LibRaw

LibRaw 0.8.5

lexa — Wed, 30 Dec 2009 14:04:56 +0000

LibRaw 0.8.5 available for download

Changes are:

Fixed bug in simple_dcraw sample parameters processing
Imported dcraw 8.99 (1.432):

LibRaw 0.8.0 Release

lexa — Thu, 27 Aug 2009 07:30:19 +0000

LibRaw 0.8.0 Release available for download

There are many changes since version 0.7.2, in short:

Large RAW files (more than 2Gb) supported.
Dcraw 8.86/1.426 imported: 23 new cameras; new color data for many cameras; new unpacking code for several formats.
LibRaw API changes: new gamma curve parameters.
Some C-API calls are implemented (was missed, but documented).
Many minor compatibility/cosmetic changes.

Image::LibRaw (LibRaw Perl interface)

lexa — Fri, 15 May 2009 07:23:28 +0000

Tokuhiro Matsuno has developed version 0.01 of LibRaw Perl bindings.

Image::LibRaw (at CPAN)

LibRaw-Lite (LGPL license)

lexa — Thu, 07 May 2009 15:21:42 +0000

LibRaw-Lite is licensed under LGPL terms and is available for download and use.

This version is slightly lighter than GPL-licensed LibRaw:

With LGPL License, you may use unmodified library in non-opensource applications.
(Sorry) Foveon support is absent due to dcraw license restrictions.
Minor enhancements found in full LibRaw are absent in Lite version:
- Black (masked) pixels are not extracted from RAW data.
- It is not possible to control black level subtraction, raw curve processing, zero pixels removal.
- Color data source (i.e. from camera/from hardcoded constant etc.) is not saved for application use.
- There is no OpenMP support.

LibRaw 0.7.2

lexa — Tue, 07 Apr 2009 17:43:01 +0000

LibRaw 0.7.2 released, changes are:

More accurate types conversion in libraw_datastream.h
New postprocessing parameter auto_bright_thr: set portion of clipped pixels for auto brightening code (instead of dcraw-derived hardcoded 1%)
-U option for dcraw_emu sample sets auto_bright_thr parameter
all client code should be recompiled due to structures size change

LibRaw 0.7.2 is available for download on this site download page

Chasing a Gray Cat In a Gray Room: the level of middle gray and the headroom in the highlights for Canon 5D Mark II

lexa — Sat, 07 Mar 2009 19:07:55 +0000

The current methods used to determine the sensitivity of digital cameras are not based on the RAW data coming from the sensor; rather they are based on the results of processing the RAW in a converter (be it an external converter or in-camera).

This approach, with all its simplicity, is in fact based on the properties of the RAW converter and on the transformations it applies to RAW data. In particular, the converter can introduce hidden exposure compensation, change the tone curve, and so on. The sensitivity of the camera resulting from such a procedure is a pretty arbitrary value. The matter is discussed in good detail in Wikipedia, in the article explaining ISO 12232 standard.

This approach allows the camera manufacturers to enjoy all sorts of tricks while stating the sensitivity, say cameras from different manufacturers but having the same rated sensitivity behave wildly different when it comes to photographic latitude. This means that switching between different camera bodies one often needs to re-adapt, changing the way he applies exposure compensation.

A simple experiment that takes no additional equipment other than already existing camera and lens allows to accurately determine how the camera exposes, that is:

which level of signal (in terms of RAW data) is obtained while setting the exposure by the exposure meter;
what headroom in highlights is left, i.e. how many exposure stops are between the middle gray and sensor saturation.

Two Paths Leading Nowhere

lexa — Sat, 31 Jan 2009 15:18:20 +0000

Why are photographers compelled to suffer the discord of RAW formats?!

During the last 10 to 15 years, digital photography forced the film out of nearly all the domains. End users purchased hundreds of millions of digital cameras; and that is not including the cameras sold integrated with cellular phones. Such a huge industry can't exist without standards and such standards appear to exist. They cover the storage media (various flash cards), and image format which happens to be JPEG. Currently JPEG is the most widely used image format and its image quality and size satisfy the overwhelming majority of users.

