LibRaw

Administrivia

lexa — Sun, 12 Oct 2008 07:22:26 +0000

This site has moved to another database engine (to PostgreSQL from MySQL). We does not expect any changes from user's point of view.

Anyway, if you have any problems with libraw.org site, please contact site team via comments to this note, or via contact form or by E-mail at info 'at' libraw 'dot' org.

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.

LibRaw 0.6.1 Release

lexa — Thu, 25 Sep 2008 18:25:18 +0000

Changes since 0.6.0:

Added new data field float LibRaw::imgdata.color.cam_xyz[4][3]. This field contains constant table (different for each camera) for Camera RGB->XYZ conversion.
All client code should be recompiled

Your can always download latest LibRaw version from this site's download page.

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

LibRaw.org site opened

lexa — Mon, 28 Apr 2008 07:36:43 +0000

All activity to prepare first public release of LibRaw has finished. Site opened.

Welcome!

LibRaw 0.5.2

lexa — Sun, 27 Apr 2008 07:38:18 +0000

There is a bug in compilation samples/identify.cpp under Linux.

Fixed, LibRaw 0.5.2 released

LibRaw Project Goals and Objectives

lexa — Sun, 27 Apr 2008 06:07:02 +0000

Who May Be Interested in This Project
Goals and Objectives
LibRaw Support Principles
Implemented Improvements of dcraw
Planned Improvements

Who May Be Interested in This Project

The proposed project and the software products generated within this project are intended for

dcraw 8.86 and LibRaw 0.5.1

lexa — Mon, 21 Apr 2008 05:36:19 +0000

dcraw 8.86 (RCS ID 1.402) has been released:

Added support for Oly E-420 and several Sony cameras
Saturation level determination has changed

All these changes imported into LibRaw 0.5.0