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Old August 21st, 2008, 08:32 AM   #1
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Sony SR11 and "Twilight mode"

Hi

At the moment I am learning to work with my Sony SR11, it is the first Sony I ever had.

I am using the cam in manual mode all the time and use either AE shift or manual exposure and I will soon start using spot focus.

I have started to follow a project about rebulding some old houses. That means that it will sometimes be not so much ligth.

I understand that Sony adds gain when it needs to and the only way to stop the cam from going up to +12/18 dB is to put the cam in "Twilight mode" that way the cam goes no futher than 9dB and if I understand everything correct the picture will have little if any noise in 9DB

What i donīt know is if I put the cam in Twilight mode does that mean it overides anything else when Iīm in manual mode?

Can I have the cam always in "Twilight mode"?

I hope someone knows.

Cheers

Hans
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Old August 21st, 2008, 04:49 PM   #2
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One limitation I have found with twilight mode is that AE shift has no effect in low light. In good light I can do + or - AE shift with autoexposure and twilight mode set to on, and the exposure changes accordingly as I change the amount of shift using the dial on the front.

In low light such as dark night scenes, I would not expect that it could do a + shift, given that the iris is already at 1.8 and the gain is at the +9 limit of twilight mode. (Well I guess it could slow the shutter speed to 1/30 but doesn't - it keeps it at 1/60.)

But in low light I would think it should be able to do a negative AE shift. I was shooting some night scenes of a city street that had points of bright lights (signs and traffic lights) along with dark areas such as the night sky. I had the SR11 set to autoexposure and twilight scene mode. (I used autoexposure because I was panning and the light level was changing as I panned, so manual exposure wasn't practical.)

The bright lights were overexposed and burning out, so I enabled AE shift and set it to -1 to try to underexpose a little and reduce the over-exposure of the lights. But it didn't change the exposure I saw on the LCD. So I tried -4 and again it did not change the exposure I saw on the LCD. When playing the video back, I saw that the exposure was 1/60, 1.8, and +9 regardless of whether the AE shift was on 0 or -4.

It seems to me it should be able to accomplish the negative AE shift by reducing the gain below +9 or closing the iris down. For some reason it doesn't. Maybe autoexposure won't let the exposure level go below a certain point and ignores AE shift if that point is reached??
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Old August 22nd, 2008, 06:24 AM   #3
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Thank you very much.

Really good to know..

Cheers

Hans
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Old August 22nd, 2008, 08:23 PM   #4
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Quote:
Originally Posted by Hans Ledel View Post
I am using the cam in manual mode all the time and use either AE shift or manual exposure and I will soon start using spot focus.
When you use Twilight, you are forced into AWB. Because exposure can fluctuate in AE Shift, I do not recommend using it. Use Manual Exposure. Then use AF or Spot Focus.
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Old August 23rd, 2008, 09:01 AM   #5
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Thank you Steve.

That was really important to know.

You are right about manual exposure and Spot focus, I actually was thinking about going that way instead of Twilight mode.

I found out that 6 "clicks" from the right (+) on the exposure scale was 9dB so I will be using that insted

Cheers

Hans
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Old August 23rd, 2008, 01:18 PM   #6
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Well, two thigs I saw today in twilight mode.
1. Spot focus is not active
2. Autofocus is very bad at 8x zoom. I switch to manual and correct, back to auto/fuzz, switch from twilight and autofocus is sharp again!
Hans, so manual exposure=limited autogain? I put in daylight 6 clicks left and the image become too dark... autoexposure is ok in daylight, in the night it's best to manual adjust.

I think to a method to do a comprehensive test for various manual setting (like scenery, etc). It involves a table with multiple sheets in which we put all variables (so it will be easy to determine which other settings are available and best to use. We must setup the same scene (camera on tripod, manual/auto focus on a moving scene like sprinkler) and on different time (day, night, etc). Each file will be indexed and played directly to HDTV; result put in table...
However, the table will be the most easy part. Actual recording/setting/playing will take a long time... from what I see nobody did such a comprehensive test for a single camera, except probably Steve...

LE: another setting inactive in twilight mode is autoslow shutter. So that's why shutter didn't go to 1/30...

Last edited by Mircea Voinea; August 23rd, 2008 at 02:06 PM. Reason: New added
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Old August 23rd, 2008, 07:18 PM   #7
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The Sony manual and my eBook tells you the modes that are locked-out when you set cetain modes. Basically, Programmed Settings lock out other settings.

When you limit gain, AF will be less effective because of less image to focus on.
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