What's up with Fuji ISO values?

[Mads Bjerke]

I was out shooting two different systems today.

Setup 1: X-T3 with XF100-400mm
Setup 2: Nikon D500 with 200-500mm

Both cameras set to the same exposure values: iso2000 - 1/2000s - f5.6

The X-T3 is at least one full stop darker:

This means I can shoot the Nikon at 1/4000s or f8.0 or iso1000 and get the same exposure.
That is a big advantage for wildlife.

Anyone else found a similar comparison with other cameras?
Not really sure what to read into this.

I would be interested in your comments and experiences.

madsbjerke.com

Simple explanation - ISO standard 12232:2006 defines what ISO means for digital sill cameras and gives three methods that can be used to calibrate the ISO.

In film the ISO was more or less directly related to the light sensitivity of the film. This was particularly true for color film, although with B&W there was some leeway since the developer used would impact the working ISO which as often not the same as the advertised (calibrated by the film maker's) ISO.

With digital - particularly CMOS sensors with the integration of amplification - the direct relationship between ISO and sensitivity is not as direct. With the advent of low noise CMOS sensors - sometimes advertised as ISO less - the ISO becomes even more ambiguous and confusing.

What you see is different camera makers used different - but all approved by ISO standard 12232:2006 to measure and calibrate their ISO.

https://en.wikipedia.org/wiki/Film_speed

As someone else has or will post - Fuji choses a measurement method that produces more headroom for digital capture. Hence the noted "under exposure." One could just claim the Nikon is over exposed. Neither is right - they are simply using different standards for measuring reporting "sensitivity." Both are correct by the standards.

If you don't like the Fuji system, the EC dial is your friend.

Thanks for the clarification.
I knew I would learn something from this thread

I will play with the two systems and see what the outcome is.

 

[Phil BH]

This never bothered me. I came from film. Different films had to be exposed differently, despite the ASA (ISO) rating. You simply need to learn your medium, in this case the particular camera you are shooting, and expose based on its characteristics, just as we did with film.

 

[atalwar]

I was out shooting two different systems today.

Setup 1: X-T3 with XF100-400mm
Setup 2: Nikon D500 with 200-500mm

Both cameras set to the same exposure values: iso2000 - 1/2000s - f5.6

The X-T3 is at least one full stop darker:

This means I can shoot the Nikon at 1/4000s or f8.0 or iso1000 and get the same exposure.
That is a big advantage for wildlife.

Anyone else found a similar comparison with other cameras?
Not really sure what to read into this.

I would be interested in your comments and experiences.

madsbjerke.com

Simple explanation - ISO standard 12232:2006 defines what ISO means for digital sill cameras and gives three methods that can be used to calibrate the ISO.

In film the ISO was more or less directly related to the light sensitivity of the film. This was particularly true for color film, although with B&W there was some leeway since the developer used would impact the working ISO which as often not the same as the advertised (calibrated by the film maker's) ISO.

With digital - particularly CMOS sensors with the integration of amplification - the direct relationship between ISO and sensitivity is not as direct. With the advent of low noise CMOS sensors - sometimes advertised as ISO less - the ISO becomes even more ambiguous and confusing.

What you see is different camera makers used different - but all approved by ISO standard 12232:2006 to measure and calibrate their ISO.

https://en.wikipedia.org/wiki/Film_speed

As someone else has or will post - Fuji choses a measurement method that produces more headroom for digital capture. Hence the noted "under exposure." One could just claim the Nikon is over exposed. Neither is right - they are simply using different standards for measuring reporting "sensitivity." Both are correct by the standards.

If you don't like the Fuji system, the EC dial is your friend.

Thanks for the clarification.
I knew I would learn something from this thread

I will play with the two systems and see what the outcome is.

I have a 35/1.8 for Nikon and 35/1.4 for fuji. If required I can do a test tomorrow at say f/4 or whatever. Can also test 18-55 against 18-140 Nikon $f/4 or above.

Also can check nikon adapted lenses wide open on fuji, but cannot tell for sure if with adapter wide open is actually the actual wide open aperture..

