Long exposures and processing time

[MarkCook]

Hi,

I'm a little confused about shooting in bulb mode in terms of how long the camera should take to process the image once you close the shutter.

Basically using a wireless shutter release I do a 10 minute exposure then after closing the shutter the camera takes another 10 minutes to process the image before I can view it on the rear screen. This occurs whether I have noise reduction disabled or not.

Is this usual for a K10D (my GX10 behaves the same) or am i doing something wrong ?

Thanks

Mark

[GDN]

No its usual.

Unfortunately K10D and the K20D do not allow you to turn off long exposure noise reduction function built into the camera. Thats what the delay is....

[MarkCook]

Pants that's what I suspected ... not nice after a 10 minute exposure on the beach at 1.40am and then having to wait another 10 minutes to see the result !!!

Wonder if the K7 has improved on this !?!?!?

[john_g]

Huh?

On my GX-10 (running the current v1.30 firmware) the camera does its dark frame subtraction only if noise reduction is enabled. If I turn it off (via Menu/Custom 1/Page 2/Noise Reduction) then the LCD preview comes up as soon as the shutter closes and I can take another picture immediately.

[MarkCook]

Yeah that's what I thought was meant to happen. Both my GX10 and K10D are running the respective 1.3 version firmware so I'm a little confused.

I'll have to take another look at this just to make doubly sure I'm not doing something stupid....

Thanks

[GDN]

Long shutter NR works by performing the "dark frame subtraction" on the raw data. The camera captures the image as normal, then immediately captures another image for the 'same duration' with the shutter closed. This second image contains only thermal sensor noise, so by subtracting it from the previous image, it yields an image without (much) sensor noise. This subtraction must be performed on the raw data, and affects the raw result.

On the K20D you can't turn this off, however having done a little digging around it appears that on the K10D, long shutter NR can be turned off.

This will let you take several long exposures without having to wait between them, and you can do your own dark frame subtraction later on the computer.

So I stand corrected Mark.

[MarkCook]

Yes thanks, so I guess I'm doing something (or not) wrong in that case as I'm sure I turned it off but it had not had any effect....

Oh well, another early morning trip to the beach next weekend for sunrise and some experimentation with more long exposures.


Cheers fellas


Mark

[john_g]

The only thing that I maybe did differently was to check this using an exposure of around ten seconds rather than ten minutes, so you can try to replicate this at a more convenient time and place! I just assume that the behaviour with a ten second exposure will be the same as with a ten minute one.

[GDN]

The camera will take the equivalent "dark frame subtraction" shot, so if it was a three minute shot then it would take a three minute dark frame image.

[MarkCook]

The only thing that I maybe did differently was to check this using an exposure of around ten seconds rather than ten minutes, so you can try to replicate this at a more convenient time and place! I just assume that the behaviour with a ten second exposure will be the same as with a ten minute one.

There is something in the manual about exposures longer than 30 seconds, however, a trip out to a very wind swept Whitstable beach last night confirmed it was operator error, somehow I must not have saved the setting correctly, suffice it so say on both K10D and GX10's with NR turned off the Dark Frame subtraction does not happen and you get your image straight back for review, no double exposure lengths or sillyness...

Thanks guys.