which really should have been cancelled out to some degree by stacking—are you sure the image stacked successfully?

PS if you don't need star alignment (I'm guessing due to it being a wide field shot you don't), you could always try pre-processing the NEF files to 16-bit TIFFs then stacking them in Photo using File>New Stack (don't stack RAWs as you get no tonal control). With a Mean operator (default is Median) you might be surprised at the noise reduction you can achieve. Possibly worth a try anyway!

Thanks again,
James

[nater973]

Hello James, and thanks again. Indeed, the grid pattern disappeared on my BenQ monitor when I set the Retina Rendering to Low. Fascinating.

I followed your recommendation to pre-process my NEF files and then stack them using Affinity Photo (though I accidentally left the operator as Median). Re: noise, here's a comparison of a single NEF (left) vs. the stack of five TIFFs:

If I'm understanding the panel correctly, this reduced the high-frequency noise. The challenge I now encounter is that as I stretch the image to bring out the Milky way, the high frequency noise increases quite a bit and the red and green airglow explode. I'm in the process of using different methods to lessen that so that the Milky Way cloud still shines (but that's another issue).

I appreciate your help figuring out the grid pattern when resizing as well as getting a better handle on the noise.

Nathaniel

 

 

[Rebecca BC]

I am new to Affinity and want to esport SVG to my Cricut. However, I need a grid or something to know what size my designs are. For example, If I need a logo to be 2X3 inches, how do I know what size it is? Thanks!

[nater973]

7 hours ago, Rebecca BC said:

I am new to Affinity and want to esport SVG to my Cricut. However, I need a grid or something to know what size my designs are. For example, If I need a logo to be 2X3 inches, how do I know what size it is? Thanks!

Hi Rebecca,

The question that you've posted is a completely different topic than this thread. However, I think I can provide you some help.

In the Photo Persona, go to the Menu Bar at the top and select View. In the View drop-down menu, select Show Grid. I think Affinity defaults to use Pixels, so to change it to inches, look below the top Menu Bar just a bit to Units. If you change this to Inches, it will overlay a grid of inches. 

When you resize your image, the grid will change to the new size and you can know what size it is.

I tried to upload a couple screenshots of what I was explaining, but the site said it had an internal error. If you need additional explanation, please let me know.

Nathaniel

[Rebecca BC]

Thank you! I found it! Sorry, I do t know how to start a new thread…

[Alfred]

16 minutes ago, Rebecca BC said:

Thank you! I found it! Sorry, I do t know how to start a new thread…

Welcome to the Serif Affinity Forums, Rebecca.

Below the topic title at the top of this page you should see two links/buttons: ‘Start new topic’ and ‘Reply to this topic’. Click on ‘Start new topic’ to … er … start a new topic.