 

[rwbaron]

the rest is just smoke and mirrors.

PDR

According to actual tests on cameras in the field by Bill Claff;

Low light ISO

X-T3 = 3258 (slight advantage)

D500 = 2557

Maximum photographic dynamic range

D500 = 10.65 at ISO 100 (slight advantage)

X-T3 = 10.35 at ISO 160

Low light EV

X-T3 = 10.03 (slight advantage)

D500 = 9.68

Pretty much a wash which makes sense as they're both most likely using very similar sensor technology which has for the most part hit a wall a few years ago.

Bob

 

[Jim Cassatt]

I have not read all of the replies, but will offer my observations. I do a lot of studio work and measure flash output with my trusty Sekonic flash meter. When I was shooting with Canon, my exposures were spot on. With Fuji (and I have owned four bodies), if I set the ISO on the camera for 200, I have to set the ISO to 125 on my flash meter. This issue has been discussed extensively over the years that I have owned Fuji's. That goes back to 2013 with my XE-2.

 

[Christof21]

the rest is just smoke and mirrors.

PDR

According to actual tests on cameras in the field by Bill Claff;

Low light ISO

X-T3 = 3258 (slight advantage)

D500 = 2557

Maximum photographic dynamic range

D500 = 10.65 at ISO 100 (slight advantage)

X-T3 = 10.35 at ISO 160

Low light EV

X-T3 = 10.03 (slight advantage)

D500 = 9.68

Pretty much a wash which makes sense as they're both most likely using very similar sensor technology which has for the most part hit a wall a few years ago.

Bob

These numbers are wrong because the ISO is not the same between brands.

"Note that the x-axis is ISO Setting and not a "measured" value"

Well except for the max photographic dynamic range

 

[rwbaron]

the rest is just smoke and mirrors.

PDR

According to actual tests on cameras in the field by Bill Claff;

Low light ISO

X-T3 = 3258 (slight advantage)

D500 = 2557

Maximum photographic dynamic range

D500 = 10.65 at ISO 100 (slight advantage)

X-T3 = 10.35 at ISO 160

Low light EV

X-T3 = 10.03 (slight advantage)

D500 = 9.68

Pretty much a wash which makes sense as they're both most likely using very similar sensor technology which has for the most part hit a wall a few years ago.

Bob

These numbers are wrong because the ISO is not the same between brands.

"Note that the x-axis is ISO Setting and not a "measured" value"

Well except for the max photographic dynamic range

The exposure triangle does not apply to digital so ISO is not a factor, only aperture and shutter value. It appears the OP is in the film mindset but with digital ISO has become an arbitrary value for brightness.

Yes, max PDR is the important measure here. What the OP was seeing was the difference in how the cameras ISO values are calibrated by the manufacturers. I'm confident that if the OP dug deeper into the raw files he'd find nearly a stop more highlight headroom in the X-T3 raw compared to the D500 and the opposite being the case in the shadows when shot at identical aperture, shutter and indicated ISO. There's also the T-value of the lenses but for the sake of this comparison I doubt it's a factor. In reality the noise floor of the sensors in the cameras are maybe a 1/3rd stop apart of which the ISO setting has no effect.

It's all about knowing your equipment and how to get the best from it.

Bob

 

[rwbaron]

Fuji underexposes to protect highlights. Nothing to worry about.

Well, actually this isn't about the cameras metering bias.
This is about what the camera says it will do compared to what it actually does.

Both systems where set to manual exposure.
I always use manual exposure, so the meter doesn't enter into it.

What I am getting at is something like this;

• Two racing cars are doing a drag race.
• Both are supposed to be 1000bhp and evenly matched in power.
• Turns out one is 500bhp, but the manufacturers used a different measuring standard to make it look it is 1000bhp.
• The real 1000bhp car pulls away and wins.

If I can do double the shutter speed (or half the iso) in one system and still get equal exposure, that is a very real difference and something I would personally care about.

Granted this only matters where speed is important, landscape photographers don't need to worry.
For sports and wildlife this is VERY important.

