D300s ISO noise at low ISO in Auto ISO mode Locked

Started Sep 7, 2011 | Discussions thread
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olyflyer Forum Pro • Posts: 24,188
D300s ISO noise at low ISO in Auto ISO mode

I don't know if I am imagining things but here is what I observed...

Some background…

During my summer holiday trip to Scotland I thought I make it easy for me, set the camera to Auto ISO with maximum ISO 3200, Auto WB, 14 bit raw and I will be fine, nothing to worry about. So I configured the camera before leaving home according to that, screwed UV filters on all the lenses I planned to take, packed the 35/1.8, 16-85 and the 70-300 in my bag together with the SB-900, batteries and a few CF and SD cards and off I went. During the trip I have used everything except the SB-900, so next time I may not take it with me at all.

The observation…

Coming home with a lot of images after two weeks I started to work on them and immediately noticed something very strange. A lot of images were taken at ISO 200 because the weather was fine most of the time, so that should normally mean clean and very nice, detailed images. But no, in fact quite the opposite, many are quite noisy, like if they were taken with much higher ISO, something like ISO 800 or even higher. This is very strange since the EXIF clearly shows ISO (Auto) 200 in the images I am talking about and at ISO 200, when not using Auto ISO, I am not used to see any ISO noise. It is a bit frustrating because from now on I will know that I can't trust Auto ISO at all. I don't normally use it but it is useful in some situations and this was one such situation when I thought it would be very useful.

Questions but no answers…

Am I imagining things? What is happening? Of course, ADL was off as always and the only difference from my usual use of the camera was the UV filters (high quality and clean), the Auto WB and the Auto ISO. Nothing else is deviating from my usual use of the camera, which I have used for two years now, so I am not exactly a newbie with it. All images I am talking about are exposed right and some are even overexposed a bit, which should improve ISO noise and bring it down.

Anyone else observed this strange behaviour? I mean, I know this sounds crazy, but I never ever used NR on ISO 200 images but now I have to with these and I am not even talking about a few taken in low light with slow shutter speed, my minimum shutter speed was set to 1/50s but these images can have shutter speeds of anything between 1/50 and 1/4000s and like I said, nice weather.

I know some people have been complaining about the ISO noise at ISO 200 in the D300s but could it be this they see? Could it be that all those people are using Auto ISO and the camera is doing some strange raw processing in Auto ISO or what is it?

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