Base ISO Levels for the FX9

First of all. Unless you are actually using a lightmeter to determine your exposure, in custom mode it is far, far easier to use dB of gain. 0dB is always optimum and each time you go up 6dB the picture gets twice as bright (one stop brighter) and the noise doubles. ISO is in most cases nothing more than a rating to use in conjunction with a lightmeter to get the right picture brightness, it will not tell you how much noise you have or whether the camera is at it’s optimum setting. So don’t use ISO just because “ISO is cool and make me sound like I know what I’m doing, it makes me a cinematographer”. This isn’t a film camera, no matter how much you dress it up it is a video camera and dB tells you exactly what it is doing.

Because different gamma curves produce different brightness images the ISO rating will change depending on the gamma curve being used, this isn’t a sensitivity change, it’s an optimum brightness change. Because of this, even when you are at 0dB gain (the native setting) when you switch between different gammas the ISO rating changes. In addition because you have two different base sensitivity modes on the FX9 there are a lot of different base ISO’s (all of which are 0dB gain). I’ve prepared a table of the different base ISO’s.

Screenshot-2019-12-30-at-11.00.53-1024x295 Base ISO Levels for the FX9

In addition if you are not careful it’s possible to end up using too much gain to achieve a certain ISO as many ISO ratings can be realised at both Hi and Low Base sensitivity. You don’t want to be at 2500 ISO in Low Base for example, you would be better off using High base. The table below should help you understand when to switch up to High base from Low base. If you use dB gain, then it’s easy. More than +11dB – switch up. Don’t forget in dB mode you can also go down to -3dB.

Screenshot-2019-12-30-at-12.26.58-1024x342 Base ISO Levels for the FX9

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5 thoughts on “Base ISO Levels for the FX9”

  1. Thanks Alister, very helpful.

    I didn’t realize the base ISO’s were now that much lower which is fantastic. It was always a PITA that HG7 and 8 were a native (and minimum) of 1600 ISO.

    1. Hi Chris!

      Long-time no – just got my first Fx9 and yeah can tell you the 320 is really nice. But grain at higher ISO’s is just so much tighter, you just have to see the difference to the F5 for yourself. And it’s a full stop faster at 800 compared to the F5.

      Quick sell your cameras and get these before everyone realizes how much better this camera is!

  2. Find it hard to believe FX9 will not operate at far lower voltages, i.e. 14.8 V-Lock. If 19.5 is truly required, you would have the same complication trying to run off line power such as from an ordinary V-Lock battery charger.

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