Why is minimum native ISO 200 on many mirrorless cameras?

[Charley123]

I shot a Canon Rebel T2i for years. Its native ISO range was a very useful 100 - 6400. It was an APS-C DSLR camera.

My Olympus E-M10ii native ISO starts at 200. My (newly aquired) Fuji X-T20 native ISO starts at 200. The latest and greatest Fuji cameras native ISO starts at 160.

Why do modern mirrorless cameras base ISO start at higher than 100? It seems like a step backward from what older digital cameras (DSLR) could do on bright sunny days.

 

[Doug Pardee]

And here we go again...

Once upon a time, cameras metered for 18% gray (I'm ignoring the arguments about the exact percentage). 18% was usually pretty good for black-and-white negatives, but color photos looked a bit dark. Back in the days when I shot color slide film, I typically added about +1 Ev of exposure compensation to get images I liked.

WIth the digital age, Canon threw out the 18% gray "standard." They brightened up the pictures by about one stop, through the simple approach of renumbering the ISO. What used to be ISO 200, they called ISO 100. That caused the metering system to expose one stop brighter. Nikon held out for a while, but eventually followed suit. When Sony bought up the Konica-Minolta line, they too went with the lower ISO numbering which gave brighter pictures.

Digital ISO as specified by ISO 12232 has two different standards for the manufacturer to choose from. "Standard Output Sensitivity" (SOS) ISO requires that the in-camera sRGB JPEG produce 18% gray when metering an 18% gray card... but there's an important exception I talk about below. "Recommended Exposure Index" (REI) ISO lets the camera manufacturer set the ISO to whatever gives exposures they think their customers will like.

Fujifilm, Olympus, Panasonic, and Ricoh/Pentax rate their ISO using SOS. If you manually set the exposure using readings from a handheld light meter, you'll get in-camera JPEGs that are exposed about the same as slide film would have been.

Everybody else, including the big three of Canon, Nikon, and Sony, rate their ISO using REI. If you manually set the exposure using readings from a handheld light meter, you'll get in-camera JPEGs that are exposed about about a stop brighter than slide film would have been.

So there you are. The same sensor that is rated at 100 ISO (REI) in a Sony is rated at 200 ISO (SOS) in a Fujifilm. [Do bear in mind that the one-stop difference is a matter of taste and can vary a bit.] Try it for yourself. Set your Canon to ISO 100 and your Fuji to ISO 200, then set shutter speed and exposure the same on both (manual exposure mode). The JPEGs produced by both cameras will be exposed about the same.

An important point:

SOS ISO only applies to "dumb" metering modes like average, spot, center-weighted, etc. (or handheld light meters). In-camera multi-zone metering (Evaluative, Matrix, Multi, ESP, or whatever) is specifically intended to deliver pleasing exposures, so it doesn't matter what the ISO numbering is.

If you take a Canon, Nikon, Sony, or whatever and snap an sRGB JPEG of an 18% gray card, it'll come out about 25% gray regardless of metering mode. But do that with a Fujifilm or any other SOS-rated camera, and you'll get about 25% gray when using multi-zone metering and about 18% gray when using a dumb metering mode.

I think a strong case can be made that Fujifilm, Olympus, Panasonic, and Ricoh/Pentax should join the other manufacturers in abandoning SOS ISO in favor of REI ISO. But they haven't. Yet.

 

[dark13star]

While your answer may have been more than this thread deserved at this point, I just wanted to let you know that I found it informative. I already knew about the differences, but not how they came to be. Thanks for that.

Rich

 

[Charley123]

My point is to ask why some (such as Fuji, Olympus, and others) have native ISO starting at 200 when they could do better?

Something to keep in mind is that the ISO standard does not specify a specific process for the implementation of ISO or tonal rendering in the processing of an image. So, when talking about one manufacturer's ISO 200, and other manufacturers' ISO 200, there's no guarantee a photo made with a Nikon camera at f/4, 1/200, ISO 200 will match the lightness of a Fuji (or any other brand) photo made at the same exposure and ISO settings. Manufacturers are free to implement ISO and tonal palettes as they see fit.

Good to know. Thanks

 

[Lettermanian]

It's because of the way companies measure ISO. Fuji and Olympus use the Standard Output Sensitivity method while Canon, Nikon and Sony use the Recommended Exposure Index.

