What happened to low ISO?

[dreed]

I seem to recall seeing photos, such as those of space shuttle launches, where the ISO of the film used was 25. No, that's not a mistake, ISO 25. Why? Because the takeoff is a very very bright event, when you're close up. But doesn't a really fast shutter make up for that? In this case, yes, but not all...

Recently I was sitting on the rocks of a stream, during daylight hours, trying to get the "smooth water" effect. But even at ISO 100, using a high grade polarising lens, it's just too bright. With a bit of research, it seems that the trick these days is to use a rather dark filter. This cost of this approach is a(nother) bit of glass in front of the lens, potentially having a negative impact on your image quality (think of Reichman's notes about how the UV/haze filter of today really doesn't add any value and that it's like shooting through a window.)

Of course, the f-stop can be reduced down to, say, f/22 or smaller, but this too can have an impact on image quality due to diffraction and airy discs.

This all got me thinking and wondering if in the pursuit of high ISO perfection in low light, we're hurting ourselves at the other end and we just haven't realised this. For instance, various DSLRs now have a minimum ISO of 200. Those "smooth water" shorts are now going to require more effort than before this.

Of course ISO 25 is not going to be of benefit to those great big white lens folks that walk around sporting events nor the paparazi flooding a star with flashes at an interview. Nor is it going to help parents at their children's party or sporting event on the weekend. But now that the "film" is part of the camera body, for those that became used to low ISO with landscape photography, it seems like that choice has been removed. And whilst some cameras today are sold with ISO 50 capability, analysis seems to suggest that this is just  a corrected, underexposed photo at ISO 100.

Comments?

[PeterAit]

I seem to recall seeing photos, such as those of space shuttle launches, where the ISO of the film used was 25. No, that's not a mistake, ISO 25. Why? Because the takeoff is a very very bright event, when you're close up. But doesn't a really fast shutter make up for that? In this case, yes, but not all...

Recently I was sitting on the rocks of a stream, during daylight hours, trying to get the "smooth water" effect. But even at ISO 100, using a high grade polarising lens, it's just too bright. With a bit of research, it seems that the trick these days is to use a rather dark filter. This cost of this approach is a(nother) bit of glass in front of the lens, potentially having a negative impact on your image quality (think of Reichman's notes about how the UV/haze filter of today really doesn't add any value and that it's like shooting through a window.)

Of course, the f-stop can be reduced down to, say, f/22 or smaller, but this too can have an impact on image quality due to diffraction and airy discs.

This all got me thinking and wondering if in the pursuit of high ISO perfection in low light, we're hurting ourselves at the other end and we just haven't realised this. For instance, various DSLRs now have a minimum ISO of 200. Those "smooth water" shorts are now going to require more effort than before this.

Of course ISO 25 is not going to be of benefit to those great big white lens folks that walk around sporting events nor the paparazi flooding a star with flashes at an interview. Nor is it going to help parents at their children's party or sporting event on the weekend. But now that the "film" is part of the camera body, for those that became used to low ISO with landscape photography, it seems like that choice has been removed. And whilst some cameras today are sold with ISO 50 capability, analysis seems to suggest that this is just  a corrected, underexposed photo at ISO 100.

Comments?

With a high-quality neutral density filter, your problems are solved. A high quality filter won't degrade the image.

[ErikKaffehr]

Hi,

The sensors essentially have a natural sensivity, there are only two ways to reduce it:

1) Putting an ND filter in front

2) Using a color grid array with sharper cut off filters.

It may be possible to make a sensor without microlenses, but that would only decrease sensitivity by one stop, or so.

The Leica S2 has a native ISO of 160, too. They have an option to "pull" but that's probably just overexposure.

Best regards
Erik

I seem to recall seeing photos, such as those of space shuttle launches, where the ISO of the film used was 25. No, that's not a mistake, ISO 25. Why? Because the takeoff is a very very bright event, when you're close up. But doesn't a really fast shutter make up for that? In this case, yes, but not all...

Recently I was sitting on the rocks of a stream, during daylight hours, trying to get the "smooth water" effect. But even at ISO 100, using a high grade polarising lens, it's just too bright. With a bit of research, it seems that the trick these days is to use a rather dark filter. This cost of this approach is a(nother) bit of glass in front of the lens, potentially having a negative impact on your image quality (think of Reichman's notes about how the UV/haze filter of today really doesn't add any value and that it's like shooting through a window.)

Of course, the f-stop can be reduced down to, say, f/22 or smaller, but this too can have an impact on image quality due to diffraction and airy discs.