We have to pay a lot of money to gain 1 stop of extra light when buying lenses.
The difference in price between a f5.6 and f4.0 lens can be thousands.

If the camera takes that stop away in effective exposure it makes the rest of the system very expensive.

madsbjerke.com

I believe I understand this in my mind after reading countless threads for years on this topic in both the Canon and Photographic Science and Tech forums. There are some very smart people on DPR's forums (some physicists, some engineers, some just plain smart) and paying attention to what they say has been enlightening. I may not get all the technical nuances correct and if so then hopefully others will set the record straight.

There are others that are much better at explaining this than I but what you're seeing is the difference in how the two cameras ISO values are calibrated in viewing what the sensors captured. Upon initial thought you might think "well, Fuji is screwing us" but that's not really the case. Fuji simply biases their ISO values differently than Nikon.

In essence what you experienced was both cameras captured the scene equally and I believe if you used a program such as "Raw Digger" it would show very similar values for the raw files. The D500 simply boosted the brightness by nearly a stop with a tag on the raw file for the raw converter.

Both cameras have about 10.5 stops of maximum photographic dynamic range to work with and it's the aperture and shutter value that determines how much of the sensor's full well capacity (FWC) is utilized, not ISO. Think of ISO as simply an aid to getting the best possible capture from the sensor. Fuji's ISO is biased toward highlight protection whereas the Nikon is biased more to protect the shadows. I know this can be difficult to wrap one's head around (it certainly was for me) but ISO is not really part of exposure for digital. With current day digital sensors we have an exposure duet being simply aperture and shutter speed. ISO is really just amplification of what the sensor captured and is a value of brightness applied to view the image. It's an aid in helping us to extract the most from the sensor but it's important to know how ISO is biased as you just found out.

What it comes down to is a paradigm shift from film. There is no "exposure triangle" with digital that was ingrained in us when we learned to shoot with film. With digital it's a matter of setting aperture and shutter speed optimally to get as close to saturating the sensor as possible (FWC) without blowing the highlights. ISO values tells us how well we did in achieving that goal but with differing standards by manufacturers.

I have to think hard about this when trying to express my thoughts because for many of us "old school photographers" this is a whole new mindset.

I hope this was of some help.

Bob

 

[ikaika777]

I'll let people with more technical knowledge than me explain it in detail, but my understanding is that Fuji uses a different ISO standard than some of the other manufacturers. A quick Google search for "Fuji ISO" results in a number of articles about this, as well as previous threads on this forum and others. Here's the first one I saw from DPR, though surely there have been others:

https://www.dpreview.com/forums/post/53391280

Yep, ISO standards for digital cameras were updated in 2006. There isn't one single standard. Fuji uses SOS (Standard Output Sensitivity) for their cameras and Nikon uses REI (Recommended Exposure Index).

Sounds like Fujifilm should play "fair" and use the REI standard since that is what appears to be a common standard.

My iso160 - 12800 X-T3 behaves like an iso320 - 6400 Nikon D500 in exposure terms.

How is Fuji, “not playing fair” when they are using an accepted industry standard? That makes absolutely no logical sense because you’re blaming Fuji for not playing fair because they ARE playing fair by using an accepted industry standard.

--
After all is said and done and your photo is hanging on the wall, no one is going to know or care what camera, lens, or what post processing you used. All they care about is if the image moves them.

 

[racin06]

I agree in your statements above.

The question is where it leaves you when light is marginal and you need to keep the shutter speed up.

I am ok with ignoring the iso value in itself, but when you are pushing the sensor towards its limits at the high iso end you will inevitably end with a poorer quality image.

Fast action requires a high shutter speed.
There is no substitute for that.

There is plenty of sports, action and wildlife being shot with the X-T3 and in low light. Losing one stop of light today is much different than losing that even just 10 years ago. Today's sensor technology combined with noise reduction software produces excellent images shot in low light. Quit belly-aching about one stop of light. Below are images I shot in poor lighting conditions in a high school gymnasium AND shot with the older X-T2. Fujifilm cameras perform very well in low light.

