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Author Topic: Nikon D800 Shutter / Mirror  (Read 8547 times)

HarperPhotos

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Re: Nikon D800 Shutter / Mirror
« Reply #20 on: January 21, 2015, 07:32:56 pm »

Hello,

The day Nikon bring out a camera with a global shutter I will be one very happy photographer.

Cheers

Simon
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Simon Harper
Harper Photographics Ltd
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Jim Kasson

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Re: Nikon D800 Shutter / Mirror
« Reply #21 on: January 21, 2015, 07:46:09 pm »

The day Nikon bring out a camera with a global shutter I will be one very happy photographer.

I hear you. The electronic shutter on the Sony alpha 7S is vibration-free, but it does take 1/30 second to activate.

http://blog.kasson.com/?p=6450

For many types of subjects, it's very effective.

Jim

Dave Ellis

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Re: Nikon D800 Shutter / Mirror
« Reply #22 on: January 23, 2015, 05:33:41 pm »

Interesting test Jim. So this means that the electronic shutter in the Sony is a rolling shutter and that the second curtain is relatively slow, presumably due to read-out speed limitations ?

This limitation would not apply if it were a global shutter (as longed for by Simon above). However my understanding is that a global shutter requires extra circuit elements on each sensel to allow storage of sensel voltage until read-out after the end of the shutter activation period. This makes it harder to achieve high noise performance from the sensor.

I also understand that "lower end" cameras use a global shutter presumably because performance is not such an issue.

So where do we currently stand with the two shutter/sensor technologies ? Can anyone advise where the changeover from one technology currently occurs eg on some mirrorless ? Is it likely to be some time off before all cameras have a global shutter ?

Appreciate anyone's thoughts

Dave
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Jim Kasson

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Re: Nikon D800 Shutter / Mirror
« Reply #23 on: January 23, 2015, 06:17:30 pm »

Interesting test Jim. So this means that the electronic shutter in the Sony is a rolling shutter and that the second curtain is relatively slow, presumably due to read-out speed limitations ?

Exactly right. In EFCS the electronic first curtain is a rolling reset that travels across the sensor at the same speed as the mechanical first curtain. The second curtain is mechanical in both cases.

In an all-electronic shutter, the rolling reset happens as in EFCS, but slower. Instead of the mechanical second curtain, the data is read out in a rolling fashion at the same speed as the reset. The faster the readout speed, the faster the rolling reset can be. You can see from the timing that in the a7s case, it appears to be a byproduct of the camera's video capabilities.

This limitation would not apply if it were a global shutter (as longed for by Simon above). However my understanding is that a global shutter requires extra circuit elements on each sensel to allow storage of sensel voltage until read-out after the end of the shutter activation period.

That is my understanding as well.


Jim
« Last Edit: January 23, 2015, 06:22:34 pm by Jim Kasson »
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ErikKaffehr

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Re: Nikon D800 Shutter / Mirror
« Reply #24 on: January 23, 2015, 06:41:27 pm »

Hi,

My take is that there is a conflict between low noise, high DR and global shutter. To utilise global shutter we may need to set aside half the sensor area for buffering. The trade off is 6 dB in lost DR, or so…

Best regards
Erik

Exactly right. In EFCS the electronic first curtain is a rolling reset that travels across the sensor at the same speed as the mechanical first curtain. The second curtain is mechanical in both cases.

In an all-electronic shutter, the rolling reset happens as in EFCS, but slower. Instead of the mechanical second curtain, the data is read out in a rolling fashion at the same speed as the reset. The faster the readout speed, the faster the rolling reset can be. You can see from the timing that in the a7s case, it appears to be a byproduct of the camera's video capabilities.

That is my understanding as well.


Jim
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Erik Kaffehr
 

Jim Kasson

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Re: Nikon D800 Shutter / Mirror
« Reply #25 on: January 23, 2015, 06:47:47 pm »

My take is that there is a conflict between low noise, high DR and global shutter. To utilise global shutter we may need to set aside half the sensor area for buffering. The trade off is 6 dB in lost DR, or so…

Back side illumination to the rescue?

Jim

Dave Ellis

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Re: Nikon D800 Shutter / Mirror
« Reply #26 on: January 23, 2015, 08:23:26 pm »

Back side illumination to the rescue?

Jim

Yes that seems to be the way it's heading.

Dave
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