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03-27-2012, 03:02 PM   #1
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Bulb in Sky/stars photography (Pentax K-r)

Well,
this is my first attempt of photographing stars/sky ... set the k-r in Manual mode and scrolled to BULB...

this photo is taken with 214s exposure / f8 / iso100
I started and stopped the exposure (using the IR-remote) and after that i had to wait nothing less than the exposure time (214 seconds) [viewing through the viewfinder i saw numbers decrement starting from 214 to zero ; and the seconds mark ( " ) ].... in other words i was unable to interact with the camera.... is this normal for the K-r? Is that the time needed to clear the buffer?
Tnx in advance,
Aleksandar





03-27-2012, 03:22 PM   #2
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That is the noise reduction in action
03-27-2012, 05:58 PM   #3
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That's the long-exposure noise reduction as jezza323 said. To turn it off, go to Menu> camera icon> 2 > Slow Shutter Speed NR> Off. Hope it helps!
03-28-2012, 01:12 AM   #4
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Sounds like dark frame subtraction. After a long exposure, the camera will take a second shot with the shutter closed (same duration) so it can remove 'hot' pixels.

Not sure if it really can be switched off on a K-r.


Last edited by sterretje; 03-28-2012 at 01:32 AM.
03-28-2012, 02:22 AM   #5
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QuoteOriginally posted by alexmkd Quote
Well,
this is my first attempt of photographing stars/sky ... set the k-r in Manual mode and scrolled to BULB...

this photo is taken with 214s exposure / f8 / iso100
I started and stopped the exposure (using the IR-remote) and after that i had to wait nothing less than the exposure time (214 seconds) [viewing through the viewfinder i saw numbers decrement starting from 214 to zero ; and the seconds mark ( " ) ].... in other words i was unable to interact with the camera.... is this normal for the K-r? Is that the time needed to clear the buffer?
Tnx in advance,
Aleksandar


Welcome to the facinating world of astrophotography. As others have pointed out, DSLR's will normally per default do a dark frame subtraction ("DFS") to remove hot pixels at very long exposure times. In astrophotography it is much more efficient to turn off the in-camera DFS (if at all possible) and take one, single Dark Frame (with cap on lens) yourself and do the DFS afterwards in software.

You should also note, that f/8 isn't very effecient to capture stars. For stars, the light capturing power of your lens will be proportional to the square of your absolute, physical aperture (not the f-ratio) and you would capture much, much more stars at, say, f/3.5 and ISO 1600 in some 30 seconds than you have done with your settings in 214 seconds. I have published some comparisons of the same star fields with different settings here:

http://www.gyes.eu/astro/camera_settings.htm
03-28-2012, 04:13 AM   #6
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Hey, thanks guys for your input
Seems logical, the DFS... i think disabling it is not possible on the k-r (no such thing in the menu, maybe in some firmware update)
@Stone G. Thank you for the link I'll take few shots this week (or weekend) with the settings you recommend.
And, what lens would you suggest for this type of photography? Probably some fast lens (the expensive ones?)) )
03-28-2012, 04:52 AM   #7
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alex.... i am also interested in star photography aswell quick question for you i have just bought an IR remote did you have to hold the button on the remote for the duration of the shot or was it press it once to fire the shutter and press it again to stop the exposure? thanks
03-28-2012, 07:53 AM   #8
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QuoteOriginally posted by alexmkd Quote
Hey, thanks guys for your input
-----
And, what lens would you suggest for this type of photography? Probably some fast lens (the expensive ones?)) )

The best lenses for astrophotography are (reasonably) fast primes - but you don't need to spend a fortune on that for astrophotography as you will not need auto focus or program settings. Purely manual lenses are perfect as long as the optical quality is fine. If you have such, try vintage pentax-M/K, tamron, zeiss....you name it. But for a start, just use what you have. There is a piece of sky for every lens!

Good luck & enjoy.

03-28-2012, 08:10 AM   #9
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QuoteOriginally posted by theflyingjocksman Quote
alex.... i am also interested in star photography aswell quick question for you i have just bought an IR remote did you have to hold the button on the remote for the duration of the shot or was it press it once to fire the shutter and press it again to stop the exposure? thanks
press once for start of exposure, and second press for ending the exposure Look in the Custom menu-> tab 3 -> Remote control in bulb -> Mode 1

QuoteQuote:
The best lenses for astrophotography are (reasonably) fast primes - but you don't need to spend a fortune on that for astrophotography as you will not need auto focus or program settings. Purely manual lenses are perfect as long as the optical quality is fine. If you have such, try vintage pentax-M/K, tamron, zeiss....you name it. But for a start, just use what you have. There is a piece of sky for every lens!

Good luck & enjoy.
Ok Stone G. Tnx for the answers!
03-28-2012, 09:29 AM   #10
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The long "freeze" after the shutter closes is the definately the noise reduction and it can be turned off. The Kr Bulb mode has two settings. Mode 1 will open the shutter when the remote button is pushed and will remain open until the button is pushed a second time. In Mode 2, the shutter will open and remain open as long as the remote button is held down and close when the remote button is released. Another option I use for starry skies is Interval shooting, Expensive lenses aren't needed for starry skies.(It doesn't hurt if you can afford them but if you just want some cheap fun....)

Pentax Kr, Da L 18-55 kit lens 30 seconds @f3.5, 3200 ISO



Pentax Kr, Da L 18-55 kit lens 30 seconds @f3.5, 6400 ISO (Your Kr is very good for low light/high ISO)

When you've got a reasonable handle on night sky photography, here are a couple of websites I use. This is a listing of annual astronomy events. Full moon, eclipses, meteor showers, etc.

Astronomy Calendar of Celestial Events 2012 - Sea and Sky


This website shows when the International Space station, Iridiun flares, and various satellites are visible from your location. The ISS overhead is quite a sight!
Heavens-Above Home Page
03-28-2012, 09:54 AM   #11
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The noise reduction can be turned off on the k-r menus can't remember which one without looking at the camera but I have seen it in one of the menus whilst flicking through. Astrophotography is amazing especially if you have an interesting foreground subject
03-28-2012, 10:51 AM   #12
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There is a group for astro here Astrophotography - PentaxForums.com
03-28-2012, 03:41 PM   #13
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Dark Frame Subtraction can be disabled. It's called something like long exposure noise reduction in the menus.
04-04-2012, 11:53 AM   #14
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tnx people
I recommend, if u have an android phone, to install the Google Sky Map application on your phone...
A great app for finding out the position of constellations (i don't know if this app is available for other phone OS)
You can find it on the Google Play (former Android Market)
05-14-2012, 01:34 PM   #15
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Guys, made a few new shots of the sky at night....
this is one of my favorite



so, tell me what is good what is wrong
Greetings, Aleksandar
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