 

[Morris0]

I agree with your observation. Don't worry about as you are now shooting mirror less and when you make exposure adjustments they will appear before your eyes in the EVF or on the LCD. You will soon wonder why you ever used and SLR.

Morris

As I have both systems I can attest to the benefits of both OVF and EVF's.
I added the mirrorless systems about 18 months ago and they are great.

It is however a worry that the X-T3 underexposes and as a result I have to sacrifice either shutter speed or iso to regain the exposure (compared to my D500).

By the numbers, I see less noise in a X-T3 ISO 1600 than a D500 ISO 800 and I used to own a D500. They are both great cameras.

Morris

 

[Morris0]

I agree with your observation. Don't worry about as you are now shooting mirror less and when you make exposure adjustments they will appear before your eyes in the EVF or on the LCD. You will soon wonder why you ever used and SLR.

Morris

As I have both systems I can attest to the benefits of both OVF and EVF's.
I added the mirrorless systems about 18 months ago and they are great.

It is however a worry that the X-T3 underexposes and as a result I have to sacrifice either shutter speed or iso to regain the exposure (compared to my D500).

Dude you are not sacrificing anything with regards to shutter speed once you hit 1/1000.

Really?
Birds erratically moving at high speed typically need 1/2000 - 1/4000 to freeze.

Let the wings blur and imply motion.

Morris

 

[SwedishPhoto]

I wouldn't say Fuji themselves are cheating anyone. But where it sometimes goes wrong, is when different sites/channels review Fuji cameras and rave about the high ISO (comparing the Fujis to other cameras). Which obviously isn't fair, considering they use a different ISO standard that "benefits" them in tests like these.

I noticed someone say that the ISO standard Fuji's using is the more common one in the industry. This can't be true, can it? I thought it was only Fuji (among Canon, Nikon, Sony, Pentax etc.) that was using this ISO standard?

 

[Mads Bjerke]

Fuji underexposes to protect highlights. Nothing to worry about.

Well, actually this isn't about the cameras metering bias.
This is about what the camera says it will do compared to what it actually does.

Both systems where set to manual exposure.
I always use manual exposure, so the meter doesn't enter into it.

What I am getting at is something like this;

• Two racing cars are doing a drag race.
• Both are supposed to be 1000bhp and evenly matched in power.
• Turns out one is 500bhp, but the manufacturers used a different measuring standard to make it look it is 1000bhp.
• The real 1000bhp car pulls away and wins.

If I can do double the shutter speed (or half the iso) in one system and still get equal exposure, that is a very real difference and something I would personally care about.

Granted this only matters where speed is important, landscape photographers don't need to worry.
For sports and wildlife this is VERY important.

We have to pay a lot of money to gain 1 stop of extra light when buying lenses.
The difference in price between a f5.6 and f4.0 lens can be thousands.

If the camera takes that stop away in effective exposure it makes the rest of the system very expensive.

madsbjerke.com

I believe I understand this in my mind after reading countless threads for years on this topic in both the Canon and Photographic Science and Tech forums. There are some very smart people on DPR's forums (some physicists, some engineers, some just plain smart) and paying attention to what they say has been enlightening. I may not get all the technical nuances correct and if so then hopefully others will set the record straight.

There are others that are much better at explaining this than I but what you're seeing is the difference in how the two cameras ISO values are calibrated in viewing what the sensors captured. Upon initial thought you might think "well, Fuji is screwing us" but that's not really the case. Fuji simply biases their ISO values differently than Nikon.

In essence what you experienced was both cameras captured the scene equally and I believe if you used a program such as "Raw Digger" it would show very similar values for the raw files. The D500 simply boosted the brightness by nearly a stop with a tag on the raw file for the raw converter.

