ISO questions

[Soocom1]

Jola one and all.

It has been a VERY long time since I have posted, but given recent events I am now searching for the answers that I do not know.

This is an ISO question that I have yet to find a comprehensive answer for and for various insundry reasons the major search engines compile answers for those less knowledgeable.

WHY is it that the major manufacturers are not producing, nor writing code for existing digital SLR's to shoot below 100 or 50 ISO.

Why cannot we see DSLR's with ISO's below 50 to say 25, 12, 6 or even 2 or 1 speed?

We can set the old film cameras as such, what's the disappeal of doing so for mid-level or even high level DSLR's?

Ill read what you can write.

 

[Mr.Photo]

I do know that in the case of Nikon, the D4 has a normal ISO range of 100-12,800, and then has "extended" ranges called "Lo-1" (ISO 50) up to "Hi-4" (ISO 204,800). I'm not entirely sure what Canon has done, but I imagine they have something comparable.

I don't know the exact specifics of it, but I have heard that much of it is due to limitations in Sensor technology. I think the reason that you don't see the very low ISO's like you did in the film days is likely due to Sensor technology advancing to the point that ISO 100 is far better with regards to dynamic range, color saturation, clarity, etc. than even the lowest speed films available.

 

[The_Traveler]

If you want a 'slower' sensor, you could use a neutral density filter.

 

[480sparky]

......Why cannot we see DSLR's with ISO's below 50 to say 25, 12, 6 or even 2 or 1 speed?..........

Lack of a market. Few people really want such low ISOs. 99% of the market is clamoring for higher & higher ISOs, so the makers oblige them.

I, for one, would be thrilled with a D6x0 or D8x0-class body with a TRUE base ISO of.............. two. But Nikon doesn't listen to me.

 

[Ysarex]

If you had an ISO 12 sensor what would you do on overcast days or indoors or when you wanted to capture fast action -- hard to shoot sports with a tripod.

The base ISO, the light sensitivity, of a sensor is fixed in manufacture. It can not otherwise be changed. Any digital camera sensor has only one fixed light sensitivity level. When you raise the ISO on a digital camera you underexpose the sensor. That's a period. When you underexpose the sensor you record less data. That's a period. The camera electronics compensate by amplifying what you do record but that amplification never brings back the data you lost to underexposure; the amplification only normalizes what's left.

So would you then really want an ISO 12 sensor such that when you set the camera ISO to 25 you were underexposing by 1 stop and when you set the camera ISO to 100 you were underexposing by 3 stops and when you set the ISO to 400 you were underexposing by 5 stops etc.?

Lew's comment was very perceptive -- you can always put an ND filter on the camera to get slower shutter speeds or larger apertures. There's no negative ND filter.

Joe

 

[480sparky]

If you had an ISO 12 sensor what would you do on overcast days or indoors or when you wanted to capture fast action -- hard to shoot sports with a tripod.....

I'd use a camera with a higher base ISO..... like all those made today. Problem solved.

 

[beagle100]

Jola one and all.



WHY is it that the major manufacturers are not producing, nor writing code for existing digital SLR's to shoot below 100 or 50 ISO.

Why cannot we see DSLR's with ISO's below 50 to say 25, 12, 6 or even 2 or 1 speed?

We can set the old film cameras as such, what's the disappeal of doing so for mid-level or even high level DSLR's?

Ill read what you can write.

you can go to 50 ISO with some Canon DSLR models - the 5D2 and 5D3. I suppose they could do it for all cameras but the market seems to be for high ISO levels, not lower.

 

[Braineack]

You mean like Nikon? (Toshiba/Sony)

The D810's base ISO is 64. It can extend to ISO 32.

Compared to my camera it can shoot 2 stops faster, natively--1/8000 at 64ISO, vs 1/4000 at 100ISO--and has almost a full stop of extra DR recovery.

Canons that can shoot 50 ISO have less DR when extended from 100. And pretty much all only have 12 stops of DR from 100-800 ISO where Nikons are just about to break 15EV and only drop to 12EV by 800 ISO.

 

[goodguy]

you can go to 50 ISO with some Canon DSLR models - the 5D2 and 5D3. I suppose they could do it for all cameras but the market seems to be for high ISO levels, not lower.

I belive on the 5d II and 5D III 50ISO is not in its native ISO thus you really dont get the advantage of quality you get when using native ISO.
The 5D III native base ISO is 100ISO which is pretty standard to most cameras except very few like the D810 which is 64ISO native.

 

[KmH]

It's all about physics and chemistry, not software code.
The short answer is they don't do it, because they can't.

