Do i still need larger lens?

[ifti]

<p><em>It should be simple but I am somehow not able to grab the concept...</em><br>

<em> 1: I understand that one f stop increase doubles the light reaching the sensor. What is the effect of doubling the iso?<P></em><br>

<em>2: With camera bodies now having less noise at higher iso (like d-200 to d-300 while D-700 is out of my range) do we still need more powerful lenses e.g. 1.4 or 2.8. <P> would be lovely see some ambient light examples. Regards ifti</em><br>

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[john_macpherson]

<p>1) Doubling the iso increases the imaging sensitivity = halving the shutter speed - eg 1/500th sec becomes 1/1000 sec - it does not affect aperture (*unless you use aperturte priority mode, but this is NOT the same as having 'more' aperture - your lens's max aperture stays the same).</p>

<p>2) Yes we do (need wider aperture lenses).<br>

Why? Because some people will always need more light-gathering ability. And - you can throw backgrounds out-of-focus using f2.8 with a 300mm telephoto in a way that is impossible with an f5.6 version.</p>

[kari v]

<p>ISO 100 --> 200, one stop<br /> f5.6 --> 4, one stop<br /> 1/250 --> 1/125, one stop<br /> more light.<br>

<br /> That's the basic nerve wrecking love triangle and all adjustments you ever need in a camera, rest is extra.</p>

[ifti]

<p>John and Kari thanks for the info. That is pretty clear to me now. I go D-300 with the hope that I will not need buyy any more lenses. But I was wrong. I have played with high ISO they are good but but my cheap Nikkor 50mm 1.8 gives far superion pictures than high ISO and f5.3.<br>

I love to take faces, or flowers. I wonder 85mm 1.8 or 105mm F2 DC which will give me better faces.</p>