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Author Topic: Ultra long exposures with H4D-60  (Read 3246 times)

jonathan.lipkin

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Ultra long exposures with H4D-60
« on: August 11, 2016, 07:41:45 pm »

I'm trying to make exposures of several minutes outside with my H4D-60. I have used a single ND filter to make exposures of up to 16 seconds. I had the idea of stacking a few ND filters together to really cut down the amount of light. I tried with a stack of 2 .9 and two 1.8, which should have resulted in a reduction of 23 stops (if I counted correctly).

I made a test exposure without the filters at f/3.5 and 1/250th of a second which came out properly exposed. I then made an exposure at 32 seconds. This was only about 12 stops down, but I did as a test. It came out very underexposed - basically black with noise. I tried then at shorter exposures, but simply got lighter images with noise on them.

Has anyone else had success with stacking filters? Am I doing something wrong?
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Joe Towner

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Re: Ultra long exposures with H4D-60
« Reply #1 on: August 11, 2016, 08:28:25 pm »

So the camera only wants to do a max of 32 seconds right?  I think stacked 6 stops gives you 36 stops total power, and adding a 3 stop on top gives you a 108 stops. adding a second gives you a 324 stops.  Stops would be multiple, not additive.

Yea, that would give you a black, noisey frame.  How does it look with (1) 1.8 and (1) .9 at 32sec exposure?

I've stacked filters, but when I do it's ND grads/reverse grads with a polarizer in the back.

-Joe
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jonathan.lipkin

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Re: Ultra long exposures with H4D-60
« Reply #2 on: August 11, 2016, 08:48:02 pm »

I tried at shorter exposures - this produced gray, then white noisy frames, so it doesn't seem to be the length of the exposure, though it was at ISO 800 so that might have something to do with it.

If I recall correctly I tried with two filters (.9 and 1.8) and also got noise

The test was done with two .9 and two 1.8

I am pretty sure it is additive, not multiplicative. I don't know the math well enough, but it has something to do with the fact that f-stops are logarithmic, not linear. Here is a quote from Breakthrough Photography's guide to long exposure (they manufacture ND filters):

"My personal recommendation is to get a 3-stop first, a 6-stop second, and when stacked together you get 9-stops. No need to buy a 10-stop!"

Tomorrow when it's light out I'll try at lower iso and with two filters at 30 sec
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tcdeveau

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Re: Ultra long exposures with H4D-60
« Reply #3 on: August 12, 2016, 12:47:24 pm »

is it possible to do exposures of several minutes with the H4D-60?  I thought that the max exposure time was 32 seconds, and that it wasn't a great candidate for long exposure shots for that reason.  Regardless, when I get black or underexposed long exposure shots using stacked ND filters with my H4D-40 I just increase the exposure time (the H4D-40 has a max exposure time of 256 seconds).  When using 10-stop, 16-stops, or more, you usually need to increase the exposure time by a lot more than you think (50-150% longer or more) to get a properly exposed image
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SZRitter

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Re: Ultra long exposures with H4D-60
« Reply #4 on: August 12, 2016, 03:14:56 pm »

Since you are capped at 30 seconds, I would work backwards from that, and arrive at how many filters to use to reach the cap. Sounds like, with the amount of filters you used, and keeping the ISO and aperture the same, you would have needed a lot longer of an exposure.

Given the filters you mentioned, which is 18 stops, if I have it right, you are looking at about 1024 seconds of exposure, more or less.
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jonathan.lipkin

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Re: Ultra long exposures with H4D-60
« Reply #5 on: August 12, 2016, 03:24:50 pm »

Thanks, everyone. I'm trying to get to exposures of several minutes. I'm not sure this is possible, though.

I have an email exchange with Hasselblad and am awaiting a reply.

