Saturday, November 12, 2011

Nikon D7000 with 50mm AF-D at f/1.4 and ISO 25,600

Yesterday and last night we had a fairly lengthy power outage. So after wandering around and gabbing with the neighbors, I grabbed my gear out of the closet to see what the D7000 could do with an Nikon 50 f/1.4 AF-D opened up all the way. Just my potted palm and candlelight. This wasn't meant to be a scientific test. The out of camera pictures shows you why this is not such a great idea. This is as high as the ISO will go on the camera, and it's shot with a lens that isn't the greatest wide open. You can see that there's quite a bit of blue channel noise, much more than previous Nikon cameras. There's a fair bit of a blue cast as well, but that's down to auto white-balance and the moonlight coming in through the blinds. But this being a Nikon, the noise pattern is still fine and speckled, not mushy and blotchy. And to be fair, the 50mm AF-D f/1.4 is soft in the corners, but still has reasonable resolution in the center. In this type of shot, you can see that it doesn't matter... the corners of the picture are dark and devoid of detail. Having said that.... come on people, it's ISO 25,600! When I was a kid, ISO 800 film didn't look this good.

Here's a 100% crop in case you wanted to pixel peep.

If you want an in depth discussion of the D7000's ISO behaviour, search's Nikon D70-D7000 forum for a few of Marianne Oelund's posts. The image pipeline apparently applies analogue amplification to the sensor output until just shy of ISO 1000... everything there after is electronic. In other words, in order to ramp up the ISO response afterwards, the camera is interpolating data. Having had the D7000 for a short period of time now, I'd say I perfectly comfortable using it to ISO3200 without thinking much about noise, but wouldn't push it past ISO 6400. When you think about it... if you are a hobby shooter, why do you need to shoot at ISO 25,600? In the shot above, it would have made more sense to shoot at base ISO on a tripod.

Any way, here's an imperfectly cleaned up image. There's a reason why I don't cover post-processing techniques on this blog... I'm simply not that good or qualified to do it. However, in this case, I selectively applied noise reduction to the blue channel before applying a little bit more to the total chroma channel. After that,  I steepened the tone curve to de-emphasize the shadow noise in the corners. Next was a very small saturation bump and a bit of warmth added to the colour balance. After all of that I had to adjust the levels of the blue channel to get rid of the blue cast, but it's still there. Oh well. Finally, a fair dose of unsharp mask. It's not a drastic improvement, but the result is a bit less digital looking.

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