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Thread: New member having trouble with downsampled image quality

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    Default New member having trouble with downsampled image quality

    Hi, I just recently came across this site and thought I might get some useful tips on improving my images, however the images posted here seems to be showing as quite poor quality on my display (5K LG Ultrafine). They are also displayed at double their actual width in the browser (1920px wide - scaled up to twice that width in screen pixels) so I guess it's not surprising they appear to be lacking sharpness - any idea why they would show at double the pixel width? I am using a Mac.

    I also see the images sizes are constrained to 1920px - which seems quite small in this day and age - unless they are intended for social media only.

    My images usually have minimal horizontal crop so they fill a 5K display - so between 5000px and 8600px wide - is it possible to downsample them to 1920px wide without loosing a lot of detail and sharpness?

    Below is a downsampled image of mine but it looks out of focus when I view it on this web site. Here is a link to the full resolution image which is best viewed on a 4K or 5K display - https://duncangroenewald.com/img/wil...2658_DxO-1.jpg - it appears to be razor sharp on my display.

    Feel free to see if you can downsample and produce better sharpness in the 1920px image as I would be interested to know how you do that.

    BTW if I view the downsampled image natively on my desktop is shows as half the size of the image in the browser and then at least looks sharp/in focus even if very small.

    Thanks.

    Name:  DAG02658_DxO-1-16x9.jpg
Views: 43
Size:  424.9 KB

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    BPN Member Andreas Liedmann's Avatar
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    Attached Images Attached Images
     
    Hi Duncan .... any better from your POV ??? I personally use a script that does all the downsampling steps for me .... it can be changed to personal needs , and the output file contains a number of layers that can be again changed , So this method is for " freaks or nerds " .... not for the one button community !!!!
    Actually for best quality I would have needed the TIF !!
    Did not care about the noise ..... quite obvious sadly .

    Cheers Andreas
    Last edited by Andreas Liedmann; 09-07-2021 at 10:11 AM.

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    Quote Originally Posted by Andreas Liedmann View Post
    Hi Duncan .... any better from your POV ??? I personally use a script that does all the downsampling steps for me .... it can be changed to personal needs , and the output file contains a number of layers that can be again changed , So this method is for " freaks or nerds " .... not for the one button community !!!!
    Actually for best quality I would have needed the TIF !!
    Did not care about the noise ..... quite obvious sadly .

    Cheers Andreas
    Thanks, yes the bird looks better than mine, noise does seem a bit more prominent in yours but some of that should be fixed in the source - I turned down luminance NR in my downsampling attempts so that won't be helping.

    I also just realised there are some other downsampling algorithms and one of them seems to look a bit more like your result does, if a little overcooked perhaps.

    Name:  DAG02658_DxO-lancos-3b.jpg
Views: 34
Size:  399.3 KB

    Still much of the detail I would usually look for in a fullscreen image is not longer present in the downsampled 1920px image, like the secondary feather detail in the near wing but I guess that's just the result of downsampling so much.

    Is there some reason for the 1920px limit, 4K seems a bit more 2021 unless you're just targeting social media?

    Name:  DAG02658_DxO copy.jpg
Views: 34
Size:  353.6 KB

    The tif file is here - https://duncangroenewald.com/img/wil...G02658_DxO.tif - it is 200+MB -

    or click here if you want the raw file (Sony A1) which is 50MB if you want to tackle the noise as well.

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    BPN Member Andreas Liedmann's Avatar
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    Hi Duncan , thanks for the reply .
    Will try to get my hands on your raw file .... but this will be later in my evening ( Europe) . So be patient I will fire you the file once I worked on it .

    As for the size limits here on BPN ... you should ask the " officials " , just think it has technical reasons !!!

    I think you use the internal PS algorithm to downsize the image ???
    I have no experience with it , so cannot tell which is the best .
    As said before i use a " script " that use the internal tools to create my " web images " .
    There are many methods floating around on Mr Google how to downsize images for the web .... I can only suggest , that you try them and find that one that suites your need .

    Cheers Andreas

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    BPN Member Andreas Liedmann's Avatar
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    Hey Duncan .... just opened the raw
    Killer shot !!!!!!
    Will try to do my best .....