Perhaps an analogy is how there are different standards in measuring speed. Here in Canada, our vehicle speed is measured in kilometres per hour. In the US, it's measured in miles per hour. When a Canadian vehicle is travelling at 160 km/h, and an American vehicle is travelling at 100 m/ph, is the Canadian vehicle somehow "cheating", or going faster? Not at all, they're both travelling at the same speed. Similarly, two different methods of measuring ISO are both legitimate, and much more benign than what some people may try to posit.

 

[JNR]

And here we go again...

Once upon a time, cameras metered for 18% gray (I'm ignoring the arguments about the exact percentage). 18% was usually pretty good for black-and-white negatives, but color photos looked a bit dark. Back in the days when I shot color slide film, I typically added about +1 Ev of exposure compensation to get images I liked.

WIth the digital age, Canon threw out the 18% gray "standard." They brightened up the pictures by about one stop, through the simple approach of renumbering the ISO. What used to be ISO 200, they called ISO 100. That caused the metering system to expose one stop brighter. Nikon held out for a while, but eventually followed suit. When Sony bought up the Konica-Minolta line, they too went with the lower ISO numbering which gave brighter pictures.

Digital ISO as specified by ISO 12232 has two different standards for the manufacturer to choose from. "Standard Output Sensitivity" (SOS) ISO requires that the in-camera sRGB JPEG produce 18% gray when metering an 18% gray card... but there's an important exception I talk about below. "Recommended Exposure Index" (REI) ISO lets the camera manufacturer set the ISO to whatever gives exposures they think their customers will like.

Fujifilm, Olympus, Panasonic, and Ricoh/Pentax rate their ISO using SOS. If you manually set the exposure using readings from a handheld light meter, you'll get in-camera JPEGs that are exposed about the same as slide film would have been.

Everybody else, including the big three of Canon, Nikon, and Sony, rate their ISO using REI. If you manually set the exposure using readings from a handheld light meter, you'll get in-camera JPEGs that are exposed about about a stop brighter than slide film would have been.

So there you are. The same sensor that is rated at 100 ISO (REI) in a Sony is rated at 200 ISO (SOS) in a Fujifilm. [Do bear in mind that the one-stop difference is a matter of taste and can vary a bit.] Try it for yourself. Set your Canon to ISO 100 and your Fuji to ISO 200, then set shutter speed and exposure the same on both (manual exposure mode). The JPEGs produced by both cameras will be exposed about the same.

An important point:

SOS ISO only applies to "dumb" metering modes like average, spot, center-weighted, etc. (or handheld light meters). In-camera multi-zone metering (Evaluative, Matrix, Multi, ESP, or whatever) is specifically intended to deliver pleasing exposures, so it doesn't matter what the ISO numbering is.

If you take a Canon, Nikon, Sony, or whatever and snap an sRGB JPEG of an 18% gray card, it'll come out about 25% gray regardless of metering mode. But do that with a Fujifilm or any other SOS-rated camera, and you'll get about 25% gray when using multi-zone metering and about 18% gray when using a dumb metering mode.

I think a strong case can be made that Fujifilm, Olympus, Panasonic, and Ricoh/Pentax should join the other manufacturers in abandoning SOS ISO in favor of REI ISO. But they haven't. Yet.

As sick as Doug must be about having to give this answer over and over for any number of years, this pretty much nails it - once again. Several years ago some reputable review site actually had the audacity of measuring sensor accuracy based on the Sunny 16 rule (roughly similar to the more scientific 18% gray) which essentially is consistent with what SOS (and ASA, ISO and DIN had established previously). Based on that, Pentax actually was determined to be the most faithful brand to those standards in the early years of digital, albeit also not terribly consistent in the application of it (from experience I can tell you various bodies and mechanical aperture lenses routinely wondered off in either direction by as much as half a stop).

Given that DPReview and other reviewers back then tended to assume that light measurement standards were not likely to be fudged, a lot of fudging commenced. So much so that the "interpretive" REI measurement was invented (yes, by any scientific measure it is a contrivance). So, now it a non-standard photography "standard" adopted by the dominant players who rarely get called out. Generally speaking, the difference between SOS and REI is a bit less than a full stop... but who can say because, well, REI is an interpretation having only a passing relationship with actual light measurement. And, you'll get many an REI advocate who will claim special consideration for the idea that "ISO is a bogus concept" in the digital light realm with little regard for the measurable scientific basis that preceded the current nonsense.