Both cameras have about 10.5 stops of maximum photographic dynamic range to work with and it's the aperture and shutter value that determines how much of the sensor's full well capacity (FWC) is utilized, not ISO. Think of ISO as simply an aid to getting the best possible capture from the sensor. Fuji's ISO is biased toward highlight protection whereas the Nikon is biased more to protect the shadows. I know this can be difficult to wrap one's head around (it certainly was for me) but ISO is not really part of exposure for digital. With current day digital sensors we have an exposure duet being simply aperture and shutter speed. ISO is really just amplification of what the sensor captured and is a value of brightness applied to view the image. It's an aid in helping us to extract the most from the sensor but it's important to know how ISO is biased as you just found out.

What it comes down to is a paradigm shift from film. There is no "exposure triangle" with digital that was ingrained in us when we learned to shoot with film. With digital it's a matter of setting aperture and shutter speed optimally to get as close to saturating the sensor as possible (FWC) without blowing the highlights. ISO values tells us how well we did in achieving that goal but with differing standards by manufacturers.

I have to think hard about this when trying to express my thoughts because for many of us "old school photographers" this is a whole new mindset.

I hope this was of some help.

Bob

Thanks Bob,

Good points indeed.
I have learnt a lot about iso standards from this thread so it's been useful for me.

I was initially very surprised to see the darker images out of the X-T3 and that prompted my curiosity.

Many here in this thread seems to take this as a dig at Fujifilm, perhaps a bit of trolling, but that is not my intention.

I have a MUCH bigger investment in Fuji gear than anything else.
I shot Nikon for 30 years - both film and digital - and made the change to Fujifilm about 18 months ago.

I sold My D500 and all my Nikon glass and converted it into XF lenses.
Very satisfied with that decision.

Today I use the X-T3 for faster action and the GFX50s when it is appropriate.

I spent an afternoon with a photographer who had the D500 and the Nikon 200-500/f5.6 lens.
We where both shooting the herons and and he kept trolling me about how much better the DSLR would be for tracking BIF.
So I borrowed his camera and took a few hundred frames.
I swapped between the X-T3 and the D500 for a while and took the images home to compare.


That prompted this thread.

 

[atalwar]

All the confusion about ISO standards etc is because there are NO ISO Units. It's the ISO (organisation) that should have thought about it instead of Just allowing multiple standards without any distinction.

 

[Truman Prevatt]

All the confusion about ISO standards etc is because there are NO ISO Units. It's the ISO (organisation) that should have thought about it instead of Just allowing multiple standards without any distinction.

ISO is a standards organization. It stands for International Organization for Standardization. It is a consortium of stake holders in various fields and who meet and set standards within that field. The address film speed or sensor sensitivity as ISO is somewhat a misnomer. ISO sets standards in many areas, e.g., banking, technical terminology, QC and QA, not just photography related, etc.

The standard for film speed and sensor sensitivity for digital photography have been developed by subcommittees that include all the stakeholders. There is a single standard. However, given every camera design is different, not all camera can test and calibrate using the same testing procedure. Hence, there are three recognized testing procedures. They don't produce the same exact to the fourth decimal point numbers. However, they are close, a 1/3 to 2/3 stop.

I don't know why this seems to be such a big deal with some. Even when it was called DIN (German) or ASA (USA) standards organizations specifying film speed - or more accurately the testing procedures to measure film speed no two films that test to ASA 100 were the same to four decimal places. If one looks at the ISO for film it was quantizied to more or less 1/3 stop increments, ASA 200, 250, 320, 400, 500, etc.

In reality you never believed the ASA (later ISO ) film speed rating - you tested it in your camera and with your meter to determine your working ASA. With B&W film, the developer used and development process used, e.g. agitation time and interval, developer dilution, water bath or stand, etc.) all determined the film density at a given exposure so something like TriX could be shot legitimately at anywhere from ASA (IS0) 100 to 800 depending of developing factors.

The key is to find a setting that works for a camera and situation. If that means set it at ISO defined by the camera and applying a +/- exposure compensation to get the exposure one wants - so be it.

ISO standards for film/sensor speed are as set of test procedures that are used to establish the sensor speed. For digital there are three. There are three simply because no standards organization is not to dictate a companies design and different designs often can't be tested using the same exact procedures.

This isn't big deal, an no one is lying.

