If we look at the sensor used in the S1H, S5 this is based on a Sony IMX410 that has saturation value of 15105 bits or 13.88 stops of dynamic range. It is true that ADC can also resolve portions of bits however this does not largely change the picture. This means the sensor dynamic range is limited to the bit depth of the analog to digital converter and in most cases sensors do not even saturate the on board ADC. In a consumer digital camera the sensor is already equipped with a digital to analog converter on board and this operates in a linear non log mode. Panasonic made this claim for the GH5s and for the S1H, S5. The claim is that you can pack the full sensor dynamic range into 10 bits video. LOG conversion is an excellent method to compress a high dynamic range into a smaller bit depth format. As a result blacks are actually at 10% IRE and whites at 80% once a conversion LUT is applied. When we look at the reality of V-LOG we can see that Panasonic sets 0 at a value of 50% IRE so generally ⅔ to 1 full stop overexposed this becomes obvious when you look at the waveform. In terms of ISO measured at 18% reflectante V-LOG should have identical ISO value to any other photo style in your camera this means at given aperture and exposure time the ISO in a standard mode must match V-LOG. Another consequence of this formula is that VLOG under 18% IRE works exactly like standard gamma corrected Rec709 so it should have exactly the same performance in the darks with a range between 7.3% and 18% instead of 0-18%. In fact the master pedestal as it is known in video or black level is shifted. So what we have here is a shift of the black level from 0% to 7.3% and a compression of all tones over 18% this gives the washout look to V-LOG that is mistakenly interpreted as flat but it is not flat at all. 100% IRE needs input reflectance 4609 which is 5.5 stops headroom for overexposure.White (90% reflectance) is 61% IRE so much lower than Rec709.Middle Grey (18% reflectance) is still 42% IRE as standard Rec709.Dark values are not compressed until IRE=18%.0 input reflectance is mapped to 7.3% IRE.There are few implications of this formula that are important: If you consider the input reflection (in) you can see how the output is related to the input using two formulas: This is well documented in Panasonic V-Log/V-Gamut technical specifications. Panasonic V-LOG/V-GamutĪ logarithmic operator is a non-linear function that processes the input signal and maps it to a different output value according to a formula. I will aim at making this write up self-contained so you have all the information you need here without having to go and search elsewhere, it is not entirely possible to create a layman version of what is after all a technical subject. Some of what you will read may be a surprise to you so I have provided the testing methods and the evidence so you can understand if LOG is something worth considering for you or not. In this short article I will explain how the Panasonic V-Log actually works on different cameras. There is no doubt that LOG formats in digital cameras have a halo of mystery around them mostly due to the lack of technical documentation on how they really work.
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