Doug, I applaud your diplomacy... nearly none of which I can contain!

 

[ISO 1 Million]

What you have stated simply isn’t true. Very few mirrorless cameras have a base ISO of 200. The only ones I know of are all M4/3 and some Fuji APSC models. Nikon, Canon, Sony, Leica, Fuji medium format, and Hasselblad all have base ISO of 100 or lower

The tone of your post sounds like an accusation. However, you're proving my point.

My point is to ask why some (such as Fuji, Olympus, and others) have native ISO starting at 200 when they could do better?

The proof that they could do better is several other brands with base ISO starting at 100, and some Sony at 50. So it's established (and you provided further proof) that it's possible to have native ISO start well below 200, and also well below 160. So why doesn't Fuji native ISO start at 50 or 100? Is there a technical reason? Cost? Something else?

It can't just be sensor size because there are many Nikon and Canon DSLR with 100 native ISO since 15 years ago. It can't be because of mirrorless combined with APS-C because Sony makes mirrorless APS-C with native 100 ISO.

Sorry you took it that way but it’s not accusatory. I am just stating the facts. M4/3 and Fuji makes up a minority of mirrorless cameras so I don’t think it’s accurate to say that many mirrorless cameras have base ISOs of 200. The vast majority of mirrorless cameras start at ISO 100. From you original post, it is clear you were of the mindset that most mirrorless cameras start at ISO 200 which simply isn’t true.

 

[Ysarex]

And here we go again...

Once upon a time, cameras metered for 18% gray (I'm ignoring the arguments about the exact percentage). 18% was usually pretty good for black-and-white negatives, but color photos looked a bit dark. Back in the days when I shot color slide film, I typically added about +1 Ev of exposure compensation to get images I liked.

WIth the digital age, Canon threw out the 18% gray "standard." They brightened up the pictures by about one stop, through the simple approach of renumbering the ISO. What used to be ISO 200, they called ISO 100. That caused the metering system to expose one stop brighter. Nikon held out for a while, but eventually followed suit. When Sony bought up the Konica-Minolta line, they too went with the lower ISO numbering which gave brighter pictures.

Digital ISO as specified by ISO 12232 has two different standards for the manufacturer to choose from. "Standard Output Sensitivity" (SOS) ISO requires that the in-camera sRGB JPEG produce 18% gray when metering an 18% gray card... but there's an important exception I talk about below. "Recommended Exposure Index" (REI) ISO lets the camera manufacturer set the ISO to whatever gives exposures they think their customers will like.

Fujifilm, Olympus, Panasonic, and Ricoh/Pentax rate their ISO using SOS. If you manually set the exposure using readings from a handheld light meter, you'll get in-camera JPEGs that are exposed about the same as slide film would have been.

Everybody else, including the big three of Canon, Nikon, and Sony, rate their ISO using REI. If you manually set the exposure using readings from a handheld light meter, you'll get in-camera JPEGs that are exposed about about a stop brighter than slide film would have been.

So there you are. The same sensor that is rated at 100 ISO (REI) in a Sony is rated at 200 ISO (SOS) in a Fujifilm. [Do bear in mind that the one-stop difference is a matter of taste and can vary a bit.] Try it for yourself.

I did. I have Canon and Fuji cameras so I ran the test you describe below. Both cameras set to the same manual exposure with 1 stop difference in ISO. My Canon base ISO is 125 so I set the Fuji to ISO 250. Both exposures at 1 second f/6.3.

Set your Canon to ISO 100 and your Fuji to ISO 200, then set shutter speed and exposure the same on both (manual exposure mode). The JPEGs produced by both cameras will be exposed about the same.

They're not. The Fuji JPEG is 2/3 stop brighter than the Canon JPEG (I measured them in PS). Here they are side by side.



I then did another interesting test. The base ISO of the Fuji is 160 so I set both cameras to ISO 160 and ran a bracket set on both to see at what exposure the sensors reach saturation. I know this has nothing to do with the ISO values on the cameras since neither manufacturer uses sensor saturation as an ISO determinant. The sensors don't have assigned ISO values. It is however listed in the standard and used for example by DXO. And for someone like me who never saves a JPEG and exposes raw files based only on the sensor response it is interesting.

