Not quite accurate, but close. There is still an amplifier there. Just multiplying the digital values you get will result in posterization at the shadow end, its math. You can't create information out of nothing. If you only have 2 bits of information (4 values), then the digitization can only result in 4 values, no matter what you multiply it by. What they mean by ISO invariance is that the sensors are so good noise-wise that those 4 values will be extremely consistent (less random/noisy) and will compare favorably with the amplification by the analog amp. The analog amp will however, result in many more values, albeit noisy. I.e. the conclusion is you can take the best pictures by utilizing as much of the histogram as possible. Its just not realistic to take all your pictures at ISO 100 and compensate in Lightroom.
On Thu, Jan 26, 2017 at 9:19 AM, Mark Roberts <postmas...@robertstech.com> wrote: > Eric Weir wrote: > >>There are things that were said, though, that I did not hear. That is, didn’t >>understand. >>And probably am not going to understand when you explain it to me. What’s an >>“ISO invariant” camera? > > In the early days of digital it was standard practice to apply some > amplification to the signal from the sensor prior to analog-to-digital > conversion. This was how one increased the ISO setting. It's still > used in some sensors today but other sensors change ISO setting > strictly through software. These are said to be "ISO Invariant". (Most > Sony sensors are ISO Invariant and all the ones used in recent Pentax > cameras. > > What this means is that if you set the camera to, say, ISO 800 and > have a scene that meters at 1/100 sec. at f/5.6 you can, using manual > exposure, turn the ISO setting down to ISO 100 while keeping the > shutter speed and aperture at 1/100 f/5.6 even though the meter will > tell you you're 3 stops underexposed. If you just compensate later in > Lightroom or Photoshop the results will be the same as you'd have if > you'd shot at ISO 800 in camera. (This assumes one is shooting raw > format, of course.) > >>If I’m to ETTR just enough to avoid clipping highlights, how much is >>too much? I shoot RAW. Should I ignore the histogram? > > Don't ignore the histogram! *Any* clipping represents image data > that's gone forever. > > -- > Mark Roberts - Photography & Multimedia > www.robertstech.com > > > > > > -- > PDML Pentax-Discuss Mail List > PDML@pdml.net > http://pdml.net/mailman/listinfo/pdml_pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above and follow > the directions. -- -- Reduce your Government Footprint -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
