Would Like To Verify Exposure Duration

Started 4 months ago | Questions thread
pforsell
pforsell Veteran Member • Posts: 4,063
Re: A simple WWW app

CharlesPhillips wrote:

ProfHankD wrote:

CharlesPhillips wrote:

All -

After solving several other difficult questions, now another one comes up. I have a Nikon D200 and use it to take photos of satellites, using mostly 10 second exposures. But it appears that the exposures are not exactly 10 seconds.

I am trying to think of way to measure the duration, I'd like to know to the tenth of a second. I think that the exposures are a little long.

I am cross posting to the Nikon discussions.

Easy check: photograph a changing computer display. Most computer displays refresh at least 24 times a second, usually 30 or 60, so you just need a program that simply outputs a character in a new position every 1/10 second. Better still, here's a javascript page I just threw together to do it for you:

http://aggregate.org/DIT/shutspeed.html

Just load that page, photograph the screen, count how many # images you see, and divide by 10 to get the number of seconds for the exposure. A complete line is 1 second. It might work better if you invert the text and background colors for white text on a black background.

That has been very illuminating (photography humor). A "5" second exposure is 2.5 seconds long! A "10" second exposure is about 5.1 seconds long!!

So I can just cut the displayed exposure time in about half.

Wow, this is terrible news. Your camera is obviously broken and for me it would be difficult if not impossible to trust any settings the camera reports. 

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Peter
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Jedem das Seine, mir das Meiste!

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