At the same ISO the difference in exposure required to bring both camera sensors to their saturation thresholds is less than 1/3 stop: the Canon at a shutter speed of 1.3 seconds and the Fuji at a shutter speed of 1.5 seconds.

An important point:

SOS ISO only applies to "dumb" metering modes like average, spot, center-weighted, etc. (or handheld light meters). In-camera multi-zone metering (Evaluative, Matrix, Multi, ESP, or whatever) is specifically intended to deliver pleasing exposures, so it doesn't matter what the ISO numbering is.

If you take a Canon, Nikon, Sony, or whatever and snap an sRGB JPEG of an 18% gray card, it'll come out about 25% gray regardless of metering mode. But do that with a Fujifilm or any other SOS-rated camera, and you'll get about 25% gray when using multi-zone metering and about 18% gray when using a dumb metering mode.

I think a strong case can be made that Fujifilm, Olympus, Panasonic, and Ricoh/Pentax should join the other manufacturers in abandoning SOS ISO in favor of REI ISO. But they haven't. Yet.

 

[Charley123]

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. 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 still have acceptable image quality at 1 stop higher ISO than would otherwise be the case.

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 ND filter.

 

[Charley123]

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. 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.

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.

 

[Ysarex]

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.

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.

 

[JNR]

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. 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.

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.

No. Really that is the complete answer, but some explanation might help.

Light is light, and its measurement at any given point has nothing to do with sensor size. To the extent that small sensors require greater magnification and consequently the spreading out of light captured to accomplish comparative viewing sizes - that is a fact, but ISO has nothing to do with that.

 

[Bill Ferris]

So there you are. The same sensor that is rated at 100 ISO (REI) in a Sony is rated at 200 ISO (SOS) in a Fujifilm. [Do bear in mind that the one-stop difference is a matter of taste and can vary a bit.]

Bear in mind the ISO standard does not specify how a manufacturer implements ISO during post-exposure processing of a photo. As a result, we can't assume the tonal palette a Nikon camera employs when rendering a JPEG at ISO 100 will have the same lightness as the tonal palette used any other manufacturer's camera at the same ISO. They could be quite noticably different.

Also, let's bear in mind the trivial role in-camera ISO often plays in final image appearance and quality. It's not that big a deal.

Try it for yourself. Set your Canon to ISO 100 and your Fuji to ISO 200, then set shutter speed and exposure the same on both (manual exposure mode). The JPEGs produced by both cameras will be exposed about the same.

Doug, I'm gonna offer a suggestion and it's only because your post goes into a lot of detail and gets a bit technical. Instead of describing the Sony and Fuji photos as being exposed about the same, say they have the same exposure. They do. They were photos of the same scene made at the same shutter speed and f-stop. Exposure was the same. ISO has no direct impact on the intensity of light delivered to the sensor and is, therefore, not an exposure setting. If they have a different lightness, it's because - again - the ISO standard does not mandate a uniform application of ISO in image processing. Any differences in lightness can typically be dealt with in processing at home with no negative affect on image quality.

It's just an adjustment in lightness. This is something the OP does not seem to grasp.

As more and more digital cameras are built around sensors being invariant across a wide range of ISOs, it's become a rather trivial setting. Once a photographer has determined which shutter speed and f-stop to use, a choice of ISO doesn't necessarily matter all that much. Sure, if a person is working in a very low light environment, they may want to use a very high ISO to benefit from a potential read noise advantage. If a photographer wishes to minimize time spent adjusting image lightness in post or if it makes image review in the field easier, they may choose to use an ISO that will render an image very close to the lightness they desire.
But strictly from an image quality standpoint, the ISO used for much of the photography a person does can be pretty trivial. It can be 4-5 stops darker than the tonal palette ultimately used to render the finished photo and image quality will not be noticeably impacted. Once exposure is set and the total amount of light a camera has to work with is determined, raw image quality is locked-in. ISO isn't a factor in that.

This is why I find all the sturm und drang over this topic a bit amusing. An awful lot of attention is being given a setting that has no impact on the appearance of a photo until after the shutter actuation has ended and, often times, does not need to be set with anything remotely close to precision.