This all got me thinking and wondering if in the pursuit of high ISO perfection in low light, we're hurting ourselves at the other end and we just haven't realised this. For instance, various DSLRs now have a minimum ISO of 200. Those "smooth water" shorts are now going to require more effort than before this.

Of course ISO 25 is not going to be of benefit to those great big white lens folks that walk around sporting events nor the paparazi flooding a star with flashes at an interview. Nor is it going to help parents at their children's party or sporting event on the weekend. But now that the "film" is part of the camera body, for those that became used to low ISO with landscape photography, it seems like that choice has been removed. And whilst some cameras today are sold with ISO 50 capability, analysis seems to suggest that this is just  a corrected, underexposed photo at ISO 100.

Comments?

[Jeremy Payne]

With a high-quality neutral density filter, your problems are solved. A high quality filter won't degrade the image.

I agree ... I don't see any noticeable image degradation at all with my B&W ND filter.

[Jeremy Payne]

I always used to complain in the other direction back in the film days ...

I shot a lot of Plus-X ... and always used to fantasize about a film that would look like Plus-X at ISO 800.

I guess the grass is always greener ...

[Rob C]

I have never had the need to use an ND filter in my work - but thinking about it, doesn't using a heavy one make focussing ever more difficult because of the darkened screen if using a reflex camera? I don't look sympathetically on the idea of focussing first and screwing filters on after the event!

It's my guess that the digital answer is really going to lie in two types of more specialized cameras: those for sport and reportage and the alternatives for fine art. The way price is going, it seems to me that such alternatives are quite feasible - people already seem willing to pay mega bucks for what's currently available; a finer tuning shouldn't go amiss.

Rob C

[Jeremy Payne]

I have never had the need to use an ND filter in my work - but thinking about it, doesn't using a heavy one make focussing ever more difficult because of the darkened screen if using a reflex camera?

That's where live view REALLY comes in handy ... the LCD monitor corrects for that.

[fredjeang]

I saw an enormous 35mm B&W portrait print made with giga film 25iso if I remember, impressive! I mean, impressive.
That would be nice a 25 iso in digital, definitely.

Fred.

[dwdallam]

You can get ISO 50 with Canon Extended. I've used it to cut light a couple of times. I then bought a Hoya Pro level ND filter worth 3 stops. Used with my B&W polarizer, I get 4.5 stops. Recently, that combo wasn't enough. So, I just purchased a Hoya Pro level ND filter worth 6 stops! They also have one at 9 stops.

[BJL]

I saw an enormous 35mm B&W portrait print made with giga film 25iso if I remember, impressive! I mean, impressive.
That would be nice a 25 iso in digital, definitely.

There is a big confusion here due to the fact that what people usually mean by the ISO speed of a sensor is very different than what is meant by the ISO speed of a film: sensor base ISO speed is a lower exposure index limit based on highlight handling, while film ISO speed is an upper exposure index limit based on a standard of adequate shadow to midtone handling.

Roughly, the ISO speed of a film is the highest exposure index (least amount of exposure) that the film needs to meet some standard of shadow handling four stops below the mid-tones: a shadow based upper limit on exposure level. Films also have another, lower exposure index which is the minimum to which the film can be "pulled" while still handling highlights sufficiently: a highlight based lower limit on exposure level.

The base ISO of a sensor is like this latter "pull processing limit": the lowest ISO setting that handles highlights adequately (up to about 3 stops above mid-tones). On the other hand, the "film ISO speed equivalent" of a DSLR sensor, the maximum at which shadows are "adequately" handled, is usually far higher: maybe 1600 to 3200 or even beyond for current SLR sensors. This higher "shadow based" figure, not the base or minimum safe ISO speed, is the natural counterpart of the ISO speed rating of a film, so modern DLSR sensors are really like about ISO 1600 film that can be pull processed down to about ISO 100 to 200 before the highlights get blown too much by over-full photosites. (And if a DSLR is used at this "film ISO like" exposure level, highlight handling can be a lot better than it is when the emphasis is on gathering as much light as possible to control shadow noise, in ETTR fashion --- a somewhat neglected trade-off!)