 

[tokumeino]

Best thread about that : https://www.dpreview.com/forums/post/55451071 (and in particular, this post : https://www.dpreview.com/forums/post/55451272)

There is a special tag in the RAF files (0x9650), indicating an exposure shift to be applied to the RAW data values so as to get a correctly exposed JPEG at the end (all this is performed "behind the scene" since the tag is an instruction to the RAW converter). RAW files are actually underexposed at capture time (less analog gain as far as I understand) and then brightened by the same amount during conversion. The exposure shift depends on ISO :

• 200 : -0.72 EV
• 400 : -0.72 EV
• 800 : -0.72 EV
• 1600 : -0.72 EV
• 3200 : -1.26 EV
• 6400 : -2.26 EV

... which means that when you shoot at ISO 6400, the stored RAW values are roughly the same as if you would have shot darker at 3200 ISO (underexposed but not by the means of SS or aperture : rather by using a lesser analog amplification) ; and you'll need to push brightness afterwards to get equivalent JPEG values. Provided that sensors are close to invariant, it is OK and it appears to me more like a highlight-conservative approach rather than a "cheat". It is actually a non-issue.

Long story, short : with Fuji, you have better highlights protection at the cost of no ISO100. At ISO 200 and above, same noise.

 

[rwbaron]

Fuji underexposes to protect highlights. Nothing to worry about.

Well, actually this isn't about the cameras metering bias.
This is about what the camera says it will do compared to what it actually does.

Both systems where set to manual exposure.
I always use manual exposure, so the meter doesn't enter into it.

What I am getting at is something like this;

• Two racing cars are doing a drag race.
• Both are supposed to be 1000bhp and evenly matched in power.
• Turns out one is 500bhp, but the manufacturers used a different measuring standard to make it look it is 1000bhp.
• The real 1000bhp car pulls away and wins.

If I can do double the shutter speed (or half the iso) in one system and still get equal exposure, that is a very real difference and something I would personally care about.

Granted this only matters where speed is important, landscape photographers don't need to worry.
For sports and wildlife this is VERY important.

We have to pay a lot of money to gain 1 stop of extra light when buying lenses.
The difference in price between a f5.6 and f4.0 lens can be thousands.

If the camera takes that stop away in effective exposure it makes the rest of the system very expensive.

madsbjerke.com

I believe I understand this in my mind after reading countless threads for years on this topic in both the Canon and Photographic Science and Tech forums. There are some very smart people on DPR's forums (some physicists, some engineers, some just plain smart) and paying attention to what they say has been enlightening. I may not get all the technical nuances correct and if so then hopefully others will set the record straight.

There are others that are much better at explaining this than I but what you're seeing is the difference in how the two cameras ISO values are calibrated in viewing what the sensors captured. Upon initial thought you might think "well, Fuji is screwing us" but that's not really the case. Fuji simply biases their ISO values differently than Nikon.

In essence what you experienced was both cameras captured the scene equally and I believe if you used a program such as "Raw Digger" it would show very similar values for the raw files. The D500 simply boosted the brightness by nearly a stop with a tag on the raw file for the raw converter.

Both cameras have about 10.5 stops of maximum photographic dynamic range to work with and it's the aperture and shutter value that determines how much of the sensor's full well capacity (FWC) is utilized, not ISO. Think of ISO as simply an aid to getting the best possible capture from the sensor. Fuji's ISO is biased toward highlight protection whereas the Nikon is biased more to protect the shadows. I know this can be difficult to wrap one's head around (it certainly was for me) but ISO is not really part of exposure for digital. With current day digital sensors we have an exposure duet being simply aperture and shutter speed. ISO is really just amplification of what the sensor captured and is a value of brightness applied to view the image. It's an aid in helping us to extract the most from the sensor but it's important to know how ISO is biased as you just found out.

What it comes down to is a paradigm shift from film. There is no "exposure triangle" with digital that was ingrained in us when we learned to shoot with film. With digital it's a matter of setting aperture and shutter speed optimally to get as close to saturating the sensor as possible (FWC) without blowing the highlights. ISO values tells us how well we did in achieving that goal but with differing standards by manufacturers.

