Exposure time vs. ISO

[jmvdigital]

I have a theoretical question for you guys...

Given an average ambient temperature, would an image exhibit higher IQ/less noise with a shorter exposure at higher ISO, or a longer exposure at a lower ISO? I caught this comment by Thierry in another post (about the eMotion 75 @ 800 ISO):

It also depends on the ambient temperature when your are shooting: my guess (but it's only a guess) is, that it will give a better result with ISO 800 at 4 sec. than at ISO 100 with 30 sec.

I have no idea if this a valid theory or not, and it probably differs greatly on the type of back. Any insight or real world experience on this?

 

[thsinar]

I am still guessing, since not had the time to experience it: yes, I believe this is true, WHEN the temperature is "high" (30 °C ++).

Thierry

I have a theoretical question for you guys...

Given an average ambient temperature, would an image exhibit higher IQ/less noise with a shorter exposure at higher ISO, or a longer exposure at a lower ISO? I caught this comment by Thierry in another post (about the eMotion 75 @ 800 ISO):



I have no idea if this a valid theory or not, and it probably differs greatly on the type of back. Any insight or real world experience on this?

 

[Jack]

I don't know either, but I have 30 second exposures at ISO 50 and 100 with my P45+ that are essentially noise free.

 

[thsinar]

the temperature is the issue, Jack: it is like poison concerning the noise.

30 seconds at 20°C are not such a problem, but then, if you shoot under tropical/equatorial temperatures it will dramatically change the game. This added to long exposures, which again adds to the internal temperature of the sensor, makes life difficult.

Thierry

I don't know either, but I have 30 second exposures at ISO 50 and 100 with my P45+ that are essentially noise free.

 

[Jack]

the temperature is the issue, Jack: it is like poison concerning the noise.

Understood Thierry, but the OP asked his question with the qualification of "average ambient temperatures" ...

Cheers,

 

[Guy Mancuso]

From someone that lives in hell out here in the sunny bake your butt Arizona i have yet to run into high temp noise issues with any length in exposures yet. But i would imagine if we let any back just sit in the sun for any length of time you may have a issue but that would be with any camera out here. i always thought about this since residing 30 years here and film I always protected but digital I just don't leave stuff in the car that can reach 140 degrees in a matter of minutes and even hotter.

 

[thsinar]

yes, understood as well, it all depends what is "average ambient": in South East Asia it's around 30°C all over the year.

cheers too,
Thierry

Understood Thierry, but the OP asked his question with the qualification of "average ambient temperatures" ...

Cheers,

 

[thsinar]

if you can protect your back, it's perfect, but there are situations (and I have experienced them) where you are shooting the whole day long with around 40°C: no way to keep the back cool, by any means, unless you bring some ice and wrap the back (I have done it).

Thierry

From someone that lives in hell out here in the sunny bake your butt Arizona i have yet to run into high temp noise issues with any length in exposures yet. But i would imagine if we let any back just sit in the sun for any length of time you may have a issue but that would be with any camera out here. i always thought about this since residing 30 years here and film I always protected but digital I just don't leave stuff in the car that can reach 140 degrees in a matter of minutes and even hotter.

 

[Don Libby]

From someone that lives in hell out here in the sunny bake your butt Arizona i have yet to run into high temp noise issues with any length in exposures yet. But i would imagine if we let any back just sit in the sun for any length of time you may have a issue but that would be with any camera out here. i always thought about this since residing 30 years here and film I always protected but digital I just don't leave stuff in the car that can reach 140 degrees in a matter of minutes and even hotter.

But it's a dry heat!

I've shot in a lot of varying climates from open the oven and stick your head in it Tucson to freeze your butt off snow up around your ankles (remember my ankles are higher up than most :ROTFL . I like keeping the ISO as low as possible and shoot about 99% of my stuff at 100 on the P30+; the big thing I'm looking forward to with the P45+ is being able to lower the ISO to 50.

By the way, Guy is being very conservative when he says the inside of a car here can get to 140 degrees. I've haven't seen it done for awhile but figure if the sidewalk can get hot enough to fry an egg figure what the inside temperature of a vehicle is.

As far as noise goes I haven't had much problems.....

don

 

[Jack]

yes, understood as well, it all depends what is "average ambient": in South East Asia it's around 30°C all over the year.

cheers too,
Thierry

I am sure it is, but Justin is from Colorado.

Moreover, I've used my back in 35 C temps without any noise issues, so in addition to outside temperatures I suspect some of it depends on the design of the back.

Cheers,

 

[carbonmetrictree]

I did notice a density of noise when in 30F weather shooting at night with the 1dsMk3. Each exposure took 3-4mins to creep into the card, but when I opened them up later, I noticed that the noise in the shadows were a bit more suppressed than at 80F. I tend to bracket when possible at night, so this wasn't too much of a concern for me.

Off the topic- I was very shocked to see that the 1dsMk3's buffer took exponentially longer as it got colder with the same exposure times. Some shots took around 4 minutes to record to the card.



I was around a steam boiler last night and the temperature was probably around 90F, no issues whatsoever with noise. With the plus series Phase backs, I can honestly tell you that at ISO 100 will be noise free especially because of the dark slide reference capture right after each long exposure.

 

[thsinar]

I was not referring to or comparing any brand, Jack, just speaking about simple physical laws: that is true for any brand.

I have shot with many brands under these conditions, even a P45+.

Best regards,
Thierry

I am sure it is, but Justin is from Colorado.

Moreover, I've used my back in 35 C temps without any noise issues, so in addition to outside temperatures I suspect some of it depends on the design of the back.

Cheers,

 

[Jack]

I was not referring to or comparing any brand, Jack, just speaking about simple physical laws: that is true for any brand.

I have shot with many brands under these conditions, even a P45+.

Best regards,
Thierry

Thierry,

I understand the physics too and was not referring to any specific brand either --- more design in general and more specifically was simply suggesting that perhaps the different methods used to cool the sensor can also come into play.

Cheers,

 

[jmvdigital]

So the moral of the story is to stay with the lowest ISO you can for prolonged exposures, unless you are in a super-hot tropical/desert environment, then experiment with higher ISO/shorter time exposures.

 

[lance_schad]

On our website (http://www.captureintegration.com/phase-one/phase-one-tech-specs/) we have a chart that maps out the maximum exposure time at various ambient temperatures.
As with any camera system, the longest exposure a Phase One back can produce before prohibitive noise is produced depends on the ambient temperature of the air. Unlike other camera systems Phase One back’s longest practical exposures are measure in minutes and hours rather than seconds.

L

 

[Jack]

And FTR, I'd like to highlight this little footnote on the chart Lance linked to:

"Note 2: Our testing has shown the P45+ to produce the best long exposures."

... Just in case that has any impact on what you decide to buy .

Cheers,

 

[Bob]

A good paper that explains this phenomenon fairly well can be read here www.hiddenloft.com/notes/CCDtemp.pdf
-bob