However it is not always what professionals want. By professionals we do not mean just professional photographers. The list includes designers, pre-press staff, archivists, photo banks and many others. It often happens that JPEG format is also deemed less than appropriate by advanced amateurs. That is why nearly all digital cameras that are positioned by manufacturers as professional or semi-professionals models (as well as all current dSLR cameras) suggest an alternative format, the so-called RAW. For a casual onlooker it may appear that RAW is also some kind of a standard format that delivers better quality – quality for pros.

This small article is to show that the matter is much more complicated. At the current stage the situation with RAW format is not just bad but really dreadful and continues to spiral downwards rapidly. This affects mostly professionals while less demanding amateurs simply enjoy the progress of digital.

Dan Margulis on RAW module

ib — Fri, 09 Jan 2009 01:01:43 +0000

The question that needs an answer is, for what purpose is the module designed. I can think of four different approaches to acquisition.

I want the module to do nothing more than open the file without damage. I understand that it will probably be flat and colorless if I do this. I intend to fix the problems in Photoshop.
Although I will refine the image in Photoshop, I would like to be able to make quick, obvious moves in the acquisition module to make life easier later.
I am not interested in the very best quality. I will do whatever is possible in the raw module but I will not work in Photoshop afterward. So I would like to be able to get attractive color from the module.
I want to make the image as perfect as possible in the module. I will intervene later in Photoshop only as necessary.

You need to decide which group(s) you appeal to.

Random And Groundless Thoughts On Color Control In a Raw Convertor

lexa — Wed, 01 Oct 2008 18:30:47 +0000

CAM book After finally finishing reading Fairchild’s Color Appearance Models I started to get deep into thought and some empirical things became clear.

Color Contrast

In the photographical community it is pretty much a common place that if you show the viewer two pictures, one with normal colors and one with an increased saturation, the viewer will in most of the cases pick the one with the higher saturation (if it is, for example a landscape scene) as the more natural one (of course if saturation is increased in the reasonable limits).

I could not quickly find the wording of this effect in books by Margulis, although I was almost certain that it was there in one way or another: in his book Photoshop Lab Color) this rule (increasing the a-b axis contrast) is used starting with the very first example.

Canon: How To Get 400/5.6 In Five Different Ways

lexa — Mon, 29 Sep 2008 17:35:32 +0000

Competitors While preparing for my summer trip to Altai, I attended to choosing the telephoto lenses I was going to carry. I needed a regular telephoto lens for shooting water attractions (Katun is very large river and the target can be very far away) and an extra long reach lens for shooting the full phase of the solar eclipse.

The goal was to select a 400 mm as a “long” lens, and as much as possible for the “extra long” one. After looking around and asking some friends I found the following possibilities for a 400mm with Canon:

EF 400/5.6
EF 300/4 + TC1.4
EF 200/2.8 + TC2
EF 70-200/4 + TC2
EF 135/2 + TC2 + TC1.4

Surprisingly, even the last option on the list (the one with two teleconverters stacked) did not seem hopeless: I tried that option for film a while ago, and it was comparable with a 70-200/2.8 with a 2x TC.

Peace in Lights

ib — Fri, 23 May 2008 13:49:42 +0000

Compensating ETTRAs it was shown earlier the direct application of exposure to the right method (ETTR) without preliminary scene analysis and evaluation often results in a major underexposure which in turn causes poor details, noise, and artefacts. In order to evaluate the necessary depth of tone correction for such underexposed shots we will use the following natural method – we will return the zones containing details of high visibility (those are zones from IV to VI) to target density values. Such a move makes sense because in order for those details to be really visible, they need to be in those zones.

How to stretch 2.5 eV to 5; and what would be the price

lexa — Thu, 22 May 2008 06:05:44 +0000

In the photographic community, the common perception is that the exposition scale is symmetrical. The perception dates back to Adams: the Zone V is in the middle of the range, with 5 zones “above” and “below” it, top and bottom being symmetrical: there are 2 zones each way containing details, then one more each way with traces of textures, with the final two (one each way) which are respectively completely void white and solid black. The 2x (1eV) changes in brightness correspond to the transition between the zones.