Thanks
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jonathan.lipkin

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Re: Ultra long exposures with H4D-60
« Reply #6 on: August 12, 2016, 03:37:09 pm »

32 sec is the max. Shutter will close after 32 sec when using T or B mode

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SZRitter

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Re: Ultra long exposures with H4D-60
« Reply #7 on: August 12, 2016, 04:19:55 pm »

Just for giggles, if I remember correctly, you could stack multiple images in photoshop and use a blend mode on the stack to "build" an exposure. Not sure if this would help you achieve your goal or not, and it isn't quite the same as doing it in camera.
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GrahamBy

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Re: Ultra long exposures with H4D-60
« Reply #8 on: August 12, 2016, 06:46:36 pm »

So the camera only wants to do a max of 32 seconds right?  I think stacked 6 stops gives you 36 stops total power, and adding a 3 stop on top gives you a 108 stops. adding a second gives you a 324 stops.  Stops would be multiple, not additive.

"Stops" are log-base-2 of exposure. So they add. 324 stops would mean 2^-324 or about 1.6x10^33 times less light... at a rough guess, that would be like shooting through 10mm of lead.
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voidshatter

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Re: Ultra long exposures with H4D-60
« Reply #9 on: August 13, 2016, 08:59:28 am »

Just for giggles, if I remember correctly, you could stack multiple images in photoshop and use a blend mode on the stack to "build" an exposure. Not sure if this would help you achieve your goal or not, and it isn't quite the same as doing it in camera.

No. The H4D-60 is a CCD and long exposure noise reduction is compulsory. There will be gaps between frames.
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voidshatter

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Re: Ultra long exposures with H4D-60
« Reply #10 on: August 13, 2016, 09:01:38 am »

Thanks, everyone. I'm trying to get to exposures of several minutes. I'm not sure this is possible, though.

I have an email exchange with Hasselblad and am awaiting a reply.

Thanks

I wouldn't bother with it. CCD is not good for long exposure at all. Even with Phase One's "Long Exposure Mode" you get corner issues.

The best way is to just get a CMOS (e.g. Nikon D810) instead for long exposure photography.
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SZRitter

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Re: Ultra long exposures with H4D-60
« Reply #11 on: August 16, 2016, 01:41:15 pm »

No. The H4D-60 is a CCD and long exposure noise reduction is compulsory. There will be gaps between frames.

Yes, yes there would be. The question is, how would it affect the final image? All depends on when/where/what he is shooting.
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voidshatter

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Re: Ultra long exposures with H4D-60
« Reply #12 on: August 16, 2016, 06:05:53 pm »

Yes, yes there would be. The question is, how would it affect the final image? All depends on when/where/what he is shooting.

I can't really think about what kind of image would benefit from a stacking of multiple frames with gaps.

The most popular long exposure shots would be motion blurs of moving clouds. Discontinuity is certainly not for my taste.
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SZRitter

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Re: Ultra long exposures with H4D-60
« Reply #13 on: August 16, 2016, 06:32:50 pm »

I can't really think about what kind of image would benefit from a stacking of multiple frames with gaps.

The most popular long exposure shots would be motion blurs of moving clouds. Discontinuity is certainly not for my taste.

When I was in school, it was a technique that was brought up with large format cameras in studio and with still lifes. You could shoot at f64, and use multiple flashes to build the exposure if you didn't have the flash power to do what you needed in one shot. Typically though, you would drag the shutter and pop the flashes multiple times. In the field, it was mentioned as a technique to use if you couldn't get a long enough exposure with your camera for the given light, typically your camera would need a multiple exposure function.

To simulate in Photoshop, my understanding was to take multiple shots, stack them, and in the stacking mode, I believe there is a mode called additive. Some also proposed this as a way to reduce noise in a given shot. Another variation is to use images with the full exposure and to blend them using mean instead of additive. I'm not sure how well it works on noise, as every time I've tried it, the sharpness has decreased enough from camera movement that I felt it outweighed the noise reduction. And I was 50/50 on results with moving water.

I don't have enough experience with the technique to call myself an expert, it's just one I've seen in passing and tried once or twice. I just threw it out as a possible workaround, and the OP can use his judgement to see if it is even a viable technique.
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