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Author Topic: Camera is cold, ideal for low noise  (Read 2681 times)
sanfairyanne
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« on: September 23, 2013, 12:07:29 AM »
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I'm currently in a really cold environment but I will soon be going somewhere quite hot where I hope to take a night shot. A cold sensor seems ideal for low noise images and a warm one seems unfavourable. I wonder therefore if it's recommended to keep a camera in a cool bag until the moment you want to shoot. I imagine you'd have to keep the lens at the ambient temperature but the body could be kept cool.

I wonder if anyone has tested this, I would try it myself but short of putting my camera in the oven I have no way of warming it up sufficiently.  Smiley
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capital
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« Reply #1 on: September 23, 2013, 03:03:14 AM »
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Have you considered using dark frame subtraction if sensor noise is an issue? I am not aware of any DSLR* that accepts active cooling, you might want to invest in a specialized peltier cooled sensor for astrophotography if your application demands very low noise. Or you might consider frame stacking as it limits shot to shot exposure times but allows you to post process a lower noise image. Finally, consider the issue might be negligible if you are not using very long exposure times.

*See here for some DIY:

http://astrophoto-sv.com/index.php?p=1_84
« Last Edit: September 23, 2013, 03:05:00 AM by capital » Logged
Tony Jay
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« Reply #2 on: September 23, 2013, 04:34:48 AM »
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The way to prevent noise for astrophotography purposes is to avoid long exposures as much as possible.
That will stop the sensor from heating up to temperatures that cause heat related noise.
A minute is fine.
Switch off any noise reduction functions on your camera otherwise the delays caused by the processing will mean gaps in a star trail when taking multiple shots(all supposing that this is your photographic purpose). Doing an image stack in post-processing will remove the noise.

I would not cool my camera in the manner you suggest - condensation will be the least of your issues causing image artifacting.
Condensation could also result in electrical short-circuiting in your camera.
Those cameras that do cool the sensor are better thought of as cameras that prevent the sensor heating up beyond ambient temperature.

I live in a real hot place (Australia) and the only issue with nocturnal photography is to prevent long exposures that really heat up the sensor.

Tony Jay
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sanfairyanne
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« Reply #3 on: September 23, 2013, 05:49:51 AM »
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I already use the multi shot method for creating star trails. The shot I want to take is will only require a single 30 second exposure but the tempature could be 35C. I just wondered if you could keep the body in a freezer bag with a couple of those dry blocks you put in the freezer, I'm not talking about freezing the camera just keeping it cold. I particularly noticed noise this year in the deserts of Arizona, if my camera was in the car during the day it would be warm to the touch when I took it out of my gadget bag in the evening. I'd then have so much noise in a 30 second iso 1600 shot that it was unusable with my 5D2.

I'll do some testing to see if this idea works. I'll warm the camera up and try a shot, then I'll cool it down and compare the difference.
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Ellis Vener
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« Reply #4 on: September 24, 2013, 07:44:40 AM »
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"The shot I want to take is will only require a single 30 second exposure but the tempature could be 35C."

Will the humidity of the place you are going be a factor? If so, won't  taking a camera that has been cooled down out in to the warm humid air cause condensation and lens fogging to be a factor?
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Ellis Vener
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sanfairyanne
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« Reply #5 on: September 24, 2013, 10:57:23 AM »
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Yes for sure that's why I was going to cool just the body. I'll do some testing this weekend and get back with a report. I really think it will work providing the body isn't too cold. As I mentioned earlier when I've left my camera sitting in a car in hot sunshine it gets really hot. I understand electronics hate the heat, not just sensors. So if I keep the body at say 10C I feel everything will be fine.
I'll be taking my shot in a dry desert so there shouldn't be much humidity.

Incidentally the link 'capital' gave me was very interesting it shows a DIY cooling system for astro photography. I'd never have the skills to make one of these, I'd love to be able to buy something that did this.
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PeterAit
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« Reply #6 on: September 24, 2013, 11:40:38 AM »
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No. It is true that the "noise" in photos is caused by thermal fluctuations, and that's why astronomical telescope sensors are cooled. But here we are talking about ambient versus liquid nitrogen temps, many many degrees. The 10 or 20 degree cooling you might achieve with your cooling bag will not make any difference that can be noticed.
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Peter
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sanfairyanne
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« Reply #7 on: September 24, 2013, 11:52:49 AM »
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Really, it's sure weird then that a night shot in 0 C has no noise whereas a shot when the camera is warm and it's 30C is more or less unusable.
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NancyP
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« Reply #8 on: September 24, 2013, 12:53:41 PM »
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This sounds like a job for better post processing.  What focal length/aperture do you shoot at, and how many frames do you collect? What is your target - Milky Way widefield? I am guessing you aren't doing fainter nebulae, what with 30 sec anticipated exposure. What is your workflow? What is your astro processing program and which algorithm do you use ? Do you use darks series taken at the same temperature, or hot pixel maps, or whatever for subtracting the noise from your series of lights frames?

