ISO 80 or 100 Setting on M8?

[photolandscape]

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The lowest current ISO setting on an M8 is 160. When future firmware updates are done, would it be possible to also offer a setting of 100 or 80?

 

With film of course, if you had the option of working with lower ISO settings (25, 50, 64 for example), it could often be an advantage. Since digital images become grainier/noisier as ISO is increased, would a setting of, let's say--80--tend to give you a bit less noise or any other advantages?

 

Just a thought.

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[cme4brain]

The lowest current ISO setting on an M8 is 160. When future firmware updates are done, would it be possible to also offer a setting of 100 or 80?

 

With film of course, if you had the option of working with lower ISO settings (25, 50, 64 for example), it could often be an advantage. Since digital images become grainier/noisier as ISO is increased, would a setting of, let's say--80--tend to give you a bit less noise or any other advantages?

 

Just a thought.

 

The engineers stated that the lowest ISO setting sets the "tone" for noise levels at higher ISO values, meaning a lower base ISO like 50 would mean more noise at higher ISO's. Therefore they chose a relatively high base ISO setting to minimize noise at higher ISO's.

[Joe Mondello]

I believe I've read that 160 is the "native sensitivity" of this sensor.

[photolandscape]

The engineers stated that the lowest ISO setting sets the "tone" for noise levels at higher ISO values, meaning a lower base ISO like 50 would mean more noise at higher ISO's. Therefore they chose a relatively high base ISO setting to minimize noise at higher ISO's.

 

Makes sense--160 is a good base. I didn't realize that was how it worked, so thanks for your response.

[dante]

That they can't do a lower speed due to a base ISO is untrue.

 

The Kodak 14n has a base ISO of 80 and a mode that does 6, 12, and 25 ISO for longer exposures.

[scott kirkpatrick]

Kodak designed this chip (which is about 5 years newer than the chip in the 14n) to collect 60,000 electrons per pixel before spilling them over. So that design point and the size of the cell sets the base ISO rating of the chip. The basic difference between operating at different ISO ratings in a digital chip is that you are using the lower portions of the (RAW) histogram and throwing away the high portions when you raise ISO. If you want to operate at lower ISO, you can't get more than 60,000 electrons to stay in the cell, and so far, no one has produced a way to get the cell to ignore, say, half of the photons incoming, or to average down.

 

The technical direction that Kodak is pursuing is to capture more electrons per cell, which increases dynamic range in a single image, so perhaps you can say that the ISO 160 chip that holds 60,000 electrons per pixel is equivalent to an ISO 80 chip that only holds 30,000 electrons per pixel.

 

scott

[luigi bertolotti]

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Hmmm.. intriguing tech issue... I think I'll try to find some tech paper about Kodak sensors; surely, I also would like to have the capabilty to choose a 80 or 40-25 ISO setting, but provided that it really gives me some advantage, like is still today fro a 100 vs. 400 ISO film... If really 160 is the "base" sensitivity of the CCD, any way to "simulate" a lower ISO would be just a simulation... no quality advantage... and so is better to use ND filters if a reason exists for you really want to go under 160.

[lars_bergquist]

Hmmm.. intriguing tech issue... I think I'll try to find some tech paper about Kodak sensors; surely, I also would like to have the capabilty to choose a 80 or 40-25 ISO setting, but provided that it really gives me some advantage, like is still today fro a 100 vs. 400 ISO film... If really 160 is the "base" sensitivity of the CCD, any way to "simulate" a lower ISO would be just a simulation... no quality advantage... and so is better to use ND filters if a reason exists for you really want to go under 160.

 

You are right there. We could 'pull' film to lower effective EI:s (Exposure Indexes) because the official EI (incorrectly called ASA or ISO) was always set at a minimium exposure, as low down on the characteristic curve as possible – for obvious marketing reasons. I did often rate T-Max 100 at EI 60, but that made a modified developer necessary. The result was better shadows and less grain. If a digital sensor has a 'native' sensitivity (i.e. one where no amplification is used) then there is nothing to be gained by lowering it by some trick however. That would be no better than using an ND filter on the lens.

 

The reason why many digital camera sensors have a lower sensitivity is essentially that the sensor cells ('pixels') are smaller and capture fewer photons to convert to electrons. So they need gain applied to reach higher EI:s, resulting in less dynamic range and more noise.

 

The old man from the Age of Stone Age Radar

[pete_g]

I was about to post on this isssue and saw this thread...I'd like to know if reducing the ISO would have adverse issues too, I'd like to have the abiltiy to reduce the ISO in steps to, say, ISO 10, that would give me a shutter speed of 60/30 th sec at 2.8 in the current gloomy daytime light we're getting in the UK, rather than 1000 th sec. The reason...I sometimes like moving objects to blur.

OK, I know I could shell out for a series of ND filters, but if it's a simple matter of adjusting a menu item, they why not?

[lars_bergquist]

I refer to Scott's and my own postings above. What you are calling for is essentially an inferior sensor. If this is really a problem for you, then the ND filter road is the only one to go. BTW a pola filter is a good though somewhat quirky ND filter!

 

The old man from the Age of Kodachrome 25

[sean_reid]

As I wrote in my first review of the M8 (September 2006), ISO 160 (a conservative rating actually) is indeed the base ISO of the M8. According to Leica, the lower the base ISO, the more amplification (roughly speaking, engineers here may clarify) it needs to reach higher ISO levels. So, again according to Leica, a sensor with a native ISO of 80 would need more amplification (read higher noise levels) to reach ISO 2500 than does one with a native ISO 160. Leica says that they chose an ISO 160 sensor base as a good compromise between low noise at base ISO and good noise performance (relatively speaking) at higher ISO.

 

With this sensor, I don't think we'd gain anything with an ISO 80 setting. But I'm not an engineer, as I'm often reminded.

 

BTW, the M8 (like the Canon DSLRs) tends to perform about 1/3 stop higher than its nominal ISO ratings. One could reasonably call the true ISO levels 200, 400, 800, 1600 and 3200. How much does 1/3 stop matter? Not a great deal but there we have it...

 

Cheers,

 

Sean

[Philinflash]

...

BTW, the M8 (like the Canon DSLRs) tends to perform about 1/3 stop higher than its nominal ISO ratings. One could reasonably call the true ISO levels 200, 400, 800, 1600 and 3200. ...

 

Hmm, that must be why I prefer to shoot 2/3 slower...

[marknorton]

Scott's explanation is as always spot on. If you want a lower effective ISO, you need to put a ND filter on the lens.

[marknorton]

Sorry, Lars, you beat me to it on the ND comment!

[Bob Ross]

There are a few examples of lower than native ISOs. The Konica-Minolta DSLRs 7D & 5D have ISO100 with a Sony 6MP sensor that has a ISO200 native ISO and the Oly E-1 can be hacked in the firmware to ISO50. Discussions that I have read refer to "reverse amplification" and it seems to introduce lower image quality performance. I have a K-M 5D and personally I don't see any gains with the lower than native ISO settings, finding the ISO200 images the cleanest. I haven't even tried to hack my E-1.

I haven't noticed that the ISO160 M8 low end is any problem and that might be explained by the 1/8000 to shutter speed.

Bob

[egibaud]

Actually when I calibrated a Gossen photometer with my friend José Luis. We found out that the Leica 160 ISO is more like a 120 ISO. All digital cameras actually need photometers to be calibrated as they rarely have the ISO rating set to what the say.

 

Eric