A daft and theoretical question

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KC Leblanc

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Is there any reason why on a digital camera that ISO settings are pegged to the nearest stop.

I'm just thinking of a scenario where you could fix both a shutter speed and aperture and the camera just adjusts the ISO to give the right exposure.
 
It is possible in Manual and Auto ISO unless I've misunderstood :thinking:
 
Errrm... I mostly have the camera in manual, set shutter and aperture and auto ISO so I don't have to bother adjusting it...
 
Not sure on the D60 if there is an option to specify 1/3rd stop for iso settings. Some older dslrs don't, some do.

With regard to an "ISO priority" then again, its possible on some cameras. (although it works better on some than others)
 
Hi. To answer your question, I don't think there is any technical reason why isos are set to 100, 400 etc. I guess the sensitivity of the sensor can be set at any value. I suspect it's a decision the camera mfrs made.
 
I suspect that full-stop (native) ISO's (100, 200, 400, 800 etc) are implemented as a software programmable hardware amplifier gain on the sensor read-out. 1/3rd stop ISO setting will likely just be software manipulations of the full ISO stops.

This has piqued my curiosity (I have an electronics background) so I'm going to do a bit of googling to see if I can find any further info.
 
I don't think it's a daft question and I'm sure it would be easy to implement - as others have suggested that's effectively what auto ISO does to a greater or lesser extent. Whilst it might be handy to fix the shutter speed/aperture to control both subject movement and depth of field, the downside is that you lose control of the noise in an image. Personally, that wouldn't be a feature I would use. Sod's law would dictate that the best shot would be the noisiest. But then I am a born optimist :-|
 
I've tried having the camera on Manual and with f/5.6 and 1/1250s + auto ISO when shooting birds.. it does work on the 7D at least, and actually works quite well. But you have to make sure you don't overexpose because it just doesn't go lower than ISO 100..

It's more a curiosity than a real option for me though, as said it's not nice to suddenly get an ISO 3200 shot that you can't salvage.. easier to salvage a stop or two of under exposure :)

However, I would REALLY like an "envelope" mode on cameras, so that I can set a maximum exposure time and a maximum aperture and leave it on Auto ISO.. so that on my 70-200/2.8 I could say that never use apertures larger than 5.6 or exposure times longer than 1/1000s using Auto ISO to compensate but if ISO can stay at 100 then go ahead and give me smaller apertures or shorter exposure times. Not sure if I explained that right.. :gag:
 
Nikon has for some time had a 'stepless' shutter and aperture system which adjusts the shutter speed and aperture regardless of what actual shutter-speed is displayed in Program and aperture priority modes.
For example, you may find that the displayed shutter speed adjusts in in 1/3 increments, but the actual shooting speed is somewhere in-between.
Likewise the aperture adjusts steplessly in Shutter-priority mode.

The only time the displayed values are matched by the actual speeds and apertures is in manual mode.

If you select auto-iso then according to the manual (I was bored some days while on deployment) that too increases or decreases in a linear fashion, not incrementally.
 
Just last night I was pondering that the ability to change ISO setting at whim, is probably one of the most significant differences between Film and Digital photography.

Ok, I'm not dismissing the over-ridding main benefit that you can review an image imeadately, but the ability to alter ISO between each shot is fundamentally different than film.

Thus (although I wasn't intending to make a point), since DSLRs are effectively built on the film cameras basics, it might not have dawned on the manufacturers haven't realised they could offer an "I" prioirty mode. I guess this would only be beneficially when they combat the noise issue at high ISO or indeed provide the ability to select a wide or narrow ISO range.

That, said I guess from the above Auto ISO does seem to cover this if shooting in manual.
 
DrRusty said:
Just last night I was pondering that the ability to change ISO setting at whim, is probably one of the most significant differences between Film and Digital photography.

Ok, I'm not dismissing the over-ridding main benefit that you can review an image imeadately, but the ability to alter ISO between each shot is fundamentally different than film.

Thus (although I wasn't intending to make a point), since DSLRs are effectively built on the film cameras basics, it might not have dawned on the manufacturers haven't realised they could offer an "I" prioirty mode. I guess this would only be beneficially when they combat the noise issue at high ISO or indeed provide the ability to select a wide or narrow ISO range.

That, said I guess from the above Auto ISO does seem to cover this if shooting in manual.
Click to expand...



Not sure if it's what you mean, but when I set mine to auto iso i can set a minimum and maximum ISO it'll go to :)
 
ChrisJ_SLH said:
I suspect that full-stop (native) ISO's (100, 200, 400, 800 etc) are implemented as a software programmable hardware amplifier gain on the sensor read-out. 1/3rd stop ISO setting will likely just be software manipulations of the full ISO stops.
Click to expand...

ISTR a discussion on DP Review a few years ago suggesting that this is exactly the case.

