Very low ISO - Useful ?

[40737015]

Hi All,
Been playing with ISO settings and wated to see if anyone can see a difference.

Both of these pics were taken with flash and processed (demosiac / crop / resize / export to JPG) through DXO Photolab 8

All comments welcome.

CHEERS
JBO

 

[petrochemist128 153]

Very low ISO can be useful where there is movement that you want to blur.
With digital cameras going below the base ISO offers no advantages for static subjects.

With film lower ISO films can have higher resolution (though film type is also very significant). I don't think the subject youve picked will show any differences unless as a huge enlargement, even ISO 400 films can have plenty of resolution for everyday shots.

As someone who's tried using direct positive paper in on of my larger cameras ISO 32 does not seem 'very low' Photographic papers are typically around ISO 3 to 6 so about 1/10 the speed of your shots

 

[40737015]

I have never

Very low ISO can be useful where there is movement that you want to blur.
With digital cameras going below the base ISO offers no advantages for static subjects.

With film lower ISO films can have higher resolution (though film type is also very significant). I don't think the subject youve picked will show any differences unless as a huge enlargement, even ISO 400 films can have plenty of resolution for everyday shots.

As someone who's tried using direct positive paper in on of my larger cameras ISO 32 does not seem 'very low' Photographic papers are typically around ISO 3 to 6 so about 1/10 the speed of your shots

I have never used a film camera and dont even know what direct positive paper is.

When the weather brightens up a bit I will have a look at trying ISO 32 on birds and bugs.

CHEERS
JBO

 

[greybeard45 18]

Anything below 64 is just like using an ND filter for a slower shutter speed. In fact, IQ is not as good as at 64.

 

[LWW2]

The colors are brighter @ ISO 64.

 

[nerwin1]

Anything below the native minimal ISO loses dynamic range but what you gain are extra stops, like @greybeard said it's basically a pseudo ND filter haha. You mainly only use the extra low ISOs for either slow shutter speeds or need it for exposure reasons. Imagine trying to capture that silky look of water without an ND filter? A low of ISO 32 on a cloudy day could work out fine! But say if 1/8000th of a second shutter speed isn't enough to stop over exposing something right, well you can drop the ISO to ISO 32 or 50 and it would be like having a shutter speed of 1/25,000 in terms of exposure, not actual shutter speed.

 

[40737015]

Anything below the native minimal ISO loses dynamic range but what you gain are extra stops, like @greybeard said it's basically a pseudo ND filter haha. You mainly only use the extra low ISOs for either slow shutter speeds or need it for exposure reasons. Imagine trying to capture that silky look of water without an ND filter? A low of ISO 32 on a cloudy day could work out fine! But say if 1/8000th of a second shutter speed isn't enough to stop over exposing something right, well you can drop the ISO to ISO 32 or 50 and it would be like having a shutter speed of 1/25,000 in terms of exposure, not actual shutter speed.

Thats interesting.....

UK has had a lot of rain over the last few days so I will head out to a wee river I know that will be running high and put the shutter exposure speed thing to the test.

CHEERS
JBO

 

[Ysarex97 91]

Thats interesting.....

Different brand cameras implement the low ISO setting differently. You need to know how your specific model camera is handling that function internally to know what possible benefit or loss may apply.

One option is that the camera does nothing at all except produce a different camera JPEG. For example if you were to put the camera is full Manual and use the same exposure (shutter and f/stop) for both ISO 64 and ISO 32 you'd get a darker JPEG at ISO 32 and that's the only thing the camera would change. The two raw files exposed the same would be identical. If you allow the camera's meter to alter exposure as you change ISO then the camera will increase exposure in response to a reduction in ISO. With a camera that works this way you could for example use the low ISO setting (assume 32) or leave the camera at base ISO (assume 64) but apply a +1 exposure compensation and again get two totally identical raw files. The internal processing of the raw files is identical while the processing of the JPEGs is different. With a camera that works this way the low ISO setting is utterly valueless unless you want the camera JPEG. For someone like me who never wants the camera JPEG I have no use for the low ISO setting, if I want to increase exposure I'll increase exposure.

