A99 vs D600 ISO6400 samples

Started Oct 19, 2012 | Discussions thread
Bruce Oudekerk
Senior MemberPosts: 2,635Gear list
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Re: Same noise day & night!
In reply to Nordstjernen, Oct 21, 2012

Nordstjernen wrote:

No, this is not true. Sensitivity of digital sensors is linear, so light level does NOT matter. What matters is exposure! You would get the same noise pattern for an underexposed daylit scene as for an equally underexposed night scene -- given that the same numbers of photons hits the measured area of the sensor.

You are not the first, nor the last, to point this truth out..  And of course you are correct.

There is, however, at least a glimmering of a rationale in believing otherwise, even if it is incorrect.

In dimly lit, yet properly exposed photographs, the entire histogram curve can often be significantly shifted to the dark end.  Thus a significantly greater proportion of the image lies in the noisy, shadow, areas of the picture.  More importantly, in dimly lit photographs (assuming the exposure correctly captures that dimly lit ‘look’) the likelihood is that visually important portions of the image are in this noisy marginal shadow/shade.  Thus the impression can be that the image is noisier than a brightly lit scene.  To make matters worse, often the image can exhibit extreme contrast and that pushes the dynamic range capabilities of the camera.  Since the image has been properly exposed to avoid overexposure and ‘blowing out’ the highlights, when the shadow areas are tweaked, noise becomes increasing apparent and ‘in your face’.  Here’s an example with an older KM7D camera…not that that matters:

The real culprits here are the nature of the lighting and the visual expectations we photographers bring to the fray, not how much overall light was available.  ‘Proper exposure’ determines the ‘amount of light’ that the sensor ‘sees’ at any given ISO.  The bottom line is that you are absolutely correct, but it’s easy for me to see how many photographers would make this mistake when evaluating image noise.

Bruce

...and for what its worth, editing replies in this forum...specifically the image insertion...is terrible. I have no idea how this will be done on a tablet with a touch screen.  I have little faith this will come out correctly now, even though the editing screen looks fine.

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http://www.pbase.com/misterpixel

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