With low speed films, finer grain and higher resolution is achieved in a way that reduces the "shadow based" ISO speed. The digital equivalent is reducing pixel size which again reduces the maximum noise-limited ISO speed --- but this does not reduce the base ISO speed. Most causes of lower base ISO involve "wasting light", such as with ND filters or omitting micro-lenses or just the plain less efficient technologies of older sensors. Such routes to lower base ISO speed are more or less unrelated to improved resolution, so there is very little interest in doing it with sensors. There are a few better options, like
(a.) increasing well capacity at equal pixel spacing, such as with deeper photosites, and maybe with full frame type CCD vs active pixel CMOS sensors.
(b.) a mix of highlight and shadow photosites such as in some of Fujifilm's Super CCD sensors, which is like having tiny ND filters over half of the photosites. Gone from the SLR market though.


I agree that this is yet another advantage of Live View: allowing ND filter use without dimming the VF image. An alternative is an internal ND filter near the sensor, not in the light path of the OVF. Another alternative is a rangefinder VF, or any non-SLR VF. Some compact digicams have ND filters that are rotated in front of the sensor to simulate high f-stops, and which do not effect the brightness of the image in either the EVF or the optical non-SLR viewfinder. They do this instead of stopping down too far, to avoid excessive diffraction effects. That is, the f/16 on some digicams is really f/8 with two stops of ND filter.

[JeffKohn]

ISO only gets you so far if trying to achieve a longish exposure in bright light; you're probably still going to need a filter, just not quite as strong of one. There's a pretty small window of exposures where ISO 25-50 would let you shoot without a filter but ISO 100-200 requires a filter. I can't see this being much of a consideration in camera choice for landscape/nature photographers, because the shots where you're most likely to want long exposures tend to work best when shot in lower light levels anyway (waterfalls/creeks in overcast night, lapping ocean waves at twilight, etc).  

My current camera has a base ISO of 100. I'd much rather it were 200 than 25 of 50, personally. Adding an ND filter when you need a slower shutter speed is most definitely preferable to raising the ISO to get a faster one, and I'm more likely to want a faster shutter speed if I can get it anyway.

It's more of a legitimate issue for location photographers using strobes, who need to be able to over-power the ambient light while still staying under their flash-sync speed.

[Guillermo Luijk]

You can get ISO 50 with Canon Extended. I've used it to cut light a couple of times.

Not really. Canon's ISO50 is fake ISO. I.e. you obtain exactly the same RAW data at ISO50 than shooting at ISO100 with the same aperture and shutter. This has been proved and discussed several times in the forum.
When shooting JPEG, ISO50 can be useful though because the camera will do a -1EV exposure adjustment for you, so that the ISO100 RAW will render as a ISO50 JPEG. But if you clipped the highlights in the RAW file, they will be gone, so it will never be a genuine ISO50 JPEG.

[stamper]

[quote name='Rob C' date='Mar 29 2010, 07:32 PM' post='356686']
I have never had the need to use an ND filter in my work - but thinking about it, doesn't using a heavy one make focussing ever more difficult because of the darkened screen if using a reflex camera? I don't look sympathetically on the idea of focussing first and screwing filters on after the event!

Unquote.

In my limited experience of using ND filters anything less than a 10 stop can be auto focused. As to screwing on filters then you do get used to it. This type of photography involves patience. The only problem is that inevitably you are likely to drop the filter somewhere where you wouldn't want it to go?

[BernardLanguillier]

Comments?

This will give you ISO 6.

http://cgi.ebay.com/Kodak-DCS-Pro-SLR-n-Di...=item19baff5a63

You end up paying only 160 US$ per ISO, whatever that means...  

Cheers,
Bernard

[MarkL]

I'm not technical expert but as I understand it the sensor manuf must make a decision on the base iso sensitivity of the sensor. If they go for a low iso, high iso (which is increased gain) performance will suffer. If they go for a higher iso, you don't get the low iso speed available without 'fake' iso settings.

Given these tradeoffs I'd take high iso performance any day of the week; getting rid of light is easier than trying to get more. In 2 years of using the Nikon D700 (base iso 200) the only occasion I even reach for the ND filter is getting shallow dof with flash due to the sync speed issue, but even then the iso 200 base means I can shoot noise free with less flash power inside saving battery power and recycle time or get more range.

The only people I can think of who care about this are photogs that use flash in bright light (fashion, wedding) or people that love shooting these milky moving water pictures both of these specific siatuations can be dealt with with ND filters.

[250swb]

The truth is that we are still waiting to see some sort of visual revolution in images from high ISO performance that photographers said they needed so much before they bought their latest Nikon's and Canon's. That photographers now need low ISO performance is pretty well in the same ballpark, in that photographers soon forget all the things they needed and make the same old photographs anyway.

