The downsizing challenge - Part 1: The Problem

[simsurace]

I have heard from a few people that they are experiencing suboptimal results when trying to downsize a high-res image -- say, from a D810 -- to a lower resolution (for web use). The downsized images are reported to have certain qualities which are not pleasant, but sometimes hard to describe.

It has been said that software has not kept up with this challenge and that it is hard to find the correct downsizing method for those images.

Another related problem is that high-res images are sometimes badly displayed by some software for previewing/culling. Since the software has to downsize the image to display it on a monitor with a much lower resolution than the image itself, the same downsizing challenge applies behind the scenes.

Of course, we have to realize that any digital image cannot properly represent detail which exceeds the Nyquist frequency, therefore we might have to reset our expectations accordingly. But we should not be getting worse results out of the high-res file compared to a lower-res file, e.g. the same scene shot with a D800 vs. a D700 should not look worse when downsized to web resolutions unless the downsizing was done in a suboptimal manner. What I understood from some people is that they are finding it hard to match the results obtained with lower-res cameras, and this is where this thread comes in.

I think it is important to thoroughly understand the problem first, for there might be several individual problems for which separate solutions have to be found. Personally, I have not experienced these problems (despite not having a 36mp cam, I have worked on panos that measure several hundreds of megapixels and I have downsized them quite successfully IMHO), so I might first need to be educated about the problems others are perceiving.

Here, my aim is to collect examples of downsizing to try and identify the problem and how it manifests itself. If you are experiencing problems when downsizing high-res files, please post an example. If possible, please make available the raw/full-res file (e.g. on dropbox or via some other hosting service) as well as your attempt at a downsized version (jpeg). If you can, please try to describe what you don't like about the downsized version.

When we have collected enough examples, we will try to find a workable solution to solve the problem. Other forum participants will be able to take your full-res file and come up with their downsize, and you will be able to judge whether an improvement has been made over your own attempt. The concept I have in mind is very similar to the RAW editing challenge, but more specifically geared towards downsizing.

[Ron Scubadiver]

I think a lot of it has to do with how the image is sharpened. 

[Andrea B.]

I'm very interested in this. I'll get back with a couple of examples this weekend. I'm still getting caught up on the domestic front after being gone 2 weeks on the Scotland NG Meetup.

[elsa hoffmann]

I am experiencing the same issue with downsizing. Images don't appear sharp. 99% of the time I dont have to sharpen my images at all - (when processing the high res) so for me it can't be an issue due to how I sharpened

[the solitaire]

For my girlfriend (not able to post here herself due to lacking English skills, especially when it comes to technical explainations) the biggest problem is tha images that appear perfectly sharp on a pixel level on her computer, even when converted from NEF to JPG, appear completely out of focus when subsequently uploaded to facebook. Since she uses facebook as the main portal to portray her work we have been looking into a solution for this for quite some time.

It does not happen with all images, but a considerable amount.

To the tehcnical details, she uses a D800 to shoot lossless compressed 14 bit NEF files
I will make a file available later today. Need to upload it to dropbox which given my slow internet connection will take a while.

I will also post a link to the uploaded file on facebook.

I think this here will be a good example.

https://scontent-fra3-1.xx.fbcdn.net/t31.0-8/13115992_878889058903527_8707603759883841782_o.jpg

Any help in how to prepare the file for an upload on facebook and ending up with a representation of the file that appears sharp is greatly appreciated.

Here is the NEF to the picture
https://www.dropbox.com/s/ozr8i2zt04pwhy3/DSC_5551.NEF?dl=0

And the processed JPG

https://www.dropbox.com/s/04z2me0zyeng1yc/DSC_5551-Bearbeitet.jpg?dl=0

[Erik Lund]

I learned long time ago, talking to Graphical designers and printer guys, to shoot/stitch at the desired size needed for the image reproduction, still holds true.

I use Photoshop - Image size 'Bicubic - Sharper' for my D810 images.

BTW do it in small steps - Several reductions instead of only one resize!

I think it does a great job,,,

[John Geerts]

Yes, agree Bicubic - Sharper can do great things. 

However if I want to control contrast-sharpness for the final print-size  I use the Image Size 'Bicubic - Smooth Gradients' in Photoshop and apply sharpness (if necessary) later at the desired size. Especially for images with a lot of bokeh (fast lenses) and lots of contrast.

[Andrea B.]

Yes, sharpening is a big factor in the resizing process.

I was one of the people at the Meetup talking to Simone S. about resizing. I've been unhappy with my D810 resizes. I know the pro shooters have lots of experience already with resizing. For some of us however, a good experiment is in order which tests all the various resizing advice we have received over the years, don't you all think so??  In particular for me - who only occasionally manages to sell a stray photo or two - this will be a very valuable experiment because I really would like to make better use of my D810. (I loved 16 MP. Got used to 24 MP. Never have quite adjusted to 36 MP.)

