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02-14-2014, 12:15 AM - 1 Like   #1
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Super low ISO??

I know most everyone wants ISO sensitivities that will let us shoot a black cat in a coal mine using a birthday candle 100 yards away as our light source.

However I wonder if there has been any movement to replicate the slower films, ASA 25 and such.
I have at times encountered a moving water scene in bright light and tried to get that milky flow look. Or a dreamy motion blur of a pretty girl wandering on a beach.

I know that I can use a neutral density filter to drop my shutter speed and allow some control over DOF, but I would prefer to just drop the ISO, and shoot, than to dig through a bag to discover that the ND I have does not fit the lens I am using.

Anyone else out there who might agree that having a low ISO is as good of a thing when needed as a high ISO???

02-14-2014, 12:38 AM   #2
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For stationary subjects, the ability to emulate low ISO is there already in a roundabout way in the K-3. If you use the Average mode of Multi Exposure, you will gain noise reduction through exposure stacking. It is very effective. Obviously will not work for mobile subjects, though.

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02-14-2014, 12:58 AM   #3
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It is a trade off, the lower the base ISO, the higher the signal must be amplified to achieve the higher ISOs. The higher the amplification, the more noise and the lower the dynamic range. Are the occasions you want ISO 25 so frequent that you'd give up ISO 1600? What about starting to lose dynamic range at ISO 100?

Maybe when we have sensors capable of clean ISO 51200 we will see a push towards lower ISOs, since that would mean a usable range of around 25-6400.
02-14-2014, 01:27 AM   #4
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QuoteOriginally posted by elliott Quote
Are the occasions you want ISO 25 so frequent that you'd give up ISO 1600?
hmm, nope. If current tech requires a compromise from one scale to the other, I vote for the cat in the coal mine!

I was just wondering, and decided to pose the question to find out if anyone else had considered the situation.


02-14-2014, 01:42 AM   #5
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There is a way of achieving both high ISO and low ISO in the same sensor.

Fuji once had a sensor that had two different photosites for each pixel, one with a high base ISO and the other with a very low ISO, both illuminated by the same microlens. Maybe they still have it but I haven't kept up to date with developents there.

Fuji did it to achieve a very high dynamic range and did this by having a large photodiode, occupying some 95% of the pixel area and a smaller one (under the same microlens) occupying just a few percent. The small pixels took care of very bright highlights while the larger pixels took care of the normal pixels just like in any camera.

I guess one could use such a sensor to achieve the ultra low ISO for long exposures in bright light (by using only the small photosites) but it wouldn't do much good in terms of reducing noise
02-14-2014, 01:46 AM   #6
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I'd greatly appreciate such low ISO capabilities. Even if it would mean sacrificing high ISO capabilities. There's more then enough cameras around with excellent high ISO capabilities already. And personally I hardly ever shoot over ISO 800 anyway.
02-14-2014, 02:11 AM   #7
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While I really like being able to shoot at ISO 3200 when needed, I must admit having a lower ISO would be very useful. I have had mixed results with ND filters (colour shifts etc) which may be that I have to buy more expensive filters but still it is a hassle by the time you carry filter holder, adapter rings etc.

Unfortunately I think its all about technical compromise as already mentioned. Sensors and related electronics to read them are designed for a specific base ISO and lowering the base will likely compromise performance in other areas.
02-14-2014, 04:43 AM   #8
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With the development of digital cameras a lot of people hoped for ISO improvements. With film you were confined to a single ISO per roll. And there were only so many different ISOs available. Oddly enough, digital went in the other way than expected. With digital, we got really high possible max ISO, something that film has a very hard time doing. But for some reason, very low ISO is missing from DSLRs! Some P&S cameras have "ISO 50" but they are usually fairly noisy anyway. I think the K-5, with its ISO 80, was the lowest a modern DSLR went. Don't know why, though. Just that this question was raised before and that yes, many of us would like ISO 80 on more cameras, even ISO 50 and 25, sure.

02-14-2014, 04:54 AM   #9
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The lowest I've seen on digital was ISO 50, but that was on a Canon that was using custom Magic Lantern firmware.
02-14-2014, 05:09 AM   #10
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I think there have been some nikon cameras that went down to ISO 50 or so.

Lower then that, well, there's the Kodak DCS line, that took multiple sequential exposures and blended them together, faking lower ISOs down to I think 6. Not quite the same, of course, as information is lost in clipping situations. But today's cameras don't even have that, and I wonder why.
02-14-2014, 07:04 AM   #11
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If you buy a Phase One system, you can have ISO down to 35. In other words, I can be done.

http://www.phaseone.com/en/Camera-Systems/IQ-Series/~/media/Phase%20One/1-Ca...t-0516-US.ashx

But, as already said, all sensors are borne with a single base sensitivity and the rest is analogue and/or digital manipulation. So compromises will have to be made, and they will go in the direction where consumer requirements direct them.

Who knows, in the good old days, we had to change film with different sensitivities (or push develop); in the future we might be given the option to change sensors/digital backs with different sensitivities - even on consumer enthusiast type cameras?????
02-14-2014, 07:19 AM   #12
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The ISO above 6400 tend to be rather useless still anyway so that shouldn't be a problem. But what the OP thought and I also do think is that regardless of what comes out of the sensor it should be possible to just de-amplify (is that the word? Reduce?) the signal so that it equals f e ISO 25. Since quality is already extremely good at ISO 100 it doesn't need to get better. The benefit would be the possibility to use a large aperture in bright light.
And don't tell me about ND filters – you don't have them, at least not the right size, when you need them. And they degrade the quality.
02-14-2014, 07:52 AM   #13
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QuoteOriginally posted by Kameraten Quote
The ISO above 6400 tend to be rather useless still anyway so that shouldn't be a problem. But what the OP thought and I also do think is that regardless of what comes out of the sensor it should be possible to just de-amplify (is that the word? Reduce?) the signal so that it equals f e ISO 25. Since quality is already extremely good at ISO 100 it doesn't need to get better. The benefit would be the possibility to use a large aperture in bright light.
And don't tell me about ND filters you don't have them, at least not the right size, when you need them. And they degrade the quality.
I don't think it is as easy as that (always). If you merely reduce signal strength by digital subtraction or analogue dampening you will soon run into troubles with as well your highlights as with your shadows - or so I think.
02-14-2014, 11:53 AM   #14
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QuoteOriginally posted by Kameraten Quote
But what the OP thought and I also do think is that regardless of what comes out of the sensor it should be possible to just de-amplify (is that the word? Reduce?) the signal so that it equals f e ISO 25.
The best digital cameras right now have 14-bit analog to digital converters, that is a possibility of 16384 (2^14) different states that can be read from the sensor. To "de-amplify" you'd be cutting each value by a percentage and because you can't have decimals you must round up or down. With each rounding you lose differences in values that were once there, which cuts dynamic range.
02-14-2014, 10:51 PM   #15
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I would like to see ISO down to 50 as a normal option. Attenuating the signal would seem easier than inventing less-sensitive sensors.
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