low ISO values

[lichtloper]

In predigital times camera's had ISO-settings as low as 25 or even 6, though I don't know if there were films available with such a 'slow character'. In digital times many a camera's default ISO-value is 200, and values below ISO 100 can not be chosen on the majority of today's camera's - which is a limitation when we wish to record movement. - What could be the reason/s behind this particularity?

[Polar01]

Peter in the olden times I used slide film that was had an ASA of 25, and used film which had an ASA of 400, I was wanting to use as fast as I could get without the problem of grain. A digital camera with a base ISO of 200 is an older model most newer models the base is 100 and the better cameras have a base of 50.

Cheers: Allan

[lichtloper]

Peter in the olden times I used slide film that was had an ASA of 25, and used film which had an ASA of 400, I was wanting to use as fast as I could get without the problem of grain. A digital camera with a base ISO of 200 is an older model most newer models the base is 100 and the better cameras have a base of 50.

Cheers: Allan

Yes Allan, but what about camera's [in my league] like Panasonic G9 -ISO 100 = "extended"-, or Fuji XT-2 -ISO 100 = "boosted minimum".
Both are (telatively) modern camera's.
My question is a bit more basic: like why don't today's camera's meter at say ISO 6 (my Leica M6 did - though it had the sophistication of a bicycle...).

[lichtloper]

btw Talking about Leica:
its newbee CompactLeica meters from ISO 100 (to an incredible 50.000)

[dje]

Peter I'm no expert on sensor design but i think you'll find that it involves trade-offs between ISO sensitivity, Full well capacity, dynamic range and noise performance. A sensor designed with an ISO sensitivity of say 25 would probably have inferior performance at a gain setting of ISO 100 than a sensor designed to have an ISO sensitivity of 100. I think most people would do most of their shooting with a minimum ISO of 100 and thus would prefer to have the best performance possible around that setting, rather than having the opportunity to use slower shutter speeds every so often.

By the way, these so called ISO extensions or boosted minimums aren't true reductions in ISO but usually just involve over-exposure of the image.

Dave

[xpatUSA]

Yes Allan, but what about camera's [in my league] like Panasonic G9 -ISO 100 = "extended"-, or Fuji XT-2 -ISO 100 = "boosted minimum".
Both are (telatively) modern camera's.
My question is a bit more basic: like why don't today's camera's meter at say ISO 6 (my Leica M6 did - though it had the sophistication of a bicycle...).

Perhaps yesterday's cameras didn't offer Exposure Compensation?

On my cameras, I can go +/- 3EV. Meaning that +3 EV on top of 50 ISO (say) gets me to 5.62 ISO, effectively.

Please, let's not get into metering 101 . . .

[pschlute]

On my cameras, I can go +/- 3EV. Meaning that +3 EV on top of 50 ISO (say) gets me to 5.62 ISO, effectively.

Exposure compensation cannot alter the fact that if a camera has a lowest ISO setting of 50, it cannot ever go lower than 50 ? Your EC will simply select a smaller aperture or faster shutter speed. While the total amount of light hitting the sensor will be the same that is very different to using ISO 5.6

As I understand it every sensor has a "native ISO" , and that any setting above or below that single ISO is achieved by signal amplification/reduction.

Perhaps the reason for ultra low ISO/ASA in film was the fact that shutter speeds faster than 1/1000 were not the norm in the early days.

The other thing is that the manipulation that is attainable now in digital format is far in excess of what one could do with film. Dynamic range and noise reduction enhancements means you can shoot at ISO 100 and print large without worrying about noise.
Can the same be said about film? Perhaps that was the need for ultra low ISO/ASA ?

I am no expert on this subject so will be interested to hear others views.

[Polar01]

Ted I know that you know better. If I set my ISO for 100, set my f-stop to 8, then let the camera determine the shutter speed it will be X. If I then use exposure compensation +/-3V, the ISO does not change it stays at 100 the f-stop does not change, only the shutter will change by the amount of exposure compensation applied. You know this, I believe that you are just nick-picking.

Allan

[Tronhard]

Perhaps yesterday's cameras didn't offer Exposure Compensation?

For what it's worth, in the case of my early 1980s SLRs, both my Nikon and Canon bodies had +-3 EV compensation dials

[pnodrog]

In the days of film, it was the film emulsion's sensitivity to light that determined the ISO. The larger the silver halides crystals were the more chance it had of being hit by sufficient energy from photons to distress the crystal structure so that it would react readily to the developer solution and the higher its ISO was. Low ISO (sensitivity) films had small crystals generally resulting in higher resolving power.

I still have ISO (ASA) 10 slide copy film sitting in the fridge that I treasure but will probably never use and my wife wants to throw out.

ISO of digital sensors is a function of well size (how much photon charge it can store), conversion efficiency and amplifier gain or scaling of A/D output. It should be possible to design an ISO 10 sensor but its performance at higher ISO would make it unsuitable for general photography.

[xpatUSA]

Ted I know that you know better.

I said "gets me to 5.62 ISO, effectively."

