Camera Labs

I've noticed on my Canon 550D that if I'm doing long exposures, say 30 seconds, that they take AGES to save and was wondering why.

Just done a quick test and its taking about 30 seconds to save a 30 second exposure.

I have a fast-ish card in there (Scandisk Extreme 16Gb 30MB/s x10)

Anyone know whats going on?

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Canon EOS 550D (with Magic Lantern)
18mm - 135mm Kit Lens, 50mm f1.8, Sigma 30mm f/1.4 EX DC HSM
430EX II Flash with Phottix Strato Wireless Tigger Set
Manfrotto 190CXPRO3 with 496 Ball Head. Gorilla Pod SLR
Canon Powershot A720IS with CHDK and intervalometer script. Pentax Optio W90

My Blog - http://www.ianganderton.wordpress.com

The camera substracts a Dark frame to reduce noise. Turn Long exp. noise red. off in the custom menu to disable it.

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Ruben

Panasonic DMC-FZ18, Panasonic DMC-FZ28, Canon G5, Canon 350D, Canon 50D + BG-E2N
Tamron 17-50 2.8, Canon EF 70-200mm f/4L USM,
Canon 18-55 II plus lots of Minolta MD/M42 lenses and bodies

Ahhhhh, cool, thanks Ruben, that info is much appreciated. I'll do a couple of trials to check the difference to see if the wait is worth it

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Canon EOS 550D (with Magic Lantern)
18mm - 135mm Kit Lens, 50mm f1.8, Sigma 30mm f/1.4 EX DC HSM
430EX II Flash with Phottix Strato Wireless Tigger Set
Manfrotto 190CXPRO3 with 496 Ball Head. Gorilla Pod SLR
Canon Powershot A720IS with CHDK and intervalometer script. Pentax Optio W90

My Blog - http://www.ianganderton.wordpress.com

Longer exposures with higher temperatures and higher ISOs, yes, there will surely be diffrences. But, 10 degrees/15 degrees, 100-200 ISO, no, it wont be that impressive the Dark frame substraction gives you.

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Ruben

Panasonic DMC-FZ18, Panasonic DMC-FZ28, Canon G5, Canon 350D, Canon 50D + BG-E2N
Tamron 17-50 2.8, Canon EF 70-200mm f/4L USM,
Canon 18-55 II plus lots of Minolta MD/M42 lenses and bodies

Actually I read somewhere after googling 550d Long Exposure Noise Reduction following your answer that the noise reduction works best on lower ISO's and that with higher ISO's it can actually make it worse.

Here in the middle east if it gets below 20 deg its considered a bit chilly, its been down as low as 15 recently and everyone has been complaining bitterly!! Temperature induced noise and whether there is anything I can do about it is something I'd like to work out.

Here's the link re higher ISO's and increased noise with LENR http://www.imaging-resource.com/PRODS/T2I/T2IA5.HTM

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Canon EOS 550D (with Magic Lantern)
18mm - 135mm Kit Lens, 50mm f1.8, Sigma 30mm f/1.4 EX DC HSM
430EX II Flash with Phottix Strato Wireless Tigger Set
Manfrotto 190CXPRO3 with 496 Ball Head. Gorilla Pod SLR
Canon Powershot A720IS with CHDK and intervalometer script. Pentax Optio W90

My Blog - http://www.ianganderton.wordpress.com

Maybe because its taking a long exposure. You can't wait a minute for a photo??

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Palkaboy- ha ha, of course I can wait a mo. The query was because I was wondering why and it turns out there was a reason (on exposures longer than 1 second its actually taking 2 exposures!!) so the question was worth asking!!

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Canon EOS 550D (with Magic Lantern)
18mm - 135mm Kit Lens, 50mm f1.8, Sigma 30mm f/1.4 EX DC HSM
430EX II Flash with Phottix Strato Wireless Tigger Set
Manfrotto 190CXPRO3 with 496 Ball Head. Gorilla Pod SLR
Canon Powershot A720IS with CHDK and intervalometer script. Pentax Optio W90

My Blog - http://www.ianganderton.wordpress.com

one thing to remember would be to disable it if your doing extremely long exposures
i did a 17minute exposure with the 500D i had earlier, and it ended up taking another 17minute exposure for the noise reduction.
it ended up using probably 75% of the battery.

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DeviantArt
Canon 1D MK3, 1x580EXII, 1x430EX
Canon 50mm 1.4 USM, Canon 100mm F2.8 USM
Canon 70-200 F2.8 L IS II, Canon 16-35 F2.8 L
Sigma 300mm F2.8

Canon Pixma PRO-9000 MKII

and a 17-40 F4L in a hundred little pieces

Generally I would turn it off, unless you're only doing "shorter" long exposures where it doesn't have much impact on shooting time. Hot pixels are usually handled quite well with modern raw converters anyway, and if needed for special applications (astrophotography) you could separately do a dark frame subtraction instead.

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Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.