I have seen good wide-field astro-landscape images taken in 30 degree C conditions (summer in Missouri) using a 5D2. I am not very sophisticated about post processing, I am stumbling my way through Nebulosity, which is considered an easy to use astro image processing program. 

The Cloudy Nights astrophotography fora are good sources of information about post-processing algorithms. The people who use home-built Peltier cooler boxes for their SLRs are generally chasing faint objects requiring a big stack of 1 to 5 minute exposures. Milky Way shots should be taken at ambient, and the camera stored at ambient before use.

Clear skies to you!
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sanfairyanne
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« Reply #9 on: September 24, 2013, 01:04:29 PM »
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Nancy P,

I'm only taking one shot of an old ruin looking down as the ruin is lit up by candle light. I'm not doing any star work whatsoever, I'm pointing the camera down rather than up. It's just that it's really hot in the desert. I could certainly make sure to keep the camera out of the heat in the daytime but I really feel a cool bag should help. As I say I'll test it at the weekend.
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PeterAit
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« Reply #10 on: September 24, 2013, 04:59:50 PM »
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Really, it's sure weird then that a night shot in 0 C has no noise whereas a shot when the camera is warm and it's 30C is more or less unusable.

If you already know the answer, why are you asking the question?
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Peter
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sanfairyanne
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« Reply #11 on: September 24, 2013, 11:08:28 PM »
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I haven't tested the cool bag yet. I just wondered if anyone has tried it. If I hadn't asked it I wouldn't have got the link by "Capital'' showing the astro cooling accessory, that idea is beyond my needs but I passed the link to a friend who was very interested.
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Tony Jay
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« Reply #12 on: September 25, 2013, 03:58:17 AM »
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Yes for sure that's why I was going to cool just the body.
I'll give this one more go:
Cooling the body only will not help.
The rear element of the lens (because it is attached to body by a metal connection) and the sensor itself will be quickly susceptible to condensation.

If the place is as hot as you say (even at night) then cooling the body to even 10 oC will result in instant condensation.
I have had this problem in North Queensland when I have simply got out of an air-conditioned vehicle to take a shot.
I learn't to prevent undue cooling of the camera in the air-conditioning to prevent these sorts of mishaps.
Waiting 10-15 minutes for the camera (and lens) to warm sufficiently to evaporate the condensation means lost images when shooting wildlife not to mention the risk of mould growing in one's lenses and camera body.

Tony Jay
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sanfairyanne
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« Reply #13 on: September 25, 2013, 06:31:53 AM »
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Ok I hear you, I'll just try to make sure the camera doesn't heat up beyond the ambient temperature. By that I mean I won't let it heat up in a parked car or in the sun.
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BartvanderWolf
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« Reply #14 on: September 25, 2013, 07:21:08 AM »
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If the place is as hot as you say (even at night) then cooling the body to even 10 oC will result in instant condensation.


Hi Tony,

While larger temperature differences generally increase the risk of cooling air that will result in condensation, it of course also depends on the relative humidity (RH) of the warm air. Only when the moist air cools enough, can it reach the dew point temperature. And indeed, a rapid drop of 20 degrees Celsius near a cooler surface will almost certainly cause issues for 30 degrees ambient temperature with 30% RH or more.

A very rough approximation for average humidities is:
   Dew-point temperature = ambient temperature - (100 - RH) / 5 ,
with temperatures expressed in Celsius.

A more accurate chart can be found here.

Cheers,
Bart
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Tony Jay
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« Reply #15 on: September 25, 2013, 03:11:01 PM »
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Hi Tony, While larger temperature differences generally increase the risk of cooling air that will result in condensation, it of course also depends on the relative humidity (RH) of the warm air. Only when the moist air cools enough, can it reach the dew point temperature. And indeed, a rapid drop of 20 degrees Celsius near a cooler surface will almost certainly cause issues for 30 degrees ambient temperature with 30% RH or more. A very rough approximation for average humidities is:    Dew-point temperature = ambient temperature - (100 - RH) / 5 , with temperatures expressed in Celsius. A more accurate chart can be found here. Cheers, Bart
Thanks Bart.
I am absolutely across the physics of this.
If you consult your resources you will see that the air will have to be amazingly dry for condensation NOT to be an issue with a rapid 20 oC drop in temperature.

Tony Jay
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BartvanderWolf
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« Reply #16 on: September 25, 2013, 03:17:15 PM »
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Thanks Bart.
I am absolutely across the physics of this.
If you consult your resources you will see that the air will have to be amazingly dry for condensation NOT to be an issue with a rapid 20 oC drop in temperature.

Correct, a drop of 20 degrees would be like looking for trouble.

Cheers,
Bart
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