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    Quote Originally Posted by Andreas Liedmann View Post
    Hey Duncan .... just opened the raw
    Killer shot !!!!!!
    Will try to do my best .....
    Yes I though that sequence was pretty decent, it seemed to have the best light angle and resulting sharpness and detail. The background could have been better - there are quite a few more like that here

    No rush btw as we are in permanent lockdown it seems so I am finding ways to reprocess old images - there is always something new to learn!!

    I don't usually spend much time on post processing - there is a fibre on the lens or sensor just above the head which I never bothered to remove - but you have probably noticed that.

    Anyway I will be interested to see what you come up with both on the 1920 downsample and a full resolution version if that happens to be part of your workflow.

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    So it seems that half the problem is the following:

    Most websites aren't designed for retina displays and only have 1x assets. If these 1x assets were drawn at native resolution on a retina display, they would appear at one quarter the size (half the height, half the width). That would obviously be impractical: it would be like browsing the web with your browser's zoom level set to 25%.

    To get around this, the browser simply draws everything at 2x (retina) by default and then upscales any 1x assets to match. This way, websites appear at the same physical size on a retina display as they do on a non-retina display.

    So all images on this site are showing upscaled 2x and therefor look pretty average on a retina display.

    I have to zoom out 2x to see the image correctly.

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    Here is an example of the problem. Note that the second image is using the 'srcset' attribute to tell the browser to load the exact same image for retina displays. So whoever owns this web site should consider updating their code to be Retina display friendly.

    HTML SNIPPET:

    DOCTYPE html>
    <html>
    <head>
    <title>HTML5 testtitle>
    head>
    <body>
    <img srcset="xxx052.jpg" alt="Image" />
    <p>p>
    <img srcset="xxx052.jpg 2x" src="xxx052.jpg" />
    body>
    html>




    And the resulting display on a retina screen - where the browser will correct size the same image.
    Name:  Retina Images.jpg
Views: 28
Size:  269.3 KB

  9. #9
    BPN Member Andreas Liedmann's Avatar
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    Hey Duncan ... is that what you found out helping you anyhow , to sort out the problem ?
    As I cannot actually follow your problem , due to language barrier and maybe technical knowledge !!!

    Anyhow I am struggling a bit with the A1 file in terms of noise level and sharpness .... need a bit more time for getting the best from my POV from the file .

    Cheers Andreas

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    Quote Originally Posted by Andreas Liedmann View Post
    Hey Duncan ... is that what you found out helping you anyhow , to sort out the problem ?
    As I cannot actually follow your problem , due to language barrier and maybe technical knowledge !!!

    Anyhow I am struggling a bit with the A1 file in terms of noise level and sharpness .... need a bit more time for getting the best from my POV from the file .

    Cheers Andreas
    Yes, it seems this web site is running on some pretty old version of forum software that has no support for retina displays (which use 2 device pixels for each display pixel) and nor are images presented in a sized frame so Safari will scale up all images 2 times when displaying them to maintain consistent sizing with 1x displays. Perhaps whoever owns it might consider migrating to a more recent version of vBulletin if that supports more modern devices.

    Retina display users currently have two choices on this web site to get images the correct size so they appear sharp/in focus:
    1. Save images locally and then change the dpi to 144 and view in a local image viewer or
    2. Zoom out the web browser 2x - but then fonts will become very small.

    With regard to the A1 image - take as long as you want. I use DxO PhotoLab with DeepPrime noise reduction as it seems to retain a bit more fine detail and give more consistently even NR than Topaz.

    I would generally also turn down luminance NR on the subject to retain maximum detail but keep it a bit higher on the background to avoid the grey tinge.

    I can't say I can notice the noise when viewing the full resolution images in fullscreen mode, which is my IQ test, and that is usually at between 50% and 80% zoom.

    Regards

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    I'll take a look at your RAW later

    If you want the best quality from your Sony A1 I recommend using capture one pro software for RAW conversion BTW. That's what I use.


    as for posting size 1920 pixel was chosen because not all members have 4K/5K displays. some members still post 1600 pixels which is too small to view for those of us using modern displays. With 5K displays you must turn off scaling otherwise image will become larger than the screen, the fonts may become too small for comfortable viewing/typing... there is also sever storage issue, BPN doesn't have $$$ to pay for more storage that would be required for larger files but you can certainly host them externally
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