ISO is a post-exposure setting used to manage the lightness of the rendered JPEG. Often, we have quite a bit of latitude to adjust image lightness in whichever image processing and editing app one uses. We've less latitude to darken an image (about a full stop) without losing detail in highlights. But when it comes to lifting shadows, we often have 4-5 stops of latitude...not that it's common to avail one's self of such an extreme adjustment, but it's nice to know the option is availabile.

Many Fuji X-T series cameras have a base ISO of 200. And...so what? It's not a big deal.

 

[Sjak]

Using fill flash on a sunny day is easier at ISO 100 than it is at ISO 200 due to easier to sync flash, which would be especially beneficial to Fuji camera, which have a rather slow max shutter flash sync speed of 1/180.

Most current cameras and flashes have the option of HSS, so you're not limited to 1/180 for fill flash.

 

[Charley123]

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.

Why do you think native ISO starts at 200?

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.

 

[Charley123]

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. 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.

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.

No. Really that is the complete answer, but some explanation might help.

Light is light, and its measurement at any given point has nothing to do with sensor size. To the extent that small sensors require greater magnification and consequently the spreading out of light captured to accomplish comparative viewing sizes - that is a fact, but ISO has nothing to do with that.

Your post confuses me. It sounds to me like you said no, yes, no. I don't understand your meaning.

 

[Charley123]

And here we go again...

Once upon a time, cameras metered for 18% gray (I'm ignoring the arguments about the exact percentage). 18% was usually pretty good for black-and-white negatives, but color photos looked a bit dark. Back in the days when I shot color slide film, I typically added about +1 Ev of exposure compensation to get images I liked.

WIth the digital age, Canon threw out the 18% gray "standard." They brightened up the pictures by about one stop, through the simple approach of renumbering the ISO. What used to be ISO 200, they called ISO 100. That caused the metering system to expose one stop brighter. Nikon held out for a while, but eventually followed suit. When Sony bought up the Konica-Minolta line, they too went with the lower ISO numbering which gave brighter pictures.

Digital ISO as specified by ISO 12232 has two different standards for the manufacturer to choose from. "Standard Output Sensitivity" (SOS) ISO requires that the in-camera sRGB JPEG produce 18% gray when metering an 18% gray card... but there's an important exception I talk about below. "Recommended Exposure Index" (REI) ISO lets the camera manufacturer set the ISO to whatever gives exposures they think their customers will like.

Fujifilm, Olympus, Panasonic, and Ricoh/Pentax rate their ISO using SOS. If you manually set the exposure using readings from a handheld light meter, you'll get in-camera JPEGs that are exposed about the same as slide film would have been.

Everybody else, including the big three of Canon, Nikon, and Sony, rate their ISO using REI. If you manually set the exposure using readings from a handheld light meter, you'll get in-camera JPEGs that are exposed about about a stop brighter than slide film would have been.

So there you are. The same sensor that is rated at 100 ISO (REI) in a Sony is rated at 200 ISO (SOS) in a Fujifilm. [Do bear in mind that the one-stop difference is a matter of taste and can vary a bit.] Try it for yourself. Set your Canon to ISO 100 and your Fuji to ISO 200, then set shutter speed and exposure the same on both (manual exposure mode). The JPEGs produced by both cameras will be exposed about the same.

An important point:

SOS ISO only applies to "dumb" metering modes like average, spot, center-weighted, etc. (or handheld light meters). In-camera multi-zone metering (Evaluative, Matrix, Multi, ESP, or whatever) is specifically intended to deliver pleasing exposures, so it doesn't matter what the ISO numbering is.

If you take a Canon, Nikon, Sony, or whatever and snap an sRGB JPEG of an 18% gray card, it'll come out about 25% gray regardless of metering mode. But do that with a Fujifilm or any other SOS-rated camera, and you'll get about 25% gray when using multi-zone metering and about 18% gray when using a dumb metering mode.

I think a strong case can be made that Fujifilm, Olympus, Panasonic, and Ricoh/Pentax should join the other manufacturers in abandoning SOS ISO in favor of REI ISO. But they haven't. Yet.

You gave a great scientific and historical lesson-explanation. Thank you!

So all the digital cameras native ISO sensitivity really starts at approx SOS 200 ISO?

