 BetterPhoto Member |
How to Make Long Exposures Hi, I've bought a Canon EOS 350D and I'm researching before it arrives. I've read loads about exposure and time-lapse photography, however I have a very basic question: When someone speaks of a 30-second exposure or a 3-hour exposure, what do they mean?? Is there some option in the camera for starting the exposure, and leaving the camera there for 3 hours and then coming back and stopping the exposure??
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Jon Close |
The camera can set timed exposures (shutter speeds) from 1/4000 sec. to 30 seconds. For exposures longer than 30 seconds, the user selects M (manual) mode and sets the shutter speed to "B" (Bulb). On this setting, the shutter remains open so long as the shutter button is pressed down. While one can do this with their finger on the shutter button, it is not practical. For such long exposures, you should use a remote shutter release. The wired RS60E3 has a shutter button that locks down for B exposure so you can set it, leave and come back to close the shutter later. With the wireless RC-1 or RC-5 remotes, the first press of the shutter button opens the shutter, then a 2nd press on the remote closes it. Note that digital cameras draw heavily from their batteries during such long exposures. To do a 3-hour exposure, it is recommended that the camera be connected to a continuous power source with the optional AC-Adapter kit, or at least powered with the optional BG-3E battery grip loaded with 2 fully charged batteries. Cold temperatures will drastically reduce battery life.
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Irene Troy |
Jon - I've been wondering about long exposures with digital. I have done them with film; however, I read somewhere that it is next to impossible to do these type exposures with digital due to problems with excessive noise (not to mention the power problems you speak of). Is this accurate info? I am now shooting with a Canon 5D if that matters. Thanks!
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Jon Close |
Not impossible, but the increased noise is a hurdle. Canon's in-camera noise reduction feature for long exposures works by taking 2 equal length exposures, one with the shutter open to record the image, then one with the shutter closed to map the noisy pixels. Works OK with exposures measured in minutes, but beyond that it is not practical. With the noise reduction feature on, a 3-hour exposure will actually take 6 hours before the image gets written to the CF card. Better to use post-processing noise reduction methods for ultra-long expsosures. Some digital camers designed specifically for astro-photography have elaborate cooling systems for the sensor to reduce heat/noise for long exposures.
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