Not sure if it influenced me consciously or otherwise, but I tend to go for full stops on my ISO settings unless I've got a good reason to pick something in between, which is rare.
 
call me narrow minded, but i cant understand why you would want to use auto-iso when shooting in manual. to me manual is for when I want to have total control of the EV of the scene that I am shooting, so if we go to auto-iso then the camera will push or pull the ISO to give you EV 0 which is a bit pointless IMO.
 
hsuffyan said:
call me narrow minded, but i cant understand why you would want to use auto-iso when shooting in manual. to me manual is for when I want to have total control of the EV of the scene that I am shooting, so if we go to auto-iso then the camera will push or pull the ISO to give you EV 0 which is a bit pointless IMO.
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It probably is narrow minded, auto ISO in manual is just another tool ,as is full manual, as is aperture priority, as is shutter priority etc etc, in all of them you have total control of of the exposure, just different ways of achieving it, and if you want to over/under expose in auto ISO in manual you can change the metering methods (for example spot metering).
 
KC Leblanc said:
Interesting, but there isn't any DSLR when I could for instance have ISO 427.
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If you set your D60 to manual with iso set to auto then picking an aperture and shutter speed will result in odd-ball iso numbers. I used to set my D40 up like this quite often - try it and see :)

Maybe you need to experiment rather than just ask the question ;)
 
hsuffyan said:
call me narrow minded, but i cant understand why you would want to use auto-iso when shooting in manual. to me manual is for when I want to have total control of the EV of the scene that I am shooting, so if we go to auto-iso then the camera will push or pull the ISO to give you EV 0 which is a bit pointless IMO.
Click to expand...

On the whole I agree with you, but what about those times when we want EV0 and can't achieve it because 1/3 stop adjustments don't quite get it? Letting the camera set odd-ball iso numbers in this scenario gets the job done .. if that's whats wanted in the first place.
 
Les McLean said:
It probably is narrow minded, auto ISO in manual is just another tool ,as is full manual, as is aperture priority, as is shutter priority etc etc, in all of them you have total control of of the exposure, just different ways of achieving it, and if you want to over/under expose in auto ISO in manual you can change the metering methods (for example spot metering).
Click to expand...

I disagree, because if you are changing the metering method, you would have to hunt around to ensure the EV0 of what the spot metering is seeing is what you are actually after. However, there is no escaping that the camera will give you EV0, which in Manual mode is completely useless your scene benefits from an EV0. If auto-iso is desired, it would probably be most suitable in AV or TV modes where you can use exposure compensation and then forget about the ISO and shoot away.
 
hsuffyan said:
I If auto-iso is desired, it would probably be most suitable in AV or TV modes where you can use exposure compensation and then forget about the ISO and shoot away.
Click to expand...

Not for me, use auto-ISO in manual mode a lot of the time, rugby, cricket and birds, also in a/v or tv mode. Please don't be so dismissive (or possibly blinkered) about it, all methods have their place, it will help you develop and grow as a photographer (as it does all of us) by being more open about the advantages and opportunities of different metering methods.
 
Arkady said:
Nikon has for some time had a 'stepless' shutter and aperture system which adjusts the shutter speed and aperture regardless of what actual shutter-speed is displayed in Program and aperture priority modes.
For example, you may find that the displayed shutter speed adjusts in in 1/3 increments, but the actual shooting speed is somewhere in-between.
Likewise the aperture adjusts steplessly in Shutter-priority mode.

The only time the displayed values are matched by the actual speeds and apertures is in manual mode.

If you select auto-iso then according to the manual (I was bored some days while on deployment) that too increases or decreases in a linear fashion, not incrementally.
Click to expand...


didn't know that

so you might actually be using say iso 562 but it records as 640 for instance?
 
In answer to the original question, ISO values (as well as apertures and shutter speeds) are only available in full or particular fractions of stop increments because that's what old-time photographers are used to. That's how photographers traditionally think and it is easy enough for people to learn to deal with and handle. Almost everything about DSLR design is a throwback to the film days, with real innovations like live-view being relatively recent.
 
ChrisJ_SLH said:
I suspect that full-stop (native) ISO's (100, 200, 400, 800 etc) are implemented as a software programmable hardware amplifier gain on the sensor read-out. 1/3rd stop ISO setting will likely just be software manipulations of the full ISO stops.
This has piqued my curiosity (I have an electronics background) so I'm going to do a bit of googling to see if I can find any further info.
Click to expand...

I believe that's true, or at least true for some cameras.

I think auto-ISO hasn't really caught on because there isn't much ISO range before quality gets hit badly, eg ISO200-1600 is only three stops which isn't that useful.

And secondly, there are already plenty of different modes for exposure setting, of which I only ever use two - Av and M. I really don't want yet another way of basically doing the same thing :shrug:
 
in structural design three supports are statically indeterminate

too many ingredients spoil the flavour

fix one parameter...the nomenclature is unimportant...then adjust the other two

in this case set iso...select aperture and speed....which are seamless to some extent..or were on slr's

this is the same thing one needs to do in ones life...make a solid foundation for your actions...then act
 
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