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Long exposures and digital

"Owners of DSLRs with CMOS sensors may not consider it a big deal, but CCD chips, such as those used in medium format backs, have (until now) had difficulty with long exposures. And by long exposures I'm not talking about minutes. I'm talking about seconds, and in many cases even large fractions of a second.

No, this is not hyperbole, as owners of some MF backs will confirm. A second or two has been the limit for many, and a few even start to get blotchy and noisy at anything more than 1/4 second. ... © 1995-2006 Michael Reichmann"

http://www.luminous-landscape.com/reviews/cameras/p45-long.shtml

I saw this published at LL and, since don't have a MF digital back, but would like to use one with hot lights "tungsten".

How bad is it. Does it bother photographers doing architectural photography.

By the way, what is more common now in the architectural-industrial field scanning or one shot backs? (or film, Canon etc)

thanks,

LeonardoBarreto.com
 

ericevans

New member
I have had some issues with long exposures and the Aptus . If the scene is well lit I usually have no problems with noise. If there are dark shadow areas the noise shows up at the 1/30th or longer exposures . I did a commercial shoot in California a few weeks ago of a building that was covered in lights and 10-15 second exposures had no noise . ISO 25-50 on the Aptus really is noise free unless there are deep shadow areas . ISO 100 is good for longer exposures as long as the subject is well lit . I have found shooting architecture (95% of my work) that shooting at the edge of day and light painting with a hot light that noise is not bad at all if there is any at all .
 

Paul Caldwell

New member
Most modern digitals will have some form of dark frame substraction built in for longer exposures. I believe this was originally for stuck pixels, now many of the algorighims will work on noise.

On my 1ds, I can get about a 5 minute max before the noise really gets out of hand. That is a 10 minute exposure on the 1ds as it does the dark frame real time, unlike the 1ds MKII, which allows you to go on to the next shot. I have always felt that that the 1ds had a better long exposure ability than the MKII.

Paul Caldwell
 
I talked to someone at BearImages because I'm considering a P 25 for the Mamiya AFD, and I asked about this regarding that PhaseOne back, and he said that "new software is changing the situation so that longer exposures are possible"

Since the new P 45 seams to be able to capture up to - i think - 30minute-long exposures, then the difference may not be in the hardware but firmware.

It was the first time that I heard about this so maybe you know about it.

take care,
LeonardoBarreto.com
 
Paul Caldwell said:
Most modern digitals will have some form of dark frame substraction built in for longer exposures. I believe this was originally for stuck pixels, now many of the algorighims will work on noise.

On my 1ds, I can get about a 5 minute max before the noise really gets out of hand.

You probably could have gotten better results by adding the results of multiple shorter exposures. The number of photons would have been the same, but the noise build-up from the sensor would have been lower. Of course there may be some subjects that won't lend themselves for multiple shots, but these very long exposure times can often tolerate a few short interruptions.

In the same spirit, one can take multiple dark-frame shots with the same exposure conditions (time and temperature) as the individual image shots, average them and subtract from the other images. That, and more, is done in Astro photography on a routine basis.

Bart
 

Daniel Harrison

pro member
Well unfortunately I have had no experience with MF but I did have a CCD 1D. it would do funny stuff like hot pixels at 1/4 of a second. So I would imagine that it would be the same with MF. And possibly worse as they do not handle noise as well (apparently)
 
with the emotion22 and e75 its very important that the blackreference is taken together with the shot. i have virtually noisefree ixperiences with both back up to 20 sec ( iso25 on the e22, iso50 on the e75 ). but its important to switch in the setup for blackref: next shot.
30sec with iso50 is pretty much, cause with the rodenstock lenses i use there is no need for a centerfilter and the HR lenses start to be very sharp at f5,6 also.
 
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