h4d-50 long exposures ?

[Steve Fines]

Hi,

Anyone happen to know -

The longest ss listed on the h4d-50 is 256 sec.

After closing the shutter from a long exposure, does anyone know how long it is before the next exposure can be taken?

I'm wondering if there are mandatory dark frames or sensor cool down times imposed by the camera, or if one could string together a number of 256s exposures.

thanks,

Steve

 

[jecxz]

Steve,

No dark frame required with the Hasselblad longer exposures. After shooting a long exposure you're able to shoot the next shot within a few moments - it does seem as if the back is processing something, but it's only a few moments (second or two), nothing more. I'm pretty familiar with long exposures and Hasselblad. Be well.

Kind regards,
Derek Jecxz
www.jecxz.com

Hi,

Anyone happen to know -

The longest ss listed on the h4d-50 is 256 sec.

After closing the shutter from a long exposure, does anyone know how long it is before the next exposure can be taken?

I'm wondering if there are mandatory dark frames or sensor cool down times imposed by the camera, or if one could string together a number of 256s exposures.

thanks,

Steve

 

[Steve Fines]

Hi,

Thanks.

Just got the official reply from Hasselblad - seems to agree with what you are saying.

I thought I had read the long exposure for the H4d was longer, but according to H-USA it is 32 seconds, with the camera then able to take the next shot about 1/10th of a second later. They said that this process could be continued until the card or battery limited things.

 

[jecxz]

I was being honest.

Kind regards,
Derek

Hi,

Thanks.

Just got the official reply from Hasselblad - seems to agree with what you are saying.

 

[dougpeterson]

Hi,

Just got the official reply from Hasselblad - seems to agree with what you are saying.

I thought I had read the long exposure for the H4d was longer, but according to H-USA it is 32 seconds, with the camera then able to take the next shot about 1/10th of a second later. They said that this process could be continued until the card or battery limited things.

If long exposures are important to you then you'd want to do this test yourself hands-on with the specific backs you are considering. If you want to shoot several sequential maximum length exposures in a row with very little time between frames then with nearly every camera I've ever personally used in that way the images will become progressively noisy as you capture more sequential frames. Sometimes by a very little bit that does not matter and sometimes by a lot - that varies a lot by the specific camera/sensor/ambient-temperature etc. I am not negatively commenting on Hasselblad here - any camera, including the Phase One / Leaf cameras that my company sell will show this tendency.

Also do your own testing of the "longest" exposure as it may be better or worse than the spec depending on your usage and requirements. Ambient temperature (and therefore the places you work) also has a lot to do with it.

Bottom line: as always your own real-world test of your intended usage with someone knowledgable on the product is the only completely dependable answer. There are several Hasselblad reps/dealers on this board that will happily assist you in such a process.

If you want to compare the results to a Phase One (known as the king of long exposures) or Leaf there's reps/dealers here for that too - my company included . Though if you absolutely MUST shoot them without pausing for the dark frame then you could also do so with a Leaf/Phase if you bought/borrowed/rented/stole two units to trade off exposures.

Doug Peterson (e-mail Me)
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[KurtKamka]

Lots of boosterism going on these days on this and other medium format forums. It's fascinating. When a perceived weakness is exposed ... the buzzards begin to circle. The stakes are high in this economy.

 

[Bob]

Long exposure facts:
The longer the exposure the more noise is generated, the higher the temperature, the higher the noise. That is why extremely long exposures (hours, days) usually use cryogenically cooled sensors.

All sensors use black reference frames, some are taken at the same length as the original, some at shorter times, some are synthesized. This is important especially in ccd sensors using external a/d converters (all current MF backs IMO) particularly since the black reference is used to "calibrate" each frame taken at a similar time and or temperature. Some vendors have different "acceptable" noise thresholds than others, so they go to greater or lesser lengths to control it. Some backs use one reference black frame for several exposures taken at similar times, some take a new one each image provided, some use only the synthetic frame, which provides zero shift information only and not pixel by pixel noise.

The choice is a design time compromise.

So for a reference on what a particular back can do in terms of inter-long-exposure wait time, refer to back specifications or empirical observations.
...and for any particular purpose, test the damn thing.

But I will point out that so far, no vendor has yet successfully violated the laws of thermodynamics at least outside of the realm of the marketing materials.

thanks
-bob

 

[Will Ophuis]

yeah Ive done some 4min 16sec exposures with my H4D-40 with very nice results, just looking through some photos I took yesterday after sunset going 32 sec, 40 sec etc up till 4:16 they did tend to get more noise probably because the sensor wasn't getting a break in between.