Canon 7D and gaps between exposures

Perhaps I don't understand the mechanism, but in continuous mode, isn't the image written to the buffer then to the card? And can't the buffer hold something like half a dozen+ RAW shots at maximum FPS before it starts delaying due to card writes? So why would this have to do with writing to the card?

amfoto1 wrote in post #9247430
First.... There is no need to use mirror lockup on a 30 second long (or longer) exposure. The duration of "mirror slap" is so short, that it's an insignificant part of an exposure that long.....

On any normal long exposure then I'd agree. For star shots though, the point intensity of some stars can be high enough to show some blurr...certainly noticeable using a 600mm lens.

Bob

Maybe it is a problem with the remote+7D?
I've just tried holding down the shutter on a 30sec shot on continuous, and although there was a slight delay the second shot started almost immediately.

all good food for thought thank you. I'll run some more tests today and see what I can find out.

Specifically:
the delay between frames on shorter exposures, this thread, on another forum showed that the delay reduces as the length of exposure reduces

I need to check the effect of the Canon remote against using the shutter and also do a check with single frame shooting mode

Since you are wildlife photog you don't have the silent shutter mode enabled?

2.6 s for the sensor to cool after running for 30s?

Raikyn wrote in post #9250030
Since you are wildlife photog you don't have the silent shutter mode enabled?

It isn't something I've played so it's set at default at the moment. Worth taking a look at it and see if it has an effect

PhotosbyKev wrote in post #9250038
It isn't something I've played so it's set at default at the moment. Worth taking a look at it and see if it has an effect

It's just that on the second day after getting my 7D I turned off every noise/quiet reduction feature I could find.
Obviously in this situation the long exp/high iso noise settings would have a far greater impact.

Even if you don't get to the bottom of what is causing the 2.6 sec delay, I am surprised it is giving you gaps in your star trails. I only say that because the stars will move so little in 2.6 secs that I am surprised it is noticeable when you stack your images. It will be more obvious if you are using a long lens, but as your exif is not intact, it's not possible to tell if that is a contributing factor.

The only other thing I can suggest to check is that you don't have an interval set in your remote. I've done that before without realising.

Well, I can tell you that this doesn't happen when I do these sorts of exposures. I set my 7D for 20 or 30 seconds, burst mode. Then just use a cheapo Ebay shutter release and lock it into the 'hold' position. Delay between shots is something like 0.26s

It's nothing to do with the amount of data (which is exactly the same for a 30s exposure as it is for a 1/3000s exposure). It's not Long-Exposure NR as that would add an interval of 30s between shots. It can't be any of the other processing things as you'd see the same delay in ordinary shooting.

It's got to be the remote. So try it just pressing and holding the shutter - I'll bet that gets rid of the delay. If it does then I'd try one of the cheaper, non-timer, remotes and see how that goes.

I just did this test as well using the shutter button on the camera and held it down continuously. It had something less than a second delay to reopen the shutter for the next 30 sec exposure, so I agree with hollis, it has to be your remote.

Sorarse wrote in post #9250093
Even if you don't get to the bottom of what is causing the 2.6 sec delay, I am surprised it is giving you gaps in your star trails. I only say that because the stars will move so little in 2.6 secs that I am surprised it is noticeable when you stack your images. It will be more obvious if you are using a long lens, but as your exif is not intact, it's not possible to tell if that is a contributing factor.

The only other thing I can suggest to check is that you don't have an interval set in your remote. I've done that before without realising.

I was using the Canon 10-22mm lens at the 10mm end. I do use the fancy Canon remote release but just use it to lock the shutter button down and use the camera shutter speed set to 30 seconds.

callaesthetics wrote in post #9247322
30 seconds is a lot of data, that 2.6 seconds is probably the camera processing the image before it can recreate a new one.

My XTi takes 20-30 secs to process a 30 secs exposure.

It's the same amount of data as any other picture file. The camera is capturing the light photons over a longer period of time is all ... same file size at end of exposure.

Write time?

callaesthetics wrote in post #9247322
My XTi takes 20-30 secs to process a 30 secs exposure.

That's almost certainly because you've got Long-Exposure Noise Reduction switched on. After the 30 second exposure the camera takes another 30s exposure without opening the shutter. It then subtracts that one from the original.

hollis_f wrote in post #9250120
Well, I can tell you that this doesn't happen when I do these sorts of exposures. I set my 7D for 20 or 30 seconds, burst mode. Then just use a cheapo Ebay shutter release and lock it into the 'hold' position. Delay between shots is something like 0.26s

It's nothing to do with the amount of data (which is exactly the same for a 30s exposure as it is for a 1/3000s exposure). It's not Long-Exposure NR as that would add an interval of 30s between shots. It can't be any of the other processing things as you'd see the same delay in ordinary shooting.

It's got to be the remote. So try it just pressing and holding the shutter - I'll bet that gets rid of the delay. If it does then I'd try one of the cheaper, non-timer, remotes and see how that goes.

and Teamspeed, it does sound like the mirror is dropping and lifting very quickly (which I would expect) but the delay is before this happens I think.

I'm not using any of the programmable modes of the remote all I do is lock the shutter release on it. This closes a mechanical switch in the remote which triggers the camera, no electronics are involved, it even works if the cr2032 battery dies in it so I tried it like that with no change to the delay problem.

I tried your test using only the shutter button but there wan't a change to the time delay. Please repeat your testing with the shutter button BUT set shutter speed to 30 seconds and then press and hold the button for 5 exposures I think you will see a total elapsed time of around 150 seconds PLUS another 13 seconds so approximately 163 seconds for the 5 exposures. This assumes all noise reduction is turned off.

Disabling the Silent Shooting mode did reduce the delay from 2.6 to 2.3 seconds per exposure

regards
Kev