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Author Topic: Understanding Nikon's Auto ISO in the dark. (For timelapse)  (Read 2074 times)
SlowPhotography
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« on: September 15, 2013, 05:23:00 PM »
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Hi everyone!

I'm doing some interval photography with Nikon D600 and D800E.
For this project I need the cameras to take well exposed photos in the daytime and pitch black night, without me being there to change settings and so on.
The cameras are capable of delivering usable photos at ISO 12800, I don't need noise free images, but the auto ISO won't go that high.
Even when I set my D600 to Auto ISO with max 12800 and 1 second exposure time it only goes up to ISO 2000.
It seems like the camera won't go below a certain EV, because when I go for a faster shutter speed the camera is willing to push the ISO up a little more.
Can anyone please tell me what is up with that? According to a friend of mine there are similar limitations in his Canons.

Johan
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RFPhotography
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« Reply #1 on: September 15, 2013, 05:50:23 PM »
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Due to the way Nikon cameras operate wrt to increased ISO, you're often no better off increasing ISO vs. pushing a lower ISO exposure up in post.  Above, about, ISO 400, if I recall, the D800 works that way.  I'd expect similar performance with the D600.
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Fine_Art
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« Reply #2 on: September 15, 2013, 10:18:16 PM »
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It will meter the scene to 18% grey. If you change ISO it will adjust the shutter to keep that exposure. To get around it go manual, setting all parameters.
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SeanBK
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« Reply #3 on: September 15, 2013, 10:46:07 PM »
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I tried it out on my D800E. It works. I usually shoot Manual mode but for your test I use 'P' mode. Shooting Menu > ISO sensitivity settings > ISO sensitivity > 100. AND Auto ISO sensitivity > 'ON'. Max Sensitivity >6,400, Minimum Shutter speed 1/50.
   One thing I did notice that it did pick speed less than 1/50 but it did follow floating ISO. It picked up ISO 5000 as I shot my dark bedroom. My lens was Zeiss manual focus, if you're shooting Auto Focus it might keep hunting. D800E goes upto 6400, so you must've used H1, then camera must not allow auto ISO with H1.. settings. There is no mention of it in manual. I also watched just the chapter auto ISO in "Using D800" on Lynda.com. Very good site.
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PhotoEcosse
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« Reply #4 on: September 16, 2013, 04:16:40 AM »
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I need the cameras to take well exposed photos in the daytime and pitch black night,

Sorry - no camera (other than one converted for light outwith the visible spectrum perhaps) will take photographs in "pitch black night", no matter how high you set the ISO. Some light is pretty much essential to photography.
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Petrus
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« Reply #5 on: September 16, 2013, 05:03:18 AM »
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For timelapse the aperture should stay constant, thus use A (shutter speed) automation.

Having short exposures is not mandatory, everything that moves will be blurred or will flash by in one frame anyway, so getting really high ISO values is not a must.

Of course the shutter speed should stay shorter than the shooting interval in any case...

How are you going to power the camera? You need mains power, as the battery will die in a few hours. At least that was my experience with Canons. They came with a battery compartment adaptor fed from the recharger as standard equipment. Do Nikons have this as an option, as my Nikons do not have the same?
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SlowPhotography
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« Reply #6 on: September 27, 2013, 04:39:46 AM »
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Sorry - no camera (other than one converted for light outwith the visible spectrum perhaps) will take photographs in "pitch black night", no matter how high you set the ISO. Some light is pretty much essential to photography.

By pitch black night I mean for example cloudy with stars, there is always some light.
If you use ISO 12800 and a F1.4 lens you can get far with a one second exposure, but the camera's light meter won't go that low.
I had a reply from Canon's product specialist confirming this. Even with the 1Dx or D4 the limitation is there.
What irritates me is that the camera can show me a histogram after the exposure which is veeery heavy on the left side.
So it can measure the exposure correctly in the file, if only it could use this information for taking a second exposure...
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Floyd Davidson
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« Reply #7 on: September 27, 2013, 09:14:49 AM »
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By pitch black night I mean for example cloudy with stars, there is always some light.

Not that it matters, but isn't that a contradiction! :-)  "Pitch Black" means no useful light at all.

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If you use ISO 12800 and a F1.4 lens you can get far with a one second exposure, but the camera's light meter won't go that low.
I had a reply from Canon's product specialist confirming this. Even with the 1Dx or D4 the limitation is there.

That is well documented in every camera's User Manual.  There are some small differences of course, but for example the Nikon D4 is specified for Matrix or Center Weighted metering from -1 to +20 EV.  For Spot metering the range is 0 to +20 EV.  (For whatever it's worth, that is improved on all models from the D1 through the D3S which had a range of 0 to +20 EV, except wtih spot metering which was +2 to +20 EV and is unchanged.)

It absolutely would be possible to extend the metering range lower, but if that significantly increases the size, the weight, or the price of the camera it won't be done because the camera would not be marketable.

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What irritates me is that the camera can show me a histogram after the exposure which is veeery heavy on the left side.
So it can measure the exposure correctly in the file, if only it could use this information for taking a second exposure...

Stop and analyze what you have there!  The image sensor and the metering sensor are two different things, and you absolutely don't want a camera, using current technology, that does it differently. However, if you open your mind and leave old biases behind, there is a very clear path to nirvana here!

Stop thinking as you would with film, where pressing the shutter release and making an exposure has financial cost.  With a digital camera it doesn't.  Start thinking of your camera's shutter release button as a dual function tool.  First you press it to activate the extremely sophisticated light meter and data readout system incorporated in the camera!  That (specifically the Hightlight and Histogram displays) will provide better exposure information than any other "light meter" you can find today.  Once you've made use of the light meter tool, switch (in your mind) to image capture mode and if necessary (noting that it might not be required because that light meter did capture an image incidental to making a reading) activate the shutter release to get the desired image data capture.  (You also have the option of using the on camera photograph generator to make that into a picture immediately, or you can do that in post processing later.)

It's not any lack of camera functionality causing the problem!  It's the mindset that a digitial camera is only a replacement for a film camera, and therefore using it as one would a film camera.  They aren't the same thing, and assuming they are loses a great deal of functionality.

Granted that does not help much, other than understanding why it is what it is, with y0ur OP about automatic operation.  It's a simple case that your light levels are lower than the functional range of the camera's light meter.
« Last Edit: September 27, 2013, 09:27:37 AM by Floyd Davidson » Logged

PhotoEcosse
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« Reply #8 on: September 27, 2013, 10:08:59 AM »
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....also remember that, using any of the auto features, the metering in your camera will always (within its limits) try to produce an image that is that mythical 18% grey. That may not be what you want with interval photography.
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"Reality is an illusion caused by lack of alcohol."
Alternatively, "Life begins at the far end of your comfort zone."
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