I have to think hard about this when trying to express my thoughts because for many of us "old school photographers" this is a whole new mindset.

I hope this was of some help.

Bob

Thanks Bob,

Good points indeed.
I have learnt a lot about iso standards from this thread so it's been useful for me.

I was initially very surprised to see the darker images out of the X-T3 and that prompted my curiosity.

Many here in this thread seems to take this as a dig at Fujifilm, perhaps a bit of trolling, but that is not my intention.

I have a MUCH bigger investment in Fuji gear than anything else.
I shot Nikon for 30 years - both film and digital - and made the change to Fujifilm about 18 months ago.

I sold My D500 and all my Nikon glass and converted it into XF lenses.
Very satisfied with that decision.

Today I use the X-T3 for faster action and the GFX50s when it is appropriate.

I spent an afternoon with a photographer who had the D500 and the Nikon 200-500/f5.6 lens.
We where both shooting the herons and and he kept trolling me about how much better the DSLR would be for tracking BIF.
So I borrowed his camera and took a few hundred frames.
I swapped between the X-T3 and the D500 for a while and took the images home to compare.

That prompted this thread.

Thanks and I understand.

I know from personal experience that this is not easy to wrap one's mind around as it certainly wasn't for me. It requires a paradigm shift in the way our cameras work from the perspective of exposure. ISO values are really just a guide as to how how much light we're exposing the sensor to at capture, nothing more. The noise performance of Nikon, Fuji, Sony and other cameras using Sony sensors are for all intents and purposes so similar as to not be a factor. The only meaningful difference in performance pertains to size (area) for light gathering (m43, APS C, FF, MF). In your example the D500 ISO setting tagged the file to be nearly a stop brighter when converted by Lr but that's no different than you adding that brightness in Lr to the X-T3 file because in reality they both received the same exposure at capture and the sensors are very similar in performance.

If this bothers you then I suggest setting the exposure comp dial to +2/3rd's for normal shooting and your results will be similar to the D500 but you'll also loose 2/3rd's of stop of highlight headroom in the raw file just as does the D500.

Bob

 

[Truman Prevatt]

Best thread about that : https://www.dpreview.com/forums/post/55451071 (and in particular, this post : https://www.dpreview.com/forums/post/55451272)

There is a special tag in the RAF files (0x9650), indicating an exposure shift to be applied to the RAW data values so as to get a correctly exposed JPEG at the end (all this is performed "behind the scene" since the tag is an instruction to the RAW converter). RAW files are actually underexposed at capture time (less analog gain as far as I understand) and then brightened by the same amount during conversion. The exposure shift depends on ISO :

• 200 : -0.72 EV
• 400 : -0.72 EV
• 800 : -0.72 EV
• 1600 : -0.72 EV
• 3200 : -1.26 EV
• 6400 : -2.26 EV

... which means that when you shoot at ISO 6400, the stored RAW values are roughly the same as if you would have shot darker at 3200 ISO (underexposed but not by the means of SS or aperture : rather by using a lesser analog amplification) ; and you'll need to push brightness afterwards to get equivalent JPEG values. Provided that sensors are close to invariant, it is OK and it appears to me more like a highlight-conservative approach rather than a "cheat". It is actually a non-issue.

Long story, short : with Fuji, you have better highlights protection at the cost of no ISO100. At ISO 200 and above, same noise.

Much of this architecture has to do with how Fuji implements their DR function. At DR 200 for example the lower the amplification out of the sensor array into the ADC to protect highlights. There is a tag that tells the raw converter to amplify digitally the jpeg.

I am sure also that something like this is common since the amplifiers have a finite set of stages and they can't set them at a large number of values. So I expect most cameras that use on chip amplification do a lot of the same thing that is set the amplification at a given ISO to not saturate - one step below saturation - and then tag it in the meta data so that the raw converter can make up for the difference. Newer sensor make that a pretty attractive approach.

 

[Ben Jenssen]

Hi. This thread inspired me to do a ISO test and start a new thread:

My little ISO test