For film the size of the silver halide grains in the emulsion determines film speed.
The smaller the grains, the slower the film.

A grain of silver halide reacts to light for a limited time.
The smaller the grain, the shorter the time frame it can react to light.
Once that time has been reached, leaving the shutter opened does not garner additional exposure because the silver halide grains in the film emulsion no longer reacts to light.
That is known as a films point of reciprocity failure.

Reciprocity failure is a major reason astronomers were among the first to embrace digital imaging.
However, they discovered they had new problems to contend with, mainly image noise from image sensor dark current, but soon realized that cooling the image sensor helped keep dark current in check.

A pixel is a photodiode and a small array of transistors.
There is a significant amount of space around each photodiode occupied by the transistors that is not used to gather light.
that unused space prevents the density of pixels from approaching the even density of silver halide crystals in a slow speed film.

Today, most DSLR cameras use CMOS image sensors because CMOS uses less power than CCD image sensors and the voltage CMOS pixels develop during an exposure can be read faster than a CCD array image sensor.
Also with CMOS signal gain amplification circuitry can be placed immediately adjacent to the pixel.

 

[Soocom1]

A number of large format digital sensors (in the 4x5 and 8x10 range) are shooting at extremely low ISOs.

Forgive me if I seem a bit naïve in this regard, but if such is possible with said large sensors, why not the smaller sensors where if Nikon can hit 50 and my 1Ds can also shoot at 50, then what is the hold up for such slow speed? Keep in mind that my 1Ds also shoots to a 1200 ISO and the newer sensors are capable of shooting to 24K and above ISOs why not slower?

For those who have never shot slow speed, get a film camera and shoot some 25 ISO Ilford and see what I mean.

 

[Nettles]

As I understand it, ISO 50 is really ISO 100 with a bit of in-camera manipulation that some claim marginally helps to suppress noise. But according to Canon there’s about 1 stop less dynamic range in the highlights at ISO 50. Typically, the last thing we want to do is aggravate a sensor's inherent highlight limitations.

But this contrived ISO speed comes into its own when shooting wide apertures in bright conditions or with flash. It's also a bit like a ND filter that restricts light allowing for longer exposures and shallower depth of field.

 

[Braineack]

Canon's 50 iso is extended. any iso thats extended uses software to extend the range. Nikon's 64 ISO is native and the base ISO -- meaning at 65 iso it has the lowest SNR well well as the highest DR.

extending ISO is like if you took a shot at 100 ISO, saved a JPG, and then bumped the exposure a full stop and called the shot 200 ISO.

it also seems that losing out the highlights at 50 iso kinda defeats the purpose.

 

[Soocom1]

So I get the concept of native v. extended.

I also understand the concept that a native ISO of a given amount would then translate to difficulty in highly extended ranges. Fair enough.
So lets approach this from one particular standpoint.
if say the actual Native ISO of a given sensor is say 64 in the case of Nikon, and lets say they are able to (given a higher Mp count or such) drop the native to 25 then have whatever it takes to get it up to say 6400 as a max limit, what (previously stated) would happen tot he contrast aspects? Would there need to be a larger actual sensor size or such?

The only reason I challenge this is because if the ISO can now hit unimaginable levels of 12K 24K or beyond, then reversing the application of same principle could bring about lower ISO's but visa vie require different mechanisms in the actual shoot itself. (Large glass, diff image size, etc).
thought?

 

[Ysarex]

So I get the concept of native v. extended.

I also understand the concept that a native ISO of a given amount would then translate to difficulty in highly extended ranges. Fair enough.
So lets approach this from one particular standpoint.
if say the actual Native ISO of a given sensor is say 64 in the case of Nikon, and lets say they are able to (given a higher Mp count or such) drop the native to 25 then have whatever it takes to get it up to say 6400 as a max limit, what (previously stated) would happen tot he contrast aspects? Would there need to be a larger actual sensor size or such?

The only reason I challenge this is because if the ISO can now hit unimaginable levels of 12K 24K or beyond, then reversing the application of same principle could bring about lower ISO's but visa vie require different mechanisms in the actual shoot itself. (Large glass, diff image size, etc).
thought?

The process/principle that permits high ISO values (analog amplification or digital scaling) can not be applied in reverse. The sensor is manufactured with a fixed light sensitivity and total dynamic range. When ISO is raised less of the total dynamic range is used and the data recorded is normalized through either amplification or scaling. This can only work if data is recorded. Lowering the ISO for the same sensor would result in more exposure and you would quickly reach the upper dynamic range limit of the sensor. At that point you stop recording data. You can't manipulate data if you don't record data.

Joe