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Posted

Hi folks,

I am wondering about the differences, especially coloring, between an astro AP doc V1 and its exported 100% files. The astro files derive from Tel. Live. , 10 SHO fits.  Using Preview a screenshot of the AP screen looks much better. Here are comparisons showing the muddy result with an exported jpg and a result with bright colors on the AP screen

Thanks for any help and regards, Irving

preview sc jpg2.jpg

preview sc2.jpg

Posted

Hi,

as no one answered I try to step in.

A few common causes:

  • color profile issues. 
  • color format issues. Exporting directly from RGB/32 to jpeg. RGB/32 can contain lightness above 1.0 and uses linear Gamma. The „downgrading“ to jpeg can lead to clipping in lightness and color gamut.

we would need more information about the actual file. Upload it if possible. To reduce file size, save a copy, then flatten, delete all snapshots, and save without history. Provide screenshots of export settings used to create jpeg.

which Mac HW, OS version, and Display do you use?

 

in general, try to make a copy of the file, convert to RGB/16, export again and inspect.

Mac mini M1 A2348 | MBP M3 

Windows 11 - AMD Ryzen 9 5900x - 32 GB RAM - Nvidia GTX 1080

LG34WK950U-W, calibrated to DCI-P3 with LG Calibration Studio / Spider 5 | Dell 27“ 4K

iPad Air Gen 5 (2022) A2589

Special interest into procedural texture filter, edit alpha channel, RGB/16 and RGB/32 color formats, stacking, finding root causes for misbehaving files, finding creative solutions for unsolvable tasks, finding bugs in Apps.

I use iPad screenshots and videos even in the Desktop section of the forum when I expect no relevant difference.

 

Posted

Hello to Hamburg,

I am sending info as requested.

The RGB-16 conversion made the picture almost go away in the dark.

Flattening reduced the size from 573mb to 402mb. I guess too large to send.

Here are 2 shots of the iMac specs and one of the jpg settings on AP.

This is the first time I have had problems with astro jpgs, except once I noticed too many stars.

Recently I have found that I can make a screenshot with Preview and then export a jpg from Preview, which gives a good result. Maybe this should somehow be mentioned by AP.

Thanks for your help and regards, Irving

Screenshot 2023-10-07 at 09.30.00.png

Screenshot 2023-10-07 at 09.31.42.png

Screenshot 2023-10-07 at 09.33.56.png

Posted
20 minutes ago, irandar said:

The RGB-16 conversion made the picture almost go away in the dark.

This should not happen.

Please check „32-bit preview“. Can you provide a screenshot?
 

 

Mac mini M1 A2348 | MBP M3 

Windows 11 - AMD Ryzen 9 5900x - 32 GB RAM - Nvidia GTX 1080

LG34WK950U-W, calibrated to DCI-P3 with LG Calibration Studio / Spider 5 | Dell 27“ 4K

iPad Air Gen 5 (2022) A2589

Special interest into procedural texture filter, edit alpha channel, RGB/16 and RGB/32 color formats, stacking, finding root causes for misbehaving files, finding creative solutions for unsolvable tasks, finding bugs in Apps.

I use iPad screenshots and videos even in the Desktop section of the forum when I expect no relevant difference.

 

Posted
23 minutes ago, irandar said:

Flattening reduced the size from 573mb to 402mb. I guess too large to send.

I forgot to mention one step:

use „save as“ to create another copy. This should be much smaller (about 130MB), 16 bytes per pixel.

Mac mini M1 A2348 | MBP M3 

Windows 11 - AMD Ryzen 9 5900x - 32 GB RAM - Nvidia GTX 1080

LG34WK950U-W, calibrated to DCI-P3 with LG Calibration Studio / Spider 5 | Dell 27“ 4K

iPad Air Gen 5 (2022) A2589

Special interest into procedural texture filter, edit alpha channel, RGB/16 and RGB/32 color formats, stacking, finding root causes for misbehaving files, finding creative solutions for unsolvable tasks, finding bugs in Apps.

I use iPad screenshots and videos even in the Desktop section of the forum when I expect no relevant difference.

 

Posted
53 minutes ago, irandar said:

The flattened file is about 170mb smaller but still 400Mb

Please try to upload if possible. Otherwise, crop to a small section with relevant colors, flatten, and save as again to a new file of far smaller size.

Mac mini M1 A2348 | MBP M3 

Windows 11 - AMD Ryzen 9 5900x - 32 GB RAM - Nvidia GTX 1080

LG34WK950U-W, calibrated to DCI-P3 with LG Calibration Studio / Spider 5 | Dell 27“ 4K

iPad Air Gen 5 (2022) A2589

Special interest into procedural texture filter, edit alpha channel, RGB/16 and RGB/32 color formats, stacking, finding root causes for misbehaving files, finding creative solutions for unsolvable tasks, finding bugs in Apps.

