is long exposure better than high iso?

[Steve Axford]

For example, am I better to use a 120sec exposure at ISO 800, or a 30sec exposure at ISO 3200? Both would be using long exposure noise reduction.

[Plays With Light]

I think that would depend on what you were photographing, Steve. If you were doing a cityscape at night for example, you'd want to keep the shutter speed as short as possible, so you still retained detail in the highlights.

[Steve Axford]

It is for time lapse of luminous fungi. The ambient light needs to be very low as the mushrooms provide their own light, but not a lot. The aperture also needs to be very small, to get as much dof as possible. I have done it before, quite successfully, but I am experimenting to see if I can extend the subject matter a little.
Ps. The time between exposures is 6 to 10 minutes, so a 2 min exposure is fine.

[ricktas]

I think it would depend on how your camera handles high ISO noise, however I personally would use the lowest ISO I could to get the cleanest image I could given that I wanted to capture something in very low light. So that in post, if I needed to clean up noise, I would hopefully not lose detail as often noise reduction results in loss of some detail.

[Tannin]

The theory is that the longer exposure will have less shot noise (which is the primary form of noise in low-light photography) but I am unsure about the Gaussian noise produced by the camera's electronics.

[jim]

I would tentatively suggest that a long exposure might give you a better signal/noise ratio. Maybe. Have you considered making several shorter exposures?

Alternatively perhaps read this:

http://www.clarkvision.com/articles/digital.sensor.performance.summary/

And then perhaps you could try to explain it to me...

[Steve Axford]

I tend to agree, but I'm not sure why. It has one other advantage in that for film, you should ideally use a shutter speed that is half the frame interval.

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I would tentatively suggest that a long exposure might give you a better signal/noise ratio. Maybe. Have you considered making several shorter exposures?

Alternatively perhaps read this:

http://www.clarkvision.com/articles/digital.sensor.performance.summary/

And then perhaps you could try to explain it to me...
I'll let you know if I can decipher it :)

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I would tentatively suggest that a long exposure might give you a better signal/noise ratio. Maybe. Have you considered making several shorter exposures?

Alternatively perhaps read this:

http://www.clarkvision.com/articles/digital.sensor.performance.summary/

And then perhaps you could try to explain it to me...
I'll let you know if I can decipher it :)

[nardes]

I would guess go for longer exposure at lower ISO with in-camera noise reduction, or separate dark frames applied. The 3 or 4 mins between exposures should also allow the sensor to cool off a little, which will help lessen the contribution of thermal noise.

I wonder if you move the camera ever so slightly between exposures, maybe one or two pixels up-down-left-right (called dithering in astrophotography) to minimise stacking artefacts, then the fixed pattern noise would average out leaving a stronger signal overall?

Cheers

Dennis

[Geoff79]

I don't know nothin' about nothin' and especially when it comes to how well your full frame cameras handle noise.

But in my limited experience, I'd also assume that the lower ISO would be preferable, and that the longer exposure would offer far less noise. Just looking at the two numbers above... with my simple equipment I know the difference between ISO 800 and 3200 is pretty massive.


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[Steve Axford]

I would guess go for longer exposure at lower ISO with in-camera noise reduction, or separate dark frames applied. The 3 or 4 mins between exposures should also allow the sensor to cool off a little, which will help lessen the contribution of thermal noise.

I wonder if you move the camera ever so slightly between exposures, maybe one or two pixels up-down-left-right (called dithering in astrophotography) to minimise stacking artefacts, then the fixed pattern noise would average out leaving a stronger signal overall?

Cheers

Dennis
iInteresting, though stacking idoesnt come into it, so it's not an issue. It's also an interesting thought re the sensor heating.

[Plays With Light]

Steve if you're only shooting for two minutes at a time, you will have no additional noise introduced by a warm sensor, that only really kicks in for exposures over five minutes on most modern era full-frame sensors. For my Canon 6D, I notice it kicks in at around five and a half minutes in length, just as an example. So with this in mind, I keep my long exposures, using a 16 stop ND filter, to under five and a half minutes, and they are nice and clean.

[Steve Axford]

Steve if you're only shooting for two minutes at a time, you will have no additional noise introduced by a warm sensor, that only really kicks in for exposures over five minutes on most modern era full-frame sensors. For my Canon 6D, I notice it kicks in at around five and a half minutes in length, just as an example. So with this in mind, I keep my long exposures, using a 16 stop ND filter, to under five and a half minutes, and they are nice and clean.
Probably right, but it may be more of a problem as it is continuous and in a warm environment and the camera is kept warm it's a heating coil (to prevent condensation). I'll just keep it I need mind.

[Plays With Light]

Ps. The time between exposures is 6 to 10 minutes, so a 2 min exposure is fine.
Steve, if this is correct, I don't think you'd have any issues with the sensor getting hot, even with the heat-pad underneath. I fire off 5 minute shots, one after the other for an hour and a half, without any issues, and that's with my lowly 6D.

[arthurking83]

This method may cost you a couple of $, as I understand it on a Sony( if you're using the Sony here).

