D300 below ISO 200?

[pit29]

Hi guys,

I need your help. I've got a D300, and I understand that it's base ISO is 200 - which should mean that this is the optimal setting for ideal circumstances. I also understand that when you increase the ISO setting, this is done (technically) by routing more current to the sensor, and that you pay for the increased sensitivity with increased noise.

Now, you can decrease ISO settings on the D300 below 200 - to 100. I don't understand how that is done technically, and I don't understand what that'd be good for (except for not having too fast shutter speeds on a very bright day...)

I'd appreciate if someone could help me out...
Pit

 

[toxic]

there is range of "native" ISOs (through hardware gain) for every camera. I've no idea what this is on the D300, but let's say it's ISO 200-1600. any other ISO you can select, like through custom functions, are software-generated. ISO 100 is ISO 200 pulled back one stop via software. ISO 3200 is ISO 1600 pushed one stop.

if you shoot in RAW, then there's no point using these expanded ISOs since you can do it yourself with more control with your own software. if you use Jpeg, then you should use them if needed.

low ISOs are used for keeping shutter speeds below flash sync speed (~1/250) in bright light, and for long exposures.

 

[firestarter]

You'd effectively be overexposing the sensor if you used the extended ISO 100 - better to use RAW as toxic says.

If you want use slow shutter effects, or studio flash with very wide apertures the best approach is to use an ND filter on the lens.

 

[pit29]

Thanks, makes sense now...