I use iPad screenshots and videos even in the Desktop section of the forum when I expect no relevant difference.

 

Posted

@Lee_T  Hi, Here is a related problem regarding the quality of exported jpgs. I am adding two jpgs, one exported from AP and one obtained using Preview on my iMac to make a screenshot and exporting this, which gives a much better result. Thanks for your help, Irving

PS the original afphoto file is 303MB

DSC07596 barlow.jpg

DSC07596 barlow prev.jpg

Posted

Check the export settings. Is quality 100% or 1%?

One is 6 MB (the brighter one), one only 64 KB large (the darker one), and has much smaller pixel size.

If you want to compare quality, ensure that both files have exact same pixel size, and viewed at 100%.

Which do you rate as „better“?

 

Mac mini M1 A2348 | MBP M3 

Windows 11 - AMD Ryzen 9 5900x - 32 GB RAM - Nvidia GTX 1080

LG34WK950U-W, calibrated to DCI-P3 with LG Calibration Studio / Spider 5 | Dell 27“ 4K

iPad Air Gen 5 (2022) A2589

Special interest into procedural texture filter, edit alpha channel, RGB/16 and RGB/32 color formats, stacking, finding root causes for misbehaving files, finding creative solutions for unsolvable tasks, finding bugs in Apps.

I use iPad screenshots and videos even in the Desktop section of the forum when I expect no relevant difference.

 

Posted

Hi NMF, They were both 100%. The larger file is from an AP export, the smaller from a screenshot with Preview. This was best, but cannot be really seen here.  Thanks and regards, Irving

Posted

Hi,

i don’t think it makes much sense to compare screenshots of an Image in RGB/16 or RGB/32 format with export to jpeg (always RGB/8).

The image rendered in Affinity while the App is open cannot show exactly how the exported image will look for various technical reasons:

  • color depths can vary, and be smaller in export
  • color gamut can be clipped due to limitations of export file format
  • Zoom level other than 100% leads to perceived sharpness or blurriness 
  • RGB/32 with unbound color values cannot be 1:1 exported to certain file formats (RGB/16 and below)

There are additional limitations of Affinity, partially bugs, but this do not play a role in your examples:

  • Affinity unable to render 16 bit color depth in canvas (but it will correctly export), leading to banding
  • Mipmap rendering will cause severe rendering artifacts for any zoom level except 100%
  • white lines may appear at the edge of documents
  • bitmap exports with size rescaling may look different due to resampling of layers
  • Forced  dithering of gradients at export

Mac mini M1 A2348 | MBP M3 

Windows 11 - AMD Ryzen 9 5900x - 32 GB RAM - Nvidia GTX 1080

LG34WK950U-W, calibrated to DCI-P3 with LG Calibration Studio / Spider 5 | Dell 27“ 4K

iPad Air Gen 5 (2022) A2589

Special interest into procedural texture filter, edit alpha channel, RGB/16 and RGB/32 color formats, stacking, finding root causes for misbehaving files, finding creative solutions for unsolvable tasks, finding bugs in Apps.

I use iPad screenshots and videos even in the Desktop section of the forum when I expect no relevant difference.

 

Posted

If you really want to check if exports differ in a relevant way from the content of a document, this needs a different approach.

  1. Screenshots are usable for comparison only if you take them from the same app, using the same rendering settings (e.g. view mode and document color format). 
  2. the best way to check export quality of Affinity apps is to export them in 2 formats, one that stores bitmap images in all relevant aspects like uncompressed, sporting alpha channel, and having full bit depth of document, and color profile. Depending on circumstances, PNG or TIFF are best suited. Those exports will contain every single pixel of your document in full color and bit depth.
  3. choose the other format like jpeg, jpegxl, wich you suspect to be flawed, and export again.
  4. now create a new stack of both documents. Put the tiff/png on bottom, and the other on top.
  5. set blend mode of top to difference. You m any add a levels adjustment  on top with white level set to 10% to boost values by factor 10.
  6. now you can spot any difference with info panel. Use channel panel to inspect individual channels, including alpha.
  7. Exports need to have identical pixel size.
  8. for jpeg, you will easily spot compression artifacts like 8 bit colors (banding), 8x8 mosaic, etc

Mac mini M1 A2348 | MBP M3 

Windows 11 - AMD Ryzen 9 5900x - 32 GB RAM - Nvidia GTX 1080

LG34WK950U-W, calibrated to DCI-P3 with LG Calibration Studio / Spider 5 | Dell 27“ 4K

iPad Air Gen 5 (2022) A2589

Special interest into procedural texture filter, edit alpha channel, RGB/16 and RGB/32 color formats, stacking, finding root causes for misbehaving files, finding creative solutions for unsolvable tasks, finding bugs in Apps.

I use iPad screenshots and videos even in the Desktop section of the forum when I expect no relevant difference.

 

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