On the higher end Nikon, we have a multiple exposure mode.
This is usually a mode to blend two expoures over each other to create interesting effects.

But, I've found that in the Nikons, if you want reduced high ISO noise with less reliance on ISO noise reduction, this multi exposure feature helps a lot.

So you'd still use that 30sec ISO3200 setting, and shoot a number of frames of the exact same scene. Hoping there is no movement in the subject for a sharp image.
On a Nikon we're limited to 10 exposures for a single final exposure.

I've looked into this on Sony's that have this feature, but know nothing of it's workings. it's available in the Play Memory section of Sony's apps area.

On Nikons we only have three otopns: On/Off, number of exposures taken(up to 10) and Gain On/Off.
How the gain system works for Sony I have no idea, they seem to have much more intricate 'software' allowing Screen/Multiply/Add/Screen/Lighten/Darken modes .. like you get in PC software for blending.
(ps. probably a reason to own a Sony too me thinks).

I don't know if it outputs a raw image tho .. Nikon's do the multi exposures and finish with a raw image .. and thus the usual raw advantages. if it's only a jpg output, then I'd say maybe not worth it **.

But I' found that with the Gain On in the Nikons, it gives a good advantage for high ISO in terms of noise and exposure latitude too.
Blacks are where noise is usually pretty bad at high ISO, and with the multi exposure feature this is almost eliminated .. so the requirement for NR is lessened greatly.

it's basically astro exposure stacking without the need for software to stack exposures.

But, watch for camera slap(ie. on the Sony shutter slap but not mirror slap :D). On the D800E it produces a fair amount of shutter slap in a 10 exposure action.
On the Sony A7rII, I'd use the EFC to eliminate that possibility.

** I've had a quick look at the specs for this app, and it does say raw and uncompressed shooting modes are supported .. so that's a bonus.

[Steve Axford]

Thanks for the input guys. I did what is always the best thing to do - I tried it. I can now say that longer exposure gives less noise than higher ISO, at least for my purposes and on this camera it does. I tried 2 minutes exposure, with dark field noise reduction, at ISO 800 and f20 on a Canon 7D II. This seems to give similar noise to 30 secs at ISO 800 and much better than 30 secs at ISO 3200. I wanted to try the Canon 7D II as I often use it, sometimes together with the other cameras at the same time. The main problem with the 7D II is the high noise profile, for luminous fungi shots, and this seems to have fixed that.
Note - I have now reduced the ISO to ISO 400 as I was 0.5 stops overexposed. It will be interesting to see if ISO 400 plus 0.5 stops is lower noise than ISO 800 - 0.5 stops.

This is a single image from the time lapse https://steveaxford.smugmug.com/Latest-Images/Latest/i-VHk4XZH/A I can't seem to post the image so here is a link https://steveaxford.smugmug.com/Latest-Images/Latest/i-VHk4XZH/A


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This method may cost you a couple of $, as I understand it on a Sony( if you're using the Sony here).

On the higher end Nikon, we have a multiple exposure mode.
This is usually a mode to blend two expoures over each other to create interesting effects.

But, I've found that in the Nikons, if you want reduced high ISO noise with less reliance on ISO noise reduction, this multi exposure feature helps a lot.

So you'd still use that 30sec ISO3200 setting, and shoot a number of frames of the exact same scene. Hoping there is no movement in the subject for a sharp image.
On a Nikon we're limited to 10 exposures for a single final exposure.

I've looked into this on Sony's that have this feature, but know nothing of it's workings. it's available in the Play Memory section of Sony's apps area.

On Nikons we only have three otopns: On/Off, number of exposures taken(up to 10) and Gain On/Off.
How the gain system works for Sony I have no idea, they seem to have much more intricate 'software' allowing Screen/Multiply/Add/Screen/Lighten/Darken modes .. like you get in PC software for blending.
(ps. probably a reason to own a Sony too me thinks).

I don't know if it outputs a raw image tho .. Nikon's do the multi exposures and finish with a raw image .. and thus the usual raw advantages. if it's only a jpg output, then I'd say maybe not worth it **.

But I' found that with the Gain On in the Nikons, it gives a good advantage for high ISO in terms of noise and exposure latitude too.
Blacks are where noise is usually pretty bad at high ISO, and with the multi exposure feature this is almost eliminated .. so the requirement for NR is lessened greatly.

it's basically astro exposure stacking without the need for software to stack exposures.

But, watch for camera slap(ie. on the Sony shutter slap but not mirror slap :D). On the D800E it produces a fair amount of shutter slap in a 10 exposure action.
On the Sony A7rII, I'd use the EFC to eliminate that possibility.

** I've had a quick look at the specs for this app, and it does say raw and uncompressed shooting modes are supported .. so that's a bonus.

I can't really use multiple exposures as that makes things far to complex and will probably muck up the final video. This is already a very complex thing to do and simple is really good.https://steveaxford.smugmug.com/Latest-Images/Latest/i-VHk4XZH/A

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https://steveaxford.smugmug.com/Latest-Images/Latest/i-VHk4XZH/A