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    <allpages gapcontinue="Reproducing_a_painting_or_artwork_-_370" />
      <page pageid="2076" ns="0" title="Reducing Random Noise from Small Sensors">
          <rev contentformat="text/x-wiki" contentmodel="wikitext" xml:space="preserve">Every photographer knows that the most expensive part of a good camera is its lens.  Lenses are expensive because we have become accustomed to sharp pictures, and there is an inescapable compromise between light-gathering power, image size, cost and sharpness of a lens.  Over the past few decades manufacturers have reduced the cost of lenses by reducing the image size.  I no longer hear of large-format cameras--though some large-format digital cameras exist, they are speciality items.  Medium-format cameras use a 2-inch by 2-inch (50 mm by 50 mm) image size.  The Hasselblad H3D-39II [;rs=172282&amp;keywords=Hasselblad%20&amp;rh=n%3A172282%2Ck%3AHasselblad%20%2Cn%3A502394]  is a good (but very expensive) example of a medium-format digital camera.

The industry standard for professional cameras uses an image size of 24 mm by 36 mm.  The size was originally chosen because it matched 35-millimeter movie film, and it was smaller than medium-format.  Good digital cameras today use this same size for their sensors.  However, manufacturers are reducing lens cost by using even smaller sensors.

Although reducing sensor size does a very good job of reducing the cost of a lens, the disadvantage of a small sensor is increase in thermal noise.  To get good resolution you need lots of light-sensing elements.  To fit them on a small sensor they need to be small, and that means they are noisier.  Again, physics imposes a barrier on camera design.

Thermal noise is random; you will get different noise on each picture.  The obvious solution is to average out the noise.  This can be done using layers and transparency in The Gimp or Adobe Photoshop, but it is easier to do using Autopano Pro.

I photographed a garage on a cold day in February, 2007, using an inexpensive digital camera.  The picture is too large for this wiki, but here is small part which shows a light fixture surrounded by smooth siding.  This is a 100 by 100 pixel section of the original image, expanded to 400 by 400 for illustration.


The siding is not dirty; what you see is noise from the small sensor in the camera.  Because thermal noise is different in every image, you can reduce the noise by capturing several images and averaging them.  Here is the average of 19 images, created with The Gimp by loading each image into a layer, positioning each layer so it matched the bottom layer, then setting each layer's transparency so it contributed 1/19 of the final image.


However, stacking and averaging images is a tedious process.  Using Autopano Pro I can get the same result automatically.  I ask Autopano Pro to process the 19 images as a panorama.  Since the images are nearly identical, it has no trouble matching them.  I then specify linear blending when rendering.  Here is the light fixture:


For comparison, here are the blends of smaller numbers of images, so you can see the progression of noise reduction.  The number of source images is in the upper left corner.

      <page pageid="4084" ns="0" title="Reproducing a painting or artwork">
          <rev contentformat="text/x-wiki" contentmodel="wikitext" xml:space="preserve">__TOC__
== Introduction ==

Autopano makes it easy to reproduce pictures and works of art with very high resolution and perfect image stitching. &lt;br/&gt;
First of all, we will explain how this can be achieved when shooting from a single viewpoint. &lt;br/&gt;
We will then see how a rough shot from multiple viewpoints can still be cleanly rendered. 

== Example 1: Shooting from a Single Viewpoint ==

=== The shooting ===

Shoot the picture from a single viewpoint, retaining the same nodal point.

| [[Image:ShootingSetup01.png|500px|Shooting setup]]

In this example we have sectioned the picture into 2 rows of 10 shots each. &lt;br/&gt;
This is enough to give good resolution for this little picture. &lt;br/&gt;
To increase the level of detail or resolution, you have to take more shots. 

=== Creation of a group in Autopano  ===

Open Autopano and create a group containing the shots that make up the picture.

| [[Image:Step01_group.png|500px|Creation of a group]]

=== Panorama/picture detection ===

Launch the Panorama Detection process.

| [[Image:Step02_detect.png|500px|Panorama detection]]

=== Choose the Projection ===

In the Panorama Editor, choose rectilinear projection:

| [[Image:Step03_planarProjection.png|500px|Panorama detection]]

'''Note:''' &lt;br/&gt;
If you have not modified the default parameters ([[Autopano_-_Main_Window_-_Group_Settings#Panorama_tab|'''Preferred projection''']], Panorama tab), Autopano will select the most suitable projection for the field angle of the shot. &lt;br/&gt;
So, in the case of our little picture above, rectilinear projection is automatically selected.

=== Correction of Alignment ===

If, as in the study case, the picture or the camera was not strictly horizontal, you need to correct it using one of the following tools:

{| cellpadding=&quot;5&quot; cellspacing=&quot;10&quot; border=&quot;0&quot; width=&quot;1000px&quot;
|valign=&quot;bottom&quot; align=&quot;left&quot;  width=&quot;20%&quot; | The Positioning Tool:
|valign=&quot;bottom&quot; align=&quot;left&quot;  width=&quot;20%&quot; | The Vertical or Horizontal Line Tool (selecting the borders of the picture): 
|valign=&quot;top&quot; align=&quot;center&quot; |[[Image:Step04_move.png|470px|Move]]
|valign=&quot;top&quot; align=&quot;center&quot; |[[Image:Step05_horizontalverticallines.png|520px|Vertical ligns]]

'''Note:''' &lt;br/&gt;
Click on the green icon '''Apply''' or ''Enter'' on your keyboard to confirm your changes. 

=== Resizing the Picture ===

Next, use the '''Crop''' tool to precisely adjust the image size to the borders of the picture.

| [[Image:Step06_crop.png|500px|Resizing the Picture]]

=== Image Rendering ===

Then, click on the Image Render icon to launch the rendering. &lt;br/&gt;
You can modify the  [[Autopano_-_Panorama_Editor_-_Render_tools|'''different render settings''']] to adjust the output to your final purpose (identical reproduction, shrinking, enlargement, etc...). 

| [[Image:Step07_render.png|500px|Image Rendering]]

== Example 2: Shooting from Multiple Viewpoints ==

=== The shooting ===

In some cases, it may be necessary to shoot a picture with an inadequate camera setup (hand-held, for example), because of a lack of equipment, time or space. 

=== Detection setting ===

In such a situation, Autopano has to be notified that the group of photos contains shots taken from [[Autopano_-_Main_Window_-_Group_Settings#Optimization_tab|'''multiple viewpoints''']] by optimizing the viewpoint scope '''(only relevant to Autopano Giga)''': 

| [[Image:Autopano 3 groupsettings optim en.png|500px|Detection setting: Multiple Viewpoints]]

The following steps are then similar to those described in Example 1 above.

=== Image Rendering  ===

Autopano corrects the errors of camera positioning, and the result achieved is very close to that obtained with a single viewpoint shot. &lt;br/&gt;
Here is the result obtained for the same picture with 6 shots taken with a hand-held camera and  movement between each photo. 

| [[Image:MultiplePOVresult.jpg|700px|Result of a Multiple viewpoints shooting]]

[[Documentation]] / [[Autopano Documentation]]

[[fr:Reproduire un tableau ou une Ĺ“uvre d'art]]

[[Category:Autopano Case studies]]</rev>