If I set my ISO for 100, set my f-stop to 8, then let the camera determine the shutter speed it will be X. If I then use exposure compensation +/-3V, the ISO does not change it stays at 100 the f-stop does not change, only the shutter will change by the amount of exposure compensation applied.

Obviously. Well, here we are in "metering 101" . .

Again, I said "effectively" - a word missing from your put-down. So, I was talking about exposure, as in aperture and shutter 'speed'. No triangles involved.

I shoot manual. For me, if I shoot at 100 ISO and +1 EC, that is just the same sensor exposure as 50 ISO and 0 EC: therefore, 100 ISO and +1 EC is effectively 50 ISO.

You know this, I believe that you are just nick-picking.

You are entitled to believe whatever you like, of course, but sayin' it don't make it so.

[pnodrog]

I said "gets me to 5.62 ISO, effectively."



Obviously. Well, here we are in "metering 101" . .

Again, I said "effectively" - a word missing from your put-down. So, I was talking about exposure, as in aperture and shutter 'speed'. No triangles involved.

I shoot manual. For me, if I shoot at 100 ISO and +1 EC, that is just the same sensor exposure as 50 ISO and 0 EC: therefore, 100 ISO and +1 EC is effectively 50 ISO.



You are entitled to believe whatever you like, of course, but sayin' it don't make it so.

Sorry Ted, I have to agree with Alan on this one.

Using exposure compensation is primarily to compensate for the exposure meter mislocating the 18% grey within the scenes exposure range. Using exposure compensation to overexpose the scene results in overexposure not a shift in ISO. In the days of film, we could overexpose by a stop and pull the development by a stop which would effectively reduce the ISO of the film. With digital, overexposure of highlights will cause the sensor well to overflow and there is no way to recover. To lower a sensors inherent ISO requires either bigger wells or lower efficiency both of which are fixed in design.

A neutral density filter is the only way to achieve longer exposures at base ISO and a chosen aperture.

[xpatUSA]

I said:

"On my cameras, I can go +/- 3EV. Meaning that +3 EV on top of 50 ISO (say) gets me to 5.62 ISO, effectively.

Please, let's not get into metering 101 . . ."

Since the use of the word "effectively" appears not have been understood, thereby leading into 'metering 101', I withdraw my comment and apologize for wasting you gentlemen's time.

[pnodrog]

I said:

"On my cameras, I can go +/- 3EV. Meaning that +3 EV on top of 50 ISO (say) gets me to 5.62 ISO, effectively.

Please, let's not get into metering 101 . . ."

Since the use of the word "effectively" appears not have been understood, thereby leading into 'metering 101', I withdraw my comment and apologize for wasting you gentlemen's time.

I confess I do not grasp what you mean by effectively. One of the problems with not talking face to face is it is very easy to end up talking at cross purposes which is probably the case now.

Regards

Paul

[xpatUSA]

I confess I do not grasp what you mean by "effectively". One of the problems with not talking face to face is it is very easy to end up talking at cross purposes which is probably the case now.

Thanks Paul. I appreciate your response.

[DanK]

Ted,

I think you have taken this thread completely off track. If I understand Peter's OP, exposure compensation has nothing to do with it. Exposure compensation is just another way of adjusting aperture or shutter speed and is no different for present purposes from doing so manually. It has no relevance to what I think was Peter's question: why is it that modern cameras have a high enough minimum ISO (generally, 100) that some shots are out of the range of what the camera can produce because there is too much light? For example, if one needs a 2-second exposure (Peter mentioned motion), under some lighting conditions, one can't achieve that with ISO 100 and a reasonable aperture (sometimes, with any available aperture at all). So I am not going to respond to the back-and-forth about EC and will return to what I think was Peter's question.

Peter, I don't know much about the engineering side of this, but my hunch is consistent with Paul's answer. But frankly, I am grateful that the base ISO is not lower. Keep in mind that each time you amplify the signal by increasing ISO, you loose dynamic range, and eventually, you add noise. If base ISO were very low, I would confront those costs in in the vast majority of my photos (probably well over 95%) for which ISO 100 is not too high. And those problems can't be entirely fixed in post. For the occasions when 100 is too high, there is a solution: an ND filter.

Dan

[xpatUSA]

Ted,

I think you have taken this thread completely off track.

Did you miss my post #15, Dan? It said "I withdraw my comment and apologize for wasting you gentlemen's time."

[DanK]

Ted,

Sorry, I did.

Dan


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[Black Pearl]

Contax made a DSLR with a base ISO of 25 that got a bit noisy above 100iso - it was also the first DSLR to feature a 'full' frame' sensor. Quite cool in its day but didn't last long.

Somewhere on some old hard drive I have a few hundred files from it but gawd knows where they are.

[Adzman808]

I think (personally) that ISO has become the new megapixel race!

And the higher the ISO starts, the bigger the end number will look on the spec sheet

This camera starts at ISO 25 and has six stops to reach up to ISO 1600

This camera starts at 200 and can reach 12800

Guess which one Joe Public will buy?