Q: Lightroom/ACR: HDR DNG?

Полтора года назад в анонсе ACR 7.1 писали:

Camera Raw can also now read 16-bit, 24-bit, and 32-bit HDR files. Supported HDR formats are TIFF and DNG.
Кроме того, в спецификациях DNG 1.4 написано следущее:
  • BitsPerSample может быть от 8 до 32
  • SampleFormat может быть unsigned integer или float.
  • Для Float поддерживаются 16,24 и 32 bits per sample.
Это, типа, теория.

А вот что с практикой?

  • Жрет ли ACR (и LR) floating point DNG?
  • Жрет ли ACR 24- и 32-битные DNG с целыми данными?
  • Кто может делать указанные выше DNG (Адобовский DNG SDK версии 1.3 - не может, а более новых нету). Ну то есть я знаю про Darktable, которая пишет, если я правильно исходники прочитал, 32-битную плавучку, а еще кто и как?
  • Встречаются ли многобитные DNG "в дикой природе"?
Вопросы пока сугубо теоретические, но если массовый софт (ACR, LR) поддерживает плавучку и/или 24-32-битные целые и нормально (без клиппинга, без постеризации) их обрабатывает, то это ж совсем другой ландшафт вокруг.

И я бы с этим ландшафтом поэкспериментировал бы, если есть готовые тулзы, которые эти многобитные DNG варят.


просто подборка комментариев :

Eric Chan :: ( http://www.luminous-landscape.com/forum/index.php?topic=77413.msg621835#... ) @ April 21, 2013 :

ACR/Lightroom assume that integer TIFFs (the vast majority of TIFFs are written as integer TIFFs) are output-referred, and that floating-point TIFFs are scene-referred (e.g., HDR files). The bit depth itself is not critical (ACR/LR will read 16-bit, 24-bit, and 32-bit floating-point formats for TIFF and DNG), but the data type itself (floating-point vs integer) matters to the default interpretation.

Eric Chan :: ( http://www.luminous-landscape.com/forum/index.php?topic=70850.msg561229#... ) @ September 24, 2012 :

To process floating-point HDR images in ACR you will need ACR 7.1 or later with PV 2012. (You can use PV 2010 and earlier but it will not preserve the floating-point data during the rendering and hence in a truly high contrast scene you will likely see banding/quantization artifacts in the shadows.) The two floating-point HDR formats that ACR / LR currently support are TIFF and DNG.

Eric Chan :: ( http://www.luminous-landscape.com/forum/index.php?topic=67528.msg534464#... ) @ June 01, 2012 :

...the white point in the 32-bit image is set differently than in the 8-bit image. So the initial exposure appears different. Simply adjust the Exposure slider till you get the overall image brightness you want.

Eric Chan :: ( http://www.luminous-landscape.com/forum/index.php?topic=67528.msg534203#... ) @ May 31, 2012 :

Yes, Lr 4.1 and ACR 7.1 have the ability to import and render floating-point HDR images. Supported formats are TIFF and DNG. (If you have HDR images in other formats like OpenEXR or Radiance, you can use Photoshop or other tools to convert them to TIFF.) Supported bit depths are 16, 24, and 32 bits per channel.

If you're using Photoshop's Merge to HDR Pro feature to perform the "merge" step, be sure to choose 32-bit output in the top-right popup menu of the HDR Pro dialog box. This will generate a floating point (but not yet tone-mapped) image, which you can then use ACR or LR to render and tone map using the new PV 2012 controls.

Eric Chan :: ( http://forums.adobe.com/message/4516798#4516798 ) @ Jun 24, 2012

Currently the noise reduction on floating point images (including 32-bit TIFFs) in ACR 7.1 / LR 4.1 is more twiddly, because there is no noise profile data. Effectively the NR methods can't assume anything about the noise content of the image (because it doesn't know "how" the image was merged), so the controls behave a bit more like they do for output referred images like JPEGs. In other words, they have much larger range to deal with a larger possible set of noise conditions. This is what makes them feel a bit more twiddly.

This situation will likely improve in the future, but I can't specify more at this time.

Eric Chan :: ( http://forums.adobe.com/message/4429851#4429851 ) @ May 22, 2012

With ACR 7.1 and Lightroom 4.1 (with PV 2012), there is now also the ability to read and process (render) HDR images, i.e., floating-point images with 16, 24, or 32 bits per channel.

> Кто может делать указанные выше DNG


Ага, спасибо. Интересно.

Я думаю не про HDR, но этих конечно же тоже посмотрю.

ну там вроде можно "zero-noise" DNG делать, не только HDR (я не вникал особо)