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Re: Sony FX9 camera test

Re: Sony FX9 camera test


alister@...
 

The base ISO’s for S-Cinetone on the FX9 are 320 and 1600. This is of course also 0dB.  0dB is virtually always the native ISO, so to discover the cameras native ISO if it has a dB mode, switch to dB and compare to the ISO value. This information is also contained in the clip metadata and the recommendation to use the base ISO’s of 320/1600ISO for the cameras 460% dynamic range curves (including S-Cinetone and HG1 to 4) is included in the manual. 

Raising the gain when you are using a power law gamma reduces the dynamic range because gain is a multiplier. If you multiply your 0 to 100% input range from the sensor by 2 it becomes 0 to 200%, but you can’t record 200%, you only have room for 100%. So you have a small change in the shadows but a much larger change in the brighter parts of the image and the dynamic range that can be recorded is reduced by 1 stop for every 6dB you add. Adding gain means you will clip earlier. If you stop down to compensate, bringing the highlights down to where they would be without the added gain you reduce the shadow range as the SNR will become worse, and the extra noise from the amplification will limit the shadow range. You gain no additional highlight range, you are simply returning it to where it would be without the extra gain, but the shadows suffer. With added gain the highlights are less pleasing because the gamma curve is designed to work with the sensors output range, when you add gain because you can now more easily exceed the recording range the highlights clip sooner and don’t look as nice as a result.


Alister Chapman 

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On 17 Apr 2021, at 16:06, alfonso parra <info@...> wrote:

We decided to use the dual ISO base settings ​​for all the curves and thus be able to compare them to the same ISO value, in this case with the cinetone curve we use 800 as for the Slog3 curve so that we can clearly see the differences. If it is interesting to observe how you have made, the curve with different ISO values ​​and compare the results. What surprises me is that by raising the value of the S-cinetone to 800, detail is lost in the highs when normally the opposite happens, by increasing the gain, or the ISO value, the ability to collect detail in the highs increases, losing in the shadows. I don't remember now, but does Sony make any recommendation on the ISO value to use with the S-cinetone or does it indicate how much the middle gray value should be? May I ask you how did you get to 320 ISO in relation to 0db? In the theoretical sensibility test that we did, it gave us that the 800 ISO would be 0db considering the STD5 curve with gamma 2.4, which is actually quite similar to S-cinetone, actually the most similar is the STD3 only that S-Cinetone compresses something else in the highlights. 
Regards


Alfonso Parra ADFC
www.alfonsoparra.com
Tel Colombia 57 311 5798776
Tel Spain 34 639109309
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