*******

FIRST TRIAL
For an initial trial, I went out this morning and made 3 photos from a 16 (Df), 24 (D750) and 32 (D810) MP camera. (The camera brand is irrelevant here, btw.) All 3 photos were made with the same lens (same field-of-view mostly) and the same aperture, ISO and other camera settings. Some of those camera settings are irrelevant to the raw file (depending on your choice of converter), but I will list them anyway. The field-of-view is a bit choppy between the 3 photos, so I hope it is acceptable.

Lens: Nikon 28/1.8G
Tripod:  Yes

Picture Control:  Standard 0 with only Sharpening set to +3.
White Balance:  Auto1
Metering:  Matrix
Mode:  Manual
ADL: Low
AF: AF-S, focused in Live View on same spot as best I could.

Aperture:  f/8
ISO:  100
EV:  0
Speed: got one @ 1/25" & two @ 1/30". I accepted the cameras suggested matrix-metered speed. The Df really should be at 1/30" though as it is a tad too bright compared to the other two. Oh well.

Subject:  I photographed a green shrub in morning light for LOTS of detail. Boring, but it will perhaps serve the purpose here. I am happy to supply later some other subjects for resizing tests if suggestions are offered. Fences? Flowers? People? Landscapes? Close-ups? Cats?? <lol>

Now let me get organized to work on this......

Simone S, a question about conversion: I'm thinking that in this first trial, I'll use the conversion software supplied by the manufacturer because it preserves in-camera settings. There will be no edits. The output will initially be a TIF so that different resizer tools can be tested. I'll add the converted TIFs to the Drobox cache with the NEFs. Does this sound OK?

Simone S, a question about resize size:  What size shall we agree on for posting a resized photo? 800, 1000, 1200 pixels width??

TESTS to be performed:
(we can perhaps make this more precise?)

• Well resizing of course. That's why we're here in this thread. But some details would be useful.
• Tests like sharpening before resizing or sharpening after resizing. Or both. Or none.
• Different types of resizing. [bicubic, next door neighbor, bicoastal flyover, random dice roll, etc. Yes, I jest. Do see: https://en.wikipedia.org/wiki/Image_scaling]
• Blur before resizing? How much?
• Lo-pass filter before resizing? How much? Is this already in some sharpeners?
• Upsize then downsize? Up-res then down-res?

DROPBOX LINK:  https://www.dropbox.com/s/emtjail7mbru4bg/Resize_Challenge.zip?dl=0
The field-of-view is a bit choppy between the 3 photos, so I hope it is acceptable.
Note that the camera was leveled, but the fence is not particularly straight in actuality.
If these photos are not suitable for the Resize Challenge, then I'm happy to reshoot.


Andrea Resize Test One:  Resized NEFs to 800 pixels width in Capture NX-D and saved as JPGs. No edits before or after.

Ok, that simple resize test drive took a little Detour to Software H3ll.
Check out this attached screenshot.
What filetype do you suppose that Capture NX-D can open??
Inquiring minds wish to know.

I'm now out of time and will return later after I've run mountains of errands, cleaned the kitchen, spoken to the long-suffering SigOth and cooled down from dealing with the World's Stupidest Converter Software.





 

[Andrea B.]

Andrea Resize Test One:
Conversion of NEF and 800-pixel resize of Df, D750, D810 raw photos in Capture NX-D with no edits.
There was a bit of preserved in-camera sharpening in this baseline view.

1. Df (16MP)
2. D750 (24MP)
3. D810 (36MP)

[Tristin]

I have found the best results yielded by upsizing the image using the smoother method, then downsizing incrementally with the sharper method. 

[Andrea B.]

Three files await application & display of your method. See Dropbox link above.
And what software are you referencing with the "smoother method" and the "sharper method" please??
(Not all of use use the same apps.)

[Alaun]

I use a "one click" method   (see picture below)

The final sharpening is (has to be) done on the final image size (the downsized picture)

Downsizing with bicubic method in one step

Sharpening of the final picture with a high pass filter 1pixel (may be 0.8 or 1.2 pixels depending on final size) overlay soft light mode

OOC jpgs need to be done without  (or only little) sharpening, else the downsized will look bad

All in all very simple and effective according to my experience

[Alaun]

Andrea, the link says no file available (404)

[Andrea B.]

Andrea Test Two:  Here is a conversion and resize of the converted TIF using Photo Mechanic with no additional sharpening.
Do these look better, worse or the same as the Capture NX-D resized photos above?

1. Df (16MP)
2. D750 (24MP)
3. D810 (36MP)

[Andrea B.]

Werner, thanks. I will repair that link right away.

ADDED:  dropbox link repaired

Here it is again.

DROPBOX LINK:  https://www.dropbox.com/s/emtjail7mbru4bg/Resize_Challenge.zip?dl=0