low iso for D300

The manual recommends ISO300 and above. I always thought you get best image quality at lower iso (less image

noise). The manual states lower contrast on iso 100-160. This is easy to fix, even in camera. I tried it and

found no difference in quality. Does anyone know what the manual is referring to?

Firstly, I presume you meant ISO200 and above.

Secondly, this topic has been discused before. May I suggest you read this thread http://www.photo.net/nikon-camera-

forum/00PCFY

On any DSLR, you should get the best image quality at its base ISO, which is 200 for the D300.

If you reach into the Low 0.3 to Low 1 range, which will bring you down to the equivalent of ISO 160 to 100, you may potentially get some clipping in the highlights. Most likely, you won't see much difference unless you have strong highlight areas.

There are a number of reasons for wanting to shoot lower than base ISO.

 

For example, say you want to use the built-in flash which syncs to 1/250 (1/320 for high sync) and the exposure

reading is 1/500 at ISO 200. You can drop the ISO to Low 1 and get correct flash-sync at 1/250 instead of

stopping down.

 

Or if you want to slow water down and you don't have or can't be bothered putting on an ND or CPL filter and

want to use a particular f-stop.

 

So even though the lowest ISO gives the "best" image quality it actually may not be what you want.

 

In photography everything is determined by the pretext "Depending on what you are trying to do".

The normal iso range is done in the analogue part of the camera by amplifying the signal, the lo and hi ranges are done in the digital part of the camera, probably with the 200 and 3200 iso settings) and they use a technic called bitshifting, but it is throwing away info so that is the reason they recommand iso 200-3200.

bitshifting is purely done on the binary representation of a number. ISO performance is largely sensor performance coupled with the gain figures of the analog signal amplification thence A/D conversion. No bitshfiting here as each shift loses one complete order of magnitude in base-2.

 

One bitshift (base-2) will either divide or multiply the binary number by two, and considering a fixed word, doubling will lose the hi-bit and insert a 0 bit in the LSB. So either way an entire magnitude is lost.

I believe the easiest way to get a lower ISO on a D300 without compromising IQ (ie, clipping) is to use an ND filter. Call me crazy, but I would have to think that the probable use is going to have enough light such that the darker scene will not cause focusing or other issues that could be said to result.