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 5D MkII 30 seconds = 33 seconds 
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Joined: Fri Mar 12, 2010 12:16 pm
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Post 5D MkII 30 seconds = 33 seconds
If you set the 5D MkII to manual 30 second exposures and continuous drive mode and then lock the shutter down with a remote release for continuous shooting and then check the file timestamps they are 33 seconds apart?

There is no audible delay between the end of one exposure and the start of the next, So if you allow approx 200ms delay between frames for the mechanics to recycle then the 30 second exposure seems to overrun by approx 10%.

Any one else seeing this with their MkIIs as I have a very similar finding for the 7D as well.

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Tue Aug 10, 2010 1:50 am
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Post Re: 5D MkII 30 seconds = 33 seconds
You're right, although it's probably closer to 32s.

Results for a 350D:

Code:
1/10s actually lasts 108ms
1/5s ... 207ms
1/2s ... 508ms
1s   ... 1009ms
2s   ... 2009ms
5s   ... 5005ms
10s  ... 10090ms
15s  ... 16010ms
20s  ... 20170ms
25s  ... 25400ms
30s  ... 32000ms


Superficially, it does seem that there's a non-obvious relationship between programmed exposure and actual exposure. The solution to the riddle is revealed when you remember that the click-wheel on your camera increases things by 1/3stop per click (or optionally 1/2stop). Start at 1s ... 3 clicks ... 2s ... 4s ... 8s ... 16s, but notice that there isn't a 16s setting; the screen lies and says 15s - presumably because Canon thinks we're more comfortable with a (deceitful) linear scale. Another three clicks and it should say 32s - it says 30s. Although the screen lies the camera does execute the correct exposure of 32s, more or less. The firmware uses interleaved look-up tables for exposure times, since that's more efficient than doing the actual floating-point mathematics.

On a personal note these results really complicated the development of the Little Bramper, as I couldn't use the camera as a reliable exposure reference. Hopefully, in the year 2047 when we finally have an open-source DSLR, the boffins will have eschewed this sort of BS.

Too bad this forum doesn't have a 'Moaning/Rants/Catharsis' section.

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Tue Aug 10, 2010 6:20 pm
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Post Re: 5D MkII 30 seconds = 33 seconds
The sequential logic is 8, 16 and 32 seconds, which Canon appears to actually use but historically it always been displayed at 8, 15 and 30 seconds for whatever reason lol


At least when I tell the Little Bramper to give me a 30 second exposure it does what it's told :)

regards
Kev

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Wed Aug 11, 2010 1:16 am
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Post Re: 5D MkII 30 seconds = 33 seconds
You have brought up an interesting observation.

I looked at the read outs on a 25+ year old digital Minolta Auto Meter 3 and the same 8, 15, 30 sec display appears.
Perhaps it was an attempt to apply the KISS principle, especially when shooting long exposures using film meant you had to factor in extra exposure to compensate for reciprocity failure. http://en.wikipedia.org/wiki/Reciprocity_(photography)

In a current more exacting digital world there is no room for such error! :ugeek: .......... and explains why it always takes about 10% longer to shoot a long exposure sequence. ;)


Wed Aug 11, 2010 7:27 pm
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Post Re: 5D MkII 30 seconds = 33 seconds
Off the topic, but kind of related.

In early July I did a star lapse using one of the Yong Nuo intervalometer, I had set the interval for 32 seconds and I found that I actually wound up with an interval of 62 seconds (thus I got half the exposures I had expected.

So I did an experiment with my Nikon D300s and D700. I set the cameras on manual exposure 30sec exposure for all of the trials. So I tried 32 second interval with the Chinese intervalometer and I got an interval of about 62-63 seconds. Then I tried 35 second interval which resulted in a 35 second interval, I worked down such that I found that a 33 second interval resulted with an actual 33-34 second interval from the time stamps and my clock. Now if I use the intervalometer inside either of my Nikons I can actually do a 32 second interval with a 30 second exposure that results with a 32 to 33 second interval according to the time stamp and agreed with my stop watch.

I am not sure what is going on, but I thought it was interesting.

Scott


Wed Aug 11, 2010 10:19 pm
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Post Re: 5D MkII 30 seconds = 33 seconds
scottbuckel wrote:
Off the topic, but kind of related.

In early July I did a star lapse using one of the Yong Nuo intervalometer, I had set the interval for 32 seconds and I found that I actually wound up with an interval of 62 seconds (thus I got half the exposures I had expected.

So I did an experiment with my Nikon D300s and D700. I set the cameras on manual exposure 30sec exposure for all of the trials. So I tried 32 second interval with the Chinese intervalometer and I got an interval of about 62-63 seconds. Then I tried 35 second interval which resulted in a 35 second interval, I worked down such that I found that a 33 second interval resulted with an actual 33-34 second interval from the time stamps and my clock. Now if I use the intervalometer inside either of my Nikons I can actually do a 32 second interval with a 30 second exposure that results with a 32 to 33 second interval according to the time stamp and agreed with my stop watch.

I am not sure what is going on, but I thought it was interesting.

Scott

It sounds like the chinese intervalometer was sending the trigger pulse before the camera is ready to accept it so the camera ignored it and was triggered by the next pulse giving the long gap between frames.

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Thu Aug 12, 2010 3:01 am
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Post Re: 5D MkII 30 seconds = 33 seconds
Photosbykev wrote:
If you set the 5D MkII to manual 30 second exposures and continuous drive mode and then lock the shutter down with a remote release for continuous shooting and then check the file timestamps they are 33 seconds apart?

There is no audible delay between the end of one exposure and the start of the next, So if you allow approx 200ms delay between frames for the mechanics to recycle then the 30 second exposure seems to overrun by approx 10%.

Any one else seeing this with their MkIIs as I have a very similar finding for the 7D as well.


When I shoot starlapse on my 5D2 at 30 sec manual exposure I set the interval at 1 sec. I notice that there is a lag as the RAW images are transfered to my slow 32Gb CF card before then next shot is triggered. The timestamps reveal the images were taken 33 secs apart.

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Thu Aug 12, 2010 3:36 pm
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Post Re: 5D MkII 30 seconds = 33 seconds
unozig wrote:
Photosbykev wrote:
If you set the 5D MkII to manual 30 second exposures and continuous drive mode and then lock the shutter down with a remote release for continuous shooting and then check the file timestamps they are 33 seconds apart?

There is no audible delay between the end of one exposure and the start of the next, So if you allow approx 200ms delay between frames for the mechanics to recycle then the 30 second exposure seems to overrun by approx 10%.

Any one else seeing this with their MkIIs as I have a very similar finding for the 7D as well.


When I shoot starlapse on my 5D2 at 30 sec manual exposure I set the interval at 1 sec. I notice that there is a lag as the RAW images are transfered to my slow 32Gb CF card before then next shot is triggered. The timestamps reveal the images were taken 33 secs apart.

I just set the camera to continuous drive mode and lock the shutter release down. That way it will be shooting as fast as it can without having to worry about interval times.

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Thu Aug 12, 2010 4:14 pm
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