Archived posting to the Leica Users Group, 2015/01/15
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Le 15 janv. 15 ? 10:09, Mark Rabiner a ?crit : > I'm not sure if we have a real > sense of what iso we can use it at now?!? This might help add to our confusion circle ;-) DR Modes and the ISOless APS-C Sensor You may have heard that Fuji?s APS-C cameras are all based on modern ?ISOless? Sony sensors. These sensors are used by several leading camera manufacturers, such as Sony (of course!), Nikon, Ricoh/Pentax, Leica and Fujifilm. The ?killer feature? of ISOless sensors is their ability to rely on digital gain (as opposed to analog amplification) for the most part of their operation. Digital gain can be applied anytime during your workflow?before and after the RAW file has been created. As a matter of fact, it?s better to apply digital gain after the fact?when the RAW in processed in a converter. This is also the reason why Fujifilm RAWs don?t go beyond ISO 1600. They remain the same?any further gain between ISO 1600 and ISO 6400 is applied digitally during RAW conversion. This means that in high-ISO scenarios, achieving ?perfect exposure? before you press the shutter button doesn?t really matter. You can just as well change the exposure later in the RAW processing phase? either in-camera, or with Lightroom (or with another RAW converter) in the comfort of your home. Click here to read a forum thread with a demonstration of this feature. Between base ISO 200 and ISO 1600, ?mixed? analog/digital amplification maintains a slight quality advantage over ?pure? digital gain. That?s why your camera is still using at least some analog signal amplification up to ISO 1600. Enabling the DR function basically switches the mixed analog/digital process over to a pure digital gain (or tone-mapping) process for either one (DR200%) or two (DR400%) analog signal amplification stops. Let me give you an example: Shooting an image at ISO 800, DR100% will result in an ISO 800 RAW file that?s based on an ISO 200 exposure with two stops of mixed analog/digital amplification/gain. Shooting the same image at ISO 800, DR400% will result in an ISO 200 RAW file with digital tone-mapping being applied during RAW conversion. This tone- mapping is pushing the result to ISO 800 in the shadows and midtones, while retaining bright highlights at ISO 200. You would have a hard time telling the ?analog? from the ?digital? ISO 800 result when looking at the shadows and midtones. You will however recognize that the digitally processed DR400% version offers two additional stops of highlight dynamic range. This is exactly what we want when shooting scenes with high DR, like christmas markets with festive lights and very strong contrasts. In other words: Yes, sensors have a fixed dynamic range, but the actual dynamic range that can fit into your actual image file is not just determined by the sensor, but by the signal processing and by whatever happens during RAW processing. By applying ?adaptive ISO? during RAW processing, you can expand the actual dynamic range of any image by 1, 2, 3 or even more stops. The sky?s the limit, but for practical reasons, there will always be quality considerations, since the application of digital gain results in a similar image degradation as raising ISO values the old-fashioned way. Much more at : http://www.fujirumors.com/exposing-right/ Amities Ph One sees clearly only with the heart. What is essential is invisible to the eye. Antoine de Saint Exup?ry in Le Petit Prince. NO ARCHIVE