High ISO, Slow(er) SS, More Noise

[pfinfante]

Tell me if this makes any sense.....

I find that at high(er) ISO's, I get less noise if the SS is faster than at that same ISO at a slower SS (i.e. more noise).

Btw, this is with my Z7

 

[DRwyoming]

Tell me if this makes any sense.....

That doesn't really make much sense but assuming the same scene, the same lighting and the same ISO a slower shutter speed means a smaller aperture so perhaps you're seeing some other image artifact resulting from greater DoF like a change in bokeh and not really a noise change.

For the same ISO and same light gathering (combo of shutter speed and aperture) you really shouldn't see different noise levels for the same captured scene. In very low light photography (e.g. astro photography) longer exposures that gather more light are actually pretty useful for lowering noise but that assumes the same aperture and more light is actually collected. In daylight photography where presumably you'd trade off shutter speed and aperture to maintain the same light collection you really should see the same amount of noise at the same ISO at different shutter speed/aperture combos that maintain the same exposure.

Could you post some examples of this higher noise at the same ISO but slower shutter speeds?

 

[pfinfante]

That doesn't really make much sense but assuming the same scene, the same lighting and the same ISO a slower shutter speed means a smaller aperture so perhaps you're seeing some other image artifact resulting from greater DoF like a change in bokeh and not really a noise change.

For the same ISO and same light gathering (combo of shutter speed and aperture) you really shouldn't see different noise levels for the same captured scene. In very low light photography (e.g. astro photography) longer exposures that gather more light are actually pretty useful for lowering noise but that assumes the same aperture and more light is actually collected. In daylight photography where presumably you'd trade off shutter speed and aperture to maintain the same light collection you really should see the same amount of noise at the same ISO at different shutter speed/aperture combos that maintain the same exposure.

Could you post some examples of this higher noise at the same ISO but slower shutter speeds?

See below...

 

[pfinfante]

Take a look here - both at 6400 ISO, both 100% crops.

You can only see EXIF info for this image if you are logged in.

 

[DRwyoming]

Take a look here - both at 6400 ISO, both 100% crops.

The Cardinal image appears to be focused on the rocks behind the bird and shows pretty classic motion blur on the bird itself. That's not a noise issue, that's really more of a focusing and motion blur issue. The Starling image was clearly shot in a lot more light given the smaller aperture (/6.3 vs f/5.6) and the much higher shutter speed (1/3200" vs 1/320").

Based on these two images I'd say you ran into camera and or subject motion issues in the slower shutter speed shot and possibly back focused a bit on the rocks but what that image shows is blur and or focusing issues and not classic noise issues. Noise shows up first in out of focus background areas and usually not so much on the primary subject itself unless it's really bad.

A high resolution camera like your Z7 or a D850 will reveal technical issues much more than lower resolution cameras so things like motion blur tend to be a lot more apparent than they might be on other cameras with lower resolution sensors. Unless you have other examples that show more noise in similar out of focus areas I'd say you're seeing motion blur issues at lower shutter speeds which would be completely normal.

 

[pfinfante]

The Cardinal image appears to be focused on the rocks behind the bird and shows pretty classic motion blur on the bird itself. That's not a noise issue, that's really more of a focusing and motion blur issue. The Starling image was clearly shot in a lot more light given the smaller aperture (/6.3 vs f/5.6) and the much higher shutter speed (1/3200" vs 1/320").

Based on these two images I'd say you ran into camera and or subject motion issues in the slower shutter speed shot and possibly back focused a bit on the rocks but what that image shows is blur and or focusing issues and not classic noise issues. Noise shows up first in out of focus background areas and usually not so much on the primary subject itself unless it's really bad.

A high resolution camera like your Z7 or a D850 will reveal technical issues much more than lower resolution cameras so things like motion blur tend to be a lot more apparent than they might be on other cameras with lower resolution sensors. Unless you have other examples that show more noise in similar out of focus areas I'd say you're seeing motion blur issues at lower shutter speeds which would be completely normal.

You're probably right. Even though I was at 1/320 on a tripod I guess that little guy could have been very sporadic in his movements.

 

[Rassie]

Patrick, how many such examples do you have that made you reach that conclusion?
I'm worried that the camera missed focus on the cardinal and focused on the rocks behind the bird. If you sharpened that image, then sharpening also tends to sharpen the noise and make it more obvious.

Otherwise I can't explain what you're seeing.

 

[pfinfante]

Patrick, how many such examples do you have that made you reach that conclusion?
I'm worried that the camera missed focus on the cardinal and focused on the rocks behind the bird. If you sharpened that image, then sharpening also tends to sharpen the noise and make it more obvious.

Otherwise I can't explain what you're seeing.

Both are SOOC nef--->jpg . The image on the right is pretty clean for 6400 ISO I'd say. I think, as mentioned above, it is motion blur causing the perceived issue.

 

[Palouse]

It could also be over saturation of the red channel.