Re: [darktable-user] Noisy exports

[Matthieu Moy]

Explaination: when your image has more pixels than your screen, there are 
several ways to reduce its size to have it fit on screen. The naive way is to 
just do nearest pixel subsampling: for each pixel on screen, grab the pixel 
that is the closest on the image. And throw away all other pixels in the 
original image. This amplifies noise, or at least it does not reduce it while 
subsampling normally does. And it tends to give overly sharp and pixelized 
edges (like font rendering without antialiasing). Less naive methods include 
bilinear and cubic, and the most widely used high-quality algorithm is lanczos.

Gimp and Darktable obviously use a good quality resampling algorithm. Web 
browser started only rather recently to do so (when possible, rescaling the 
picture on the server is better to get full control on how it's done regardless 
of the browser).

- Original Message -
> Hi,
> 
> I think you nailed it. I installed gimp and exported images look much
> better in gimp. I'll try opening in a browser when I get a chance to see
> what shows up.
> 
> Regards,
> 
> Niranjan
> 
> On 08/24/2016 05:10 PM, Jason Polak wrote:
> > If your exported image is being viewed at the same zoom as in the
> > darkroom, can you check whether it still looks noisy in the gimp? Some
> > version of image viewers on Linux don't render large resolution images
> > "correctly".
> >
> > If it looks ok in the GIMP, then it's the image viewer's fault.
> >
> > On 16-08-25 09:44 AM, Niranjan Rao wrote:
> >> Greetings,
> >>
> >> I am new to raw image development and trying to figure out what I am
> >> doing wrong.
> >>
> >> My main problem seem to be stemming out from the fact that when I export
> >> the image, it does not look like image in darkroom screen. I am trying
> >> to process images generated by Canon PowerShot SX60 HS. Exported image
> >> always felt more noisy or grainy.
> >>
> >> A little bit of experimentation and tinkering of many knobs, I figured
> >> that exported image quality seems to be function of size. If I leave
> >> exported size to 0, darktable exports in default size (in my case, it's
> >> 4768 X 3516), exported images look grainy. If I export in smaller size -
> >> say 1600, they look much nicer.
> >>
> >> Is this normal - having noise in default sized exported image and
> >> looking cleaner in smaller image? Is there anything I can do to address
> >> this issue?
> >>
> >> Alternatively, what would be good or usual size to export the image? I
> >> am just a home user of camera and darktable, rarely print my images and
> >> images are used only for viewing by family and sharing across various
> >> mediums such as facebook and WhatsApp.
> >>
> >> I on Ubuntu 16.04, using darktable version 2.0.3 from standard ubuntu
> >> repositories. I am using standard Ubuntu image viewer to view exported
> >> image.
> >>
> >>
> >> Best,
> >>
> >> Niranjan
> >>
> >> 
> >>
> >>
> >> darktable user mailing list
> >> to unsubscribe send a mail to
> >> darktable-user+unsubscr...@lists.darktable.org
> >>
> > 
> >
> > darktable user mailing list
> > to unsubscribe send a mail to
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> >
> 
> 
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> 
> 

-- 
Matthieu Moy
http://www-verimag.imag.fr/~moy/

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Re: [darktable-user] Noisy exports

[Jason Polak]

If your exported image is being viewed at the same zoom as in the 
darkroom, can you check whether it still looks noisy in the gimp? Some 
version of image viewers on Linux don't render large resolution images 
"correctly".


If it looks ok in the GIMP, then it's the image viewer's fault.

On 16-08-25 09:44 AM, Niranjan Rao wrote:

Greetings,

I am new to raw image development and trying to figure out what I am
doing wrong.

My main problem seem to be stemming out from the fact that when I export
the image, it does not look like image in darkroom screen. I am trying
to process images generated by Canon PowerShot SX60 HS. Exported image
always felt more noisy or grainy.

A little bit of experimentation and tinkering of many knobs, I figured
that exported image quality seems to be function of size. If I leave
exported size to 0, darktable exports in default size (in my case, it's
4768 X 3516), exported images look grainy. If I export in smaller size -
say 1600, they look much nicer.

