low ISO settings (Nikon)

[spacevoid8]

Is there any reason to use LO-ISO modes (50-100-160 ISO)?
As i understand the physic of process, using higger ISO then basic 200 ISO is pure amplification of signal and that leads to noise.
which means that low iso settings gives nothing but only detail loss?

[Panopeeper]

Which camera do you have?

[spacevoid8]

Which camera do you have?

d300

[ejmartin]

I analyzed a D300 for which the lowest actual hardware gain (for ISO Lo) was 125; others have tested D300's for which the lowest hardware gain was 160.  So to be safe, one can go to ISO 160 and get a performance improvement, in that the S/N throughout the dynamic range is improved.

For ISO's lower than the lowest gain implemented in hardware, the camera uses that lowest hardware gain, but meters according to that lower ISO, ie it simply overexposes the image  -- the camera is doing ETTR under the hood, which is OK if you've got the headroom not to clip highlights.  If highlights are not clipped, there will not be any loss of detail.  Even if highlights are clipped, there will not be any loss of detail in lower exposure zones.

[Panopeeper]

d300

1. You can save the head-ache re ISO 50, as that is not available.

2. As far as I see it, ISO 160 is the "native". However, as Emil pointed it out, there is no noise/DR related disadvantage with using lower ISO, except for the metering: ISO 100 should be used with -2/3 EV bias (if, for some reasons you don't want to use the 1/3 stop ISO steps).

If you upload a set of raw files, ISO 100, 125, 160 and 200, whatever but shot immediately after each other, 14bit, losslessly compressed, then I can measure if 125 or 160 is the "native".

3. Increasing the ISO does not increase the noise; just the opposite, it decreases it, up to some limit, with the D300 up to 800 or 1600. See Source of noise.

[spacevoid8]

1. You can save the head-ache re ISO 50, as that is not available.

i`ve made a mistake

2. As far as I see it, ISO 160 is the "native". However, as Emil pointed it out, there is no noise/DR related disadvantage with using lower ISO, except for the metering: ISO 100 should be used with -2/3 EV bias (if, for some reasons you don't want to use the 1/3 stop ISO steps).

i thought 200 is native ISO

3. Increasing the ISO does not increase the noise; just the opposite, it decreases it, up to some limit, with the D300 up to 800 or 1600. See Source of noise.

hmm interesting, i try to read this article. i hope my knowledge of english is enough to understand the point:)
but strange i always seen on the internet suggestions to use lowest ISO to achieve noise-free captures..

[Panopeeper]

i always seen on the internet suggestions to use lowest ISO to achieve noise-free captures

1. Forget about noise free. The issue is, how you can minimize the noise.

2. The lowest ISO is often not really an ISO step in hardware sense. Example: ISO 100 with your D300.

3. The noise depends primarily on the exposure. However, you have to think of the light-gathering of the pixels, not of shutter and aperture (the same exposure in terms of shutter time and aperture yields much lower ´light-gathering in darkness than in bright sunlight, right?).

You can have very dark patches even with ISO 100, even if you exposed as high as possible; the high-intensity patches (the bright areas) will be free of perceivable noise, while the very dark patches will be noisy even with the lowest ISO, except if the raw conversion "immerses" those in blackness.

High ISO shots are noisy, because the exposure is low.

[ejmartin]

but strange i always seen on the internet suggestions to use lowest ISO to achieve noise-free captures..

Quite right.  You want to increase the exposure as much as possible; gathering more light increases S/N ratio by increasing the signal, which improves image quality.  Higher ISO will clip the exposure (blown highlights) earlier than lower ISO, by lowering the ISO you create enough headroom in highlights to increase the exposure without clipping the highlights.  If however the exposure is limited -- you need a minimum shutter speed to freeze the action, or a minimum aperture for adequate depth of field -- then it pays to increase the ISO as much as possible without clipping the highlights; this lowers some contributors to noise coming from the camera electronics (so-called read noise).  In this case S/N is increased not by increasing S, which is fixed by the fixed exposure; but rather by decreasing one of the sources of noise.