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-   -   Problem with bulb exposure + remote (https://e-group.uk.net/forum/showthread.php?t=13929)

chrisdoig24k 10th April 2011 02:31 PM

Problem with bulb exposure + remote
 
I was trying to do some nice star trail photos on the weekend but I noticed that after I'd left the shutter open for about 10 minutes, the camera would freeze up and not save the picture. I was using the wireless remote doodad.
Anybody else got the same problem / way to fix it?

Ian 10th April 2011 03:32 PM

Re: Problem with bulb exposure + remote
 
Were you keeping the shutter open by keeping the IR remote button pressed? It's not really designed to work like that. You really need to get a cable release that attaches to the USB port on the camera. The Olympus part is RM-UC1, but there are lots of cheaper third party options.

Ian

David Gethin 10th April 2011 04:41 PM

Re: Problem with bulb exposure + remote
 
Are you sure it had frozen? Was the noise reduction on? I think it is that where after a long exposure, another exposure of the same length of time is taken with the mirror down that is then subtracted from the first exposure. The idea is that any hot pixels from taking such a long exposure are located and deleted. It would perhaps give you the impression that your camera had frozen.

chrisdoig24k 10th April 2011 11:31 PM

Re: Problem with bulb exposure + remote
 
The remote I'm using is the Olympus RM-1.
David - I think the noise reduction was on standard. Would it be worth turning off? I was only at ISO 100 or 200 (I forget - it was late and after a few beers!).

And do you think a cable release would be more reliable than the infra red one?

David Gethin 11th April 2011 12:56 PM

Re: Problem with bulb exposure + remote
 
Hi Chris, I will try to remember to reply when I have access to my camera again to look through what might be happening here.

Graham_of_Rainham 11th April 2011 02:15 PM

Re: Problem with bulb exposure + remote
 
With the RM-1 you can open the shutter with the "W" button and close it with the "T" button, so you don't have to hold the main button

Ian 11th April 2011 03:50 PM

Re: Problem with bulb exposure + remote
 
Noise Reduction is pretty essential for long exposures and works regardless of ISO speed. Basically the longer the exposure the higher the chance of random pixels producing the wrong colour or brightness - so-called hot pixels.

With Noise Reduction after the long exposure shot has been taken, it's stored in a memory buffer and the sensor is refreshed and left sensitised for the same length of time as when the shot was taken, but with the shutter closed. The same hot pixels will appear (they are independent of exposure by light) and the exposed image is compensated for according to the hot pixels recorded. This is also called dark frame subtraction.

But it does mean the camera is tied up for as much time again after the original exposure has finished and it may indeed look like the camera has frozen up. So if you do a 10 minute exposure, you will have to wait for a further ten minutes for the dark frame subtraction process.

Ian

chrisdoig24k 12th April 2011 12:15 PM

Re: Problem with bulb exposure + remote
 
That's interesting, I'll give it another go properly some time soon. If I remember rightly I couldn't even get the shutter to close though. But I'm not sure, so I'll try again and get back to you!
Thanks

Who's_E 12th April 2011 05:14 PM

Re: Problem with bulb exposure + remote
 
Quote:

Originally Posted by Ian (Post 109821)
But it does mean the camera is tied up for as much time again after the original exposure has finished and it may indeed look like the camera has frozen up. So if you do a 10 minute exposure, you will have to wait for a further ten minutes for the dark frame subtraction process.

Ian

To add to Ian's point, the card-write light should be flashing while it is subtracting the frame.

Nick

chrisdoig24k 13th April 2011 07:56 AM

Re: Problem with bulb exposure + remote
 
I know I saw the write light flashing after I got a successful exposure over a couple of minutes so I assume that was noise reduction.
(the other alternative to my worries is that I may have had auto sleep on, in which case I will actually kick myself)
But the problem will still remain. When we take a shot with several hours exposure, do we just accept that we'll have to wait another few hours for noise reduction? Or is there some other way to fix it up without having to wait? I have a bad feeling leaving the camera essentially taking photos for 8 hours would murder my battery and I wouldn't want to lose a shot that took so long to take just because of battery!

David Gethin 13th April 2011 08:15 AM

Re: Problem with bulb exposure + remote
 
Quote:

Originally Posted by chrisdoig24k (Post 110080)
... (the other alternative to my worries is that I may have had auto sleep on, in which case I will actually kick myself)
But the problem will still remain. When we take a shot with several hours exposure, do we just accept that we'll have to wait another few hours for noise reduction?

Well I would turn off the NR if you want a single exposure star trail, and then deal with the hot pixels in PP - laborious but it will be clear where there are as they will be the single pixel stars rather than trails (unless you have the North Star in the image - what is the Southern hemisphere equivalent?).

Alternatively, you could shoot multiple 30 second exposures and combine using photoshop or startrails software using image stacking processing. Have a google for how to do this. After long periods of shooting multiple exposures the sensor will still get warm and you will still probably suffer from hot pixels appearing.

Ian 13th April 2011 08:19 AM

Re: Problem with bulb exposure + remote
 
Quote:

Originally Posted by David Gethin (Post 110083)
Well I would turn off the NR if you want a single exposure star trail, and then deal with the hot pixels in PP - laborious but it will be clear where there are as they will be the single pixel stars rather than trails (unless you have the North Star in the image - what is the Southern hemisphere equivalent?).

Alternatively, you could shoot multiple 30 second exposures and combine using photoshop or startrails software using image stacking processing. Have a google for how to do this. After long periods of shooting multiple exposures the sensor will still get warm and you will still probably suffer from hot pixels appearing.

I tried the multiple shots method but got hyphenated trails!

Ian

chrisdoig24k 13th April 2011 08:46 AM

Re: Problem with bulb exposure + remote
 
Next time I'm somewhere nice and somewhere dry (rain seems to be coming back into fashion here in Aus), I'll give it a try with no NR.
AND MAKE SURE I HAVE SLEEP OFF!!

theMusicMan 13th April 2011 11:52 AM

Re: Problem with bulb exposure + remote
 
Just to add to Ians very informative post #7 above; this may sound obvious but it's also something people may wonder about - I also learned from Ian telling me on one of our eGroup meets that it is OK to move and reposition your camera while this #2nd exposure for dark frame subtraction is going on.

Just to say... :)


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