Hi all, Until now I haven't heared of a chip that can replace the 50 ISO film. Are there problems developing such, or is the public interest so low, that the companies think that it isn't worth the time and money. Whenever I want to shoot very sharp images, such like macros, I use 50 ISO slides. Safak
I guess it's understandable, but I believe it's a fallacy to assume that, just because a particular 50 ISO film gives better resolution, the same must apply to digital capture. Each sensor design has its own native sensitivity, and making it "slower" (if it were possible) would not necessarily improve things.
There is at least one camera that has a chip which can be rated down to ISO 50 but it isn't a Nikon and it's only accessible through a custom function. By my understanding the chip is actually rated ISO 100 but is pulled to ISO 50 with some slightly adverse effects in increased saturation hence the reason it's not part of the normal ISO range for that camera.
But you have to ask yourself why you need an ISO 50 rated camera. The whole reason for using low rated film is to keep the grain as fine as possible. For digital thats irrelevant as for a particular chip the ISO rating has no effect on pixel density only on noise.
Just as higher ISOs require signal amplification which empasises noise, the longer eposures for lower ISOs generate more chip heating and so also contribute to increased noise. It's a balancing game between reducing signal amplification and reducing heat generation. At the momnent the current technology appears to have a optimal point of between ISO 100and ISO 200. If chips which can use less power and so generate less heat can be developed then an ISO 50 or lower camera could be produced. But just as ISO 50 films and lower were always a rather specialist field and only for professionals and keen amateurs, is there any demand large enough to produce a chip optimised for ISO 50 or lower? Remembering that any ISO 50 chip means that ISOs higher than that would use more signal amplification than the equivalent image taken on a chip rated to ISO 100.
I'm guessing here but given that we know on very long exposures chip heating does have an effect on noise. Usually in a burst the shutter speed is pretty high compared to a say a landscape shot then I'd guess that the cumulative effect isn't high enough for the noise to be noticeable. But assuming you could run a burst with the shutter speed as low as possible but without dropping the frame rate and also a large enough buffer to get a good long burst then I'd suppose that the last frame could well exhibit more noise than the first shot. How much extra noise and whether it would be a significant enough to be noticeable though is anyone's guess.
There is no "signal amplification" in a physical/electronic sense for digital camera exposures. The sensor's sensitivity and power use is the same no matter what the ISO setting. The output of the sensor is digitally processed at higher ISOs to compensate for underexposure - or with raw files the data is tagged with the ISO setting so the capture software can apply compensation. This curve processing exaggerates noise and the net effect is digital "amplification" of sensor noise artifacts. However you imply that more power is run through the sensor at progressively higher ISO settings. That's not true - at least not with the cameras and sensors I've used.
Because I can't be bothered testing it. If the sensor showed significant extra noise in burst modes during normal use someone would have picked it up before now. Pushing the issue by using both long shutter speeds and high speed burst is not a normal mode of use.
>However you imply that more power is run through the sensor at progressively higher ISO settings.
No, that might have been how you read my post but I never said nor implied that. If anything I said the opposite as with lower ISOs the sensor is used for longer because of the longer exposure time required. At higher isos why would there be a need to use higher power - it's duration of use that matters.
Well, there are reasons for ISO 50. At least I would like to have IS0 50 on my D2x, but for the moment I have to stick to a ND-Filter. The reaseon is that our studio flash generators can't be turned down below f11 (ISO100) when using direct flash (no hazylight). This makes always some additional work necessary when using small format (second/third flash or ND filter). Before you ask, the strobes have 3000 W/s.