Two 'linear' scales The photographic “zone” step wedge is not visually (perceptually) even. For instance in the Kodak Q13 grey wedge (the top scale on the image to the left), where the distance between the two neighboring patches is 1/3 eV, we can clearly see that in the lighter part, this distance between the patches seems visually large, and in shadows – visually small, as if the steps are compressed. The Q13 wedge encompasses Zones I through VII, although not representing the brightest part (further on, we will see that they cannot be represented at all by an evenly distributed wedge).

Headroom in Highlights : Where is Zone V in The Digital World?

ib — Sat, 10 May 2008 15:50:23 +0000

Creating a linear test fileWe will try to demonstrate here why there is no more then 3 stops headroom in highlights between the exposure suggested by the spot-meter and the clipping point of the raw data. We presume the camera follows the current ISO standards; the sensor is single-structure (not like those Fuji S5 cameras have); the capture is obtained in 1 shot; and that the raw data is linear.

Using Magenta Filter for Shooting With a dSLR Camera Under the Daylight

lexa — Sat, 10 May 2008 04:38:31 +0000

Lee Holder with CC30M filter In the previous article and during lengthy discussions on various forums, we promised to demonstrate the usefulness of magenta filters. Those filters compensate the imbalance between the sensitivities of color channels in digital cameras. Promises should be fulfilled, and having this filter, it takes nearly no time to prepare the demonstration – given that you have that sunlight...

Channel Noise and Raw Converters

lexa — Wed, 07 May 2008 06:39:36 +0000

As we mentioned in our previous article, the difference in sensitivity between the color channels of a digital camera leads to different per channel levels of details. Consequently, we have a different level of noise in different channels. The other factor which determines the difference in the levels of noise, is the greater number of green pixels in the Bayer sensor. This allows to decrease the level of noise in the green channel by approximately 1.4 times and makes the difference in noise between channels even greater.

Renditions of Three Popular Colour Targets

ib — Tue, 06 May 2008 15:28:37 +0000

These Lab renditions of Macbeth ColorChecker, ColorChecker DC, and ColorChecker SG (attached archive contains three 16-bit Lab TIFF files of the targets; if you need them larger please upsize in Photoshop using "Nearest Neighbor" method in Image -> Image Size) can serve as a visual reference as well as for adjustments "by numbers" during raw conversion and post-processing.

Please note that ColorChecker SG contains a structure very similar in appearance to 24-patch regular ColorChecker; but the values of patches are in fact different.

White Balance in Digital Cameras: Problems

lexa — Mon, 05 May 2008 16:10:31 +0000

Current digital cameras provide the photographer with what is considered to be excellent means for instant diagnostics of an image right after the shot is taken.

We can evaluate the shot on the LCD screen.
The camera is nice enough to display a histogram (luminosity histogram and for many high quality cameras, per channel histograms as well).
Finally, the camera can display zones of clipping for both under and overexposed parts of the image.

Zones and Digital: Two Methods of Exposing

ib — Mon, 05 May 2008 13:03:29 +0000

The question whether one should expose "to the right" or should it be "exposure for the subject" (centred exposure) causes a lot of discussions when it comes to digital capture. Technically, this boils down to a simple question of placement lightly textured whites, like snow - should those be hitting the right wall of the histogram; or should they be placed about 2 stops lower, to the left on the histogram; or even somewhere between 0 and 2.

Spot-Metering: Reading Adams in Reverse Direction

ib — Sat, 03 May 2008 19:47:19 +0000

Zone Intervals

What is the connection between exposure and raw converters? Or, to put it another way, why consider exposure on this site?

For that, there are two reasons. First, we would like to discuss various photography-related topics. Second, the quality of the resulting image largely depends on the correct exposure, as do the time and the effort spent during the conversion.

Lets start with the definitions Adams suggested to the zones.

LibRaw 0.5.3

lexa — Fri, 02 May 2008 12:49:26 +0000

Dave Coffin has released several bugfixes for dcraw 8.86:

workaround for too large jpeg thumbnails in Foveon files
workaround for out of range data in ljpeg-compressed files

All these changes are imported into LibRaw 0.5.3