Some other brand cameras however can apply amplification or scaling to the sensor signal above the base level when you use the intermediary low ISO settings. With this brand camera if you then do as noted above and use the same exposure for both the low ISO (assume 50) and base ISO (assume 64) the low ISO raw file will in fact receive applied gain that the base ISO file doesn't get. This one needs a visual: Photographic Dynamic Range versus ISO Setting That's a link to Photons to Photos Dynamic Range graph for a Fuji X-T5. Base ISO is 125 and the representative circle on the graph is solid. Note the three open circles that represent the low ISO options of 100, 80, and 64. Using the ISO 100 and ISO 80 values applies gain to the sensor signal beyond the base ISO level and that affects the raw files. The full stop lower ISO 64 and base ISO 125 receive the same signal gain and so produce identical raw files with the same exposure. Again if you want the camera JPEGs the low ISO settings can be useful. For someone who only wants raw files, while the first implementation I described is neutral -- I can use low ISO or increase exposure and get the same raw file, this one isn't neutral, you get different raw files if you lower the ISO versus just increase exposure at base ISO. Looking at that graph you see the intermediary ISO values of 100 and 80 are producing less dynamic range than the base ISO -- that's because you're gain clipping the raw files. In the first implementation I described that doesn't happen since internally the camera doesn't alter the raw file processing but in this implementation it does.

 

[40737015]

Different brand cameras implement the low ISO setting differently. You need to know how your specific model camera is handling that function internally to know what possible benefit or loss may apply.

One option is that the camera does nothing at all except produce a different camera JPEG. For example if you were to put the camera is full Manual and use the same exposure (shutter and f/stop) for both ISO 64 and ISO 32 you'd get a darker JPEG at ISO 32 and that's the only thing the camera would change. The two raw files exposed the same would be identical. If you allow the camera's meter to alter exposure as you change ISO then the camera will increase exposure in response to a reduction in ISO. With a camera that works this way you could for example use the low ISO setting (assume 32) or leave the camera at base ISO (assume 64) but apply a +1 exposure compensation and again get two totally identical raw files. The internal processing of the raw files is identical while the processing of the JPEGs is different. With a camera that works this way the low ISO setting is utterly valueless unless you want the camera JPEG. For someone like me who never wants the camera JPEG I have no use for the low ISO setting, if I want to increase exposure I'll increase exposure.

Some other brand cameras however can apply amplification or scaling to the sensor signal above the base level when you use the intermediary low ISO settings. With this brand camera if you then do as noted above and use the same exposure for both the low ISO (assume 50) and base ISO (assume 64) the low ISO raw file will in fact receive applied gain that the base ISO file doesn't get. This one needs a visual: Photographic Dynamic Range versus ISO Setting That's a link to Photons to Photos Dynamic Range graph for a Fuji X-T5. Base ISO is 125 and the representative circle on the graph is solid. Note the three open circles that represent the low ISO options of 100, 80, and 64. Using the ISO 100 and ISO 80 values applies gain to the sensor signal beyond the base ISO level and that affects the raw files. The full stop lower ISO 64 and base ISO 125 receive the same signal gain and so produce identical raw files with the same exposure. Again if you want the camera JPEGs the low ISO settings can be useful. For someone who only wants raw files, while the first implementation I described is neutral -- I can use low ISO or increase exposure and get the same raw file, this one isn't neutral, you get different raw files if you lower the ISO versus just increase exposure at base ISO. Looking at that graph you see the intermediary ISO values of 100 and 80 are producing less dynamic range than the base ISO -- that's because you're gain clipping the raw files. In the first implementation I described that doesn't happen since internally the camera doesn't alter the raw file processing but in this implementation it does.

That post is very informative. Thank You.

That river I mentioned in earlier post has inexplicably dropped level but a handy pond on a very windy day became my test subject.

I see clearly the difference. The second pic (ISO 32) does allow for extended exposure time and also displays the loss of colour depth mentioned earlier.

I learned something today.

CHEERS
JBO

 

[Ysarex97 91]

That post is very informative. Thank You.

That river I mentioned in earlier post has inexplicably dropped level but a handy pond on a very windy day became my test subject.

View attachment 293876

View attachment 293877

I see clearly the difference. The second pic (ISO 32) does allow for extended exposure time and also displays the loss of colour depth mentioned earlier.

I learned something today.

CHEERS
JBO

The ISO values you're using suggest a Nikon camera (photos do not have EXIF data). You're seeing a difference because the exposure used at ISO 32 is clipping the sensor while the exposure at ISO 64 is not. If you take an ISO 32 exposure and make sure the sensor is not clipped then the camera will make two JPEGs of identical lightness and quite frankly you'll be unable to tell them apart.

I have a Nikon and I did that; I made sure the ISO 32 exposure did not clip the sensor but otherwise I let the camera set the exposure in A priority mode. Then took the photo at ISO 64 in which case the camera exposed 1 stop less and the two JPEGs are indistinguishable. At those low ISO values any quality difference between the two images is going to be basically undetectable unless the photo contains extreme DR and you're extremely lifting the shadows. Then you'll see a noise difference.

 

[40737015]

I just found out why some of my pics dont have EXIF Data.

If I use Windows photo viewer to do a quick resize it strips the data but if I use Affinity it stays.

CHEERS
JBO