Is this normal - having noise in default sized exported image and
looking cleaner in smaller image? Is there anything I can do to address
this issue?

Alternatively, what would be good or usual size to export the image? I
am just a home user of camera and darktable, rarely print my images and
images are used only for viewing by family and sharing across various
mediums such as facebook and WhatsApp.

I on Ubuntu 16.04, using darktable version 2.0.3 from standard ubuntu
repositories. I am using standard Ubuntu image viewer to view exported
image.


Best,

Niranjan



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[darktable-user] Noisy exports

[Niranjan Rao]

Greetings,

I am new to raw image development and trying to figure out what I am 
doing wrong.


My main problem seem to be stemming out from the fact that when I export 
the image, it does not look like image in darkroom screen. I am trying 
to process images generated by Canon PowerShot SX60 HS. Exported image 
always felt more noisy or grainy.


A little bit of experimentation and tinkering of many knobs, I figured 
that exported image quality seems to be function of size. If I leave 
exported size to 0, darktable exports in default size (in my case, it's 
4768 X 3516), exported images look grainy. If I export in smaller size - 
say 1600, they look much nicer.


Is this normal - having noise in default sized exported image and 
looking cleaner in smaller image? Is there anything I can do to address 
this issue?


Alternatively, what would be good or usual size to export the image? I 
am just a home user of camera and darktable, rarely print my images and 
images are used only for viewing by family and sharing across various 
mediums such as facebook and WhatsApp.


I on Ubuntu 16.04, using darktable version 2.0.3 from standard ubuntu 
repositories. I am using standard Ubuntu image viewer to view exported 
image.



Best,

Niranjan


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Re: [darktable-user] Lighttable Performance on Mac

[Rafa García]

2016-08-24 22:20 GMT+02:00 Leander Hutton :

> I also prefer to get things right in camera, but that isn’t always an
> option.
>
>- "Leaving aside OpenCL, I think latest dt (2.0.5) uses a GTK version
>which doesn't work well with Mac (bad perfomance and usability problems)."
>
> I think this is another big issue for me. This is why drop down menus (new
> instance, duplicate instance, etc.) hang or don’t work at all.
>
> Let me know if you have any luck with gfxCarStatus app. I’ll try reverting
> to 2.0.4 and see if that helps.
>
>
>
> Sorry it took me so long to get back to this, but I did do some testing
> with OpenCL and the M370X on 2.0.4. DT 2.0.5 is slow on OS X no matter how
> you cut it.
>
>
That's true. I profiled darktable 2.0.4 and 2.0.5 using dt-cli (command
line interface). It gave me more or less same times. Then I wondered it
could be a problem with GTK+



> To make things even I started with a fresh library.db file each time and
> imported a directory of 22 RAW files. I also removed the XMP files between
> each run just to make sure it everything was exactly the same. One log is
> from CPU only mode and the other is with OpenCL enabled and the M370X
> forced into use via gfxCardStatus. I did see a measured improvement in
> thumbnail rendering times according to the attached logs. It still felt
> slower in use with OpenCL enabled but the data doesn’t reflect that.
>


I also did some tests with OpenCL enabled and disabled (I'm using a Intel
Iris graphic) and dt-cli versions 2.0.4 and 2.0.5. Times with OpenCL were
~1.5 faster than CPU in both versions.



>
> Sadly, I did see the green rendering with OpenCL enabled on the M370X
> however it was limited to Nikon RAWs. The Fuji files were mostly OK outside
> of a few that looked like they had a blur effect applied to them (see the
> attached screen capture). After disabling OpenCL both of those bugs
> disappeared. Has anyone else noticed the  blurring on OS X? Has a bug
> report been filed on it? None of my Nikon RAWs had the blur effect going
> on. Anyone out there with an OpenCL capable nVidia card on OS X and want to
> give this a go to see what happens? I may look into sticking an nVidia card
> in my old Mac Pro and seeing what I come up with there.
>

With Intel Iris graphic card I don't have blur effect in previews but I
have green rendering.
It's reported as issue for Intel graphic cards.

I didn't know it only happens with Nikon NEF files.

Regards


>
> Thanks again!
>
> Leander
>
>


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