Why is minimum native ISO 200 on many mirrorless cameras?

Started 1 month ago | Questions thread
OP Charley123 Senior Member • Posts: 1,054
Re: Plausible Answer...

Ysarex wrote:

Charley123 wrote:

Ysarex wrote:

Charley123 wrote:

In this this thread, and at other online sources, many possible answers have been put forward.

The explanation I consider most plausible-likely is the following...

Crop sensor cameras are at a disadvantage in low light compared to full frame sensors.

Bigger sensors do better in low light than smaller sensors all else equal.

To (partially) offset that, smaller sensor cameras' are sometimes designed with ISO 200 (instead of 100) as their lowest native ISO. This gains the camera one stop higher ISO capability at the high end of its native ISO range, and allows it to have acceptable image quality at 1 stop higher ISO than would otherwise be the case.

Sounds like silly nonsense to me. First of all if that were the case then wouldn't other small sensor and even smaller sensor cameras do the same? We should find even more examples of higher base ISOs in 1 inch sensor and smaller sensor cameras right? But we don't -- there's no such trend.

Perhaps it's not that it actually improves high ISO performance, but that it allows the manufacterer to claim that it's native ISO can go higher. i.e. - a marketing trick.

Makes no sense.

Why do you think native ISO starts at 200?

Native ISO doesn't start at 200.

You're being intentionally argumentative and obtuse.

Base ISO starts at 200 on X-E3, X-T30, and many other Fuji, Olympus, Panasonic cameras. Surely know that for Fuji. Why does it start at 200 in those cameras?

Why does it start at 160 in newer Fuji cameras?

Can you offer a plausible explanation without being rude?

Base ISO on my Nikon is 64. Base ISO on my Canon is 125. Base ISO on my Leica is 50. Base ISO on my Fuji X-T4 is 160 and Base ISO on my Fuji X-T2 is 200. Only 1 out of 5 of my cameras is base ISO 200.

My cameras adhere to either the ISO REI (Nikon, Canon) or ISO SOS (Fuji, Leica) standards for establishing the ISO values on the cameras.

I think there are a number of reasons why each manufacturer makes engineering choices about their cameras and the ISO values they assign.

Fundamentally they have to deal with the hardware characteristics of the components they put in their cameras. Each model sensor is going to have a light sensitivity and saturation capacity that will determine how much light is required for exposure and at what point the sensor will saturate. I think modern sensors are fairly similar in this regard and that explains why base ISO on all of our cameras is pretty close one to another and within the range of 1 stop give or take around the average base value of 100.

I'm not a sensor engineer but I assume the sensor manufacture's don't have a whole lot of leeway to make big changes to the light sensitivity and saturation capacity of their products. So I think if you buy a digital camera you can expect a base ISO close to 100 with some cameras as high as 200 and fewer dropping below 100.

Beyond that the ISO values are assigned to the camera's output image (JPEG) and implemented by the camera's image processor. Two different camera makers therefore could use the same sensor and yet assign different ISO values because their engineering teams decided to more or less protect highlights for example.

And where's that advantage? I have a mirrorless Leica SL that's FF and base ISO is 50. (Yep, it's not about mirrorless). My Fuji X-T4 (APS-C) has a base ISO of 160. If I set both cameras to the same high ISO (say 12K) and set the same exposures for both I get pretty close output JPEGs. The SL JPEG has more contrast which makes it seem lighter, but it is also actually a tad lighter so where is Fuji's higher base ISO providing an edge?

The Fuji is in the range of 1/3 stop darker at most. The SL's + contrast is tricky. The curtain behind the fish looks a lot lighter in the SL JPEG but compare the jar of dried mushrooms in front of the fish. The X-T4 table top looks lighter than the SL's -- brightness is overall pretty close. So the X-T4 isn't coming out ahead here but it's just a smidge behind. The Fuji could use a little more exposure than the SL at the same high ISO.

What I did was put the SL on a tripod first and took the photo at the SL's metered exposure. Then I replaced the SL with the X-T4 and used the same ISO, shutter speed and f/stop and took the X-T4 exposure. Both JPEGs are dark and would be improved with more exposure but the critical factor is they're a lot closer together than 1 stop and since the Fuji is in fact darker that argues for the opposite of the suggestion that a higher base ISO is handing the camera a high ISO advantage.

The sacrifice being there is no native 100 ISO, but that doesn't affect most of the public.

The people likely to be affected by this (me) are enthusiasts wanting to use fill flash on a sunny day, or wanting shallow DOF on a sunny day, but these people will know enough to figure out a solution, such as using an ND filter.

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