Is there a technological reason that native ISO of digital cameras can't start at a true SOS 50 or 100 ISO? Wouldn't that be an advantage on bright sunny days?

 

[Ysarex]

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. 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.

 

[Ysarex]

And here we go again...

Once upon a time, cameras metered for 18% gray (I'm ignoring the arguments about the exact percentage). 18% was usually pretty good for black-and-white negatives, but color photos looked a bit dark. Back in the days when I shot color slide film, I typically added about +1 Ev of exposure compensation to get images I liked.

WIth the digital age, Canon threw out the 18% gray "standard." They brightened up the pictures by about one stop, through the simple approach of renumbering the ISO. What used to be ISO 200, they called ISO 100. That caused the metering system to expose one stop brighter. Nikon held out for a while, but eventually followed suit. When Sony bought up the Konica-Minolta line, they too went with the lower ISO numbering which gave brighter pictures.

Digital ISO as specified by ISO 12232 has two different standards for the manufacturer to choose from. "Standard Output Sensitivity" (SOS) ISO requires that the in-camera sRGB JPEG produce 18% gray when metering an 18% gray card... but there's an important exception I talk about below. "Recommended Exposure Index" (REI) ISO lets the camera manufacturer set the ISO to whatever gives exposures they think their customers will like.

Fujifilm, Olympus, Panasonic, and Ricoh/Pentax rate their ISO using SOS. If you manually set the exposure using readings from a handheld light meter, you'll get in-camera JPEGs that are exposed about the same as slide film would have been.

Everybody else, including the big three of Canon, Nikon, and Sony, rate their ISO using REI. If you manually set the exposure using readings from a handheld light meter, you'll get in-camera JPEGs that are exposed about about a stop brighter than slide film would have been.

So there you are. The same sensor that is rated at 100 ISO (REI) in a Sony is rated at 200 ISO (SOS) in a Fujifilm. [Do bear in mind that the one-stop difference is a matter of taste and can vary a bit.] Try it for yourself. Set your Canon to ISO 100 and your Fuji to ISO 200, then set shutter speed and exposure the same on both (manual exposure mode). The JPEGs produced by both cameras will be exposed about the same.

An important point:

SOS ISO only applies to "dumb" metering modes like average, spot, center-weighted, etc. (or handheld light meters). In-camera multi-zone metering (Evaluative, Matrix, Multi, ESP, or whatever) is specifically intended to deliver pleasing exposures, so it doesn't matter what the ISO numbering is.

If you take a Canon, Nikon, Sony, or whatever and snap an sRGB JPEG of an 18% gray card, it'll come out about 25% gray regardless of metering mode. But do that with a Fujifilm or any other SOS-rated camera, and you'll get about 25% gray when using multi-zone metering and about 18% gray when using a dumb metering mode.

I think a strong case can be made that Fujifilm, Olympus, Panasonic, and Ricoh/Pentax should join the other manufacturers in abandoning SOS ISO in favor of REI ISO. But they haven't. Yet.

You gave a great scientific and historical lesson-explanation. Thank you!

So all the digital cameras native ISO sensitivity really starts at approx SOS 200 ISO?

Is there a technological reason that native ISO of digital cameras can't start at a true SOS 50 or 100 ISO?

No. And they do. Differences between the SOS and REI standards do not determine base ISO values on different cameras that use either standard.

Wouldn't that be an advantage on bright sunny days?

 

[Charley123]

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.

 

[Ysarex]

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?

You'll have to ask them. Since Fuji cameras use the same Sony sensor that Sony uses in their own cameras with base ISO set to 100 it's fair to assume Fuji could also have set the base ISO to 100. My Fuji X-T2 with base ISO 200 does have a L ISO setting of 100.

I would assume Fuji's decision to establish 200 as the base ISO is a feature that the engineers deemed attractive. It doesn't have any effect on the camera's higher ISO values or high ISO performance -- that isn't affected by where the base ISO is set. It may be because the engineers thought it was an appropriate choice to protect highlights from clipping on the sensor. It may be that they did a market study and asked users what they wanted and took that into consideration.

But again, since Sony can use the same sensor in one of their cameras and set the base ISO to 100 it's fair to assume Fuji's choice to use ISO 200 or 160 with that sensor was a design decision -- a feature. It helps sell 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.