Steve

[MarkL]

The truth is that we are still waiting to see some sort of visual revolution in images from high ISO performance that photographers said they needed so much before they bought their latest Nikon's and Canon's. That photographers now need low ISO performance is pretty well in the same ballpark, in that photographers soon forget all the things they needed and make the same old photographs anyway.

I don't think there was ever going to be a 'visual revolution' with a few stops of improvement in high iso performance and no on promised one. You could shoot film at 6400 just like you can shoot a dslr at 6400 but what is does mean is that pictures that were once taken in these situations with loads of noise and fell apart at anything over 6x4" can now look very good printed to make larger sizes which is great for both photographers and clients.

Ask any good wedding photographer what high iso has done for them during church ceremonies where no flash is allowed.

[fredjeang]

There is a big confusion here due to the fact that what people usually mean by the ISO speed of a sensor is very different than what is meant by the ISO speed of a film: sensor base ISO speed is a lower exposure index limit based on highlight handling, while film ISO speed is an upper exposure index limit based on a standard of adequate shadow to midtone handling.

Roughly, the ISO speed of a film is the highest exposure index (least amount of exposure) that the film needs to meet some standard of shadow handling four stops below the mid-tones: a shadow based upper limit on exposure level. Films also have another, lower exposure index which is the minimum to which the film can be "pulled" while still handling highlights sufficiently: a highlight based lower limit on exposure level.

The base ISO of a sensor is like this latter "pull processing limit": the lowest ISO setting that handles highlights adequately (up to about 3 stops above mid-tones). On the other hand, the "film ISO speed equivalent" of a DSLR sensor, the maximum at which shadows are "adequately" handled, is usually far higher: maybe 1600 to 3200 or even beyond for current SLR sensors. This higher "shadow based" figure, not the base or minimum safe ISO speed, is the natural counterpart of the ISO speed rating of a film, so modern DLSR sensors are really like about ISO 1600 film that can be pull processed down to about ISO 100 to 200 before the highlights get blown too much by over-full photosites. (And if a DSLR is used at this "film ISO like" exposure level, highlight handling can be a lot better than it is when the emphasis is on gathering as much light as possible to control shadow noise, in ETTR fashion --- a somewhat neglected trade-off!)


With low speed films, finer grain and higher resolution is achieved in a way that reduces the "shadow based" ISO speed. The digital equivalent is reducing pixel size which again reduces the maximum noise-limited ISO speed --- but this does not reduce the base ISO speed. Most causes of lower base ISO involve "wasting light", such as with ND filters or omitting micro-lenses or just the plain less efficient technologies of older sensors. Such routes to lower base ISO speed are more or less unrelated to improved resolution, so there is very little interest in doing it with sensors. There are a few better options, like
(a.) increasing well capacity at equal pixel spacing, such as with deeper photosites, and maybe with full frame type CCD vs active pixel CMOS sensors.
(b.) a mix of highlight and shadow photosites such as in some of Fujifilm's Super CCD sensors, which is like having tiny ND filters over half of the photosites. Gone from the SLR market though.


I agree that this is yet another advantage of Live View: allowing ND filter use without dimming the VF image. An alternative is an internal ND filter near the sensor, not in the light path of the OVF. Another alternative is a rangefinder VF, or any non-SLR VF. Some compact digicams have ND filters that are rotated in front of the sensor to simulate high f-stops, and which do not effect the brightness of the image in either the EVF or the optical non-SLR viewfinder. They do this instead of stopping down too far, to avoid excessive diffraction effects. That is, the f/16 on some digicams is really f/8 with two stops of ND filter.

Thanks for this extended and interesting technical explaination.
So, how can be acheived the equivalent (or something close) to what could be done with the Pan films with digital? (in term of rendering and resolution?)
Something is not clear for me there.

Fred.

[JeffKohn]

Thanks for this extended and interesting technical explaination.
So, how can be acheived the equivalent (or something close) to what could be done with the Pan films with digital? (in term of rendering and resolution?)
Something is not clear for me there.

Fred.

Just because ISO-25 films had better resolution than higher-ISO films, doesn't mean that we're missing something by having DSLR's with higher native ISO's. Digital is a completely different beast. What exactly are you wanting to achieve that you don't think you can do with digital?

[fredjeang]

Just because ISO-25 films had better resolution than higher-ISO films, doesn't mean that we're missing something by having DSLR's with higher native ISO's. Digital is a completely different beast. What exactly are you wanting to achieve that you don't think you can do with digital?

Jeff,
I think we can acheive almost everything in digital.
My point was a question that reflects my ignorance on how to get close to the look of these Pan film with digital.
I know it can be done, I just can't find how.

Fred.