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Old Jan 8, 2011, 2:16 AM   #1
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Default DSLR's that can do exposures longer than 30 seconds?

I have another thread in here where I have been looking at pentax K-r and slowly added the Nikon D90 to my list of possibilities. I was starting to settle on the D90 but I cam across something today that said the max exposure time on the D90 was 30 seconds. Some of the night time photo's i would like to take would be star shots over several hours. Are any of the DSLR's going to be able to do that? I am having a hard time finding the spec i need to look at although it may be I am looking for the wrong thing.
Or is this a feature that going to be above the Nikon D90?
other options i was considering is the canon T2i.
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Old Jan 8, 2011, 6:25 AM   #2
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What you're looking for is a shutter speed of "B" or "Bulb". At that setting, the shutter is open as long as the shutter button is depressed (or the remote is locked). There are also third party devices that can be programed to keep the shutter open for a specific long time as well as multiple exposures at fixed intervals.

This setting was originally intended for use when the shutter remained open and the exposure was made when the flash bulb went off, hence the name.

The K-r, D90, and T2i all have a shutter speed setting of "Bulb".
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Old Jan 8, 2011, 8:56 AM   #3
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Quote:
Originally Posted by TCav View Post
This setting was originally intended for use when the shutter remained open and the exposure was made when the flash bulb went off, hence the name.
I had always assumed that the name 'bulb' referred to a flash bulb
or some form of light bulb. I was reading recently that this is not
the case. The name refers to the rubber air bulb that operated a
pneumatic shutter mechanism which held the shutter open while
the bulb was squeezed.
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Old Jan 8, 2011, 9:17 AM   #4
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Quote:
Originally Posted by corkpix View Post
I had always assumed that the name 'bulb' referred to a flash bulb
or some form of light bulb. I was reading recently that this is not
the case. The name refers to the rubber air bulb that operated a
pneumatic shutter mechanism which held the shutter open while
the bulb was squeezed.
Exactly. Here's a photo of the front of my father's old Crown Graphic. Notice that the shutter speeds include two letters at the end, 'B' and 'T.' 'B' was bulb. As long as the cable trigger on the left was held pressed (you would squeeze it like injecting a syringe), the shutter would stay open. The 'T' (timed) was considerably more convenient for long exposures -- the first squeeze of the trigger opened the shutter, and the second squeeze closed it. FWIW.

[ETA: The 19th century version of the cable trigger was the pneumatic bulb you describe. Notice that the cable trigger has a knurled ring around the base of the plunger. If you pressed the plunger in, you could tighten that knurled ring to hold it for you, providing a poor man's timed exposure functionality for those cameras that lacked the fancy-shmancy 'T' option.]


Last edited by tclune; Jan 8, 2011 at 9:34 AM.
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Old Jan 8, 2011, 10:48 AM   #5
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You're right. Thanks for the correction.

(See http://en.wikipedia.org/wiki/Bulb_(photography) )
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Old Jan 8, 2011, 11:23 AM   #6
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Quote:
Originally Posted by TCav View Post
What you're looking for is a shutter speed of "B" or "Bulb". At that setting, the shutter is open as long as the shutter button is depressed (or the remote is locked). There are also third party devices that can be programed to keep the shutter open for a specific long time as well as multiple exposures at fixed intervals.

This setting was originally intended for use when the shutter remained open and the exposure was made when the flash bulb went off, hence the name.

The K-r, D90, and T2i all have a shutter speed setting of "Bulb".
This is the statement I came across
Just like most of its competitors, the Nikon D90 features bulb exposure, but unfortunately the exposure button has to remain pressed during the whole exposure. In addition the camera offers only a maximal exposure time of 30 seconds.

Its the "exposure time of 30 seconds " thats got me confused as to what i need to look for as I would like to be able to take photo over the course of hours.
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Old Jan 8, 2011, 11:56 AM   #7
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A little more reading seems to indicate using the bulb setting on the camera will get me 30 seconds. using a remote trigger will get me 30 minutes on the d90. Vs the several hours I am looking for. It may be this is just not going to be an option on these dslr where as film cameras were more mechanical and could take the 8 hour over night images.
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Old Jan 8, 2011, 12:10 PM   #8
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The shutter speeds are controlled by the camera in the modes other than "B"ulb. In Bulb, the shutter stays open as long as you hold down the shutter, or have the shutter active via an external shutter release. There are external wired shutter releases for all camera makes. You can get a manual one where you push it in and hold it, or have a mechanical hold down, or you can get one that has a timer, where you can set it and it takes care of the duration.
Just ensure that your camera has an external shutter release capability - usually wired or IR.

You can also just google "shutter release timer" for your camera make that you are interested in.

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Old Jan 8, 2011, 12:12 PM   #9
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Quote:
Originally Posted by mr_onmyway View Post
This is the statement I came across
Just like most of its competitors, the Nikon D90 features bulb exposure, but unfortunately the exposure button has to remain pressed during the whole exposure. In addition the camera offers only a maximal exposure time of 30 seconds.
Use a Nikon ML-L3 Wireless Remote. In bulb mode, click it once to open the shutter and it will stay open until you click it again (although it may be limited to 30 minutes from what the D90 manual says about it). See page 85:

http://www.nikonusa.com/pdf/manuals/..._ennoprint.pdf

You'll find similar remotes for many other cameras (either wired or wireless). But, you'd need to check each one on a case by case basis to see how bulb mode works with them.
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Old Jan 8, 2011, 1:08 PM   #10
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If you're looking to do unusual night shots or astronomy requiring very very long exposure time, you may need to use film.

Scientific telescopes use refrigerated CCDs to reduce noise. Films do not accumulate noise with time regardless of ISO. Film is always "turned on" from the day its made until its developed. CMOS or CCD, if you leave it turned on total darkness long enough, it will generate noise beyond post correction ability.

My Panasonic P&S has a special long exposure mode, which I use fairly often. It locks the lens at widest aperture and CCD at lowest ISO but the exposure time is set manually from 15, 30 and 60 seconds.

In each setting, it will expose the image for the set time, then it will go through a process equivalent to the exposure time and display "wait". I think what it is doing is taking a picture with the shutter closed to use as a black reference to remove noise from the first image before it is compressed into JPG.
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